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RFC2625 - IP and ARP over Fibre Channel

王朝other·作者佚名  2008-05-31
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Network Working Group M. Rajagopal

Request for Comments: 2625 R. Bhagwat

Category: Standards Track W. Rickard

Gadzoox Networks

June 1999

IP and ARP over Fibre Channel

Status of this Memo

This document specifies an Internet standards track protocol for the

Internet community, and requests discussion and suggestions for

improvements. Please refer to the current edition of the "Internet

Official Protocol Standards" (STD 1) for the standardization state

and status of this protocol. Distribution of this memo is unlimited.

Copyright Notice

Copyright (C) The Internet Society (1999). All Rights Reserved.

Abstract

Fibre Channel (FC) is a high speed serial interface technology that

supports several higher layer protocols including Small Computer

System Interface (SCSI) and Internet Protocol(IP). Until now, SCSI

has been the only widely used protocol over FC. Existing FC standards

[3] do not adequately specify how IP packets may be transported over

FC and how IP addresses are resolved to FC addresses. The purpose of

this document is to specify a way of encapsulating IP and Address

Resolution Protocol(ARP) over Fibre Channel and also to describe a

mechanism(s) for IP address resolution.

Table of Contents

1. IntrodUCtion ............................................... 3

2. Problem Statement .......................................... 5

3. IP and ARP Encapsulation ................................... 5

3.1 FC Frame Format ........................................ 5

3.2 MTU .................................................... 7

3.2.1 IP MTU ........................................... 7

3.2.2 Maximally Minimum IPv4 packet .................... 8

3.2.3 ARP MTU .......................................... 8

3.2.4 FC Data Field containing FARP Packet ............. 9

3.3 FC Port and Node Network Addresses ..................... 9

3.4 FC Sequence Payload Format ............................. 10

3.5 Bit and Byte Ordering .................................. 12

4. ARP ........................................................ 12

4.1 Address Resolution .................................... 12

4.2 ARP Packet Format ...................................... 13

4.3 ARP Layer Mapping and Operation ........................ 15

4.4 ARP Broadcast in a Point-to-Point Topology ............. 16

4.5 ARP Broadcast in a Private Loop Topology ............... 16

4.6 ARP Broadcast in a Public Loop Topology ................ 16

4.7 ARP Operation in a Fabric Topology ..................... 17

5. FARP ....................................................... 18

5.1 Scope .................................................. 18

5.2 FARP Overview .......................................... 18

5.3 FARP Command Format .................................... 20

5.4 Match Address Code Points .............................. 22

5.5 Responder Flags ........................................ 23

5.6 FARP Support Requirements .............................. 24

6. Exchange Management ........................................ 25

6.1 Exchange Origination ................................... 25

6.2 Exchange Termination ................................... 25

7. Summary of Supported Features .............................. 25

7.1 FC-4 Header ............................................ 25

7.2 R_CTL .................................................. 26

7.3 F_CTL .................................................. 27

7.4 Sequences .............................................. 28

7.5 Exchanges .............................................. 29

7.6 ARP and InARP ......................................... 30

7.7 Extended Link Services (ELS) ........................... 31

7.8 Login Parameters ....................................... 31

7.8.1 Common Service Parameters - FLOGI ............... 32

7.8.2 Common Services Parameters - PLOGI ............... 32

7.8.3 Class Service Parameters - PLOGI ................. 32

8. Security Considerations .................................... 32

8.1 IP and ARP Related ..................................... 32

8.2 FC Related ............................................. 32

9. Acknowledgements ........................................... 33

10. References ................................................ 33

11. Authors' Addresses ........................................ 35

Appendix A: Additional Matching Mechanisms in FARP ............ 36

Appendix B: InARP ............................................. 40

B.1 General Discussion ..................................... 40

B.2 InARP Protocol Operation ............................... 40

B.3 InARP Packet Format .................................... 40

B.4 InARP Support Requirements ............................. 41

Appendix C: Some Informal Mechanisms for FC Layer Mappings .... 42

C.1 Login on cached Mapping Information .................... 42

C.2 Login on ARP parsing ................................... 42

C.3 Login to Everyone ...................................... 43

C.4 Static Table ........................................... 43

Appendix D: FC Layer Address Validation........................ 44

D.1 General Discussion ..................................... 44

D.2 FC Layer Address Validation in a Point-to-Point Topology 45

D.3 FC Layer Address Validation in a Private Loop Topology . 45

D.4 FC Layer Address Validation in a Public Loop Topology .. 45

D.5 FC layer Address Validation in a Fabric Topology ....... 46

Appendix E: Fibre channel Overview ............................ 47

E.1 Brief Tutorial ......................................... 47

E.2 Exchange, Information Unit, Sequence, and Frame ........ 48

E.3 Fibre Channel Header Fields ............................ 49

E.4 Code Points for FC Frame ............................... 52

E.4.1 Code Points with IP and ARP Packet .............. 52

E.4.2 Code Points with FARP Command ................... 54

Appendix F: Fibre Channel Protocol Considerations.............. 58

F.1 Reliability in Class 3 ................................. 58

F.2 Continuously Increasing SEQ_CNT ........................ 58

Appendix G: Acronyms and Glossary of FC Terms ................. 60

Full Copyright Statement ...................................... 63

1. Introduction

Fibre Channel (FC) is a gigabit speed networking technology primarily

used for Storage Area Networking (SAN). FC is standardized under

American National Standard for Information Systems of the National

Committee for Information Technology Standards (NCITS) and has

specified a number of documents describing its protocols, operations,

and services.

Need:

Currently, Fibre Channel is predominantly used for communication

between storage devices and servers using the SCSI protocol, with

most of the servers still communicating with each other over LANs.

Although, there exists a Fibre Channel Standard [3] that has

architecturally defined support for IP encapsulation and address

resolution, it is inadequately specified. ([3] prohibits broadcasts,

thus loops are not covered; [10] has no support for Class 3).

This has lead to a nonstandard way of using IP over FC in the past.

Once such a standard method is completely specified, servers can

directly communicate with each other using IP over FC, possibly

boosting performance in Server host-to-host communications. This

technique will be especially useful in a Clustering Application.

Objective and Scope:

The major objective of this specification is to promote interoperable

implementations of IPv4 over FC. This specification describes a

method for encapsulating IPv4 and Address Resolution Protocol (ARP)

packets over FC. This specification accommodates any FC topology

(loop, fabric, or point-to-point) and any FC class of service (1, 2

or 3). This specification also describes a FC Address Resolution

Protocol(FARP) for associating World Wide Port Names (MAC addresses)

and FC Port identifiers.

A secondary objective of this specification is to describe other

optional address resolution mechanisms:

- Other FARP mechanisms that directly build IPv4 address and FC

Port Identifier (Port_ID) associations.

- Inverse ARP (InARP) that allows learning the IP address of a

remote node given its World Wide Port Name (WW_PN) and Port_ID.

"Multicasting" in Fibre Channel is defined as an optional service

[11] for FC Classes 3 and 6 only, with no definition for Classes 1

and 2. Currently, there are no vendor implementations of this service

for either Class of service. Broadcast service available within Fibre

Channel can be used to do multicasting, although less efficiently.

Presently, there appears to be no IP applications over Fibre Channel

that require support for IP multicasting. This specification

therefore does not support IP Multicasting.

Organization:

Section 2 states the problem that is solved in this specification.

Section 3 describes the techniques used for encapsulating IP and ARP

packets in a FC sequence. Section 4 discusses the ARP protocol(IP

address to WW_PN). Section 5 discusses the FARP protocol used in FC

Layer mappings (WW_PN to Port_ID). Section 6 describes the

"Exchange" Management in FC. Section 7 is a summary section and

provides a quick reference to FC header settings, FC Link Service

Commands, supported features in ARP, FARP, InARP, FC Sequences, FC

Exchanges, and FC Login Parameters. Section 8 discusses security.

Section 9 acknowledges the technical contributors of this document.

Section 10 provides a list of references, and Section 11 provides the

authors' addresses.

Appendix A discusses other optional FARP mechanisms. Appendix B

discusses the Inverse ARP protocol(WW_PN to IP address) as an

alternate and optional way of building MAC and IP address

associations. Appendix C lists some informal mechanisms for FC Layer

Mappings. Appendix D provides a discussion on validation of the FC-

layer mappings for the different FC topologies. Appendix E provides

a brief overview of the FC Protocols and Networks. Appendix F

addresses reliability in Class 3 and Sequence Count FC Protocol

issues. Appendix G provides a list of acronyms and a glossary of FC

Terms used in this specification.

The key Words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",

"SHOULD", SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this

document are to be interpreted as described in RFC2119 [19].

2. Problem Statement

This specification addresses two problems:

- A format definition and encapsulation mechanism for IPv4

and ARP packets over FC

- Mechanisms for Address Resolution

As noted earlier, the existing FC Standard [3] ([10]) is inadequate

to solve the above problems. A solution to both problems was first

proposed by the Fibre Channel Association (FCA)[1]. FCA is an

industry consortium of FC vendor companies and not a Standards Body.

This specification is based on the proposed solution in [1] and

builds on it.

Address Resolution is concerned with resolving IP addresses to WW_PN

(MAC address) and WW_PN to FC Port Identifiers (Port_ID). ARP

provides a solution to the first resolution problem and FARP the

second.

An optional FARP mechanism resolves IP address directly to FC

Port_IDs. This is useful in some upper layer applications.

InARP is another optional mechanism that resolves WW_PN and Port_ID

to an IP address. InARP is useful when a node after performing a

PLOGI with another node, knows its WW_PN and Port_ID, but not its IP

address.

3. IP and ARP Encapsulation

3.1 FC Frame Format

All FC frames have a standard format much like LAN 802.x protocols.

(See Appendix E and F). However, the exact size of each frame varies

depending on the size of the variable fields. The size of the

variable field ranges from 0 to 2112-bytes as shown in the FC Frame

Format in Fig. 1.

+------+--------+-----------+----//-------+------+------+

SOF Frame Optional Frame CRC EOF

(4B) Header Header Payload (4B) (4B)

(24B) <----------------------->

Data Field = (0-2112B)

+------+--------+-----------+----//-------+------+------+

Fig. 1 FC Frame Format

The Start of Frame (SOF) and End of Frame (EOF) are both 4-bytes long

and act as frame delimiters.

The CRC is 4-bytes long and uses the same 32-bit polynomial used in

FDDI and is specified in ANSI X3.139 Fiber Distributed Data

Interface.

The Frame Header is 24-bytes long and has several fields that are

associated with the identification and control of the payload. Some

of the values and options for this field that are relevant to the IP

and ARP payloads are discussed in Section 7.

Current FC Standards allow up to 3 Optional Header fields [11]:

- Network_Header (16-bytes)

- Association_Header (32-bytes)

- Device_Header (up to 64-bytes).

The IP and ARP FC Sequences SHALL carry only the Network_Header field

which is 16-bytes long. Other types of optional headers SHALL NOT be

used. The Network_Header is REQUIRED in all ARP packets and in the

first frame of a logical sequence carrying an IP payload as described

below.

An application level payload such as IP is called an Information Unit

at the FC-4 Level. Lower FC levels map this to a FC Sequence. (See

Appendix E.2 for a description of Sequences and Information Units.)

Typically, a Sequence consists of more than one frame. Larger user

data is segmented and reassembled using two methods: Sequence Count

and Relative Offset [18]. With the use of Sequence Count, data blocks

are sent using frames with increasing sequence counts (modulo 65536)

and it is quite straightforward to detect the first frame that

contains the Network_Header. When Relative Offset is used, as frames

arrive, some computation is required to detect the first frame that

contains the Network_Header. Sequence Count and Relative Offset field

control information, is carried in the FC Header.

In FC, the physical temporal ordering of the frames as it arrives at

a destination can be different from that of the order sent because of

traversing through a FC Network.

When IP forms the FC Payload then only the first frame of the logical

Sequence SHALL include the FC Network_Header. Fig. 2 shows the

logical First Frame and logical subsequent frames. Since frames may

arrive out of order, detection of the first frame of the logical FC

Sequence is necessary.

ARP packets map to a single frame FC Sequence and SHALL always carry

the FC Network_Header.

Note the definition of FC Data Field and FC Frame Payload in Fig. 1.

FC Data Field includes the FC Frame Payload and the FC Optional

Header, that is, Frame Payload definition does not include the FC

Optional Header. One or more Frame Payloads together make the FC

Sequence Payload as shown in Fig 2 and discussed further in Sections

3.2 and 3.4. FC Sequence Payload includes the mapped IP or ARP packet

along with the LLC/SNAP headers.

First Frame of a Logical FC Sequence

---+------------+---------------------------+----------//----------+---

FC Header FC Network_Header FC Sequence Payload

---+------------+---------------------------+---------//-----------+---

Subsequent Frames of a Logical FC Sequence

--+-----------+--------------//----------------+--

FC Header Additional FC Sequence Payload

--+-----------+-------------//-----------------+--

Fig. 2 FC Network_Header in a Frame Sequence

The SOF, CRC, EOF control fields of the FC frame and other optional

headers have been omitted in the figure for clarity.

3.2 MTU

3.2.1 IP MTU

An FC Information Unit specific to each protocol such as IP is

defined in FC-4. This defines the upper bound on the size of the

information that can be transported.

Each IP or ARP Packet is mapped to a single FC Information Unit,

which in turn is mapped to a single FC Sequence. There is a one-to-

one mapping between an IP or ARP packet and a FC Sequence.

Fibre Channel limits the size of a single Information Unit to 2^32-1,

which is very large [2]. However, since the Maximum Transmission

Unit (MTU) size of an IPv4 packet does not exceed 65,536-bytes, the

mapped IPv4 size is far below the 2^32-1 limit.

IPv4 Packet definition includes the IP Payload and IP Headers - both

fixed and optional. The corresponding FC Sequence Payload includes

the LLC/SNAP Header and the IPv4 packet.

As noted above, the greatest length allowed for an IPv4 Packet

including any optional headers and independent of this standard is

65,536-bytes. However, limiting the IP MTU size to 65,280-bytes helps

in buffer resource allocation at N_Ports and also allows for up to

256-bytes of overhead. Since the FC Network_Header requires 16-bytes

and the IEEE 802.2 LLC/SNAP header requires 8 bytes, it leaves 232

bytes for future use.

All implementations SHALL restrict the IP MTU size to 65,280 bytes

and the corresponding FC Sequence Payload size to 65536-bytes.

3.2.2 Maximally Minimum IPv4 Packet

In order for IP fragmentation and reassembly to work properly it is

necessary that every implementation of IP be capable of transporting

a maximally minimum size IP packet without fragmentation. A maximally

minimum size IP Packet is defined as an IP Packet with an 8-byte

payload (the smallest possible non-zero payload size for a fragment)

and a 60-byte header (the largest possible header consisting of a

20-byte fixed part and a maximum size option field of 40-bytes) [17].

All implementations SHALL support a FC Data Field of 92-bytes, which

is required to support 68-bytes of the maximally minimum sized IP

Packet, 16-bytes of the FC Network_Header, and 8-bytes of the

LLC/SNAP Header.

3.2.3 ARP MTU

The ARP packet has a fixed size of 28-bytes. All implementations

SHALL support a FC Data Field size of 52-bytes, which is required to

support 28-bytes of an ARP Packet, 16-bytes of the FC Network_Header,

and 8-bytes of the LLC/SNAP Header. Note that the minimum MTU

requirement for ARP is already covered by the minimum MTU requirement

for IP but it is mentioned here for completeness.

The InARP packet is identical in size to the ARP and the same MTU

requirements apply.

3.2.4 FC Data Field containing FARP Packet

The FARP Command is a FC Extended Link Service (ELS) command and maps

directly to the FC Data Field without the LLC/SNAP or the FC

Network_Header. The FARP Command has a fixed size of 76-bytes.

Because FARP operates purely in the FC space, it places no special

MTU requirements in this specification.

3.3 FC Port and Node Network Addresses

FC devices are identified by Nodes and their Ports. A Node is a

collection of one or more Ports identified by a unique nonvolatile

64-bit World Wide Node name (WW_NN). Each Port in a node, is

identified with a unique nonvolatile 64-bit World Wide Port name

(WW_PN), and a volatile Port Identifier (Port_ID).

Port_IDs are 24-bits long. A FC frame header carries a Source Port_ID

(S_ID) and a Destination Port_ID (D_ID). The Port_ID of a given port

is volatile. (The mechanism(s) by which a Port_ID may change in a FC

topology is outside the scope of this document. See Appendix D).

The FC Network_Header is normally optional in FC Standards, but

REQUIRED in this specification. A FC Network_Header carries source

and destination WW_PNs. A WW_PN consists of a 60-bit Network Address

and a upper 4-bit Network Address Authority (NAA) field as shown in

Fig. 3. The 4-bit NAA field is used to distinguish between the

various name registration authorities used to define the Network

Address [2].

In this specification, both the Source and Destination 4-bit NAA

identifiers SHALL be set to binary '0001' indicating that an IEEE

48-bit MAC address is contained in the lower 48 bits of the network

address fields. The high order 12 bits in the network address fields

SHALL be set to 0x0000. The NAA field value equal to binary '0001'

allows FC networks to be bridged with other FC networks or

traditional LANs.

+--------+---------------------------------------+

D_NAA Network_Dest_Address (High-order bits)

(4 bits) (28 bits)

+--------+---------------------------------------+

Network_Dest_Address (Low-order bits)

(32 bits)

+--------+---------------------------------------+

S_NAA Network_Source_Address(High-order bits)

(4 bits) (28 bits)

+--------+---------------------------------------+

Network_Source_Address (Low-order bit)

(32 bits)

+--------+---------------------------------------+

Fig. 3 Format of the Network_Header Field

3.4 FC Sequence Payload Format

FC Payload with IP:

An FC Sequence Payload carrying an IP and ARP packet SHALL use the

formats shown in Figs. 4 and 5 respectively. Both formats use the

8-byte LLC/SNAP header.

+-----------------+-----------+------------+-------------//----------+

LLC/SNAP Header IP Header Opt.IP Hdr. IP Data

(8 bytes) (20 bytes) (40 bytes (65280 -IP Header

Max) - Opt. IP Hdr.) bytes

+-----------------+-----------+------------+-------------//----------+

Fig. 4 Format of FC Sequence Payload carrying IP

FC Sequence Payload with ARP:

As noted earlier, FC frames belonging to the same Sequence may be

delivered out of order over a Fabric. If the Relative Offset method

is used to identify FC Sequence Payload fragments, then the IP Header

MUST appear in the frame that has a relative offset of 0.

+-----------------+-------------------+

LLC/SNAP Header ARP Packet

(8 bytes) (28 bytes)

+-----------------+-------------------+

Fig. 5 Format of FC Sequence Payload carrying ARP

FC Sequence Payload with FARP:

FARP Protocol commands are directly mapped to the Frame Sequence

Payload and are 76-bytes long. No LLC/SNAP Header or FC

Network_Header is used and therefore the FC Data Field size simply

consists of the FC Sequence Payload.

LLC:

A Logical Link Control (LLC) field along with a Sub Network Access

Protocol (SNAP) field is a method used to identify routed and bridged

non-OSI protocol PDUs and is defined by IEEE 802.2 and applied to IP

in [8]. In LLC Type 1 operation (i.e., unacknowledged connectionless

mode), the LLC header is 3-bytes long and consists of a 1-byte

Destination Service Access Point (DSAP)field, a 1-byte Source Service

Access Point (SSAP)field, and a 1-byte Control field as shown in Fig.

6.

+----------+----------+----------+

DSAP SSAP CTRL

(1 byte) (1 byte) (1 byte)

+----------+----------+----------+

Fig. 6 LLC Format

The LLC's DSAP and SSAP values of 0xAA indicate that an IEEE 802.2

SNAP header follows. The LLC's CTRL value equal to 0x03 specifies an

Unnumbered Information Command PDU. In this specification the LLC

Header value SHALL be set to 0xAA-AA-03. Other values of DSAP/SSAP

indicate support for other protocols and SHALL NOT be used in this

specification.

SNAP:

The SNAP Header is 5-bytes long and consists of a 3-byte

Organizationally Unique Identifier (OUI) field and a 2-byte Protocol

Identifier (PID) as shown in Fig. 7

+------+------+-------+------+------+

OUI PID

( 3 bytes) (2 bytes)

+------+------+-------+------+------+

Fig. 7 SNAP Format

SNAP was invented to "encapsulate" LAN frames within the payload.

The SNAP OUI value equal to 0x00-00-00 specifies that the PID is an

EtherType (i.e., routed non-OSI protocol).

The SNAP OUI value equal to 0x00-80-C2 indicates Bridged Protocols.

With the OUI value set to 0x00-00-00, the SNAP PID value equal to

0x08-00 indicates IP and a PID value equal to 0x08-06 indicates ARP

(or InARP).

The complete LLC/SNAP Header is shown in Fig. 8.

+-----------+----------+----------+-------+-------+-------+-------+------+

DSAP SSAP CTRL OUI PID

(1 byte) (1 byte) (1 byte) ( 3 bytes) (2 bytes

+-----------+----------+----------+-------+-------+-------+-------+------+

Fig. 8 LLC/SNAP Header

3.5 Bit and Byte Ordering

IP or ARP Packets are mapped to FC-4 Level using the big endian byte

ordering, which corresponds to the standard network byte order or

canonical form [20]. FC-4 Payload maps with no change in order to the

FC-2 Level.

FC-1 Level defines the method used to encode data prior to

transmission and subsequently decode the data upon reception. The

method encodes 8-bit bytes into 10-bit transmission characters to

improve the transmission characteristics of the serial data stream.

In Fibre Channel, data fields are aligned on word boundaries. See

Appendix E. A word in FC is defined as 4 bytes or 32 bits. The

resulting transmission word after the 8-bit to 10-bit encoding

consists of 40 bits.

Data words or Ordered Sets (special FC-2 Level control words) from

the FC-2 Level map to the FC-1 Level with no change in order and the

bytes in the word are transmitted in the Most Significant Byte first

to Least Significant Byte order. The transmission order of bits

within each byte is the Least Significant Bit to the Most Significant

Bit.

4. ARP

4.1 Address Resolution

Address Resolution in this specification is primarily concerned with

associating IP addresses with FC Port addresses. As described

earlier, FC device ports have two types of addresses:

- a non-volatile unique 64-bit address called World Wide Port_Name

(WW_PN)

- a volatile 24-bit address called a Port_ID

The Address Resolution mechanism therefore will need two levels of

mapping:

1. A mapping from the IP address to the WW_PN (i.e., IEEE

48-bit MAC address)

2. A mapping from the WW_PN to the Port_ID (see Appendix G for a

definition of Port_ID)

The address resolution problem is compounded by the fact that the

Port_ID is volatile and the second mapping MUST be valid before use.

Moreover, this validation process can be different depending on the

network topology used. Appendix D provides a discussion on validation

for the different FC topologies.

Architecturally, the first level of mapping and control operation is

handled by the Address Resolution Protocol (ARP), and the second

level by the FC Address Resolution Protocol (FARP). FARP is described

in Section 5.

Other optional mechanisms in FARP that directly map an IP address to

a Port_ID, or WW_NN to a Port_ID are described in Appendix A.

The Inverse Address Resolution Protocol (InARP) is yet another

optional mechanism that resolves WW_PN and Port_IDs to IP addresses.

InARP is described in Appendix B.

4.2 ARP Packet Format

The Address Resolution Protocol (ARP) given in [9] was designed to be

a general purpose protocol, and to work with many network

technologies, and with many upper layer protocols. Fig 9 shows the

ARP packet format based on [9], where the upper layer protocol uses a

4 octet protocol (IP) address and the network technology uses six-

octet hardware (MAC) address.

The ARP uses two packet types - Request and Reply - and each type of

packet is 28 -bytes long in this specification. The ARP Packet fields

are common to both ARP Requests and ARP Replys.

The LLC/SNAP encapsulated ARP Request Packet is mapped to a FC

Broadcast Sequence and the exact mechanism used to broadcast a FC

Sequence depends on the FC topology. This is discussed later in this

section. Compliant ARP Request Broadcasts SHALL include

Network_Headers.

The LLC/SNAP encapsulated ARP Reply Packet is mapped to a FC

Sequence. Compliant ARP Replys SHALL include Network_Headers.

Note that in all discussions to follow, the WW_PN and the 48-bit MAC

address conceptually mean the same thing.

The 'HW Type' field SHALL be set to 0x00-01.

Technically, the correct HW Type value should be set to 0x00-06

according to RFC1700 indicating IEEE 802 networks. However, as a

practical matter a HW Type value of 0x00-06 is known to cause

rejections from some Ethernet end stations when FC is bridged to

Ethernet. Translational bridges are normally eXPected to change this

field from Type 6 to 1 and vice versa under these configurations, but

many do not. It is because of this reason that the Type Code is set

to 1 rather than 6. However, both HW Type values of 0x00-01 and

0x00-06 SHALL be accepted.

The 'Protocol' field SHALL be set to 0x08-00 indicating IP protocol.

The 'HW Addr Length' field SHALL be set to 0x06 indicating 6-bytes of

HW address.

The 'Protocol Addr Length' field SHALL be set to 0x04 indicating 4-

bytes of IPv4 address.

The 'Operation' Code field SHALL be set as follows:

0x00-01 for ARP Request

0x00-02 for ARP Reply

The 'HW Addr of Sender' field SHALL be the 6-byte IEEE MAC address of

the sender. It is either the Requester (ARP Request) or the Responder

(ARP Reply) address.

The 'Protocol Addr of Sender' field SHALL be the 4-byte IP address of

the Requester (ARP Request) or that of the Responder (ARP Reply).

The 'HW Addr of Target' field SHALL be set to zero during an ARP

Request and to the 6-byte MAC address of the Requester (ARP Request)

in an ARP Reply.

The 'Protocol Addr of Target' field SHALL be set to the 4-byte IP

address of the Responder (ARP Reply) in a ARP Request, and to the

4-byte IP address of the Requester (ARP Request) in an ARP Reply.

+-------------------------+

HW Type 2 bytes

+-------------------------+

Protocol 2 bytes

+-------------------------+

HW Addr Length 1 byte

+-------------------------+

Protocol Addr Length 1 byte

+-------------------------+

Op Code 2 bytes

+-------------------------+

HW Addr of Sender 6 bytes

+-------------------------+

Protocol Addr of Sender 4 bytes

+-------------------------+

HW Addr of Target 6 bytes

+-------------------------+

Protocol Addr of Target 4 bytes

+-------------------------+

Total 28 bytes

Fig. 9 ARP Packet Format

4.3 ARP Layer Mapping and Operation

Whenever a FC port wishes to send IP data to another FC port, then

the following steps are taken:

1. The source port should first consult its local mapping tables to

determine the <destination IP address, destination WW_PN>.

2. If such a mapping is found, then the source sends the IP

data to the port whose WW_PN address was found in the table.

3. If such a mapping is not found, then the source sends an

ARP Request broadcast to its connected FC network in

anticipation of getting a reply from the correct destination

along with its WW_PN.

4. When an ARP Request Broadcast frame is received by a node with

the matching IP address, it generates an ARP Reply. Since the

ARP Reply must be addressed to a specific destination Port_ID,

the FC layer mapping between the WW_PN and Port_ID (of the ARP

Request orginator) MUST be valid before the reply is sent.

5. If no node has the matching IP address, the result is a silent

behavior.

4.4 ARP Broadcast in a Point-to-Point Topology

The ARP Request (Broadcast) and Reply mechanism described above still

apply, although there is only one node that receives the ARP Request.

4.5 ARP Broadcast in a Private Loop Topology

In a private loop, the ARP Request Broadcast frame is sent using the

broadcast method specified in the FC-AL [7]standard.

1. The source port first sends an Open Broadcast Replicate

primitive (OPN(fr))Signal forcing all the ports in the loop

(except itself), to replicate the frames that they receive

while examining the frame header's Destination_ID field.

2. The source port then removes this OPN(fr) signal when it

returns to it.

3. The loop is now ready to receive the ARP broadcast. The source

now sends the ARP Request as a single-frame Broadcast Sequence

in a Class 3 frame with the following FC Header D_ID field and

F_CTL bits setting:

Destination ID <Word 0, bit 0:23>: D_ID = 0xFF-FF-FF

Sequence Initiative <Word 2, bit23>: SI=0

Last Sequence <Word 2, bit 20>: LS=1

End Sequence <Word 2, bit 19>: ES=1.

4. A compliant ARP Broadcast Sequence frame SHALL include the

Network_Header with destination MAC address set to 0xFF-FF-FF-

FF-FF-FF and with NAA = b'0001'

5. The destination port recognizing its IP address in the ARP

Request packet SHALL respond with an ARP Reply.

4.6 ARP Broadcast in a Public Loop Topology

The following steps will be followed when a port is configured in a

public loop:

1. A public loop device attached to a fabric through a FL_Port

MUST NOT use the OPN(fr) signal primitive. Rather, it sends the

broadcast sequence to the FL_Port at AL_PA = 0x00.

2. A FC Fabric propagates the broadcast to all other ports

including the FL_Port which the broadcast arrived on. This

includes all F_Ports, and other FL_Ports.

3. On each FL_Port, the fabric propagates the broadcast by first

using the primitive signal OPNfr, in order to prepare the loop

to receive the broadcast sequence.

4. A Broadcast Sequence is now sent on all ports (all FL_ports,

F_Ports) in Class 3 frame with:

Destination ID <Word 0, bit 23:0>: D_ID = 0xFF-FF-FF

Sequence Initiative <Word 2, bit23>: SI=0

Last Sequence <Word 2, bit 20>: LS=1

End Sequence <Word 2, bit 19>: ES=1.

5. A compliant ARP Broadcast Sequence frame SHALL include the

Network_Header with destination MAC address set to 0xFF-FF-FF-

FF-FF-FF and with NAA = b'0001'

6. The destination port recognizing its IP address in the ARP

Request packet SHALL respond with an ARP Reply.

4.7 ARP Operation in a Fabric Topology

1. Nodes directly attached to fabric do not require the OPN(fr)

primitive signal.

2. A Broadcast Sequence is now sent on all ports (all FL_ports,

F_Ports) in Class 3 frame with:

Destination ID <Word 0, bit 23:0>: D_ID = 0xFF-FF-FF

Sequence Initiative <Word 2, bit23>: SI=0

Last Sequence <Word 2, bit 20>: LS=1

End Sequence <Word 2, bit 19>: ES=1.

3. A compliant ARP Broadcast Sequence frame SHALL include the

Network_Header with destination MAC address set to

0xFF-FF-FF-FF-FF-FF and with NAA = b'0001'

4. The destination port recognizing its IP address in

the ARP packet SHALL respond with an ARP Reply.

5. FARP

5.1 Scope

FC Layer Mapping between the WW_PN and the Port_ID is independent of

the ARP mechanism and is more closely associated with the details of

the FC protocols. Name Server and FC Address Resolution Protocol

(FARP) are two formal mechanisms that can be used to create and

maintain WW_PN to Port_ID tables.

FARP is a method using Extended Link Service (ELS) commands that

resolves <WW_PN, Port_ID> mappings. The WW_PN to Port_ID address

resolution using FARP is especially useful in instances where the

Login table entries at a node expire and a Name Server is not

available. It is outside the scope of this document to describe Name

Server. (See [14].)

Additional address matching mechanisms that resolve <WW_NN, Port_ID>

and <IP addr., Port_ID> mapping have been added to FARP. These

additional mechanisms are optional and described in Appendix A.

Direct IP address to Port_ID mapping is useful in applications where

there is no visibility of the MAC address.

Other less formal FC Layer Mapping mechanisms are described in

Appendix C.

Since Port_IDs are volatile, all mapped Port_IDs at all times MUST

be valid before use. There are many events that can invalidate this

mapping. Appendix D discusses conditions when such a validation is

required.

5.2 FARP Overview

The FARP protocol uses two ELS commands - FARP-REQ and FARP-REPLY.

Note: In the following discussion 'Requester' means the node

issuing the FARP-REQ ELS message; 'Responder' means the

node replying to the request by sending the FARP-REPLY

command.

The FARP-REQ ELS Broadcast Request command is used to retrieve a

specific node's current Port_ID given its unique WW_PN. This Port_ID

is sent in a FARP-REPLY unicast command.

The FARP-REQ may indicate that the Responder:

- Perform only a Login with it (Requester) or,

- Send only a FARP-REPLY or,

- Perform a Login and send a FARP-REPLY.

No sequence initiative is transferred with the FARP-REQ and therefore

no Reply (ACCEPT or REJECT) follows this command.

Since a Sequence Initiative is transferred with the FARP-REPLY,

either a ACCEPT or REJECT follows this command as a response.

Reception of a FARP-REQ requires a higher level entity at the

responding node to send a FARP-REPLY or perform a Port Login.

You do not have to be logged in to issue a FARP Request. Also, you do

not have to be logged in to the FARP Requester to issue a FARP-REPLY.

The FARP Protocol Steps:

FARP-REQ (ELS broadcast) Request Sequence

(No Reply Sequence)

FARP-REPLY (ELS command) Sequence

Accept/Reject Reply Sequence

The FARP Protocol Format [2] and Size:

FT_1, 76-bytes fixed size

The FARP Protocol Addressing:

- In a FARP-REQ, the S_ID in the FC Header designates the

Requester's Port ID. The D_ID in the FC Header is the broadcast

identifier 0xFF-FF-FF.

- In a FARP-REPLY, the S_ID in the FC Header designates the

Responder's Port_ID. The D_ID in the FC Header is the Requester's

Port_ID.

5.3 FARP Command Format

FARP-REQ and FARP-REPLY commands have identical formats (76-bytes

fixed size) and fields but use different command codes. See tables

below.

+---------------------------------------------------------------------+

FARP-REQ Command

+-------------------------------------+---------+---------------------+

Field Size Remarks

(Bytes)

+-------------------------------------+---------+---------------------+

0x54-00-00-00 4 Request Command Code

+-------------------------------------+---------+---------------------+

Match Address Code Points 1 Indicates Address

Matching Mechanism

+-------------------------------------+---------+---------------------+

Port_ID of Requester 3 Supplied by

Requester =

S_ID in FC Header

+-------------------------------------+---------+---------------------+

Responder Flags 1 Response Action to

be taken

+-------------------------------------+---------+---------------------+

Port_ID of Responder 3 Set to 0x00-00-00

+-------------------------------------+---------+---------------------+

WW_PN of Requester 8 Supplied by Requester

+-------------------------------------+---------+---------------------+

+ WW_NN of Requester 8 OPTIONAL;

See Appendix A

+-------------------------------------+---------+---------------------+

WW_PN of Responder 8 Supplied by Requester

+-------------------------------------+---------+---------------------+

WW_NN of Responder 8 OPTIONAL; see App. A

+-------------------------------------+---------+---------------------+

IP Address of Requester 16 OPTIONAL; see App. A

+-------------------------------------+---------+---------------------+

IP Address of Responder 16 OPTIONAL; see App. A

+-------------------------------------+---------+---------------------+

+---------------------------------------------------------------------+

FARP-REPLY Command

+-------------------------------------+---------+---------------------+

Field Size Remarks

(Bytes)

+-------------------------------------+---------+---------------------+

0x55-00-00-00 4 Reply Command Code

+-------------------------------------+---------+---------------------+

Match Address Code Points 1 Not Used and

Unchanged from the

FARP-REQ

+-------------------------------------+---------+---------------------+

Port_ID of Requester 3 Extracted from

FARP-REQ

+-------------------------------------+---------+---------------------+

Responder Flags 1 Not Used and

Unchanged from the

FARP-REQ

+-------------------------------------+---------+---------------------+

Port_ID of Responder 3 Supplied by

Responder =

S_ID in FC Header

+-------------------------------------+---------+---------------------+

WW_PN of Requester 8 Supplied by Requester

+-------------------------------------+---------+---------------------+

WW_NN of Requester 8 OPTIONAL; see App. A

+-------------------------------------+---------+---------------------+

WW_PN of Responder 8 Supplied by Requester

+-------------------------------------+---------+---------------------+

WW_NN of Responder 8 OPTIONAL; see App. A

+-------------------------------------+---------+---------------------+

IP Add. of Requester 16 OPTIONAL; see App. A

+-------------------------------------+---------+---------------------+

IP Address of Responder 16 OPTIONAL; see App. A

+-------------------------------------+---------+---------------------+

Following is a description of the address fields in the FARP

Commands.

Port_ID of Requester:

It is the 24-bit Port_ID used in the S_ID field of the FC Header of a

FARP-REQ. It is supplied by the Requester in a FARP-REQ and retained

in a FARP-REPLY.

Port_ID of Responder:

It is the 24-bit Port_ID used in the S_ID field of the FC Header of a

FARP-REPLY. It SHALL be set to 0x00-00-00 in a FARP-REQ. It is

supplied by the Responder in a FARP-REPLY.

WW_PN:

This address field is used with the b'001', b'011', b'101, b'111',

Match Address Code Points. See Match Address Code Point Table below.

The Requester supplies the unique 8-byte WW_PN of the Requester and

the Responder. It is retained in a FARP-REPLY.

WW_NN:

The WW_NN address field is used with Match Address Code Points

b'010', b'011', b'110', and b'111', which are all optional. Its usage

is fully described in Appendix A. When the WW_NN field is not used it

SHALL be either set to '0' or a valid non-zero address.

IPv4:

The IPv4 address field is used with the Match Address Code Points

b'100', b'101', b'110', and b'111', which are all optional. Its usage

is fully described in Appendix A. When the IP Address field is not

used it SHALL be either set to '0' or a valid IP address. A valid IP

address consists of the 32-bit IPv4 Address with the upper 96 bits

set to '0'.

5.4 Match Address Code Points

For each receipt of the FARP-REQ Broadcast ELS, the recipients match

one or more addresses based on the encoded bits of the "FARP Match

Address Code Points" field shown in the table below. FARP operation

with the Match Address Code Point equal to b'001' is described in

this section. Other code points are OPTIONAL and are discussed in

Appendix A. The upper 5 bits of the Match Address Code Point byte are

unused and their use is not currently defined.

+------------------------------------------------------------------+

Match Address Code Points

+------------------------------------------------------------------+

LSBits Bit name Action

+-----------+--------------------+---------------------------------+

000 Reserved

+-----------+--------------------+---------------------------------+

001 MATCH_WW_PN If 'WW_PN of Responder' =

Node's WW_PN then respond

+-----------+--------------------+---------------------------------+

010 MATCH_WW_NN OPTIONAL; see Appendix A

+-----------+--------------------+---------------------------------+

011 MATCH_WW_PN_NN OPTIONAL; see Appendix A

+-----------+--------------------+---------------------------------+

100 MATCH_IPv4 OPTIONAL; see Appendix A

+-----------+--------------------+---------------------------------+

101 MATCH_WW_PN_IPv4 OPTIONAL; see Appendix A

+-----------+--------------------+---------------------------------+

110 MATCH_WW_NN_IPv4 OPTIONAL; see Appendix A

+-----------+--------------------+---------------------------------+

111 MATCH_WW_PN_NN_IPv4 OPTIONAL; see Appendix A

+-----------+--------------------+---------------------------------+

When a node receives a FARP-REQ with Code Point b'001', it checks its

WW_PN against the one set in 'WW_PN of Responder' field of the FARP-

REQ command. If there is a match, then the node issues a response

according to the action indicated by the FARP Responder Flag. See

table below.

WW_NN and IPv4 address fields are not used with the b'001' Code Point

operation. They SHALL be set to '0' or a valid address either by the

Requester or the Requester and the Responder.

Note that there can be utmost one FARP-REPLY per FARP-REQ.

5.5 Responder Flags

The Responder Flags define what Responder action to take if the

result of the Match Address Code Points is successful. 'Responder

Flags' is an 8-bit field (bits 0-7) and is defined in the table

below. This field is used only in a FARP-REQ. This field is retained

unchanged in a FARP-REPLY. If no bits are set, the Responder will

take no action.

+----------+-------------------------------------------------------+

FARP Responder Flag

+----------+----------------+--------------------------------------+

Bit Bit Name Action

Position

+----------+----------------+--------------------------------------+

0 INIT_P_LOGI Initiate a P_LOGI to the Requester

+----------+----------------+--------------------------------------+

1 INIT_REPLY Send FARP_REPLY to Requester

+----------+----------------+--------------------------------------+

2 to 7 Reserved

+----------+----------------+--------------------------------------+

If INIT_P_LOGI bit is set then, a Login is performed with the port

identified by "Port_ID of Requester" field.

If INIT_REPLY is set then, a FARP-REPLY is sent to the Port

Identified by "Port_ID of Requester" field.

If both bits are set at the same time, then both Actions are

performed.

All other bit patterns are undefined at this time and are reserved

for possible future use.

5.6 FARP Support Requirements

Responder action - FARP-REPLY and/or Port Login - for a successful

MATCH_WW_PN is always REQUIRED. If there is no address match then a

silent behavior is specified.

Support for all other Match Address Code Points is OPTIONAL and a

silent behavior from the Responder is valid when it is not supported.

Recipients of the FARP-REQ ELS SHALL NOT issue a Service Reject

(LS_RJT) if FARP OPTIONAL mechanisms are not supported.

In all cases, if there are no matches, then a silent behavior is

specified.

If an implementation issues a FARP-REQ with a Match Address Code

Point that is OPTIONAL, and fails to receive a response, and the

implementation has not oBTained the Port_ID of the Responder's port

by other means (e.g., prior FARP-REQ with other Code Points), then

the implementation SHALL reattempt the FARP-REQ with the MATCH_WW_PN

Code Point.

Getting multiple FARP Replies corresponding to a single FARP-REQ

should normally never occur. It is beyond the scope of this document

to specify conditions under which this error may occur or what the

corrective action ought to be.

6. Exchange Management

6.1 Exchange Origination

FC Exchanges shall be established to transfer data between ports.

Frames on IP exchanges shall not transfer Sequence Initiative. See

Appendix E for a discussion on FC Exchanges.

6.2 Exchange Termination

With the exception of the recommendations in Appendix F, Section F.1,

"Reliability in Class 3", the mechanism for aging or expiring

exchanges based on activity, timeout, or other method is outside the

scope of this document.

Exchanges may be terminated by either port. The Exchange Originator

may terminate Exchanges by setting the LS bit, following normal FC

standard FC-PH [2] rules. This specification prohibits the use of the

NOP ELS with LS set for Exchange termination.

Exchanges may be torn down by the Exchange Originator or Exchange

Responder by using the ABTS_LS protocol. The use of ABTS_LS for

terminating aged Exchanges or error recovery is outside the scope of

this document.

The termination of IP Exchanges by Logout is discouraged, since this

may terminate active Exchanges on other FC-4s.

7. Summary of Supported Features

Note: 'Settable' means support is as specified in the relevant

standard; all other key words are as defined earlier in this

document.

7.1 FC-4 Header

+--------------------------------------------------------------------+

Feature Support Notes

+--------------------------------------------------------------------+

Type Code ( = 5) ISO8802-2 LLC/SNAP REQUIRED 2

Network_Headers REQUIRED 3

Other Optional Headers MUST NOT

+--------------------------------------------------------------------+

Notes:

1. This table applies only to FC-4 related data, such as IP and

ARP packets. This table does not apply to link services and

other non-FC-4 sequences (PLOGI, for example) that must occur

for normal operation.

2. The TYPE field in the FC Header (Word 2 bits 31-24) MUST

indicate ISO 8802-2 LLC/SNAP Encapsulation (Type 5). This

revision of the document focuses solely on the issues related

to running IP and ARP over FC. All other issues are outside

the scope of this document, including full support for IEEE

802.2 LLC.

3. DF_CTL field (Word 3, bits 23-16 of FC-Header) MUST indicate

the presence of a Network_Header (0010 0000) on the First

logical Frame of FC-4 Sequences. It should not indicate the

presence of a Network_Header on any subsequent frames of the

Sequence.

7.2 R_CTL

R_CTL in FC-Header: Word 0, bits 31-24

+--------------------------------------------------------------------+

Feature Support Notes

+--------------------------------------------------------------------+

Information Category (R_CTL Routing):

FC-4 Device Data REQUIRED 1

Extended Link Data REQUIRED

FC-4 Link Data MUST NOT

Video Data MUST NOT

Basic Link Data REQUIRED

Link Control REQUIRED

R_CTL information :

Uncategorized MUST NOT

Solicited Data MUST NOT

Unsolicited Control REQUIRED

Solicited Control REQUIRED

Unsolicited Data REQUIRED 1

Data Descriptor MUST NOT

Unsolicited Command MUST NOT

Command Status MUST NOT

+--------------------------------------------------------------------+

Notes:

1. This is REQUIRED for FC-4 (IP and ARP) packets

- Routing bits of R_CTL field MUST indicate Device Data

frames (0000)

- Information Category of R_CTL field MUST indicate

Unsolicited Data (0100)

7.3 F_CTL

F_CTL in FC-Header: Word 2, bits 23-0

+--------------------------------------------------------------------+

Feature Support Notes

+--------------------------------------------------------------------+

Exchange Context Settable

Sequence Context Settable

First / Last / End Sequence (FS/LS/ES) Settable

Chained Sequence MUST NOT

Sequence Initiative (SI) Settable 1

X_ID Reassigned / Invalidate MUST NOT

Unidirectional Transmit Settable

Continue Sequence Condition REQUIRED 2

Abort Seq. Condition -continue and single Seq. REQUIRED 3

Relative Offset - Unsolicited Data Settable 4

Fill Bytes Settable

+--------------------------------------------------------------------+

Notes

1. For FC-4 frames, each N_Port shall have a dedicated OX_ID for

sending data to each N_Port in the network and a dedicated

RX_ID for receiving data from each N_Port as well. Exchanges

are used in a unidirectional mode, thus setting Sequence

Initiative is not valid for FC-4 frames. Sequence Initiative is

valid when using Extended Link Services.

2. This field is required to be 00, no information.

3. Sequence error policy is requested by an exchange originator in

the F_CTL Abort Sequence Condition bits in the first data frame

of the exchange. For Classes 1 and 2, ACK frame is required to

be "continuous sequence".

4. Relative offset prohibited on all other types (Information

Category) of frames.

7.4 Sequences

+---------------------------------------------------------------------+

Feature Support Notes

+---------------------------------------------------------------------+

Class 2 open Sequences / Exchange 1 1

Length of Seq. not limited by end-to-end credit REQUIRED 2

IP and ARP Packet and FC Data Field sizes REQUIRED 3

Capability to receive Sequence of maximum size OPTIONAL 4

Sequence Streaming MUST NOT 5

Stop Sequence Protocol MUST NOT

ACK_0 support OPTIONAL 6

ACK_1 support REQUIRED 6

ACK_N support MUST NOT

Class of Service for transmitted Sequences Class 7

1, 2, or 3

Continuously Increasing Sequence Count OPTIONAL 8, 9

+---------------------------------------------------------------------+

Notes:

1. Only one active sequence per exchange is optional.

2. A Sequence Initiator shall be capable of transmitting Sequences

containing more frames than the available credit indicated by a

Sequence recipient at Login. FC-PH [2] end-to-end flow control

rules will be followed when transmitting such Sequences.

3. a) IP MTU size is 65280-bytes and resulting FC Sequence

Payload size is 65536-bytes.

b) Maximally Minimum IP Packet size is 68-bytes and resulting

FC Data Field size is 92-bytes.

c) ARP (and InARP) Packet size is 28-bytes and resulting FC

Data Field size is 52-bytes.

4. Some OS environments may not handle the max Sequence Payload

size of 65536. It is up to the administrator to configure the

Max size for all systems.

5. All class 3 sequences are assumed to be non-streamed.

6. Only applies for Class 1 and 2. Use of ACK_1 is default, ACK_0

used if indicated by Sequence recipient at Login.

7. The administrator configured class of service is used, except

where otherwise specified (e.g. Broadcasts are always sent in

Class 3).

8. Review Appendix F, "Reliability in Class 3".

9. The first frame of the first sequence of a new Exchange must

have SEQ_CNT = 0 [2].

7.5 Exchanges

+--------------------------------------------------------------------+

Feature Support Notes

+--------------------------------------------------------------------+

X_ID interlock support OPTIONAL 1

OX_ID=FFFF MUST NOT

RX_ID=FFFF OPTIONAL 2

Action if no exchange resources available P_RJT 3

Long Lived Exchanges OPTIONAL 4

Reallocation of Idle Exchanges OPTIONAL

+--------------------------------------------------------------------+

Notes:

1. Only applies to Classes 1 and 2, supported by the Exchange

Originator. A Port SHALL be capable of interoperating with

another Port that requires X_ID interlock. The Exchange

Originator facility within the Port shall use the X_ID

Interlock protocol in such cases.

2. An Exchange Responder is not required to assign RX_IDs. If a

RX_ID of FFFF is assigned, it is identifying Exchanges based on

S_ID / D_ID / OX_ID only.

3. In Classes 1 and 2, a Port shall reject a frame that would

create a new Exchange with a P_RJT containing reason code

"Unable to establish Exchange". In Class 3, the frame would be

dropped.

4. When an Exchange is created between 2 Ports for IP/ARP data, it

remains active while the ports are logged in with each other.

An Exchange SHALL NOT transfer Sequence Initiative (SI).

Broadcasts and ELS commands may use short lived Exchanges.

7.6 ARP and InARP

+--------------------------------------------------------------------+

Feature Support Notes

+--------------------------------------------------------------------+

ARP Server Support MUST NOT 1

Response to ARP requests REQUIRED 2

Class of Service for ARP requests Class 3 3

Class of Service for ARP replies Class 4

1, 2, or 3

Response to InARP requests OPTIONAL

Class of Service for InARP requests/replies Class

1, 2 or 3 5

+--------------------------------------------------------------------+

Notes:

1. Well-known Address FFFFFC is not used for ARP requests. Frames

from Well-known address FFFFFC are not considered to be ARP

frames. Broadcast support is REQUIRED for ARP.

2. The IP Address is mapped to a specific MAC address with ARP.

3. An ARP request is a Broadcast Sequence, therefore Class 3

is always used.

4. An ARP reply is a normal Sequence, thus the administrator

configured class of service is used.

5. An InARP Request or Reply is a normal Sequence, thus an

administrator configured class of service is used.

7.7 Extended Link Services (ELS)

+--------------------------------------------------------------------+

Feature Support Notes

+--------------------------------------------------------------------+

Class of service for ELS commands / responses Class

1,2 or 3 1

Explicit N-Port Login REQUIRED

Explicit F-Port Login REQUIRED

FLOGI ELS command REQUIRED

PLOGI ELS command REQUIRED

ADISC ELS command REQUIRED

PDISC ELS command OPTIONAL 2

FAN ELS command REQUIRED 5

LOGO ELS command REQUIRED

FARP-REQ/FARP-REPLY ELS commands REQUIRED 3

Other ELS command support OPTIONAL 4

+-----------------------------------------------+------------+-------+

Notes:

1. The administrator configured class of service is used.

2. PDISC shall not be used as a Requester; ADISC shall be used

instead. As a Responder, an implementation may need to respond

to both ADISC and PDISC for compatibility with other

specifications.

3. Responder Action - FARP-REPLY and/or Port Login - for a

successful MATCH_WW_PN is always REQUIRED.

Support for all other match Address Codes Points is a silent

behavior from the Responder is valid when it is not supported.

Recipients of the FARP-REQ ELS shall not issue a Service Reject

(LS_RJT) if FARP is not supported.

4. If other ELS commands are received an LS_RJT may be sent. NOP

is not required by this specification, and shall not be used as

a mechanism to terminate exchanges.

5. Required for FL_Ports

7.8 Login Parameters

Unless explicitly noted here, a compliant implementation shall use

the login parameters as described in [4].

7.8.1 Common Service Parameters - FLOGI

- FC-PH Version, lowest version may be 0x09 to indicate

'minimum 4.3'.

- Can't use BB_Credit=0 for N_Port on a switched Fabric

(F_Port).

7.8.2 Common Service Parameters - PLOGI

- FC-PH Version, lowest version may be 0x09 to indicate

'minimum 4.3'.

- Can't use BB_Credit=0 for N_Port in a Point-to-Point

configuration

- Random Relative Offset is optional.

- Note that the 'Receive Data Field Size' fields specified in

the PLOGI represent both optional headers and payload.

- The MAC Address can therefore be extracted from the 6 lower

bytes of the WW_PN field (when the IEEE 48-bit Identifier

format is chosen as the NAA) during PLOGI or ACC payload

exchanged during Fibre Channel Login [2].

- The MAC Address can also be extracted from the WW_PN field in

the Network_Header during ADISC (and ADISC ACC), or PDISC

(and PDISC ACC).

7.8.3 Class Service Parameters - PLOGI

- Discard error policy only.

8. Security Considerations

8.1 IP and ARP Related

IP and ARP do not introduce any new security concerns beyond what

already exists within the Fibre Channel Protocols and Technology.

Therefore IP and ARP related Security does not require special

consideration in this document.

8.2 FC Related

FC Standards [11] specify a Security Key Server (independent of IP

and ARP) as an optional service. However, there are no known

implementations of this server yet. Also, the previously defined [2]

use of a Security Header has been discontinued [11].

9. Acknowledgement

This specification is based on FCA IP Profile, Version 3.3. The FCA

IP Profile was a joint work of the Fibre Channel Association (FCA)

vendor community. The following organizations or individuals have

contributed to the creation of the FCA IP Profile: Adaptec, Ancor,

Brocade, Clariion, Crossroads, emf Associates, eMulex, Finisar,

Gadzoox, Hewlett Packard, Interphase, Jaycor, McData, Migration

Associates, Orca Systems, Prisa, Q-Logic, Symbios, Systran,

Tektronix, Univ. of Minnesota, Univ. of New Hamshire. Jon Infante

from Emulex deserves special mention for his contributions to the

FARP Protocol. The authors extend their thanks to all who provided

comments and especially to Lansing Sloan from LLNL for his detailed

comments.

10. References

[1] FCA IP Profile, Revision 3.3, May 15, 1997

[2] Fibre Channel Physical and Signaling Interface (FC-PH) , ANSI

X3.230-1994

[3] Fibre Channel Link Encapsulation (FC-LE), Revision 1.1, June 26,

1996

[4] Fibre Channel Fabric Loop Attachment (FC-FLA), Rev. 2.7, August

12, 1997

[5] Fibre Channel Private Loop SCSI Direct Attach (FC-PLDA),

Rev. 2.1, September 22, 1997

[6] Fibre Channel Physical and Signaling Interface-2 (FC-PH-2),

Rev. 7.4, ANSI X3.297-1996

[7] Fibre Channel Arbitrated Loop (FC-AL), ANSI X3.272-1996

[8] Postel, J. and J. Reynolds, "A standard for the Transmission of

IP Datagrams over IEEE 802 Networks", STD 43, RFC1042, February

1988.

[9] Plummer, D. "An Ethernet Address Resolution Protocol -or-

Converting Network Addresses to 48-bit Ethernet Address for

Transmission on Ethernet Hardware", STD 37, RFC826, November

1982.

[10] FCSI IP Profile, FCSI-202, Revision 2.1, September 8, 1995

[11] Fibre Channel Physical and Signaling Interface -3 (FC-PH-3),

Rev. 9.3, ANSI X3.303-199x

[12] Fibre Channel-The Basics, "Gary R. Stephens and Jan V. Dedek",

Ancot Corporation

[13] Fibre Channel -Gigabit Communications and I/O for Computers

Networks "Alan Benner", McGraw-Hill, 1996, ISBN 0-07-005669-2

[14] Fibre Channel Generic Services -2 (FC-GS-2), Rev. 5.2

X3.288-199x

[15] Bradley, T. and C. Brown, "Inverse Address Resolution Protocol",

RFC1293, January 1992.

[16] Bradley, T., Brown, C. and A. Malis, "Inverse Address Resolution

Protocol", RFC2390, August 1992.

[17] Postel, J., "Internet Protocol", STD 5, RFC791, September 1981.

[18] The Fibre Channel Consultant: A Comprehensive Introduction,

"Robert W. Kembel", Northwest Learning Associates, 1998

[19] Bradner, S., "Key Words for use in RFCs to Indicate Requirement

Levels", BCP 14, RFC2119, March 1997.

[20] Narten, T. and C. Burton, "A Caution on The Canonical Ordering

of Link-Layer Addresses", RFC2469, December 1998.

11. Authors' Addresses

Murali Rajagopal

Gadzoox Networks, Inc.

711 Kimberly Avenue, Suite 100

Placentia, CA 92870

Phone: +1 714 577 6805

Fax: +1 714 524 8508

EMail: murali@gadzoox.com

Raj Bhagwat

Gadzoox Networks, Inc.

711 Kimberly Avenue, Suite 100

Placentia, CA 92870

Phone: +1 714 577 6806

Fax: +1 714 524 8508

EMail: raj@gadzoox.com

Wayne Rickard

Gadzoox Networks, Inc.

711 Kimberly Avenue, Suite 100

Placentia, CA 92870

Phone: +1 714 577 6803

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EMail: wayne@gadzoox.com

Appendix A: Additional Matching Mechanisms in FARP

Section 5 described the FC Layer mapping between the WW_PN and the

Port_ID using the FARP Protocol. This appendix describes other

optional criteria for address matching and includes:

- WW_NN

- WW_PN & WW_NN at the same time

- IPv4

- IPv4 & WW_PN at the same time

- IPv4 & WW_NN at the same time

- IPv4 & WW_PN & WW_NN at the same time

Depending on the Match Address Code Points, the FARP protocol

fundamentally resolves three main types of addresses to Port_IDs and

is described in table below.

- For Match Address Code Point b'001': WW_PN Names fields are

used to resolve the WW_PN names to Port_IDs. WW_NN and IP

address fields are not used with these Code Points and SHALL be

set to either '0' or valid addresses by Requester or Requester

and Responder.

- For Match Address Code Point b'010': WW_NN Names fields are

used to resolve the WW_NN names to Port_IDs. WW_PN and IP

address fields are not used with these Code Points and SHALL be

set to either '0' or valid addresses by Requester or Requester

and Responder.

- For Match Address Code Point b'100': IPv4 fields are used to

resolve the IPv4 addresses to Port_IDs. WW_PN and WW_NN fields

are not used with these Code Points and SHALL be set to either '

0' or valid addresses by Requester or Requester and Responder.

- For all other Match Address Code Points b'011', b'101',b'110',

b'111', depending on set bits one or more addresses are jointly

resolved to a Port_ID. See table below. If fields are not used,

then they are set either to '0' or valid addresses.

The Responder Flags remain the same as before. Note that there can be

utmost one FARP-REPLY per FARP-REQ.

Tables showing FARP-REQ and FARP-REPLY and address fields setting are

given below:

+--------------------------------------------------------------------+

Match Address Code Points

+--------------------------------------------------------------------+

LSBits Bit name Action

+-------+--------------------+---------------------------------------+

000 Reserved

+-------+--------------------+---------------------------------------+

001 MATCH_WW_PN If 'WW_PN of Responder' =

Node's WW_PN then respond

+-------+--------------------+---------------------------------------+

010 MATCH_WW_NN If 'WW_NN of Responder' =

Node's WW_NN then respond

+-------+--------------------+---------------------------------------+

011 MATCH_WW_PN_NN If both 'WW_PN of Responder' &

'WW_NN of Responder' =

Node's WW_PN & WW_NN then respond

+-------+--------------------+---------------------------------------+

100 MATCH_IPv4 If 'IPv4 Address of Responder' =

Node's IPv4 Address then respond

+-------+--------------------+---------------------------------------+

101 MATCH_WW_PN_IPv4 If 'WW_PN & IPv4 of Responder' =

Node's WW_PN and IPv4 then respond

+-------+--------------------+---------------------------------------+

110 MATCH_WW_NN_IPv4 If both 'WW_NN of Responder' &

'IPv4 Address of Responder' =

Node's WW_NN & IPv4 then respond

+-------+--------------------+---------------------------------------+

111 MATCH_WW_PN_NN_IPv4 If 'WW_PN of Responder' &

'WW_NN of Responder' &

'IPv4 Address of Responder' =

Nodes' WW_PN & WW_NN & IPv4

then respond

+-------+--------------------+---------------------------------------+

+---------------------------------------------------------------------+

FARP-REQ Command

+-------------------------------+---------+---------------------------+

Field Size Remarks

(Bytes)

+-------------------------------+---------+---------------------------+

0x54-00-00-00 4 Request Command Code

+-------------------------------+---------+---------------------------+

Match Address Code Points 1 Indicates Address

Matching Mechanism

+-------------------------------+---------+---------------------------+

Port_ID of Requester 3 Supplied by Requester

+-------------------------------+---------+---------------------------+

Responder Flags 1 Response Action to be taken

+-------------------------------+---------+---------------------------+

Port_ID of Responder 3 Set to 0x00-00-00

+-------------------------------+---------+---------------------------+

WW_PN of Requester 8 Supplied by Requester

+-------------------------------+---------+---------------------------+

WW_NN of Requester 8 OPTIONAL;

Supplied by Requester

+-------------------------------+---------+---------------------------+

WW_PN of Responder 8 Supplied by Requester

+-------------------------------+---------+---------------------------+

WW_NN of Responder 8 OPTIONAL ;Supplied by

Requester or Responder

+-------------------------------+---------+---------------------------+

IP Add. of Requester 16 OPTIONAL; Supplied by

Requester

IPv4 Add.=low 32 bits

+-------------------------------+---------+---------------------------+

IP Address of Responder 16 OPTIONAL; Supplied by

Requester or Responder

IPv4 Add.=low 32 bits

+-------------------------------+---------+---------------------------+

+---------------------------------------------------------------------+

FARP-REPLY Command

+-------------------------------+---------+---------------------------+

Field Size Remarks

(Bytes)

+-------------------------------+---------+---------------------------+

0x55-00-00-00 4 Reply Command Code

+-------------------------------+---------+---------------------------+

Match Address Code Points 1 Not Used and unchanged

from the FARP-REQ

+-------------------------------+---------+---------------------------+

Port_ID of Requester 3 Supplied by Requester

+-------------------------------+---------+---------------------------+

Responder Flags 1 Not Used and unchanged

from the FARP-REQ

+-------------------------------+---------+---------------------------+

Port_ID of Responder 3 Supplied by Responder

+-------------------------------+---------+---------------------------+

WW_PN of Requester 8 Supplied by Requester

+-------------------------------+---------+---------------------------+

WW_NN of Requester 8 OPTIONAL; Supplied by

Requester

+-------------------------------+---------+---------------------------+

WW_PN of Responder 8 Supplied by Requester

+-------------------------------+---------+---------------------------+

WW_NN of Responder 8 OPTIONAL; Supplied by

Requester or Responder

+-------------------------------+---------+---------------------------+

IP Add. of Requester 16 OPTIONAL; Supplied by

Requester

IPv4 Add.=low 32 bits

+-------------------------------+---------+---------------------------+

IP Address of Responder 16 OPTIONAL; Supplied by

Requester or Responder

IPv4 Add.=low 32 bits

+-------------------------------+---------+---------------------------+

Appendix B: InARP

B.1 General Discussion

Inverse ARP (InARP) is a mechanism described in RFC1293/2390 [15,

16], which is useful when a node desires to know the protocol address

of a target node whose hardware address is known. Situations where

this could occur are described in [15, 16]. The motivation for using

InARP in FC is to allow a node to learn the IP address of another

node with which it has performed a Port Login (PLOGI). PLOGI is a

normal FC process that happens between nodes, independent of this

standard. PLOGI makes it possible for a node to discover the WW_PN

and the Port_ID of the other node but not its IP address. A node in

this way may potentially obtain the IP address of all nodes with

which it can PLOGI.

Note that the use of the InARP mechanism can result in resolving all

WW_PN to IP addresses and ARP may no longer be required. This can be

beneficially applied in cases where a particular FC topology makes it

inefficient to send out an ARP broadcast.

B.2 InARP Protocol Operation

InARP uses the same ARP Packet format but with different 'Op Codes',

one for InARP Request and another for InARP Reply.

The InARP protocol operation is very simple. The requesting node

fills the hardware address (WW_PN) of the target device and sets the

protocol address to 0x00-00-00-00. Because, the request is sent to a

node whose WW_PN and Port_ID are known, there is no need for a

broadcast. The target node fills in its Protocol address (IP address

in this case) and sends an InARP Reply back to the sender. A node

may collect, all such WW_PN and IP addresses pairs in a similar way.

B.3 InARP Packet Format

Since the InARP protocol uses the same packet format as the ARP

protocol, much of the discussion on ARP formats given in Section 4

applies here.

The InARP is 28-bytes long in this application and uses two packet

types: Request and Reply. Like ARP, the InARP Packet fields are

common to both InARP Requests and InARP Replies.

InARP Request and Reply Packets are encapsulated in a single frame FC

Sequence much like ARP. Compliant InARP Request and Reply FC

Sequences SHALL include Network_Headers.

The 'HW Type' field SHALL be set to 0x00-01.

The 'Protocol' field SHALL be set to 0x08-00 indicating IP protocol.

The 'HW Addr Length' field SHALL be set to 0x06 indicating 6-bytes of

HW address.

The 'Protocol Addr Length' field SHALL be set to 0x04 indicating

4-bytes of IP address.

The 'Operation' Code field SHALL be set as follows:

0x00-08 for InARP Request

0x00-09 for InARP Reply

The 'HW Addr of Sender' field SHALL be the 6-byte IEEE MAC address of

the Requester (InARP Request) or Responder (InARP Reply).

The 'Protocol Addr of Sender' field SHALL be the 4-byte IP address of

the Requester (InARP Request) or Responder (InARP Reply).

The 'HW Addr of Target' field SHALL be set to the 6-byte MAC address

of the Responder in an InARP Request and to the 6-byte MAC address of

the Requester in an InARP Reply.

The 'Protocol Addr of Target' field SHALL be set to 0x00-00-00-00 in

an InARP Request and to the 4-byte IP address of the Requester in an

InARP Reply.

B.4 InARP Support Requirements

Support for InARP is OPTIONAL. If a node does not support InARP and

it receives an InARP Request message then a silent behavior is

specified.

APPENDIX C: Some Informal Mechanisms for FC Layer Mappings

Each method SHALL have some check to ensure PLOGI has completed

successfully before data is sent. A related concern in large networks

is limiting concurrent logins to only those ports with active IP

traffic.

C.1 Login on Cached Mapping Information

This method insulates the level performing Login from the level

interpreting ARP. It is more accommodating of non-ARP mechanisms for

building the FC-layer mapping table.

1. Broadcast messages that carry a Network_Header contain the S_ID

on the FC-header and WW_PN in the Network-Header. Caching this

information provides a correlation of Port_ID to WW_PN. If the

received Broadcast message is compliant with this

specification, the WW_PN will contain the MAC Address.

2. The WW_PN is "available" if Login has been performed to the

Port_ID and flagged. If Login has not been performed, the WW_PN

is "unavailable".

3. If an outbound packet is destined for a port that is

"unavailable", the cached information (from broadcast) is used

to look up the Port_ID.

4. After sending an ELS PLOGI command (Port Login) to the Port

(from a higher level entity at the host), waiting for an

outbound packet before sending this Port Login conserves

resources for only those ports which wish to establish

communication.

5. After Port Login completes (ACC received), the outbound packet

can be forwarded. At this point in time, both ends have the

necessary information to complete their <IP address, MAC

Address, Port_ID> association.

C.2 Login on ARP Parsing

This method performs Login sooner by parsing ARP before passing it up

to higher levels for IP/MAC Address correlation. It requires a low-

level awareness of the IP address, and is therefore protocol-

specific.

1. When an ARP Broadcast Message is received, the S_ID is

extracted from the FC-header and the corresponding

Network_Source_Address from the Network_Header.

2. The ARP payload is parsed to determine if

(a) this host is the target of the ARP request (Target IP

Address match), and

(b) if this host is currently logged in with the port

(Port_ID = S_ID) originating the ARP broadcast.

3. The ARP is passed to a higher level for ARP Response

generation.

4. If a Port Login is required, an ELS PLOGI command (Port Login)

is sent immediately to the Port originating the ARP Broadcast.

5. After Port Login completes, an ARP response can be forwarded.

Note that there are two possible scenarios:

- The ACC to PLOGI returns before the ARP reply is processed

and the ARP Reply is immediately forwarded.

- The ARP reply is delayed, waiting for ACC (successful

Login).

6. At this point in time, both ends have the necessary

information to complete their

<IP address, MAC Address, Port_ID> association.

C.3 Login to Everyone

In Fibre Channel topologies with a limited number of ports, it may be

efficient to unconditionally Login to each port. This method is

discouraged in fabric and public loop environments.

After Port Login completes, the MAC Address to Port_ID Address tables

can be constructed.

C.4 Static Table

In some loop environments with a limited number of ports, a static

mapping from a MAC Address to Port_ID (D_ID or AL_PA) may be

maintained. The FC layer will always know the destination Port_ID

based on the table. The table is typically downloaded into the driver

at configuration time. This method scales poorly, and is therefore

not recommended.

Appendix D: FC Layer Address Validation

D.1 General Discussion

At all times, the <WW_PN, Port_ID> mapping MUST be valid before use.

There are many events that can invalidate this mapping. The

following discussion addresses conditions when such a validation is

required.

After a FC link interruption occurs, the Port_ID of a port may

change. After the interruption, the Port_IDs of all other ports that

have previously performed PLOGI (N_Port Login) with this port may

have changed, and its own Port_ID may have changed.

Because of this, address validation is required after a LIP in a loop

topology [7] or after NOS/OLS in a point-to-point topology [6].

Port_IDs will not change as a result of Link Reset (LR),thus address

validation is not required.

In addition to actively validating devices after a link interruption,

if a port receives any FC-4 data frames (other than broadcast

frames), from a port that is not currently logged in, then it shall

send an explicit Extended Link Service (ELS) Request logout (LOGO)

command to that port.

ELS commands (Requests and Replies) are used by an N_Port to solicit

a destination port (F_Port or N_Port) to perform some link-level

function or service.) The LOGO Request is used to request

invalidation of the service parameters and Port_ID of the recipient

N_Port.

The level of initialization and subsequent validation and recovery

reported to the upper (FC-4) layers is implementation-specific.

In general, an explicit Logout (LOGO) SHALL be sent whenever the FC-

Layer mapping between the Port_ID and WW_PN of a remote port is

removed.

The effect of power-up or re-boot on the mapping tables is outside

the scope of this specification.

D.2 FC Layer Address Validation in a Point-to-Point Topology

No validation is required after LR. In a point-to-point topology,

NOS/OLS causes implicit Logout of each port and after a NOS/OLS, each

port must perform a PLOGI [2].

D.3 FC Layer Address Validation in a Private Loop Topology

After a LIP, a port SHALL not transmit any link data to another port

until the address of the other port has been validated. The

validation consists of completing either ADISC or PDISC. (See

Appendix G.)

ADISC (Address Discovery) is an ELS command for discovering the hard

addresses - the 24-bit identifier- of NL_Ports [5], [6].

PDISC (Discover Port) is an ELS command for exchanging service

parameters without affecting Login state [5], [6].

As a requester, this specification prohibits PDISC and requires

ADISC.

As a responder, an implementation may need to respond to both ADISC

and PDISC for compatibility with other FC specifications.

If the three addresses, Port_ID, WW_PN, WW_NN, exactly match the

values prior to the LIP, then any active exchanges may continue.

If any of the three addresses have changed, then the node must be

explicitly Logged out [4], [5].

If a port's N_Port ID changes after a LIP, then all active Port-ID to

WW_PN mappings at this port must be explicitly Logged out.

D.4 FC Layer Address Validation in a Public Loop Topology

A FAN (Fabric Address Notification) ELS command is sent by the fabric

to all known previously logged in ports following an initialization

event. Therefore, after a LIP, hosts may wait for this notification

to arrive or they may perform a FLOGI.

If the WW_PN and WW_NN of the fabric FL_Port contained in the FAN ELS

or FLOGI response exactly match the values before the LIP, and if the

AL_PA obtained by the port is the same as the one before the LIP,

then the port may resume all exchanges. If not, then FLOGI (Fabric

Login) must be performed with the fabric and all nodes must be

explicitly Logged out.

A public loop device will have to perform the private loop

authentication to any nodes on the local loop which have an Area +

Domain Address == 0x00-00-XX

D.5 FC Layer Address Validation in a Fabric Topology

No validation is required after LR (link reset).

After NOS/OLS, a port must perform FLOGI. If, after FLOGI, the S_ID

of the port, the WW_PN of the fabric, and the WW_NN of the fabric are

the same as before the NOS/OLS, then the port may resume all

exchanges. If not, all nodes must be explicitly, Logged out [2].

APPENDIX E: Fibre Channel Overview

E.1 Brief Tutorial

The FC Standard [2] defines 5 "levels" (not layers) for its protocol

description: FC-0, FC-1, FC-2, FC-3, and FC-4. The first three levels

(FC-0, FC-1, FC-2) are largely concerned with the physical formatting

and control ASPects of the protocol. FC-3 has been architected to

provide a place holder for functions that might need to be performed

after the upper layer protocol has requested the transmission of an

information unit, but before FC-2 is asked to deliver that piece of

information by using a sequence of frames [18]. At this time, no FC-3

functions have been defined. FC-4 is meant for supporting profiles

of Upper Layer Protocols (ULP) such as IP and Small Computer System

Interface (SCSI), and supports a relatively small set compared to LAN

protocols such as IEEE 802.3.

FC devices are called "Nodes", each of which has at least one "Port"

to connect to other ports. A Node may be a workstation, a disk drive

or disk array, a camera, a display unit, etc. A "Link" is two

unidirectional paths flowing in opposite directions and connecting

two Ports within adjacent Nodes.

FC Nodes communicate using higher layer protocols such as SCSI and IP

and are configured to operate using Point-to-Point, Private Loop,

Public Loop (attachment to a Fabric), or Fabric network topologies.

The point-to-point is the simplest of the four topologies, where only

two nodes communicate with each other. The private loop may connect a

number of devices (max 126) in a logical ring much like Token Ring,

and is distinguished from a public loop by the absence of a Fabric

Node participating in the loop. The Fabric topology is a switched

network where any attached node can communicate with any other. For a

detail description of FC topologies refer to [18].

Table below summarizes the usage of port types depending on its

location [12]. Note that E-Port is not relevant to any discussion in

this specification but is included below for completeness.

+-----------+-------------+-----------------------------------------+

Port Type Location Topology Associated with

+-----------+-------------+-----------------------------------------+

N_Port Node Point-to-Point or Fabric

+-----------+-------------+-----------------------------------------+

NL_Port Node In N_Port mode -Point-to-Point or Fabric

In NL_Port mode - Arbitrated Loop

+-----------+-------------+-----------------------------------------+

F_Port Fabric Fabric

+-----------+-------------+-----------------------------------------+

FL_Port Fabric In F_Port mode - Fabric

In FL_Port mode - Arbitrated Loop

+-----------+-------------+-----------------------------------------+

E_Port Fabric Internal Fabric Expansion

+-----------+-------------+-----------------------------------------+

E.2 Exchange, Information Unit, Sequence, and Frame

The FC 'Exchange' is a mechanism used by two FC ports to identify and

manage an operation between them [18]. An Exchange is opened whenever

an operation is started between two ports. The Exchange is closed

when this operation ends.

The FC-4 Level specifies data units for each type of application

level payload called 'Information Unit' (IU). Each protocol carried

by FC has a defined size for the IU. Every operation must have at

least one IU. Lower FC levels map this to a FC Sequence.

Typically, a Sequence consists of more than one frame. Larger user

data is segmented and reassembled using two methods: Sequence Count

and Relative Offset [18]. With the use of Sequence Count, data blocks

are sent using frames with increasing sequence counts (modulo 65536)

and it is quite straightforward to detect the first frame that

contains the Network_Header. When Relative Offset is used, as frames

arrive, some computation is required to detect the first frame that

contains the Network_Header. Sequence Count and Relative Offset field

control information, is carried in the FC Header.

The FC-4 Level makes a request to FC-3 Level when it wishes it to be

delivered. Currently, there are no FC-3 level defined functions, and

this level simply converts the Information Unit delivery request into

a 'Sequence' delivery request and passes it on to the FC-2 Level.

Therefore, each FC-4 Information Unit corresponds to a FC-2 Level

Sequence.

The maximum data carried by a FC frame cannot exceed 2112-bytes [2].

Whenever, the Information Unit exceeds this value, the FC-2 breaks it

into multiple frames and sends it in a sequence.

There can be multiple Sequences within an Exchange. Sequences within

an Exchange are processed sequentially. Only one Sequence is active

at a time. Within an Exchange information may flow in one direction

only or both. If bi-directional then one of the ports has the

initiative to send the next Sequence for that Exchange. Sequence

Initiative can be passed between the ports on the last frame of

Sequence when control is transferred. This amounts to half-duplex

behavior.

Ports may have more than one Exchange open at a time. Ports can

multiplex between Exchanges. Exchanges are uniquely identified by

Exchange IDs (X_ID). An Originator OX_ID and a Responder RX_ID

uniquely identify an Exchange.

E.3 Fibre Channel Header Fields

The FC header as shown in the diagrams below contains routing and

other control information to manage Frames, Sequences, and Exchanges.

The Frame-header is sent as 6 transmission words immediately

following an SOF delimiter and before the Data Field.

D_ID and S_ID:

FC uses destination address routing [12], [13]. Frame routing in a

point-to-point topology is trivial.

For the Arbitrated Loop topology, with the destination NL_Port on

the same AL, the source port must pick the destination port,

determine its AL Physical Address, and "Open" the destination

port. The frames must pass through other NL_Ports or the FL_Port

on the loop between the source and destination, but these ports do

not capture the frames. They simply repeat and transmit the frame.

Either communicating port may "Close" the circuit.

When the destination port is not on the same AL, the source

NL_Port must open the FL_Port attached to a Fabric. Once in the

Fabric, the Fabric routes the frames again to the destination.

In a Fabric topology, the Fabric looks into the Frame-header,

extracts the destination address (D_ID), searches its own routing

tables, and sends the frame to the destination port along the path

chosen. The process of choosing a path may be performed at each

fabric element or switch until the F_Port attached to the

destination N_Port is reached.

Fibre Channel Frame Header, Network_Header, and Payload carrying IP

Packet

+---+----------------+----------------+----------------+--------------+

Wrd <31:24> <23:16> <15:08> <07:00>

+---+----------------+----------------+----------------+--------------+

0 R_CTL D_ID

+---+----------------+----------------+----------------+--------------+

1 CS_CTL S_ID

+---+----------------+----------------+----------------+--------------+

2 TYPE F_CTL

+---+----------------+----------------+----------------+--------------+

3 SEQ_ID DF_CTL SEQ_CNT

+---+----------------+----------------+----------------+--------------+

4 OX_ID RX_ID

+---+--------+-------+----------------+----------------+--------------+

5 Parameter (Control or Relative Offset for Data )

+---+-----------------------------------------------------------------+

6 NAA Network_Dest_Address (Hi order bits)

+---+--------+-------+----------------+----------------+--------------+

7 Network_Dest_Address (Lo order bits)

+---+--------+-------+----------------+----------------+--------------+

8 NAA Network_Src_Address (Hi order bits)

+---+--------+-------+----------------+----------------+--------------+

9 Network_Src_Address (Lo order bits)

+---+----------------+----------------+----------------+--------------+

10 DSAP SSAP CTRL OUI

+---+----------------+----------------+----------------+--------------+

11 OUI PID

+---+----------------+----------------+----------------+--------------+

12 IP Packet Data ...

+---+----------------+----------------+----------------+--------------+

R_CTL (Routing Control) and TYPE(data structure):

Frames for each FC-4 can be easily distinguished from the others

at the receiving port using the R_CTL (Routing Control) and TYPE

(data structure) fields in the Frame-header.

The R_CTL has two sub-fields: Routing bits and Information

category. The Routing bits sub-field has specific values that mean

FC-4 data follows and the Information Category tells the receiver

the "Type" of data contained in the frame. The R_CTL and TYPE code

points are shown in the diagrams.

Other Header fields:

F_CTL (Frame Control) and SEQ_ID (Sequence Identification),

SEQ_CNT (Sequence Count), OX_ID (Originator exchange Identifier),

RX_ID (Responder exchange Identifier), and Parameter fields are

used to manage the contents of a frame, and mark information

exchange boundaries for the destination port.

F_CTL(Frame Control):

The FC_CTL field is a 3-byte field that contains information

relating to the frame content. Most of the other Frame-header

fields are used for frame identification. Among other things, bits

in this field indicate the First Sequence, Last Sequence, or End

Sequence. Sequence Initiative bit is used to pass control of the

next Sequence in the Exchange to the recipient.

SEQ_ID (Sequence Identifier) and SEQ_CNT (Sequence Count):

This is used to uniquely identify sequences within an Exchange.

The <S_ID, D_ID, SEQ_ID> uniquely identifies any active Sequence.

SEQ_CNT is used to uniquely identify frames within a Sequence to

assure sequentiality of frame reception, and to allow unique

correlation of link control frames with their related data frames.

Originator Exchange Identifier (OX_ID) and Responder Exchange

Identifier (RX_ID):

The OX_ID value provides association of frames with specific

Exchanges originating at a particular N_Port. The RX_ID field

provides the same function that the OX_ID provides for the

Exchange Originator. The OX_ID is meaningful on the Exchange

Originator, and the RX_ID is meaningful on the Responder.

DF_CTL (Data Field Control):

The DF_CTL field specifies the presence or absence of optional

headers between the Frame-header and Frame Payload

PARAMETER:

The Parameter field has two meanings, depending on Frame type.

For Link Control Frames, the Parameter field indicates the

specific type of Link Control frame. For Data frames, this field

contains the Relative Offset value. This specifies an offset from

an Upper Layer Protocol buffer from a base address.

E.4 Code Points for FC Frame

E.4.1 Code Points with IP and ARP Packets

The Code Points for FC Frames with IP and ARP Packets are very

similar with the exception of PID value in Word 11 which is set to

0x08-00 for IP and 0x08-06 for ARP. Also, the Network_Header appears

only in the first logical frame of a FC Sequence carrying IP. In the

case, where FC frames carry ARP packets it is always present because

these are single frame Sequences.

Code Points for FC Frame with IP packet Data

+---+----------------+----------------+----------------+------------+

Wrd <31:24> <23:16> <15:08> <07:00>

+---+----------------+----------------+----------------+------------+

0 0x04 D_ID

+---+----------------+----------------+----------------+------------+

1 0x00 S_ID

+---+----------------+----------------+----------------+------------+

2 0x05 F_CTL

+---+----------------+----------------+----------------+------------+

3 SEQ_ID 0x20 SEQ_CNT

+---+----------------+----------------+----------------+------------+

4 OX_ID RX_ID

+---+----------------+----------------+----------------+------------+

5 0xXX-XX-XX-XX Parameter Relative Offset

+---+------+--------------------------------------------------------+

6 0001 0x000 Dest. MAC (Hi order bits)

+---+------+---------+----------------+----------------+------------+

7 Dest. MAC (Lo order bits)

+---+------+----------+----------------+----------------------------+

8 0001 0x000 Src. MAC (Hi order bits)

+---+------+---------+----------------+----------------+------------+

9 Src. MAC (Lo order bits)

+---+----------------+----------------+----------------+------------+

10 0xAA 0xAA 0x03 0x00

+---+----------------+----------------+----------------+------------+

11 0x00-00 0x08-00

+---+----------------+----------------+----------------+------------+

12 IP Packet Data

+---+----------------+----------------+----------------+------------+

13 ...

+---+----------------+----------------+----------------+------------+

Code Points for FC Frame with ARP packet Data

+---+----------------+----------------+----------------+------------+

Wrd <31:24> <23:16> <15:08> <07:00>

+---+----------------+----------------+----------------+------------+

0 0x04 D_ID

+---+----------------+----------------+----------------+------------+

1 0x00 S_ID

+---+----------------+----------------+----------------+------------+

2 0x05 F_CTL

+---+----------------+----------------+----------------+------------+

3 SEQ_ID 0x20 SEQ_CNT

+---+----------------+----------------+----------------+------------+

4 OX_ID RX_ID

+---+----------------+----------------+----------------+------------+

5 0xXX-XX-XX-XX Parameter Relative Offset

+---+------+--------------------------------------------------------+

6 0001 0x000 Dest. MAC (Hi order bits)

+---+------+---------+----------------+----------------+------------+

7 Dest. MAC (Lo order bits)

+---+------+----------+----------------+----------------------------+

8 0001 0x000 Src. MAC (Hi order bits)

+---+------+---------+----------------+----------------+------------+

9 Src. MAC (Lo order bits)

+---+----------------+----------------+----------------+------------+

10 0xAA 0xAA 0x03 0x00

+---+----------------+----------------+----------------+------------+

11 0x00-00 0x08-06

+---+----------------+----------------+----------------+------------+

12 ARP Packet Data

+---+----------------+----------------+----------------+------------+

13 ...

+---+----------------+----------------+----------------+------------+

The Code Points for a FARP-REQ for a specific Match Address Code

Point MATCH_WW_PN_NN ( b'011') is shown below. In particular, note

the IP addresses field of the Requester set to a valid address and

that of the responder set to '0'. Note also the setting of the D_ID

address and the Port_ID of the Responder.

The corresponding code point for a FARP-REPLY is also shown below.

In particular, note the setting of the Port_ID of Responder and the

IP address setting of the Responder.

E.4.2 Code Points with FARP Command

Code Points for FC Frame with FARP-REQ Command for MATCH_WW_PN_NN

+---+----------------+----------------+----------------+------------+

Wrd <31:24> <23:16> <15:08> <07:00>

+---+----------------+----------------+----------------+------------+

0 0x04 D_ID =

0xFF 0xFF 0xFF

+---+----------------+----------------+----------------+------------+

1 0x00 S_ID

+---+----------------+----------------+----------------+------------+

2 0x05 F_CTL

+---+----------------+----------------+----------------+------------+

3 SEQ_ID 0x20 SEQ_CNT

+---+----------------+----------------+----------------+------------+

4 OX_ID RX_ID

+---+----------------+----------------+----------------+------------+

5 0xXX-XX-XX-XX Parameter Relative Offset

+---+----------------+----------------+----------------+------------+

6 0x54 0x00 0x00 0x00

+---+----------------+----------------+----------------+------------+

7 Port_ID of Requester = S_ID Match Addr.

Code Points

xxxxx011

+---+----------------+----------------+----------------+------------+

8 Port_ID of Responder = Responder

0x00 0x00 0x00 Flags

+---+----------------+----------------+----------------+------------+

9 0001 0x000 WW_PN Src. MAC(Hi order bits)

+---+------+---------+----------------+----------------+------------+

10 WW_PN Src. MAC (Lo order bits)

+---+------+----------+---------------+-----------------------------+

11 0001 0x000 WW_NN Src. MAC(Hi order bits)

+---+------+---------+----------------+----------------+------------+

12 WW_NN Src. MAC (Lo order bits)

+---+----------------+----------------+----------------+------------+

13 0001 0x000 WW_PN Src. MAC(Hi order bits)

+---+------+---------+----------------+----------------+------------+

14 WW_PN Dest. MAC (Lo order bits)

+---+------+----------+---------------+-----------------------------+

15 0001 0x000 WW_NN Dest.MAC(Hi order bits)

+---+------+---------+----------------+----------------+------------+

16 WW_NN Dest. MAC (Lo order bits)

+---+----------------+----------------+----------------+------------+

17 0x00-00-00-00

+--------------------+----------------+---------+-------------------+

18 0x00-00-00-00

+--------------------+----------------+---------+-------------------+

19 0x00-00-00-00

+--------------------+----------------+---------+-------------------+

20 set to a valid IPv4 Address by Requester if Available

+--------------------+----------------+---------+-------------------+

21 0x00-00-00-00

+--------------------+----------------+---------+-------------------+

22 0x00-00-00-00

+--------------------+----------------+---------+-------------------+

23 0x00-00-00-00

+--------------------+----------------+---------+-------------------+

0x00-00-00-00

24 set to a valid IPv4 Address of Responder if available

+--------------------+----------------+---------+-------------------+

Code Points for FC Frame with FARP-REPLY Command

+---+----------------+----------------+----------------+------------+

Wrd <31:24> <23:16> <15:08> <07:00>

+---+----------------+----------------+----------------+------------+

0 0x04 D_ID

+---+----------------+----------------+----------------+------------+

1 0x00 S_ID

+---+----------------+----------------+----------------+------------+

2 0x05 F_CTL

+---+----------------+----------------+----------------+------------+

3 SEQ_ID 0x20 SEQ_CNT

+---+----------------+----------------+----------------+------------+

4 OX_ID RX_ID

+---+----------------+----------------+----------------+------------+

5 0xXX-XX-XX-XX Parameter Relative Offset

+---+----------------+----------------+----------------+------------+

6 0x55 0x00 0x00 0x00

+---+----------------+----------------+----------------+------------+

7 Port_ID of Requester = D_ID xxxxx011

+---+----------------+----------------+----------------+------------+

8 Port_ID of Responder = S_ID Resp. Flag

+---+----------------+----------------+----------------+------------+

9 0001 0x000 WW_PN Src. MAC(Hi order bits)

+---+------+---------+----------------+----------------+------------+

10 WW_PN Src. MAC (Lo order bits)

+---+------+----------+---------------+-----------------------------+

11 0001 0x000 WW_NN Src. MAC(Hi order bits)

+---+------+---------+----------------+----------------+------------+

12 WW_NN Src. MAC (Lo order bits)

+---+----------------+----------------+----------------+------------+

13 0001 0x000 WW_PN Src. MAC(Hi order bits)

+---+------+---------+----------------+----------------+------------+

14 WW_PN Dest. MAC (Lo order bits)

+---+------+----------+---------------+-----------------------------+

15 0001 0x000 WW_NN Dest.MAC(Hi order bits)

+---+------+---------+----------------+----------------+------------+

16 WW_NN Dest. MAC (Lo order bits)

+---+----------------+----------------+----------------+------------+

17 0x00-00-00-00

+--------------------+----------------+---------+-------------------+

18 0x00-00-00-00

+--------------------+----------------+---------+-------------------+

19 0x00-00-00-00

+--------------------+----------------+---------+-------------------+

20 set to a valid IPv4 Address by Requester

+--------------------+----------------+---------+-------------------+

21 0x00-00-00-00

+--------------------+----------------+---------+-------------------+

22 0x00-00-00-00

+--------------------+----------------+---------+-------------------+

23 0x00-00-00-00

+--------------------+----------------+---------+-------------------+

24 set to a valid IPv4 Address by Responder

+--------------------+----------------+---------+-------------------+

APPENDIX F: Fibre Channel Protocol Considerations

F.1 Reliability In Class 3

Problem: Sequence ID reuse in Class 3 can conceivably result in

missing frame aliasing, which could result in delivery of corrupted

(incorrectly-assembled) data, with no corresponding detection at the

FC level.

Prevention: This specification requires one of the following methods

if Class 3 is used.

- Continuously increasing Sequence Count (new Login Bit) - both

sides must set When an N_Port sets the PLOGI login bit for

continuously increasing SEQ_CNT, it is guaranteeing that it

will transmit all frames within an Exchange using a

continuously increasing SEQ_CNT (see description in Section

B.1 below).

- After using all SEQ_IDs (0-255) once, must start a new

Exchange. It is recommended that a minimum of 4 Exchanges be

used before an OX_ID can be reused.

- Note: If an implementation is not checking the OX_ID when

reassembling Sequences, the problem can still occur. Cycling

through some number of SEQ_IDs, then jumping to a new Exchange

does not solve the problem. SEQ_IDs must still be unique

between two N_Ports, even across Exchanges.

- Use only single-frame Sequences.

F.2 Continuously Increasing SEQ_CNT

This method allows the recipient to check incoming frames, knowing

exactly what SEQ_CNT value to expect next. Since the SEQ_CNT will not

repeat for 65,536 frames, the aliasing problem is significantly

reduced.

A Login bit (PLOGI) is used to indicate that a device always uses a

continuously increasing SEQ_CNT, even across transfers of Sequence

Initiative. This bit is necessary for interoperability with some

devices, and it provides other benefits as well.

In the FC-PH-3 [11], the following is supported:

Word 1, bit 17 - SEQ_CNT (S)

0 = Normal FC-PH rules apply

1 = Continuously increasing SEQ_CNT

Any N_Port that sets Word 1, Bit 17 = 1, is guaranteeing that it will

transmit all frames within an Exchange using a continuously

increasing SEQ_CNT. Each Exchange SHALL start with SEQ_CNT = 0 in the

first frame, and every frame transmitted after that SHALL increment

the previous SEQ_CNT by one, even across transfers of Sequence

Initiative. Any frames received from the other N_Port in the Exchange

shall have no effect on the transmitted SEQ_CNT.

Appendix G: Acronyms and Glossary of FC Terms

It is assumed that the reader is familiar with the terms and acronyms

used in the FC protocol specification [2]. The following is provided

for easy reference.

First Frame: The frame that contains the SOFi field. This means a

logical first and may not necessarily be the first frame temporally

received in a sequence.

Code Point: The coded bit pattern associated with control fields in

frames or packets.

PDU: Protocol Data Unit

ABTS_LS: Abort Sequence Protocol - Last Sequence. A protocol for

aborting an exchange based on the ABTS recipient setting the

Last_Sequence bit in the BA_ACC ELS to the ABTS

ADISC: Discover Address. An ELS for discovering the Hard Addresses

(the 24 bit NL_Port Identifier) of N_Ports

D_ID: Destination ID

ES: End sequence. This FCTL bit in the FC header indicates this frame

is the last frame of the sequence.

FAN: Fabric Address Notification. An ELS sent by the fabric to all

known previously Logged in ports following an initialization event.

FLOGI: Fabric Login.

LIP: Loop Initialization. A primitive Sequence used by a port to

detect if it is part of a loop or to recover from certain loop

errors.

Link: Two unidirectional paths flowing in opposite directions and

connecting two Ports within adjacent Nodes.

LOGO: Logout.

LR: Link reset. A primitive sequence transmitted by a port to

initiate the link reset protocol or to recover from a link timeout.

LS: Last Sequence of Exchange. This FCTL bit in the FC header

indicates the Sequence is the Last Sequence of the Exchange.

Network Address Authority: A 4-bit field specified in Network_Headers

that distinguishes between various name registration authorities that

may be used to identify the WW_PN and the WW_NN. NAA=b'0001'

indicates IEEE-48-bit MAC addresses

Node: A collection of one or more Ports identified by a unique World

Wide Node Name (WW_NN).

NOS: Not Operational. A primitive Sequence transmitted to indicate

that the port transmitting this Sequence has detected a link failure

or is offline, waiting for OLS to be received.

OLS: Off line. A primitive Sequence transmitted to indicate that the

port transmitting this Sequence is either initiating the link

initialization protocol, receiving and recognizing NOS, or entering

the offline state.

PDISC: Discover Port. An ELS for exchanging Service Parameters

without affecting Login state.

Primitive Sequence: A primitive Sequence is an Ordered Set that is

transmitted repeatedly and continuously.

Private Loop Device: A device that does not attempt Fabric Login

(FLOGI) and usually adheres to PLDA. The Area and Domain components

of the NL_Port ID must be 0x0000. These devices cannot communicate

with any port not in the local loop.

Public Loop Device: A device whose Area and Domain components of the

NL_Port ID cannot be 0x0000. Additionally, to be FLA compliant, the

device must attempt to open AL_PA 0x00 and attempt FLOGI. These

devices communicate with devices on the local loop as well as devices

on the other side of a Fabric.

Port: The transmitter, receiver and associated logic at either end of

a link within a Node. There may be multiple Ports per Node. Each Port

is identified by a unique Port_ID, which is volatile, and a unique

World Wide Port Name (WW_PN), which is unchangeable. In this

document, the term "port" may be used interchangeably with NL_Port or

N_Port.

Port_ID: Fibre Channel ports are addressed by unique 24-bit Port_IDs.

In a Fibre Channel frame header, the Port_ID is referred to as S_ID

(Source ID) to identify the port originating a frame, and D_ID to

identify the destination port. The Port_ID of a given port is

volatile (changeable).

PLOGI: Port Login.

SI: Sequence Initiative

World Wide Port_Name (WW_PN): Fibre Channel requires each Port to

have an unchangeable WW_PN. Fibre Channel specifies a Network Address

Authority (NAA) to distinguish between the various name registration

authorities that may be used to identify the WW_PN. A 4-bit NAA

identifier, 12-bit field set to 0x0 and an IEEE 48-bit MAC address

together make this a 64-bit field.

World Wide Node_Name (WW_NN): Fibre Channel identifies each Node with

a unchangeable WW_NN. In a single port Node, the WW_NN and the WW_PN

may be identical.

Full Copyright Statement

Copyright (C) The Internet Society (1999). All Rights Reserved.

This document and translations of it may be copied and furnished to

others, and derivative works that comment on or otherwise explain it

or assist in its implementation may be prepared, copied, published

and distributed, in whole or in part, without restriction of any

kind, provided that the above copyright notice and this paragraph are

included on all such copies and derivative works. However, this

document itself may not be modified in any way, such as by removing

the copyright notice or references to the Internet Society or other

Internet organizations, except as needed for the purpose of

developing Internet standards in which case the procedures for

copyrights defined in the Internet Standards process must be

followed, or as required to translate it into languages other than

English.

The limited permissions granted above are perpetual and will not be

revoked by the Internet Society or its successors or assigns.

This document and the information contained herein is provided on an

"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING

TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING

BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION

HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF

MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

Funding for the RFCEditor function is currently provided by the

Internet Society.

 
 
 
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