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RFC1376 - The PPP DECnet Phase IV Control Protocol (DNCP)

王朝other·作者佚名  2008-05-31
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Network Working Group S. Senum

Request for Comments: 1376 Network Systems Corporation

November 1992

The PPP DECnet Phase IV Control Protocol (DNCP)

Status of this Memo

This RFCspecifies an IAB standards track protocol for the Internet

community, and requests discussion and suggestions for improvements.

Please refer to the current edition of the "IAB Official Protocol

Standards" for the standardization state and status of this protocol.

Distribution of this memo is unlimited.

Abstract

The Point-to-Point Protocol (PPP) [1] provides a standard method of

encapsulating Network Layer protocol information over point-to-point

links. PPP also defines an extensible Link Control Protocol, and

proposes a family of Network Control Protocols (NCPs) for

establishing and configuring different network-layer protocols.

This document defines the NCP for establishing and configuring

Digital's DNA Phase IV Routing protocol (DECnet Phase IV) over PPP.

This document applies only to DNA Phase IV Routing messages (both

data and control), and not to other DNA Phase IV protocols (MOP, LAT,

etc.).

1. IntrodUCtion

There are two basic approaches to running the DNA Phase IV Routing

protocol over a serial line:

1. The approached that several router vendors have taken which is to

treat the serial link as an Ethernet, using the same data and

control messages an Ethernet would use.

2. The approach defined by Digital, which uses DDCMP and slightly

different control messages.

This document will define a method that uses the first approach.

2. Overview Of Phase IV DNA Protocols

The Phase IV DNA protocols which act as data link clients are:

o DNA Phase IV Routing

The Phase IV Digital Network Architecture (DNA) Routing

protocol is a network layer protocol providing services similar

to that of DoD IP. It routes messages in Phase IV DECnet

networks and manages the packet flow. The complete definition

of the DNA Phase IV Routing protocol can be found in [2].

o DNA System Console

The Digital Network Architecture (DNA) System Console protocol

is a maintenance protocol providing low level Access to a

system for the functions of:

. Identify processor

. Read data link counters

. Boot system

. Console carrier (a general purpose i/o channel)

The complete definition of the DNA System Console protocol can

be found in [3].

o Digital Customer Use

The Digital Customer Use protocol type is a value reserved for

use by Digital customers. It allocates a type for private use

which will not conflict with Digital or other vendor protocols.

o DNA Diagnostics

The Digital Network Architecture (DNA) Diagnostics protocol

type is reserved to allow diagnostic software communications in

parallel with other data link clients.

o DNA Naming Service (DNS)

The Digital Network Architecture Naming Service (DNS) provides

a distributed naming service. It allows clients to register

named objects and to bind a set of attributes to the objects in

a distributed database.

o DNA Time Service (DTS)

The Digital Network Architecture Time Service (DTS) is a

protocol providing global clock synchronization in a

distributed environment.

o DNA Load/Dump

The Digital Network Architecture (DNA) Load/Dump protocol is a

maintenance protocol for copying the contents of processor

memory to or from a remote system. For example, a system

manager can load an operating system into an unattended, remote

system. The complete definition of the Phase IV DNA Load/Dump

protocol can be found in [3].

o DNA EXPerimental Use

The Digital Network Architecture (DNA) Experimental Use

protocol type allows Digital experimental protocols to share a

data link with other data link clients. It is for use by

Digital Equipment Corporation only.

o DNA Communications Test

The Digital Network Architecture (DNA) Communications Test

protocol is a maintenance protocol for testing the data link

communications path. The complete definition of the DNA

Communications Test protocol can be found in [3].

o Digital Protocol X1

The Digital X1 protocol is a network layer protocol currently

private to Digital.

This document defines the NCP for establishing and configuring

Digital's DNA Phase IV Routing protocol (DECnet Phase IV) over PPP.

This document applies only to DNA Phase IV Routing messages (both

data and control), and not to other DNA Phase IV protocols (MOP, LAT,

etc.).

3. A PPP Network Control Protocol for DNA Phase IV Routing

The DNA Phase IV Routing Control Protocol (DNCP) is responsible for

configuring, enabling, and disabling the DNA Phase IV Routing

protocol modules on both ends of the point-to-point link. DNCP uses

the same packet exchange mechanism as the Link Control Protocol

(LCP). DNCP packets may not be exchanged until PPP has reached the

Network-Layer Protocol phase. DNCP packets received before this

phase is reached should be silently discarded.

The DNA Phase IV Routing Control Protocol is exactly the same as the

Link Control Protocol [1] with the following exceptions:

Frame Modifications

The packet may utilize any modifications to the basic frame format

which have been negotiated during the Link Establishment phase.

Data Link Layer Protocol Field

Exactly one DNCP packet is encapsulated in the Information field

of a PPP Data Link Layer frame where the Protocol field indicates

type hex 8027 (DNA Phase IV Control Protocol).

Code field

Only Codes 1 through 7 (Configure-Request, Configure-Ack,

Configure-Nak, Configure-Reject, Terminate-Request, Terminate-Ack

and Code-Reject) are used. Other Codes should be treated as

unrecognized and should result in Code-Rejects.

Timeouts

DNCP packets may not be exchanged until PPP has reached the

Network-Layer Protocol phase. An implementation should be

prepared to wait for Authentication and Link Quality Determination

to finish before timing out waiting for a Configure-Ack or other

response. It is suggested that an implementation give up only

after user intervention or a configurable amount of time.

Configuration Option Types

DNCP has no Configuration Options.

4. Sending DNA Phase IV Routing Packets

Before any DNA Phase IV Routing packets may be communicated, PPP must

reach the Network-Layer Protocol phase, and the DNA Phase IV Routing

Control Protocol must reach the Opened state.

Exactly one octet-count field and one DNA Phase IV Routing packet are

encapsulated in the information field of a PPP Data Link Layer frame

where the Protocol field indicates type hex 0027 (DNA Phase IV

Routing). The octet-count contains a count of the number of octets

in the DNA Phase IV Routing packet. It is two octets in length

itself, and is stored in VAX byte ordering, to be more consistent

with DNA Phase IV Routing over Ethernet (i.e. least significant byte

first). It is needed to disambiguate optional padding octets from

real information.

The maximum length of an DNA Phase IV Routing packet transmitted over

a PPP link is the same as the maximum length of the Information field

of a PPP data link layer frame minus 2 octets (for the Length field).

The format of the packets themselves is the same as the format used

over Ethernet, without the Ethernet header, Pad, and FCS fields.

A summary of the information field is shown below. The fields are

transmitted from left to right.

0 1 2 3

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

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

Length LSB Length MSB DATA ...

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

...

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

Length LSB

Least significant byte of length field

Length MSG

Most significant byte of length field

DATA

DNA Phase IV Routing data, as specified in [2]

5. General Considerations

When a topology change in the network occurs, DNA Phase IV Routing

nodes immediately propagate changes via Level 1 and Level 2 Routing

messages, with a 1 second minimum delay between updates. DNA Phase

IV Routing nodes also periodically retransmit the complete Level 1

and Level 2 distance vectors to guard against data corruption in host

memory, and (in the case of Ethernet) loss of packets due to media

errors. Because Digital's serial links run a protocol that

guarantees delivery of packets (DDCMP), the recommended default

retransmit time is long (600 seconds), whereas for Ethernet, where

packet delivery is not guaranteed, the recommended default is short

(10 seconds), as documented in [2]. To achieve convergence of routes

within a satisfactory time, the interval between updates should be

based upon the error rate of underlying data link. As such, it is

recommended that the time between routing updates be user

configurable per PPP interface.

The Hello timer and Listen timer should be set according to the

recommendations for broadcast links (15 and 45 seconds,

respectively).

Routers are not required to send routing updates if the remote node

connected via the PPP link is an endnode. Endnodes are required to

discard all routing updates received over a PPP link. The type of a

node (endnode versus routing) can be determined from the hello

messages received from it.

References

[1] Simpson, W., "The Point-to-Point Protocol (PPP)", RFC1331,

Daydreamer, May 1992.

[2] Digital Equipment Corporation, "DNA Routing Layer Functional

Specification", Version 2.0.0, Order No. AA-X435A-TK.

[3] Digital Equipment Corporation, "DNA Maintenance Operations

Functional Specification", Version 3.0.0, Order No. AA-X436A-TK.

Acknowledgments

Some of the text in this document is taken from previous documents

produced by the Point-to-Point Protocol Working Group of the Internet

Engineering Task Force (IETF).

The author wishes to thank Jim Muchow (Network Systems Corporation),

and Arthur Harvey (Digital Equipment Corporation) for their input to

this memo.

Security Considerations

Security issues are not discussed in this memo.

Chair's Address

The working group can be contacted via the current chair:

Brian Lloyd

Lloyd & Associates

3420 Sudbury Road

Cameron Park, California 95682

Phone: (916) 676-1147

EMail:

brian@lloyd.com

Author's Address

Questions about this memo can also be directed to the author:

Steven J. Senum

Network Systems Corporation

7600 Boone Avenue North

Minneapolis, Minnesota 55428

Phone: (612) 424-4888

EMail: sjs@network.com

 
 
 
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