分享
 
 
 

RFC2748 - The COPS (Common Open Policy Service) Protocol

王朝other·作者佚名  2008-05-31
窄屏简体版  字體: |||超大  

Network Working Group D. Durham, Ed.

Request for Comments: 2748 Intel

Category: Standards Track J. Boyle

Level 3

R. Cohen

Cisco

S. Herzog

IPHighway

R. Rajan

AT&T

A. Sastry

Cisco

January 2000

The COPS (Common Open Policy Service) Protocol

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 (2000). All Rights Reserved.

Conventions used in this document

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 [RFC-2119].

Abstract

This document describes a simple client/server model for supporting

policy control over QoS signaling protocols. The model does not make

any assumptions about the methods of the policy server, but is based

on the server returning decisions to policy requests. The model is

designed to be extensible so that other kinds of policy clients may

be supported in the future. However, this document makes no claims

that it is the only or the preferred approach for enforcing future

types of policies.

Table Of Contents

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

1.1 Basic Model....................................................4

2. The Protocol....................................................6

2.1 Common Header..................................................6

2.2 COPS Specific Object Formats...................................8

2.2.1 Handle Object (Handle).......................................9

2.2.2 Context Object (Context).....................................9

2.2.3 In-Interface Object (IN-Int)................................10

2.2.4 Out-Interface Object (OUT-Int)..............................11

2.2.5 Reason Object (Reason)......................................12

2.2.6 Decision Object (Decision)..................................12

2.2.7 LPDP Decision Object (LPDPDecision).........................14

2.2.8 Error Object (Error)........................................14

2.2.9 Client Specific Information Object (ClientSI)...............15

2.2.10 Keep-Alive Timer Object (KATimer)..........................15

2.2.11 PEP Identification Object (PEPID)..........................16

2.2.12 Report-Type Object (Report-Type)...........................16

2.2.13 PDP Redirect Address (PDPRedirAddr)........................16

2.2.14 Last PDP Address (LastPDPAddr).............................17

2.2.15 Accounting Timer Object (AcctTimer)........................17

2.2.16 Message Integrity Object (Integrity).......................18

2.3 Communication.................................................19

2.4 Client Handle Usage...........................................21

2.5 Synchronization Behavior......................................21

3. Message Content................................................22

3.1 Request (REQ) PEP -> PDP.....................................22

3.2 Decision (DEC) PDP -> PEP....................................24

3.3 Report State (RPT) PEP -> PDP................................25

3.4 Delete Request State (DRQ) PEP -> PDP........................25

3.5 Synchronize State Request (SSQ) PDP -> PEP...................26

3.6 Client-Open (OPN) PEP -> PDP.................................26

3.7 Client-Accept (CAT) PDP -> PEP...............................27

3.8 Client-Close (CC) PEP -> PDP, PDP -> PEP.....................28

3.9 Keep-Alive (KA) PEP -> PDP, PDP -> PEP.......................28

3.10 Synchronize State Complete (SSC) PEP -> PDP..................29

4. Common Operation...............................................29

4.1 Security and Sequence Number Negotiation......................29

4.2 Key Maintenance...............................................31

4.3 PEP Initialization............................................31

4.4 Outsourcing Operations........................................32

4.5 Configuration Operations......................................32

4.6 Keep-Alive Operations.........................................33

4.7 PEP/PDP Close.................................................33

5. Security Considerations........................................33

6. IANA Considerations............................................34

7. References.....................................................35

8. Author Information and Acknowledgments.........................36

9. Full Copyright Statement.......................................38

1. Introduction

This document describes a simple query and response protocol that can

be used to exchange policy information between a policy server

(Policy Decision Point or PDP) and its clients (Policy Enforcement

Points or PEPs). One example of a policy client is an RSVP router

that must exercise policy-based admission control over RSVP usage

[RSVP]. We assume that at least one policy server exists in each

controlled administrative domain. The basic model of interaction

between a policy server and its clients is compatible with the

framework document for policy based admission control [WRK].

A chief objective of this policy control protocol is to begin with a

simple but extensible design. The main characteristics of the COPS

protocol include:

1. The protocol employs a client/server model where the PEP sends

requests, updates, and deletes to the remote PDP and the PDP

returns decisions back to the PEP.

2. The protocol uses TCP as its transport protocol for reliable

exchange of messages between policy clients and a server.

Therefore, no additional mechanisms are necessary for reliable

communication between a server and its clients.

3. The protocol is extensible in that it is designed to leverage

off self-identifying objects and can support diverse client

specific information without requiring modifications to the

COPS protocol itself. The protocol was created for the general

administration, configuration, and enforcement of policies.

4. COPS provides message level security for authentication, replay

protection, and message integrity. COPS can also reuse existing

protocols for security such as IPSEC [IPSEC] or TLS to

authenticate and secure the channel between the PEP and the

PDP.

5. The protocol is stateful in two main ASPects: (1)

Request/Decision state is shared between client and server and

(2) State from various events (Request/Decision pairs) may be

inter-associated. By (1) we mean that requests from the client

PEP are installed or remembered by the remote PDP until they

are eXPlicitly deleted by the PEP. At the same time, Decisions

from the remote PDP can be generated asynchronously at any time

for a currently installed request state. By (2) we mean that

the server may respond to new queries differently because of

previously installed Request/Decision state(s) that are

related.

6. Additionally, the protocol is stateful in that it allows the

server to push configuration information to the client, and

then allows the server to remove such state from the client

when it is no longer applicable.

1.1 Basic Model

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

Network Node Policy Server

+-----+ COPS +-----+

PEP <-------------------> PDP

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

^

\-->+-----+

LPDP

+-----+

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

Figure 1: A COPS illustration.

Figure 1 Illustrates the layout of various policy components in a

typical COPS example (taken from [WRK]). Here, COPS is used to

communicate policy information between a Policy Enforcement Point

(PEP) and a remote Policy Decision Point (PDP) within the context of

a particular type of client. The optional Local Policy Decision Point

(LPDP) can be used by the device to make local policy decisions in

the absence of a PDP.

It is assumed that each participating policy client is functionally

consistent with a PEP [WRK]. The PEP may communicate with a policy

server (herein referred to as a remote PDP [WRK]) to oBTain policy

decisions or directives.

The PEP is responsible for initiating a persistent TCP connection to

a PDP. The PEP uses this TCP connection to send requests to and

receive decisions from the remote PDP. Communication between the PEP

and remote PDP is mainly in the form of a stateful request/decision

exchange, though the remote PDP may occasionally send unsolicited

decisions to the PEP to force changes in previously approved request

states. The PEP also has the capacity to report to the remote PDP

that it has successfully completed performing the PDP's decision

locally, useful for accounting and monitoring purposes. The PEP is

responsible for notifying the PDP when a request state has changed on

the PEP. Finally, the PEP is responsible for the deletion of any

state that is no longer applicable due to events at the client or

decisions issued by the server.

When the PEP sends a configuration request, it expects the PDP to

continuously send named units of configuration data to the PEP via

decision messages as applicable for the configuration request. When a

unit of named configuration data is successfully installed on the

PEP, the PEP should send a report message to the PDP confirming the

installation. The server may then update or remove the named

configuration information via a new decision message. When the PDP

sends a decision to remove named configuration data from the PEP, the

PEP will delete the specified configuration and send a report message

to the PDP as confirmation.

The policy protocol is designed to communicate self-identifying

objects which contain the data necessary for identifying request

states, establishing the context for a request, identifying the type

of request, referencing previously installed requests, relaying

policy decisions, reporting errors, providing message integrity, and

transferring client specific/namespace information.

To distinguish between different kinds of clients, the type of client

is identified in each message. Different types of clients may have

different client specific data and may require different kinds of

policy decisions. It is expected that each new client-type will have

a corresponding usage draft specifying the specifics of its

interaction with this policy protocol.

The context of each request corresponds to the type of event that

triggered it. The COPS Context object identifies the type of request

and message (if applicable) that triggered a policy event via its

message type and request type fields. COPS identifies three types of

outsourcing events: (1) the arrival of an incoming message (2)

allocation of local resources, and (3) the forwarding of an outgoing

message. Each of these events may require different decisions to be

made. The content of a COPS request/decision message depends on the

context. A fourth type of request is useful for types of clients that

wish to receive configuration information from the PDP. This allows a

PEP to issue a configuration request for a specific named device or

module that requires configuration information to be installed.

The PEP may also have the capability to make a local policy decision

via its Local Policy Decision Point (LPDP) [WRK], however, the PDP

remains the authoritative decision point at all times. This means

that the relevant local decision information must be relayed to the

PDP. That is, the PDP must be granted Access to all relevant

information to make a final policy decision. To facilitate this

functionality, the PEP must send its local decision information to

the remote PDP via an LPDP decision object. The PEP must then abide

by the PDP's decision as it is absolute.

Finally, fault tolerance is a required capability for this protocol,

particularly due to the fact it is associated with the security and

service management of distributed network devices. Fault tolerance

can be achieved by having both the PEP and remote PDP constantly

verify their connection to each other via keep-alive messages. When a

failure is detected, the PEP must try to reconnect to the remote PDP

or attempt to connect to a backup/alternative PDP. While

disconnected, the PEP should revert to making local decisions. Once a

connection is reestablished, the PEP is expected to notify the PDP of

any deleted state or new events that passed local admission control

after the connection was lost. Additionally, the remote PDP may

request that all the PEP's internal state be resynchronized (all

previously installed requests are to be reissued). After failure and

before the new connection is fully functional, disruption of service

can be minimized if the PEP caches previously communicated decisions

and continues to use them for some limited amount of time. Sections

2.3 and 2.5 detail COPS mechanisms for achieving reliability.

2. The Protocol

This section describes the message formats and objects exchanged

between the PEP and remote PDP.

2.1 Common Header

Each COPS message consists of the COPS header followed by a number of

typed objects.

0 1 2 3

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

Version Flags Op Code Client-type

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

Message Length

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

Global note: //// implies field is reserved, set to 0.

The fields in the header are:

Version: 4 bits

COPS version number. Current version is 1.

Flags: 4 bits

Defined flag values (all other flags MUST be set to 0):

0x1 Solicited Message Flag Bit

This flag is set when the message is solicited by

another COPS message. This flag is NOT to be set

(value=0) unless otherwise specified in section 3.

Op Code: 8 bits

The COPS operations:

1 = Request (REQ)

2 = Decision (DEC)

3 = Report State (RPT)

4 = Delete Request State (DRQ)

5 = Synchronize State Req (SSQ)

6 = Client-Open (OPN)

7 = Client-Accept (CAT)

8 = Client-Close (CC)

9 = Keep-Alive (KA)

10= Synchronize Complete (SSC)

Client-type: 16 bits

The Client-type identifies the policy client. Interpretation of

all encapsulated objects is relative to the client-type. Client-

types that set the most significant bit in the client-type field

are enterprise specific (these are client-types 0x8000 -

0xFFFF). (See the specific client usage documents for particular

client-type IDs). For KA Messages, the client-type in the header

MUST always be set to 0 as the KA is used for connection

verification (not per client session verification).

Message Length: 32 bits

Size of message in octets, which includes the standard COPS

header and all encapsulated objects. Messages MUST be aligned on

4 octet intervals.

2.2 COPS Specific Object Formats

All the objects follow the same object format; each object consists

of one or more 32-bit words with a four-octet header, using the

following format:

0 1 2 3

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

Length (octets) C-Num C-Type

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

// (Object contents) //

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

The length is a two-octet value that describes the number of octets

(including the header) that compose the object. If the length in

octets does not fall on a 32-bit word boundary, padding MUST be added

to the end of the object so that it is aligned to the next 32-bit

boundary before the object can be sent on the wire. On the receiving

side, a subsequent object boundary can be found by simply rounding up

the previous stated object length to the next 32-bit boundary.

Typically, C-Num identifies the class of information contained in the

object, and the C-Type identifies the subtype or version of the

information contained in the object.

C-num: 8 bits

1 = Handle

2 = Context

3 = In Interface

4 = Out Interface

5 = Reason code

6 = Decision

7 = LPDP Decision

8 = Error

9 = Client Specific Info

10 = Keep-Alive Timer

11 = PEP Identification

12 = Report Type

13 = PDP Redirect Address

14 = Last PDP Address

15 = Accounting Timer

16 = Message Integrity

C-type: 8 bits

Values defined per C-num.

2.2.1 Handle Object (Handle)

The Handle Object encapsulates a unique value that identifies an

installed state. This identification is used by most COPS operations.

A state corresponding to a handle MUST be explicitly deleted when it

is no longer applicable. See Section 2.4 for details.

C-Num = 1

C-Type = 1, Client Handle.

Variable-length field, no implied format other than it is unique from

other client handles from the same PEP (a.k.a. COPS TCP connection)

for a particular client-type. It is always initially chosen by the

PEP and then deleted by the PEP when no longer applicable. The client

handle is used to refer to a request state initiated by a particular

PEP and installed at the PDP for a client-type. A PEP will specify a

client handle in its Request messages, Report messages and Delete

messages sent to the PDP. In all cases, the client handle is used to

uniquely identify a particular PEP's request for a client-type.

The client handle value is set by the PEP and is opaque to the PDP.

The PDP simply performs a byte-wise comparison on the value in this

object with respect to the handle object values of other currently

installed requests.

2.2.2 Context Object (Context)

Specifies the type of event(s) that triggered the query. Required for

request messages. Admission control, resource allocation, and

forwarding requests are all amenable to client-types that outsource

their decision making facility to the PDP. For applicable client-

types a PEP can also make a request to receive named configuration

information from the PDP. This named configuration data may be in a

form useful for setting system attributes on a PEP, or it may be in

the form of policy rules that are to be directly verified by the PEP.

Multiple flags can be set for the same request. This is only allowed,

however, if the set of client specific information in the combined

request is identical to the client specific information that would be

specified if individual requests were made for each specified flag.

C-num = 2, C-Type = 1

0 1 2 3

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

R-Type M-Type

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

R-Type (Request Type Flag)

0x01 = Incoming-Message/Admission Control request

0x02 = Resource-Allocation request

0x04 = Outgoing-Message request

0x08 = Configuration request

M-Type (Message Type)

Client Specific 16 bit values of protocol message types

2.2.3 In-Interface Object (IN-Int)

The In-Interface Object is used to identify the incoming interface on

which a particular request applies and the address where the received

message originated. For flows or messages generated from the PEP's

local host, the loop back address and ifindex are used.

This Interface object is also used to identify the incoming

(receiving) interface via its ifindex. The ifindex may be used to

differentiate between sub-interfaces and unnumbered interfaces (see

RSVP's LIH for an example). When SNMP is supported by the PEP, this

ifindex integer MUST correspond to the same integer value for the

interface in the SNMP MIB-II interface index table.

Note: The ifindex specified in the In-Interface is typically relative

to the flow of the underlying protocol messages. The ifindex is the

interface on which the protocol message was received.

C-Num = 3

C-Type = 1, IPv4 Address + Interface

0 1 2 3

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

IPv4 Address format

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

ifindex

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

For this type of the interface object, the IPv4 address specifies the

IP address that the incoming message came from.

C-Type = 2, IPv6 Address + Interface

0 1 2 3

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

+ +

+ IPv6 Address format +

+ +

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

ifindex

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

For this type of the interface object, the IPv6 address specifies the

IP address that the incoming message came from. The ifindex is used

to refer to the MIB-II defined local incoming interface on the PEP as

described above.

2.2.4 Out-Interface Object (OUT-Int)

The Out-Interface is used to identify the outgoing interface to which

a specific request applies and the address for where the forwarded

message is to be sent. For flows or messages destined to the PEP's

local host, the loop back address and ifindex are used. The Out-

Interface has the same formats as the In-Interface Object.

This Interface object is also used to identify the outgoing

(forwarding) interface via its ifindex. The ifindex may be used to

differentiate between sub-interfaces and unnumbered interfaces (see

RSVP's LIH for an example). When SNMP is supported by the PEP, this

ifindex integer MUST correspond to the same integer value for the

interface in the SNMP MIB-II interface index table.

Note: The ifindex specified in the Out-Interface is typically

relative to the flow of the underlying protocol messages. The ifindex

is the one on which a protocol message is about to be forwarded.

C-Num = 4

C-Type = 1, IPv4 Address + Interface

Same C-Type format as the In-Interface object. The IPv4 address

specifies the IP address to which the outgoing message is going. The

ifindex is used to refer to the MIB-II defined local outgoing

interface on the PEP.

C-Type = 2, IPv6 Address + Interface

Same C-Type format as the In-Interface object. For this type of the

interface object, the IPv6 address specifies the IP address to which

the outgoing message is going. The ifindex is used to refer to the

MIB-II defined local outgoing interface on the PEP.

2.2.5 Reason Object (Reason)

This object specifies the reason why the request state was deleted.

It appears in the delete request (DRQ) message. The Reason Sub-code

field is reserved for more detailed client-specific reason codes

defined in the corresponding documents.

C-Num = 5, C-Type = 1

0 1 2 3

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

Reason-Code Reason Sub-code

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

Reason Code:

1 = Unspecified

2 = Management

3 = Preempted (Another request state takes precedence)

4 = Tear (Used to communicate a signaled state removal)

5 = Timeout (Local state has timed-out)

6 = Route Change (Change invalidates request state)

7 = Insufficient Resources (No local resource available)

8 = PDP's Directive (PDP decision caused the delete)

9 = Unsupported decision (PDP decision not supported)

10= Synchronize Handle Unknown

11= Transient Handle (stateless event)

12= Malformed Decision (could not recover)

13= Unknown COPS Object from PDP:

Sub-code (octet 2) contains unknown object's C-Num

and (octet 3) contains unknown object's C-Type.

2.2.6 Decision Object (Decision)

Decision made by the PDP. Appears in replies. The specific non-

mandatory decision objects required in a decision to a particular

request depend on the type of client.

C-Num = 6

C-Type = 1, Decision Flags (Mandatory)

0 1 2 3

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

Command-Code Flags

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

Commands:

0 = NULL Decision (No configuration data available)

1 = Install (Admit request/Install configuration)

2 = Remove (Remove request/Remove configuration)

Flags:

0x01 = Trigger Error (Trigger error message if set)

Note: Trigger Error is applicable to client-types that

are capable of sending error notifications for signaled

messages.

Flag values not applicable to a given context's R-Type or

client-type MUST be ignored by the PEP.

C-Type = 2, Stateless Data

This type of decision object carries additional stateless

information that can be applied by the PEP locally. It is a

variable length object and its internal format SHOULD be

specified in the relevant COPS extension document for the given

client-type. This object is optional in Decision messages and is

interpreted relative to a given context.

It is expected that even outsourcing PEPs will be able to make

some simple stateless policy decisions locally in their LPDP. As

this set is well known and implemented ubiquitously, PDPs are

aware of it as well (either universally, through configuration,

or using the Client-Open message). The PDP may also include this

information in its decision, and the PEP MUST apply it to the

resource allocation event that generated the request.

C-Type = 3, Replacement Data

This type of decision object carries replacement data that is to

replace existing data in a signaled message. It is a variable

length object and its internal format SHOULD be specified in the

relevant COPS extension document for the given client-type. It is

optional in Decision messages and is interpreted relative to a

given context.

C-Type = 4, Client Specific Decision Data

Additional decision types can be introduced using the Client

Specific Decision Data Object. It is a variable length object and

its internal format SHOULD be specified in the relevant COPS

extension document for the given client-type. It is optional in

Decision messages and is interpreted relative to a given context.

C-Type = 5, Named Decision Data

Named configuration information is encapsulated in this version

of the decision object in response to configuration requests. It

is a variable length object and its internal format SHOULD be

specified in the relevant COPS extension document for the given

client-type. It is optional in Decision messages and is

interpreted relative to both a given context and decision flags.

2.2.7 LPDP Decision Object (LPDPDecision)

Decision made by the PEP's local policy decision point (LPDP). May

appear in requests. These objects correspond to and are formatted the

same as the client specific decision objects defined above.

C-Num = 7

C-Type = (same C-Type as for Decision objects)

2.2.8 Error Object (Error)

This object is used to identify a particular COPS protocol error.

The error sub-code field contains additional detailed client specific

error codes. The appropriate Error Sub-codes for a particular

client-type SHOULD be specified in the relevant COPS extensions

document.

C-Num = 8, C-Type = 1

0 1 2 3

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

Error-Code Error Sub-code

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

Error-Code:

1 = Bad handle

2 = Invalid handle reference

3 = Bad message format (Malformed Message)

4 = Unable to process (server gives up on query)

5 = Mandatory client-specific info missing

6 = Unsupported client-type

7 = Mandatory COPS object missing

8 = Client Failure

9 = Communication Failure

10= Unspecified

11= Shutting down

12= Redirect to Preferred Server

13= Unknown COPS Object:

Sub-code (octet 2) contains unknown object's C-Num

and (octet 3) contains unknown object's C-Type.

14= Authentication Failure

15= Authentication Required

2.2.9 Client Specific Information Object (ClientSI)

The various types of this object are required for requests, and used

in reports and opens when required. It contains client-type specific

information.

C-Num = 9,

C-Type = 1, Signaled ClientSI.

Variable-length field. All objects/attributes specific to a client's

signaling protocol or internal state are encapsulated within one or

more signaled Client Specific Information Objects. The format of the

data encapsulated in the ClientSI object is determined by the

client-type.

C-Type = 2, Named ClientSI.

Variable-length field. Contains named configuration information

useful for relaying specific information about the PEP, a request, or

configured state to the PDP server.

2.2.10 Keep-Alive Timer Object (KATimer)

Times are encoded as 2 octet integer values and are in units of

seconds. The timer value is treated as a delta.

C-Num = 10,

C-Type = 1, Keep-alive timer value

Timer object used to specify the maximum time interval over which a

COPS message MUST be sent or received. The range of finite timeouts

is 1 to 65535 seconds represented as an unsigned two-octet integer.

The value of zero implies infinity.

0 1 2 3

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

////////////// KA Timer Value

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

2.2.11 PEP Identification Object (PEPID)

The PEP Identification Object is used to identify the PEP client to

the remote PDP. It is required for Client-Open messages.

C-Num = 11, C-Type = 1

Variable-length field. It is a NULL terminated ASCII string that is

also zero padded to a 32-bit word boundary (so the object length is a

multiple of 4 octets). The PEPID MUST contain an ASCII string that

uniquely identifies the PEP within the policy domain in a manner that

is persistent across PEP reboots. For example, it may be the PEP's

statically assigned IP address or DNS name. This identifier may

safely be used by a PDP as a handle for identifying the PEP in its

policy rules.

2.2.12 Report-Type Object (Report-Type)

The Type of Report on the request state associated with a handle:

C-Num = 12, C-Type = 1

0 1 2 3

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

Report-Type /////////////

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

Report-Type:

1 = Success : Decision was successful at the PEP

2 = Failure : Decision could not be completed by PEP

3 = Accounting: Accounting update for an installed state

2.2.13 PDP Redirect Address (PDPRedirAddr)

A PDP when closing a PEP session for a particular client-type may

optionally use this object to redirect the PEP to the specified PDP

server address and TCP port number:

C-Num = 13,

C-Type = 1, IPv4 Address + TCP Port

0 1 2 3

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

IPv4 Address format

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

///////////////////////// TCP Port Number

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

C-Type = 2, IPv6 Address + TCP Port

0 1 2 3

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

+ +

+ IPv6 Address format +

+ +

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

///////////////////////// TCP Port Number

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

2.2.14 Last PDP Address (LastPDPAddr)

When a PEP sends a Client-Open message for a particular client-type

the PEP SHOULD specify the last PDP it has successfully opened

(meaning it received a Client-Accept) since the PEP last rebooted.

If no PDP was used since the last reboot, the PEP will simply not

include this object in the Client-Open message.

C-Num = 14,

C-Type = 1, IPv4 Address (Same format as PDPRedirAddr)

C-Type = 2, IPv6 Address (Same format as PDPRedirAddr)

2.2.15 Accounting Timer Object (AcctTimer)

Times are encoded as 2 octet integer values and are in units of

seconds. The timer value is treated as a delta.

C-Num = 15,

C-Type = 1, Accounting timer value

Optional timer value used to determine the minimum interval between

periodic accounting type reports. It is used by the PDP to describe

to the PEP an acceptable interval between unsolicited accounting

updates via Report messages where applicable. It provides a method

for the PDP to control the amount of accounting traffic seen by the

network. The range of finite time values is 1 to 65535 seconds

represented as an unsigned two-octet integer. A value of zero means

there SHOULD be no unsolicited accounting updates.

0 1 2 3

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

////////////// ACCT Timer Value

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

2.2.16 Message Integrity Object (Integrity)

The integrity object includes a sequence number and a message digest

useful for authenticating and validating the integrity of a COPS

message. When used, integrity is provided at the end of a COPS

message as the last COPS object. The digest is then computed over all

of a particular COPS message up to but not including the digest value

itself. The sender of a COPS message will compute and fill in the

digest portion of the Integrity object. The receiver of a COPS

message will then compute a digest over the received message and

verify it matches the digest in the received Integrity object.

C-Num = 16,

C-Type = 1, HMAC digest

The HMAC integrity object employs HMAC (Keyed-Hashing for Message

Authentication) [HMAC] to calculate the message digest based on a key

shared between the PEP and its PDP.

This Integrity object specifies a 32-bit Key ID used to identify a

specific key shared between a particular PEP and its PDP and the

cryptographic algorithm to be used. The Key ID allows for multiple

simultaneous keys to exist on the PEP with corresponding keys on the

PDP for the given PEPID. The key identified by the Key ID was used to

compute the message digest in the Integrity object. All

implementations, at a minimum, MUST support HMAC-MD5-96, which is

HMAC employing the MD5 Message-Digest Algorithm [MD5] truncated to

96-bits to calculate the message digest.

This object also includes a sequence number that is a 32-bit unsigned

integer used to avoid replay attacks. The sequence number is

initiated during an initial Client-Open Client-Accept message

exchange and is then incremented by one each time a new message is

sent over the TCP connection in the same direction. If the sequence

number reaches the value of 0xFFFFFFFF, the next increment will

simply rollover to a value of zero.

The variable length digest is calculated over a COPS message starting

with the COPS Header up to the Integrity Object (which MUST be the

last object in a COPS message) INCLUDING the Integrity object's

header, Key ID, and Sequence Number. The Keyed Message Digest field

is not included as part of the digest calculation. In the case of

HMAC-MD5-96, HMAC-MD5 will produce a 128-bit digest that is then to

be truncated to 96-bits before being stored in or verified against

the Keyed Message Digest field as specified in [HMAC]. The Keyed

Message Digest MUST be 96-bits when HMAC-MD5-96 is used.

0 1 2 3

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

Key ID

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

Sequence Number

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

+ +

...Keyed Message Digest...

+ +

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

2.3 Communication

The COPS protocol uses a single persistent TCP connection between the

PEP and a remote PDP. One PDP implementation per server MUST listen

on a well-known TCP port number (COPS=3288 [IANA]). The PEP is

responsible for initiating the TCP connection to a PDP. The location

of the remote PDP can either be configured, or obtained via a service

location mechanism [SRVLOC]. Service discovery is outside the scope

of this protocol, however.

If a single PEP can support multiple client-types, it may send

multiple Client-Open messages, each specifying a particular client-

type to a PDP over one or more TCP connections. Likewise, a PDP

residing at a given address and port number may support one or more

client-types. Given the client-types it supports, a PDP has the

ability to either accept or reject each client-type independently.

If a client-type is rejected, the PDP can redirect the PEP to an

alternative PDP address and TCP port for a given client-type via

COPS. Different TCP port numbers can be used to redirect the PEP to

another PDP implementation running on the same server. Additional

provisions for supporting multiple client-types (perhaps from

independent PDP vendors) on a single remote PDP server are not

provided by the COPS protocol, but, rather, are left to the software

architecture of the given server platform.

It is possible a single PEP may have open connections to multiple

PDPs. This is the case when there are physically different PDPs

supporting different client-types as shown in figure 2.

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

Network Node Policy Servers

+-----+ COPS Client Type 1 +-----+

<-------------------------> PDP1

+ PEP + COPS Client Type 2 +-----+

<--------------\ +-----+

+-----+ \---------- PDP2

^ +-----+

\-->+-----+

LPDP

+-----+

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

Figure 2: Multiple PDPs illustration.

When a TCP connection is torn down or is lost, the PDP is expected to

eventually clean up any outstanding request state related to

request/decision exchanges with the PEP. When the PEP detects a lost

connection due to a timeout condition it SHOULD explicitly send a

Client-Close message for each opened client-type containing an

<Error> object indicating the "Communication Failure" Error-Code.

Additionally, the PEP SHOULD continuously attempt to contact the

primary PDP or, if unsuccessful, any known backup PDPs. Specifically

the PEP SHOULD keep trying all relevant PDPs with which it has been

configured until it can establish a connection. If a PEP is in

communication with a backup PDP and the primary PDP becomes

available, the backup PDP is responsible for redirecting the PEP back

to the primary PDP (via a <Client-Close> message containing a

<PDPRedirAddr> object identifying the primary PDP to use for each

affected client-type). Section 2.5 details synchronization behavior

between PEPs and PDPs.

2.4 Client Handle Usage

The client handle is used to identify a unique request state for a

single PEP per client-type. Client handles are chosen by the PEP and

are opaque to the PDP. The PDP simply uses the request handle to

uniquely identify the request state for a particular Client-Type over

a particular TCP connection and generically tie its decisions to a

corresponding request. Client handles are initiated in request

messages and are then used by subsequent request, decision, and

report messages to reference the same request state. When the PEP is

ready to remove a local request state, it will issue a delete message

to the PDP for the corresponding client handle. A handle MUST be

explicitly deleted by the PEP before it can be used by the PEP to

identify a new request state. Handles referring to different request

states MUST be unique within the context of a particular TCP

connection and client-type.

2.5 Synchronization Behavior

When disconnected from a PDP, the PEP SHOULD revert to making local

decisions. Once a connection is reestablished, the PEP is expected to

notify the PDP of any events that have passed local admission

control. Additionally, the remote PDP may request that all the PEP's

internal state be resynchronized (all previously installed requests

are to be reissued) by sending a Synchronize State message.

After a failure and before a new connection is fully functional,

disruption of service can be minimized if the PEP caches previously

communicated decisions and continues to use them for some appropriate

length of time. Specific rules for such behavior are to be defined in

the appropriate COPS client-type extension specifications.

A PEP that caches state from a previous exchange with a disconnected

PDP MUST communicate this fact to any PDP with which it is able to

later reconnect. This is accomplished by including the address and

TCP port of the last PDP for which the PEP is still caching state in

the Client-Open message. The <LastPDPAddr> object will only be

included for the last PDP with which the PEP was completely in sync.

If the service interruption was temporary and the PDP still contains

the complete state for the PEP, the PDP may choose not to synchronize

all states. It is still the responsibility of the PEP to update the

PDP of all state changes that occurred during the disruption of

service including any states communicated to the previous PDP that

had been deleted after the connection was lost. These MUST be

explicitly deleted after a connection is reestablished. If the PDP

issues a synchronize request the PEP MUST pass all current states to

the PDP followed by a Synchronize State Complete message (thus

completing the synchronization process). If the PEP crashes and loses

all cached state for a client-type, it will simply not include a

<LastPDPAddr> in its Client-Open message.

3. Message Content

This section describes the basic messages exchanged between a PEP and

a remote PDP as well as their contents. As a convention, object

ordering is expected as shown in the BNF for each COPS message unless

otherwise noted. The Integrity object, if included, MUST always be

the last object in a message. If security is required and a message

was received without a valid Integrity object, the receiver MUST send

a Client-Close message for Client-Type=0 specifying the appropriate

error code.

3.1 Request (REQ) PEP -> PDP

The PEP establishes a request state client handle for which the

remote PDP may maintain state. The remote PDP then uses this handle

to refer to the exchanged information and decisions communicated over

the TCP connection to a particular PEP for a given client-type.

Once a stateful handle is established for a new request, any

subsequent modifications of the request can be made using the REQ

message specifying the previously installed handle. The PEP is

responsible for notifying the PDP whenever its local state changes so

the PDP's state will be able to accurately mirror the PEP's state.

The format of the Request message is as follows:

<Request Message> ::= <Common Header>

<Client Handle>

<Context>

[<IN-Int>]

[<OUT-Int>]

[<ClientSI(s)>]

[<LPDPDecision(s)>]

[<Integrity>]

<ClientSI(s)> ::= <ClientSI> <ClientSI(s)> <ClientSI>

<LPDPDecision(s)> ::= <LPDPDecision>

<LPDPDecision(s)> <LPDPDecision>

<LPDPDecision> ::= [<Context>]

<LPDPDecision: Flags>

[<LPDPDecision: Stateless Data>]

[<LPDPDecision: Replacement Data>]

[<LPDPDecision: ClientSI Data>]

[<LPDPDecision: Named Data>]

The context object is used to determine the context within which all

the other objects are to be interpreted. It also is used to determine

the kind of decision to be returned from the policy server. This

decision might be related to admission control, resource allocation,

object forwarding and substitution, or configuration.

The interface objects are used to determine the corresponding

interface on which a signaling protocol message was received or is

about to be sent. They are typically used if the client is

participating along the path of a signaling protocol or if the client

is requesting configuration data for a particular interface.

ClientSI, the client specific information object, holds the client-

type specific data for which a policy decision needs to be made. In

the case of configuration, the Named ClientSI may include named

information about the module, interface, or functionality to be

configured. The ordering of multiple ClientSIs is not important.

Finally, LPDPDecision object holds information regarding the local

decision made by the LPDP.

Malformed Request messages MUST result in the PDP specifying a

Decision message with the appropriate error code.

3.2 Decision (DEC) PDP -> PEP

The PDP responds to the REQ with a DEC message that includes the

associated client handle and one or more decision objects grouped

relative to a Context object and Decision Flags object type pair. If

there was a protocol error an error object is returned instead.

It is required that the first decision message for a new/updated

request will have the solicited message flag set (value = 1) in the

COPS header. This avoids the issue of keeping track of which updated

request (that is, a request reissued for the same handle) a

particular decision corresponds. It is important that, for a given

handle, there be at most one outstanding solicited decision per

request. This essentially means that the PEP SHOULD NOT issue more

than one REQ (for a given handle) before it receives a corresponding

DEC with the solicited message flag set. The PDP MUST always issue

decisions for requests on a particular handle in the order they

arrive and all requests MUST have a corresponding decision.

To avoid deadlock, the PEP can always timeout after issuing a request

that does not receive a decision. It MUST then delete the timed-out

handle, and may try again using a new handle.

The format of the Decision message is as follows:

<Decision Message> ::= <Common Header>

<Client Handle>

<Decision(s)> <Error>

[<Integrity>]

<Decision(s)> ::= <Decision> <Decision(s)> <Decision>

<Decision> ::= <Context>

<Decision: Flags>

[<Decision: Stateless Data>]

[<Decision: Replacement Data>]

[<Decision: ClientSI Data>]

[<Decision: Named Data>]

The Decision message may include either an Error object or one or

more context plus associated decision objects. COPS protocol problems

are reported in the Error object (e.g. an error with the format of

the original request including malformed request messages, unknown

COPS objects in the Request, etc.). The applicable Decision object(s)

depend on the context and the type of client. The only ordering

requirement for decision objects is that the required Decision Flags

object type MUST precede the other Decision object types per context

binding.

3.3 Report State (RPT) PEP -> PDP

The RPT message is used by the PEP to communicate to the PDP its

success or failure in carrying out the PDP's decision, or to report

an accounting related change in state. The Report-Type specifies the

kind of report and the optional ClientSI can carry additional

information per Client-Type.

For every DEC message containing a configuration context that is

received by a PEP, the PEP MUST generate a corresponding Report State

message with the Solicited Message flag set describing its success or

failure in applying the configuration decision. In addition,

outsourcing decisions from the PDP MAY result in a corresponding

solicited Report State from the PEP depending on the context and the

type of client. RPT messages solicited by decisions for a given

Client Handle MUST set the Solicited Message flag and MUST be sent in

the same order as their corresponding Decision messages were

received. There MUST never be more than one Report State message

generated with the Solicited Message flag set per Decision.

The Report State may also be used to provide periodic updates of

client specific information for accounting and state monitoring

purposes depending on the type of the client. In such cases the

accounting report type should be specified utilizing the appropriate

client specific information object.

<Report State> ::== <Common Header>

<Client Handle>

<Report-Type>

[<ClientSI>]

[<Integrity>]

3.4 Delete Request State (DRQ) PEP -> PDP

When sent from the PEP this message indicates to the remote PDP that

the state identified by the client handle is no longer

available/relevant. This information will then be used by the remote

PDP to initiate the appropriate housekeeping actions. The reason code

object is interpreted with respect to the client-type and signifies

the reason for the removal.

The format of the Delete Request State message is as follows:

<Delete Request> ::= <Common Header>

<Client Handle>

<Reason>

[<Integrity>]

Given the stateful nature of COPS, it is important that when a

request state is finally removed from the PEP, a DRQ message for this

request state is sent to the PDP so the corresponding state may

likewise be removed on the PDP. Request states not explicitly deleted

by the PEP will be maintained by the PDP until either the client

session is closed or the connection is terminated.

Malformed Decision messages MUST trigger a DRQ specifying the

appropriate erroneous reason code (Bad Message Format) and any

associated state on the PEP SHOULD either be removed or re-requested.

If a Decision contained an unknown COPS Decision Object, the PEP MUST

delete its request specifying the Unknown COPS Object reason code

because the PEP will be unable to comply with the information

contained in the unknown object. In any case, after issuing a DRQ,

the PEP may retry the corresponding Request again.

3.5 Synchronize State Request (SSQ) PDP -> PEP

The format of the Synchronize State Query message is as follows:

<Synchronize State> ::= <Common Header>

[<Client Handle>]

[<Integrity>]

This message indicates that the remote PDP wishes the client (which

appears in the common header) to re-send its state. If the optional

Client Handle is present, only the state associated with this handle

is synchronized. If the PEP does not recognize the requested handle,

it MUST immediately send a DRQ message to the PDP for the handle that

was specified in the SSQ message. If no handle is specified in the

SSQ message, all the active client state MUST be synchronized with

the PDP.

The client performs state synchronization by re-issuing request

queries of the specified client-type for the existing state in the

PEP. When synchronization is complete, the PEP MUST issue a

synchronize state complete message to the PDP.

3.6 Client-Open (OPN) PEP -> PDP

The Client-Open message can be used by the PEP to specify to the PDP

the client-types the PEP can support, the last PDP to which the PEP

connected for the given client-type, and/or client specific feature

negotiation. A Client-Open message can be sent to the PDP at any time

and multiple Client-Open messages for the same client-type are

allowed (in case of global state changes).

<Client-Open> ::= <Common Header>

<PEPID>

[<ClientSI>]

[<LastPDPAddr>]

[<Integrity>]

The PEPID is a symbolic, variable length name that uniquely

identifies the specific client to the PDP (see Section 2.2.11).

A named ClientSI object can be included for relaying additional

global information about the PEP to the PDP when required (as

specified in the appropriate extensions document for the client-

type).

The PEP may also provide a Last PDP Address object in its Client-Open

message specifying the last PDP (for the given client-type) for which

it is still caching decisions since its last reboot. A PDP can use

this information to determine the appropriate synchronization

behavior (See section 2.5).

If the PDP receives a malformed Client-Open message it MUST generate

a Client-Close message specifying the appropriate error code.

3.7 Client-Accept (CAT) PDP -> PEP

The Client-Accept message is used to positively respond to the

Client-Open message. This message will return to the PEP a timer

object indicating the maximum time interval between keep-alive

messages. Optionally, a timer specifying the minimum allowed interval

between accounting report messages may be included when applicable.

<Client-Accept> ::= <Common Header>

<KA Timer>

[<ACCT Timer>]

[<Integrity>]

If the PDP refuses the client, it will instead issue a Client-Close

message.

The KA Timer corresponds to maximum acceptable intermediate time

between the generation of messages by the PDP and PEP. The timer

value is determined by the PDP and is specified in seconds. A timer

value of 0 implies no secondary connection verification is necessary.

The optional ACCT Timer allows the PDP to indicate to the PEP that

periodic accounting reports SHOULD NOT exceed the specified timer

interval per client handle. This allows the PDP to control the rate

at which accounting reports are sent by the PEP (when applicable).

In general, accounting type Report messages are sent to the PDP when

determined appropriate by the PEP. The accounting timer merely is

used by the PDP to keep the rate of such updates in check (i.e.

Preventing the PEP from blasting the PDP with accounting reports).

Not including this object implies there are no PDP restrictions on

the rate at which accounting updates are generated.

If the PEP receives a malformed Client-Accept message it MUST

generate a Client-Close message specifying the appropriate error

code.

3.8 Client-Close (CC) PEP -> PDP, PDP -> PEP

The Client-Close message can be issued by either the PDP or PEP to

notify the other that a particular type of client is no longer being

supported.

<Client-Close> ::= <Common Header>

<Error>

[<PDPRedirAddr>]

[<Integrity>]

The Error object is included to describe the reason for the close

(e.g. the requested client-type is not supported by the remote PDP or

client failure).

A PDP MAY optionally include a PDP Redirect Address object in order

to inform the PEP of the alternate PDP it SHOULD use for the client-

type specified in the common header.

3.9 Keep-Alive (KA) PEP -> PDP, PDP -> PEP

The keep-alive message MUST be transmitted by the PEP within the

period defined by the minimum of all KA Timer values specified in all

received CAT messages for the connection. A KA message MUST be

generated randomly between 1/4 and 3/4 of this minimum KA timer

interval. When the PDP receives a keep-alive message from a PEP, it

MUST echo a keep-alive back to the PEP. This message provides

validation for each side that the connection is still functioning

even when there is no other messaging.

Note: The client-type in the header MUST always be set to 0 as the KA

is used for connection verification (not per client session

verification).

<Keep-Alive> ::= <Common Header>

[<Integrity>]

Both client and server MAY assume the TCP connection is insufficient

for the client-type with the minimum time value (specified in the CAT

message) if no communication activity is detected for a period

exceeding the timer period. For the PEP, such detection implies the

remote PDP or connection is down and the PEP SHOULD now attempt to

use an alternative/backup PDP.

3.10 Synchronize State Complete (SSC) PEP -> PDP

The Synchronize State Complete is sent by the PEP to the PDP after

the PDP sends a synchronize state request to the PEP and the PEP has

finished synchronization. It is useful so that the PDP will know when

all the old client state has been successfully re-requested and,

thus, the PEP and PDP are completely synchronized. The Client Handle

object only needs to be included if the corresponding Synchronize

State Message originally referenced a specific handle.

<Synchronize State Complete> ::= <Common Header>

[<Client Handle>]

[<Integrity>]

4. Common Operation

This section describes the typical exchanges between remote PDP

servers and PEP clients.

4.1 Security and Sequence Number Negotiation

COPS message security is negotiated once per connection and covers

all communication over a particular connection. If COPS level

security is required, it MUST be negotiated during the initial

Client-Open/Client-Accept message exchange specifying a Client-Type

of zero (which is reserved for connection level security negotiation

and connection verification).

If a PEP is not configured to use COPS security with a PDP it will

simply send the PDP Client-Open messages for the supported Client-

Types as specified in section 4.3 and will not include the Integrity

object in any COPS messages.

Otherwise, security can be initiated by the PEP if it sends the PDP a

Client-Open message with Client-Type=0 before opening any other

Client-Type. If the PDP receives a Client-Open with a Client-Type=0

after another Client-Type has already been opened successfully it

MUST return a Client-Close message (for Client-Type=0) to that PEP.

This first Client-Open message MUST specify a Client-Type of zero and

MUST provide the PEPID and a COPS Integrity object. This Integrity

object will contain the initial sequence number the PEP requires the

PDP to increment during subsequent communication after the initial

Client-Open/Client-Accept exchange and the Key ID identifying the

algorithm and key used to compute the digest.

Similarly, if the PDP accepts the PEP's security key and algorithm by

validating the message digest using the identified key, the PDP MUST

send a Client-Accept message with a Client-Type of zero to the PEP

carrying an Integrity object. This Integrity object will contain the

initial sequence number the PDP requires the PEP to increment during

all subsequent communication with the PDP and the Key ID identifying

the key and algorithm used to compute the digest.

If the PEP, from the perspective of a PDP that requires security,

fails or never performs the security negotiation by not sending an

initial Client-Open message with a Client-Type=0 including a valid

Integrity object, the PDP MUST send to the PEP a Client-Close message

with a Client-Type=0 specifying the appropriate error code.

Similarly, if the PDP, from the perspective of a PEP that requires

security, fails the security negotiation by not sending back a

Client-Accept message with a Client-Type=0 including a valid

Integrity object, the PEP MUST send to the PDP a Client-Close message

with a Client-Type=0 specifying the appropriate error code. Such a

Client-Close message need not carry an integrity object (as the

security negotiation did not yet complete).

The security initialization can fail for one of several reasons: 1.

The side receiving the message requires COPS level security but an

Integrity object was not provided (Authentication Required error

code). 2. A COPS Integrity object was provided, but with an

unknown/unacceptable C-Type (Unknown COPS Object error code

specifying the unsupported C-Num and C-Type). 3. The message digest

or Key ID in the provided Integrity object was incorrect and

therefore the message could not be authenticated using the identified

key (Authentication Failure error code).

Once the initial security negotiation is complete, the PEP will know

what sequence numbers the PDP expects and the PDP will know what

sequence numbers the PEP expects. ALL COPS messages must then include

the negotiated Integrity object specifying the correct sequence

number with the appropriate message digest (including the Client-

Open/Client-Accept messages for specific Client-Types). ALL

subsequent messages from the PDP to the PEP MUST result in an

increment of the sequence number provided by the PEP in the Integrity

object of the initial Client-Open message. Likewise, ALL subsequent

messages from the PEP to the PDP MUST result in an increment of the

sequence number provided by the PDP in the Integrity object of the

initial Client-Accept message. Sequence numbers are incremented by

one starting with the corresponding initial sequence number. For

example, if the sequence number specified to the PEP by the PDP in

the initial Client-Accept was 10, the next message the PEP sends to

the PDP will provide an Integrity object with a sequence number of

11... Then the next message the PEP sends to the PDP will have a

sequence number of 12 and so on. If any subsequent received message

contains the wrong sequence number, an unknown Key ID, an invalid

message digest, or is missing an Integrity object after integrity was

negotiated, then a Client-Close message MUST be generated for the

Client-Type zero containing a valid Integrity object and specifying

the appropriate error code. The connection should then be dropped.

4.2 Key Maintenance

Key maintenance is outside the scope of this document, but COPS

implementations MUST at least provide the ability to manually

configure keys and their parameters locally. The key used to produce

the Integrity object's message digest is identified by the Key ID

field. Thus, a Key ID parameter is used to identify one of

potentially multiple simultaneous keys shared by the PEP and PDP. A

Key ID is relative to a particular PEPID on the PDP or to a

particular PDP on the PEP. Each key must also be configured with

lifetime parameters for the time period within which it is valid as

well as an associated cryptographic algorithm parameter specifying

the algorithm to be used with the key. At a minimum, all COPS

implementations MUST support the HMAC-MD5-96 [HMAC][MD5]

cryptographic algorithm for computing a message digest for inclusion

in the Keyed Message Digest of the Integrity object which is appended

to the message.

It is good practice to regularly change keys. Keys MUST be

configurable such that their lifetimes overlap allowing smooth

transitions between keys. At the midpoint of the lifetime overlap

between two keys, senders should transition from using the current

key to the next/longer-lived key. Meanwhile, receivers simply accept

any identified key received within its configured lifetime and reject

those that are not.

4.3 PEP Initialization

Sometime after a connection is established between the PEP and a

remote PDP and after security is negotiated (if required), the PEP

will send one or more Client-Open messages to the remote PDP, one for

each client-type supported by the PEP. The Client-Open message MUST

contain the address of the last PDP with which the PEP is still

caching a complete set of decisions. If no decisions are being cached

from the previous PDP the LastPDPAddr object MUST NOT be included in

the Client-Open message (see Section 2.5). Each Client-Open message

MUST at least contain the common header noting one client-type

supported by the PEP. The remote PDP will then respond with separate

Client-Accept messages for each of the client-types requested by the

PEP that the PDP can also support.

If a specific client-type is not supported by the PDP, the PDP will

instead respond with a Client-Close specifying the client-type is not

supported and will possibly suggest an alternate PDP address and

port. Otherwise, the PDP will send a Client-Accept specifying the

timer interval between keep-alive messages and the PEP may begin

issuing requests to the PDP.

4.4 Outsourcing Operations

In the outsourcing scenario, when the PEP receives an event that

requires a new policy decision it sends a request message to the

remote PDP. What specifically qualifies as an event for a particular

client-type SHOULD be specified in the specific document for that

client-type. The remote PDP then makes a decision and sends a

decision message back to the PEP. Since the request is stateful, the

request will be remembered, or installed, on the remote PDP. The

unique handle (unique per TCP connection and client-type), specified

in both the request and its corresponding decision identifies this

request state. The PEP is responsible for deleting this request state

once the request is no longer applicable.

The PEP can update a previously installed request state by reissuing

a request for the previously installed handle. The remote PDP is then

expected to make new decisions and send a decision message back to

the PEP. Likewise, the server MAY change a previously issued decision

on any currently installed request state at any time by issuing an

unsolicited decision message. At all times the PEP module is expected

to abide by the PDP's decisions and notify the PDP of any state

changes.

4.5 Configuration Operations

In the configuration scenario, as in the outsourcing scenario, the

PEP will make a configuration request to the PDP for a particular

interface, module, or functionality that may be specified in the

named client specific information object. The PDP will then send

potentially several decisions containing named units of configuration

data to the PEP. The PEP is expected to install and use the

configuration locally. A particular named configuration can be

updated by simply sending additional decision messages for the same

named configuration. When the PDP no longer wishes the PEP to use a

piece of configuration information, it will send a decision message

specifying the named configuration and a decision flags object with

the remove configuration command. The PEP SHOULD then proceed to

remove the corresponding configuration and send a report message to

the PDP that specifies it has been deleted.

In all cases, the PEP MAY notify the remote PDP of the local status

of an installed state using the report message where appropriate.

The report message is to be used to signify when billing can begin,

what actions were taken, or to produce periodic updates for

monitoring and accounting purposes depending on the client. This

message can carry client specific information when needed.

4.6 Keep-Alive Operations

The Keep-Alive message is used to validate the connection between the

client and server is still functioning even when there is no other

messaging from the PEP to PDP. The PEP MUST generate a COPS KA

message randomly within one-fourth to three-fourths the minimum KA

Timer interval specified by the PDP in the Client-Accept message. On

receiving a Keep-Alive message from the PEP, the PDP MUST then

respond to this Keep-Alive message by echoing a Keep-Alive message

back to the PEP. If either side does not receive a Keep-Alive or any

other COPS message within the minimum KA Timer interval from the

other, the connection SHOULD be considered lost.

4.7 PEP/PDP Close

Finally, Client-Close messages are used to negate the effects of the

corresponding Client-Open messages, notifying the other side that the

specified client-type is no longer supported/active. When the PEP

detects a lost connection due to a keep-alive timeout condition it

SHOULD explicitly send a Client-Close message for each opened

client-type specifying a communications failure error code. Then the

PEP MAY proceed to terminate the connection to the PDP and attempt to

reconnect again or try a backup/alternative PDP. When the PDP is

shutting down, it SHOULD also explicitly send a Client-Close to all

connected PEPs for each client-type, perhaps specifying an

alternative PDP to use instead.

5. Security Considerations

The COPS protocol provides an Integrity object that can achieve

authentication, message integrity, and replay prevention. All COPS

implementations MUST support the COPS Integrity object and its

mechanisms as described in this document. To ensure the client (PEP)

is communicating with the correct policy server (PDP) requires

authentication of the PEP and PDP using a shared secret, and

consistent proof that the connection remains valid. The shared secret

minimally requires manual configuration of keys (identified by a Key

ID) shared between the PEP and its PDP. The key is used in

conjunction with the contents of a COPS message to calculate a

message digest that is part of the Integrity object. The Integrity

object is then used to validate all COPS messages sent over the TCP

connection between a PEP and PDP.

Key maintenance is outside the scope of this document beyond the

specific requirements discussed in section 4.2. In general, it is

good practice to regularly change keys to maintain security.

Furthermore, it is good practice to use localized keys specific to a

particular PEP such that a stolen PEP will not compromise the

security of an entire administrative domain.

The COPS Integrity object also provides sequence numbers to avoid

replay attacks. The PDP chooses the initial sequence number for the

PEP and the PEP chooses the initial sequence number for the PDP.

These initial numbers are then incremented with each successive

message sent over the connection in the corresponding direction. The

initial sequence numbers SHOULD be chosen such that they are

monotonically increasing and never repeat for a particular key.

Security between the client (PEP) and server (PDP) MAY be provided by

IP Security [IPSEC]. In this case, the IPSEC Authentication Header

(AH) SHOULD be used for the validation of the connection;

additionally IPSEC Encapsulation Security Payload (ESP) MAY be used

to provide both validation and secrecy.

Transport Layer Security [TLS] MAY be used for both connection-level

validation and privacy.

6. IANA Considerations

The Client-type identifies the policy client application to which a

message refers. Client-type values within the range 0x0001-0x3FFF are

reserved Specification Required status as defined in [IANA-

CONSIDERATIONS]. These values MUST be registered with IANA and their

behavior and applicability MUST be described in a COPS extension

document.

Client-type values in the range 0x4000 - 0x7FFF are reserved for

Private Use as defined in [IANA-CONSIDERATIONS]. These Client-types

are not tracked by IANA and are not to be used in standards or

general-release products, as their uniqueness cannot be assured.

Client-type values in the range 0x8000 - 0xFFFF are First Come First

Served as defined in [IANA-CONSIDERATIONS]. These Client-types are

tracked by IANA but do not require published documents describing

their use. IANA merely assures their uniqueness.

Objects in the COPS Protocol are identified by their C-Num and C-Type

values. IETF Consensus as identified in [IANA-CONSIDERATIONS] is

required to introduce new values for these numbers and, therefore,

new objects into the base COPS protocol.

Additional Context Object R-Types, Reason-Codes, Report-Types,

Decision Object Command-Codes/Flags, and Error-Codes MAY be defined

for use with future Client-types, but such additions require IETF

Consensus as defined in [IANA-CONSIDERATIONS].

Context Object M-Types, Reason Sub-Codes, and Error Sub-codes MAY be

defined relative to a particular Client-type following the same IANA

considerations as their respective Client-type.

7. References

[RSVP] Braden, R., Zhang, L., Berson, S., Herzog, S.

and S. Jamin, "Resource ReSerVation Protocol

(RSVP) Version 1 - Functional Specification",

RFC2205, September 1997.

[WRK] Yavatkar, R., Pendarakis, D. and R. Guerin, "A

Framework for Policy-Based Admission Control",

RFC2753, January 2000.

[SRVLOC] Guttman, E., Perkins, C., Veizades, J. and M.

Day, "Service Location Protocol , Version 2",

RFC2608, June 1999.

[INSCH] Shenker, S. and J. Wroclawski, "General

Characterization Parameters for Integrated

Service Network Elements", RFC2215, September

1997.

[IPSEC] Atkinson, R., "Security Architecture for the

Internet Protocol", RFC2401, August 1995.

[HMAC] Krawczyk, H., Bellare, M. and R. Canetti,

"HMAC: Keyed-Hashing for Message

Authentication", RFC2104, February 1997.

[MD5] Rivest, R., "The MD5 Message-Digest Algorithm",

RFC1321, April 1992.

[RSVPPR] Braden, R. and L. Zhang, "Resource ReSerVation

Protocol (RSVP) - Version 1 Message Processing

Rules", RFC2209, September 1997.

[TLS] Dierks T. and C. Allen, "The TLS Protocol

Version 1.0", RFC2246, January 1999.

[IANA] http://www.isi.edu/in-

notes/iana/assignments/port-numbers

[IANA-CONSIDERATIONS] Alvestrand, H. and T. Narten, "Guidelines for

Writing an IANA Considerations Section in

RFCs", BCP 26, RFC2434, October 1998.

8. Author Information and Acknowledgments

Special thanks to Andrew Smith and Timothy O'Malley our WG Chairs,

Raj Yavatkar, Russell Fenger, Fred Baker, Laura Cunningham, Roch

Guerin, Ping Pan, and Dimitrios Pendarakis for their valuable

contributions.

Jim Boyle

Level 3 Communications

1025 Eldorado Boulevard

Broomfield, CO 80021

Phone: 720.888.1192

EMail: jboyle@Level3.net

Ron Cohen

CISCO Systems

4 Maskit St.

Herzeliya Pituach 46766 Israel

Phone: +972.9.9700064

EMail: ronc@cisco.com

David Durham

Intel

2111 NE 25th Avenue

Hillsboro, OR 97124

Phone: 503.264.6232

EMail: David.Durham@intel.com

Raju Rajan

AT&T Shannon Laboratory

180 Park Avenue

P.O. Box 971

Florham Park, NJ 07932-0971

EMail: rajan@research.att.com

Shai Herzog

IPHighway, Inc.

55 New York Avenue

Framingham, MA 01701

Phone: 508.620.1141

EMail: herzog@iphighway.com

Arun Sastry

Cisco Systems

4 The Square

Stockley Park

Uxbridge, Middlesex UB11 1BN

UK

Phone: +44-208-756-8693

EMail: asastry@cisco.com

9. Full Copyright Statement

Copyright (C) The Internet Society (2000). 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.

 
 
 
免责声明:本文为网络用户发布,其观点仅代表作者个人观点,与本站无关,本站仅提供信息存储服务。文中陈述内容未经本站证实,其真实性、完整性、及时性本站不作任何保证或承诺,请读者仅作参考,并请自行核实相关内容。
2023年上半年GDP全球前十五强
 百态   2023-10-24
美众议院议长启动对拜登的弹劾调查
 百态   2023-09-13
上海、济南、武汉等多地出现不明坠落物
 探索   2023-09-06
印度或要将国名改为“巴拉特”
 百态   2023-09-06
男子为女友送行,买票不登机被捕
 百态   2023-08-20
手机地震预警功能怎么开?
 干货   2023-08-06
女子4年卖2套房花700多万做美容:不但没变美脸,面部还出现变形
 百态   2023-08-04
住户一楼被水淹 还冲来8头猪
 百态   2023-07-31
女子体内爬出大量瓜子状活虫
 百态   2023-07-25
地球连续35年收到神秘规律性信号,网友:不要回答!
 探索   2023-07-21
全球镓价格本周大涨27%
 探索   2023-07-09
钱都流向了那些不缺钱的人,苦都留给了能吃苦的人
 探索   2023-07-02
倩女手游刀客魅者强控制(强混乱强眩晕强睡眠)和对应控制抗性的关系
 百态   2020-08-20
美国5月9日最新疫情:美国确诊人数突破131万
 百态   2020-05-09
荷兰政府宣布将集体辞职
 干货   2020-04-30
倩女幽魂手游师徒任务情义春秋猜成语答案逍遥观:鹏程万里
 干货   2019-11-12
倩女幽魂手游师徒任务情义春秋猜成语答案神机营:射石饮羽
 干货   2019-11-12
倩女幽魂手游师徒任务情义春秋猜成语答案昆仑山:拔刀相助
 干货   2019-11-12
倩女幽魂手游师徒任务情义春秋猜成语答案天工阁:鬼斧神工
 干货   2019-11-12
倩女幽魂手游师徒任务情义春秋猜成语答案丝路古道:单枪匹马
 干货   2019-11-12
倩女幽魂手游师徒任务情义春秋猜成语答案镇郊荒野:与虎谋皮
 干货   2019-11-12
倩女幽魂手游师徒任务情义春秋猜成语答案镇郊荒野:李代桃僵
 干货   2019-11-12
倩女幽魂手游师徒任务情义春秋猜成语答案镇郊荒野:指鹿为马
 干货   2019-11-12
倩女幽魂手游师徒任务情义春秋猜成语答案金陵:小鸟依人
 干货   2019-11-12
倩女幽魂手游师徒任务情义春秋猜成语答案金陵:千金买邻
 干货   2019-11-12
 
推荐阅读
 
 
 
>>返回首頁<<
 
靜靜地坐在廢墟上,四周的荒凉一望無際,忽然覺得,淒涼也很美
© 2005- 王朝網路 版權所有