COPS and RAP Overview Raj Yavatkar, Intel (on behalf of the RAP - - PowerPoint PPT Presentation

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Mar 01, 2023 384 likes •579 views

COPS and RAP Overview Raj Yavatkar, Intel (on behalf of the RAP working group) 9/10/98 Policy BOF, Chicago IETF 1 Outline Background on RAP working group COPS Overview Use of COPS with RSVP Use of COPS with Diff-Serv Policy

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COPS and RAP Overview

Raj Yavatkar, Intel (on behalf of the RAP working group)

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Outline

■ Background on RAP working group ■ COPS Overview ■ Use of COPS with RSVP ■ Use of COPS with Diff-Serv

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Background

■ RAP working group

– Specify a framework for providing policy-based control

ver QoS admission control decisions

– focus on policy-based control over admission control using RSVP – allow for policy-based admission control in other QoS contexts, whenever possible – support for monitoring and accounting – drafts

draft-ietf-rap-framework-01.txt
draft-ietf-rap-cops-02.txt, draft-ietf-rap-cops-ds-

00.txt, draft-ietf-rap-user-identity-00.txt

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Architectural Elements

PEP PDP PEP -- Policy Enforcement Point; decisions are enforced here PDP -- makes policy decisions/pushes policy configuration

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Interaction between PEP, PDP

■ Two types of operations performed by PEPs

– Outsource decisions

When PEP requires a policy decision, PEP

contacts PDP for a policy decision

Request contains policy elements and

admission control information (e.g., flowspec).

PDP returns policy decision and additional info

– Configuration requests

PDP configures PEP with device-specific policy

information

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LDAP Auth. server SNMP

PDP itself may use other services/protocols such as

LDAP for accessing policy database, an authentication server for user authentication, SNMP for configuration/mgmt, etc.

PEP always runs on a policy-aware node

PEP PDP COPS

Topology and Policy Database

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COPS (Common Open Policy Service)

■ A request-response protocol for PEP-PDP

interaction

– uses TCP for transport – its own Keep-Alives to detect failures – includes a state synchronization mechanism to handle recovery from failures, etc. – PDP can send an asynchronous notification to PEP when policy decision or configured information changes (e.g., preemption) – facilities to report status, stats, monitoring info

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PEP PDP

Request (handle) Decision (handle) Time Decision(handle)

COPS

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Example of a COPS Session

■ PEP opens a COPS session

– specifies ClientType

■ PEP sends requests and receives

responses/decisions

– a handle associated with each request

■ PDP can send Unsolicited Decisions any time to

change previously installed state(s) at PEP

■ PEP sends back report messages to report resource

usage and accounting info

■ KeepAlive messages sent when no activity

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Use of COPS with RSVP/Intserv

Outsourcing request/response (COPS) RSVP RESV Policy server (PDP) RSVP router Next hop

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Use of COPS with Diff-Serv

■ Edge routers (ERs) rely on BB/PDP to make

policy decisions

– No explicit e2e signaling to ER to trigger policy decision (ex., IP telephony call setup) – provides a way to configure ERs with a list of packet filters and accompanying actions – provides a way to asynchronously notify ERs about changes to filters/actions – allows ERs to log usage/accounting info

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BB/PDP ER ER ER

BB/PDP

BR BR

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Use of COPS for Diffserv (contd.)

■ Use the configuration operation in COPS ■ Example of Interaction:

– PEP opens COPS session with ClientType=DiffServ – PEP requests a filter list

response: Filter list -- <filter criteria, action>+
policy tree defined for data format

– BB/PDP can update the filter list any time using unsolicited response – PEP notifies BB/PDP of status/usage via report messages

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ER BB/PDP

Open (ClientType = DiffServ) Time Request (handle) Unsolicited Response(handle, chnages) Response (handle, filter list) Report (handle)

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Backup

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Points

■ Support for preemption

– e.g., remove previously installed reservations

■ Support for many styles of policies

– relative priority, bi-lateral, multi-lateral – Scalability:

not necessary to contact PDP at each node

■ Provision for monitoring and accounting ■ Fault tolerance/recovery (PDP failures,

partitions and merging, etc.)

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