Znyx-networks bh5700 Manuel d'utilisateur télécharger pdf (Page 71)

• The PDP sends that policy to the PEP.

• The PEP installs the policy and applies it to future traffic.

As long as COPS is running, a connection between the PEP and PDP should stay open. A PEP

could query a PDP at any time asking for a policy decision. Alternatively, an administrator could

modify the policy on a PDP, which would then push any policy changes to its PEPs.

Protocol Architecture

The COPS protocol is broken into several components. The base layer is the COPS protocol

itself, which defines the messaging format. This protocol defines how communication is handled

without specifying the details of the message data.

The base COPS protocol is then used by different client types. These client types apply the COPS

messaging scheme to particular types of data. The currently standardized client types deal with

the RSVP model (COPS-RSVP) and provisioning model (COPS-PR).

The COPS-RSVP scheme is designed around the requirement that a PEP will have to query a

PDP in response to events. An RSVP PEP is constantly listening for resource reservation requests

and relaying those requests to its PDP.

By contrast, the provisioning model is based on longer lasting policy. The expectation is that

policy should be administratively defined at the PDP and pushed to the PEPs as needed.

OpenArchitect is a COPS-PR client.

The most common use of COPS-PR is for distributing Differentiated Services (Diffserv) policy.

Diffserv is concerned with such Quality of Service elements as queues and schedulers.

OpenArchitect PEP

The OpenArchitect PEP implementation is known as pepd. The pepd utility is based on:

RFC 2478: Common Open Policy Service (COPS)

RFC 3084: COPS Usage for Policy Provisioning

RFC 3159: Structure of Policy Provisioning Information

RFC 3289: Management Information Base (MIB) for the Differentiated Services Architecture

Internet Draft: Differentiated Services Quality of Service Policy Information Base (latest version

draft-ietf-diffserv-pib-09)

Internet Draft: Framework Policy Information Base (latest version draft-ietf-rap-frameworkpib-

09)

A Policy Information Base (PIB) defines the representation of a particular data set. For example,

the Diffserv PIB specifies the structures used to represent all Diffserv elements. PIBs are

functionally equivalent to Management Information Bases (MIBs) such as those used by SNMP.

The OA PEP has implemented those portions of the Diffserv and Framework PIBs that are

supported by the underlying switch architecture.

Ethernet Switch Blade User's Guide release 3.2.2j page 71

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Znyx-networks bh5700 Manuel d'utilisateur Page 71