Side_1_360

Signalling PEP PDP Other servers

Admission

control

LPDP

Packet

classifier

Packet

scheduler

Router

the framework being standardised in the IETF

Policy Working Group. COPS is a query res-

ponse protocol used to exchange policy informa-

tion between a policy server and a set of clients.

The PEP reports all its role combinations to the

PDP in the initial COPS request message. This is

also done in subsequent request messages gener-

ated in response to COPS state synchronisation

requests and local configuration changes. A pol-

icy can then be given for each role combination.

COPS may also be used between Bandwidth

Brokers, which essentially act as PDPs for

dynamic interdomain policy exchange (see

Section 5.6.1).

Policy Management Function provides the inter-

face to the network manager. It comprises func-

tions of policy editing, rules translation and vali-

dation. With the Policy Editor the administrator

can enter, view and edit policy rules in the Pol-

icy Repository.

Once a policy rule has been entered into the Edi-

tor and before it is stored in the repository, sim-

ple validation is performed that checks for

potential policy conflicts with other rules. Rule

translation will resolve high level description

into the specific parameters. An example is

translation from names to IP addresses.

Policy Repository is a rule storage that is used

for policy retrieval performed by the Policy

Decision Points. The repository is also accessed

in the rule validation process to detect conflicts.

Access to the database is accomplished by a

repository access protocol.

An architecture for QoS provisioning is des-

cribed in [eTOM]. This is depicted in Figure 15.

The network management system keeps the view

of the total network, including functions like:

possibly sending a request to a PDP. This is

depicted in Figure 13.

Figure 13 shows an example of relating traffic

control/signalling and PEP/PDP. When a sig-

nalling message arrives at a router, the signalling

module has to direct the request to the PEP. The

PEP asks PDP and LPDP (PDP may override a

policy given by LPDP) for decisions and returns

the reply to the signalling module. Note that a

PDP may also send notifications to a PEP based

on other triggers, for instance to change previous

decisions. In addition to PEP and PDP, reposi-

tion and management are needed, ref. Figure 14.

The Resource Allocation (RAP) Working Group

(WG) is establishing a scalable policy control

model for RSVP and IntServ by specifying a

protocol for use among RSVP-capable network

nodes and policy servers. In addition, this WG is

planning to define directives for use of the Com-

mon Open Policy Service (COPS) base protocol

to support policy information exchange within

Figure 13 Relationships
between policy points and
other traffic control
components

Figure 14 Reference Model
of Policy Framework

Policy Repository

Policy Decision Function

Policy Enforcement Function

Policy Management Function

Repository access

protocol

Repository access

protocol, e.g. LDAP

Policy transfer protocol,

e.g. COPS, RSVP