Side_1_360

To get access to a service, the user sends a ser-

vice request to the AAA server. This checks the

authorisation of the user and, assuming access

is granted, forwards the necessary information

(Application Specific Information, ASI) to the

ASM. The ASM finds the information relevant

for configuration of the network resources (ser-

vice equipment) and distributes this information

to the network nodes. In case of DiffServ, the

accounting system, QoS control, and Bandwidth

Broker are noted.

5 Policy and Traffic

Engineering

Considering the heterogeneous network ele-

ments and traffic flows that are expected to be

observed, a number of high-level requirements

are placed on the management solutions:

• Automation of management task;
  
  
  • Centralised management with fewer classes of
    management interfaces;
  
  
  • Abstracted (or simplified) management data;
  
  
  • End-to-end provisioning of the network;
  
  
  • Consistent and uniform provisioning across all
    network elements;
  
  
  • Standards-based solutions in order to allow
    inter-operability at network element and OSS
    level;
  
  
  • Scalable solution for large networks.
  
  
  
  

The IETF Policy Management Framework has

been devised keeping these requirements in

mind.

5.1 Policy – What is it?

Policy can be considered as a set of principles

for usage of resources, given by business con-

siderations. That is, the business decisions are

translated into statements relevant for the usage

of resources in the network.

The semantics of a policy ruleis a conditional

imperative statement in the form

if <condition> then <action>

Thus, applying a rule means to evaluate its con-

dition (matching the rule) and, depending on the

outcome of that, either execute the action or not.

Policy rules may be nested.

Policy-based network management would pro-

vide a centralised platform for network man-

agers for defining and distributing network poli-

cies to enforcement points throughout a network.

In a typical policy-based framework, see Figure

Figure 9 Policy-based
integrated accounting,
using DiffServ

Figure 10 Policy Framework
components and protocols

AAA server

ASM

Bandwidth

Broker

QoS auditing

control

Accounting

configuration

Measurement infrastructure

accounting

policies

policy parameters

QoS-related

policies bandwidth

request

meter

instruction

measurement

setup

other

bandwidth

brokers

service request

user

service

equipment

ASI

Policy

Repository

Policy Entry Console

Policy

Decision Point

(Policy Server)

(PDP)

LDAP

LDAP

COPS

Policy Enforcement

Points (PEPs)