ZyXEL ADSL Prestige 2602R-61 VoIP 91-006-024004B Manual Do Utilizador

Prestige 2602R Series User’s Guide

Chapter 36 IP Policy Routing

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This chapter covers setting and applying policies used for IP routing.

Traditionally, routing is based on the destination address only and the IAD takes the shortest 
path to forward a packet. IP Routing Policy (IPPR) provides a mechanism to override the 
default routing behavior and alter the packet forwarding based on the policy defined by the 
network administrator. Policy-based routing is applied to incoming packets on a per interface 
basis, prior to the normal routing.

Source-Based Routing – Network administrators can use policy-based routing to direct traffic 
from different users through different connections.

Quality of Service (QoS) – Organizations can differentiate traffic by setting the precedence or 
TOS (Type of Service)  values in the IP header at the periphery of the network to enable the 
backbone to prioritize traffic.

Cost Savings – IPPR allows organizations to distribute interactive traffic on high-bandwidth, 
high-cost paths while using low-cost paths for batch traffic.

Load Sharing – Network administrators can use IPPR to distribute traffic among multiple 
paths.

Individual routing policies are used as part of the overall IPPR process. A policy defines the 
matching criteria and the action to take when a packet meets the criteria. The action is taken 
only when all the criteria are met. The criteria includes the source address and port, IP protocol 
(ICMP, UDP, TCP, etc.), destination address and port, TOS and precedence (fields in the IP 
header) and length. The inclusion of length criterion is to differentiate between interactive and 
bulk traffic. Interactive applications, for example, telnet, tend to have short packets, while bulk 
traffic, for example, file transfer, tends to have large packets.

The actions that can be taken include: