Chapter 40 Ip Policy Routing; Ip Policy Routing Overview; Benefits Of Ip Policy Routing; Routing Policy - ZyXEL Communications Prestige 662HW Series User Manual

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

40.1 IP Policy Routing Overview

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.

40.2 Benefits of IP Policy 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.

40.3 Routing Policy

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:
•
routing the packet to a different gateway (and hence the outgoing interface).
•
setting the TOS and precedence fields in the IP header.
IPPR follows the existing packet filtering facility of RAS in style and in implementation. The policies
are divided into sets, where related policies are grouped together. A user defines the policies before
applying them to an interface or a remote node, in the same fashion as the filters. There are 12 policy
sets with six policies in each set.
IP Policy Routing
Prestige 662HW Series User's Guide
Chapter 40
IP Policy Routing
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