Chapter 29 Ip Policy Routing; Ip Policy Routing Overview; Benefits Of Ip Policy Routing; Routing Policy - ZyXEL Communications Prestige 861H-G1 User Manual

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

29.1 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.

29.2 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.

29.3 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.

29.4 IP Routing Policy Setup

Menu 25 shows all the policies defined.
IP Policy Routing
Prestige 861H User's Guide
Chapter 29
IP Policy Routing
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