Motorola 7000, 3352N, 3342, 2200 Policy-based Routing using Filtersets, TOS field matching, 177

Policy-based Routing using Filtersets

Netopia Embedded Software Version 7.7.4 offers the ability to route IP packets using criteria other than the destination IP address. This is called policy-based routing.

You specify the routing criteria and routing information by using IP filtersets to determine the forwarding action of a particular filter.

You specify a gateway IP address, and each packet matching the filter is routed according to that gateway address, rather than by means of the global routing table.

In addition, the classifier list in a filter includes the TOS field. This allows you to filter on TOS field settings in the IP packet, if you want.

To use the policy-based routing feature, you create a filter that forwards the traffic.

•Check the Forward checkbox. This will display the Force Rout- ing options.

•Check the Force Route checkbox.

•Enter the Gateway IP address in standard dotted-quad nota- tion to which the traffic should be forwarded.

•You can enter Source and Destination IP Address(es) and Mask(s), Protocol Type, and Source and Destination Port ID(s) for the filter, if desired.

TOS field matching

Netopia Embedded Software Version 7.7.4 includes two parameters for an IP filter: TOS and TOS Mask. Both fields accept values in the range 0 – 255.

Certain types of IP packets, such as voice or multimedia packets, are sensitive to latency introduced by the network. A delay-sensitive packet is one that has the low-latency bit set in the TOS field of the IP header. This means that if such packets are not received rapidly, the quality of service degrades. If you expect to route significant amounts of such traffic you can configure your router to route this type of traffic to a gateway

other than your normal gateway using this feature.

The TOS field matching check is consistent with source and destination address matching.

If you check the Idle Reset checkbox, a match on this rule will keep the WAN connection alive by resetting the idle-timeout status.

The Idle Reset setting is used to determine if a packet which matches the filter will cause an “instant-on” link to connect, if it is down; or reset its idle timer, if it is already up. For example, if you wanted ping traffic not to keep the link up, you would create a filter which forwards a ping, but with the Idle Reset checkbox unchecked.

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