Cisco IOS Cookbook, 2nd Edition

Supporting SNA Priorities

Problem

You want DLSw to preserve and support the SNA or APPN Class of Service definitions for forwarding packets through your IP network.

Solution

To configure DLSw to follow the SNA or APPN priorities defined in the traffic flow, you must configure the peer relationship to allow multiple distinct data streams:

Router-A#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router-A(config)#dlsw remote-peer 0 tcp 10.1.1.5 lsap-output-list 200 priority
Router-A(config)#end
Router-A#

You can then go further and map the individual priority streams to specific IP Precedence values, as in the previous example. The default values are shown in Table 15-4:

Router-A#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router-A(config)#dlsw tos map low 0 normal 1 medium 2 high 3
Router-A(config)#end
Router-A#

The TOS map does not need to match at both ends of a DLSw connection. But if you use the priority option on the dlsw remote-peer command on one router, you must also use it on the other.

Discussion

Recipe 15.10 showed how to configure the router to tag the IP Precedence field in all DLSw packets for preferential treatment through the network. This example allows for the creation of four separate DLSw priority levels that follow the SNA priorities. This is useful, for example, if the SNA traffic stream includes both bulk data transfers and interactive traffic.

As soon as you enable SNA prioritization in the dlsw remote-peer ...