IBM BC-203 manual DLSw Standard, DLSw Version 2 Standard, BC-207

Overview of IBM Networking

DLSw+

This section contains a brief overview of DLSw+ which is described in the following topics:

•DLSw Standard, page 207

•DLSw Version 2 Standard, page 207

•DLSw+ Features, page 208

DLSw Standard

The DLSw standard, documented in RFC 1795, defines the switch-to-switch protocol between DLSw routers. The standard also defines a mechanism to terminate data-link control connections locally and multiplex the traffic from the data-link control connections to a TCP connection. The standard always calls for the transport protocol to be TCP and always requires that data-link control connections be locally terminated (the equivalent of Cisco’s local acknowledgment option). The standard also requires that the SRB RIF be terminated at the DLSw router. The standard describes a means for prioritization and flow control and defines error recovery procedures that ensure data-link control connections are appropriately disabled if any part of their associated circuits breaks.

The DLSw standard does not specify when to establish TCP connections. The capabilities exchange allows compliance to the standard, but at different levels of support. The standard does not specify how to cache learned information about MAC addresses, RIFs, or NetBIOS names. It also does not describe how to track either capable or preferred DLSw partners for either backup or load-balancing purposes.The standard does not provide the specifics of media conversion, but leaves the details up to the implementation. It does not define how to map switch congestion to the flow control for data-link control. Finally, the MIB is documented under a separate RFC.

DLSw Version 2 Standard

In the Version 1 standard, a network design requires fully meshed connectivity so that all peers were connect to every other peer. This design creates unnecessary broadcast traffic because an explorer propagates to every peer for every broadcast.

The Version 2 standard is documented in RFC 2166. It includes RFC 1795 and adds the following enhancements:

•IP Multicast, page 208

•UDP Unicast, page 208

•Enhanced Peer-on-Demand Routing Feature, page 208

•Expedited TCP Connection, page 208

Users implement DLSw+ Version 2 for scalability if they are using multivendor DLSw devices with an IP multicast network. DLSw Version 2 requires complex planning because it involves configuration changes across an IP network.

Cisco IOS Bridging and IBM Networking Configuration Guide

BC-207