3Com 10014299 manual DLSw Protocol

25 CONFIGURING DLSW

	This chapter contains information on the following topics:
	■	DLSw Protocol Overview
	■	Configuration of DLSw
	■ Display and Debug DLSw
	■ Typical DLSw Configuration Example
	■ Diagnosis and Troubleshooting of DLSw Fault
DLSw Protocol	Data Link Switch Protocol (DLSw) is a method designed by Advanced Peer-to-Peer
Overview	Networking (APPN) Implementers Workshop (AIW) to load SNA through TCP/IP
	(SNA is a network protocol introduced by IBM in 1970's and completely

correspondent with OSI reference model). DLSw technology is one of the solutions for implementing the transmission across WANs via SNA protocol.

The operating principle of DLSw is shown in the following diagram:

Figure 138 DLSw principle diagram

End System

LAN

LLC2

DLSw

TCP/IP

SSP

DLSw

LAN

LLC2

End System

From the above diagram, you may find out the router with DLSw transforms the frame in format LLC2 on the local SNA equipment into SSP frame which can be encapsulated into TCP messages. Then it sends SSP frame to the remote end through TCP channel across WANs, and transforms SSP frame into the corresponding frame in LLC2 format at the remote end site, finally sends the latter to the next-hop SNA equipment. In another words, DLSw makes the local terminating equipment “think” the remote equipment locates in the same network. With the differences from transparent bridge, DLSw transforms the original LLC2 protocol frame into SSP protocol frame instead of transparent-transmitting to the next hop directly, so as to encapsulate the existing data into TCP messages. It features local acknowledgement mechanism, thus reducing unnecessary data transmission (confirming frame and maintaining alive frame) and resolving the overtime problem of data link control.

With DLSw technology, the transmission across TCP/IP via SDLC link protocol can also be implemented. The procedure is to transform the messages in SDLC format into the messages in LLC2 format, then utilize DLSw to intercommunicate with the remote end. DLSw also supports intercommunication of different media between LAN and SDLC.