Dls W Configuration; Dlsw Overview; Introduction - 3Com MSR 50 Series Configuration Manual

7

DLSw Overview

Introduction

DLS C
W ONFIGURATION
Data link switching (DLSw) was jointly developed by Advanced Peer-to-Peer
Networking (APPN) and Implementers Workshop (AIW) for transmitting Systems
Network Architecture (SNA) traffic over a TCP/IP network. SNA was developed by
IBM in correspondence with the OSI reference model. The DLSw technique is a
solution for cross-WAN transmission of SNA traffic.
The DLSw mechanism is shown in the following figure:
Figure 34 DLSw mechanism
LAN
LLC2
Router A
Terminal
1 The router that runs DLSw converts logical link control type 2 (LLC2) frames from
the local SNA device into Switch-to-Switch Protocol (SSP) frames that can be
encapsulated in TCP packets,
2 The SSP frames are forwards across the WAN over a TCP connection to the remote
router
3 The remote router converts the SSP frames back into LLC2 frames and sends them
to the peer SNA device.
As a result, the remote SNA device appears to be on the same network with the
local SNA device.
DLSw is different from transparent bridging in that it does not forward LLC2
frames transparently to the peer - instead it converts the LLC2 frames into SSP
frames for data encapsulation in TCP packets. The local termination mechanism of
DLSw eliminates the requirement for link layer acknowledgments and keepalive
messages to flow across a WAN. It also solves the data link control timeout
problem.
DLSw also enables transmission of synchronous data link control (SDLC) traffic
across a TCP/IP WAN by first converting SDLC frames to LLC2 frames, and then
transporting them to the remote end system through SSP. Thus, DLSw can be used
for interconnection between LAN and SDLC media.
Currently, two DLSw versions are available: version 1.0 and version 2.0. DLSw v1.0
is implemented based on RFC1795, while DLSw v2.0 is implemented based on
RFC2166 and is intended to improve product maintainability and to reduce
TCP/IP
SSP
Router B
LAN
LLC2
Terminal