Data Link Switching Remote Access Protocol
RFC 2106

Document Type RFC - Informational (February 1997; No errata)
Obsoleted by RFC 2114
Was draft-rfced-info-chiang (individual)
Last updated 2013-03-02
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Network Working Group                                          S. Chiang
Request for Comments: 2106                                        J. Lee
Category: Informational                              Cisco Systems, Inc.
                                                               H. Yasuda
                                               Mitsubishi Electric Corp.
                                                           February 1997

               Data Link Switching Remote Access Protocol

Status of this Memo

   This memo provides information for the Internet community.  This memo
   does not specify an Internet standard of any kind.  Distribution of
   this memo is unlimited.

Abstract

   This memo describes the Data Link Switching Remote Access Protocol
   that is used between workstations and routers to transport SNA/
   NetBIOS traffic over TCP sessions. Any questions or comments should
   be sent to drap@cisco.com.

1.  Introduction

   Since the Data Link Switching Protocol, RFC 1795, was published, some
   software vendors have begun implementing DLSw on workstations. The
   implementation of DLSw on a large number of workstations raises
   several important issues that must be addressed. Scalability is the
   major concern. For example, the number of TCP sessions to the DLSw
   router increases in direct proportion to the number of workstations
   added. Another concern is efficiency. Since DLSw is a switch-to-
   switch protocol, it is not efficient when implemented on
   workstations.

   DRAP addresses the above issues. It introduces a hierarchical
   structure to resolve the scalability problems. All workstations are
   clients to the router (server) rather than peers to the router. This
   creates a client/server model. It also provides a more efficient
   protocol between the workstation (client) and the router (server).

Chiang, et. al.              Informational                      [Page 1]
RFC 2106                         DLSRAP                    February 1997

2.  Overview

2.1.  DRAP Client/Server Model

      +-----------+              +-----------+       +---------+
      | Mainframe |              | IP Router +- ppp -+ DLSw    |
      +--+--------+              +-----+-----+       | Work    |
         |                             |             | Station |
         |                             |             +---------+
      +--+--+      +-------------+     |
      | FEP +- TR -+ DLSw Router +-- IP Backbone
      +-----+      +-------------+     |
                                       |
                                       |
                                 +-----------+       +---------+
                                 | IP Router +- ppp -+ DLSw    |
                                 +-----+-----+       | Work    |
                                                     | Station |
                                                     +---------+

                           |         DLSw Session          |
                           +-------------------------------+
  Figure 2-1. Running DLSw on a large number of workstations creates a
                         scalability problem.

   Figure 2-1 shows a typical DLSw implementation on a workstation. The
   workstations are connected to the central site DLSw router over the
   IP network.  As the network grows, scalability will become an issue
   as the number of TCP sessions increases due to the growing number of
   workstations.

Chiang, et. al.              Informational                      [Page 2]
RFC 2106                         DLSRAP                    February 1997

                                  +-----------+       +-------+
       +-----------+              | DLSw/DRAP |       | DRAP  |
       | Mainframe |              |   Router  +- ppp -+ Client|
       +--+--------+              +-----+-----+       +-------+
          |                             |
          |                             |
       +--+--+      +-------------+     |
       | FEP +- TR -+ DLSw Router +-- IP Backbone
       +-----+      +-------------+     |
                                        |
                                        |
                                  +-----------+       +-------+
                                  | DLSw/DRAP |       | DRAP  |
                                  |   Router  +- ppp -+ Client|
                                  +-----+-----+       +-------+

                         | DLSw Session |  | DRAP Session |
                         +--------------+  +--------------+
Figure 2-2. DLSw Remote Access Protocol solves the scalability problem.

   In a large network, DRAP addresses the scalability problem by
   significantly reducing the number of peers that connect to the
   central site router. The workstations (DRAP client) and the router
   (DRAP server) behave in a Client/Server relationship. Workstations
   are attached to a DRAP server. A DRAP server has a single peer
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