RFC 2106 (rfc2106) - Page 3 of 19

Data Link Switching Remote Access Protocol

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
   connection to the central site router.

2.2.  Dynamic Address Resolution

   In a DLSw network, each workstation needs a MAC address to
   communicate with a FEP attached to a LAN. When DLSw is implemented on
   a workstation, it does not always have a MAC address defined. For
   example, when a workstation connects to a router through a modem via
   PPP, it only consists of an IP address. In this case, the user must
   define a virtual MAC address. This is administratively intensive
   since each workstation must have an unique MAC address.

   DRAP uses the Dynamic Address Resolution protocol to solve this
   problem. The Dynamic Address Resolution protocol permits the server
   to dynamically assign a MAC address to a client without complex
   configuration.

   For a client to initiate a session to a server, the workstation sends
   a direct request to the server. The request contains the destination
   MAC address and the destination SAP. The workstation can either
   specify its own MAC address, or request the server to assign one to
   it. The server's IP address must be pre-configured on the
   workstation. If IP addresses are configured for multiple servers at a



Chiang, et. al.              Informational