Subject: Loop exists in TOKEN RING environment

From: [email-masked] (Thang Do)
Date: Tue, 20 Sep 1994 16:23:02 -0700 (PDT)

I am running into the LOOP in Token-Ring environment. Please take a look it, the
loop may happen in Token Ring as well. Here is the configuration
 
                             +------------+
                             |  IBM       |
                             | LAN SERVER |
                             +------------+
                                   |
                                   |
                                _______
          +========+           /       \           +========+
          |  DLSw  |-----------| RING 1 |----------|  DLSw  |
          |   1    |           \_______/           |   2    |
          +========+                               +========+
              |                                        |
              |                                        |
              |                                        |
              |                 _______                |
          +========+           /       \           +========+
          |  DLSw  |-----------| RING 2 |----------|  DLSw  |
          |   3    |           \_______/           |   4    |
          +========+               |               +========+
                                   |
                                   |
                                   |
                             +------------+
                             |    DOS     |
                             |   LAN WS   |
                             +------------+

 DLSw 1 has DLSw 3 as partner
 DLSw 2 has DLSw 4 as partner
 
 IBM Lan Server starts sending Multicast for example ADD-GROUP-NAME-QUERY, DLSw1
 and DLSw2 converts to DATAGRAME and sends to its partners. DLSw3 and DLSw4
 receive DATAGRAME frames so it broadcasts to the RING2. The DLSw3, DLSw4, and
 DOS LAN WS will receive these Multicast frames, so the LOOP is started...

 -Thang Do

---

From: [email-masked] (Thang Do)
Date: Wed, 21 Sep 1994 12:54:12 -0700 (PDT)

Ravi,

I believe that virtual RING technology is the implementation choice. I am not
sure if you break the BRIDGE network when you set the virtual RING the same in
DLSw1 and DLSw2 in the following configuration since the bridge software may be
confused and stop sending traffic from network A to network B.

           _____
          /     \
         / other \
        <  Network>
         \   A   /
          \_____/
             |
             |
             |              +------------+                           _____
          ___|___           |  IBM       |          ________        /     \
         /       \          | LAN SERVER |         /        \      / other \
         | RING 3 |         +------------+         | RING 4  |----<  Network>
         \_______/                |                \________/      \   B   /
             |                    |                    |            \_____/
             |                 _______                 |                   
         +========+           /       \           +========+
         |  DLSw  |-----------| RING 1 |----------|  DLSw  |
         |   1    |           \_______/           |   2    |
         +========+                               +========+
             |                                        |
             |                                        |
             /                                        \
             \                                        /
             /                                        \
             \                                        /
             |                                        |
             |                 _______                |
         +========+           /       \           +========+
         |  DLSw  |-----------| RING 2 |----------|  DLSw  |
         |   3    |           \_______/           |   4    |
         +========+               |               +========+
                                  |
                                  |
                                  |
                            +------------+
                            |    DOS     |
                            |   LAN WS   |
                            +------------+

-Thang Do