RFC 2173 (rfc2173) - Page 3 of 6

A MAPOS version 1 Extension - Node Switch Protocol

RFC 2173                         MAPOS                         June 1997


   the node address is 0 + 01 + 00011, that is, 00100011(0x23). Node N3
   has an address 01001001(0x49), since the switch number of S2 is 0x2
   (10 in binary) and the port number is 0x09. Note that all the port
   numbers are odd because the LSBs are always 1.

                           +------+
                           | node |
                           |  N1  |
                           +------+
                               | 00100011(0x23)
                               |
                               |0x3             |0x3
               +------+    +---+----+       +---+----+     +------+
               | node +----+ SONET  +-------+ SONET  +-----+ node |
               |  N2  | 0x5| Switch |0x9 0x5| Switch |0x9  |  N3  |
               +------+    |   S1   |       |   S2   |     +------+
           00100101(0x25)  |  0x1   |       |  0x2   |   01001001(0x49)
                           +---+----+       +---+----+
                               |0x7             |0x7


          Figure 2  Addressing in Multiple Switch Environment

4 NSP(Node-Switch Protocol)

   This section describes the NSP protocol used for automatic node
   address assignment.

4.1 NSP protocol

   NSP is introduced to provide an automatic node address assignment
   function in MAPOS version 1. It reduces the administrative overhead
   of node address configuration for each node and prevents troubles
   such as address inconsistency and collision. When a node is connected
   to a switch and receives SONET signal correctly, the node sends an
   address request packet to the control processor in the local switch.
   The destination address of this packet is 00000001(0x01). When the
   control processor receives the packet, it replies with an address
   assignment packet. The destination is the assigned node address. If
   the node does not receive the address assignment packet within 5
   seconds, it retransmits the address request packet. The
   retransmission continues until the node successfully receives the
   address assignment packet.

   Whenever a node detects a transmission error such as carrier loss or
   out-of-synchronization, it SHOULD send an address request packet to
   the control processor and verify its current address. In addition, a
   node MUST verify its address by sending address request packets every



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