RFC 2173 (rfc2173) - Page 2 of 6
A MAPOS version 1 Extension - Node Switch Protocol
Alternative Format: Original Text Document
RFC 2173 MAPOS June 1997 2.1 Address Format In MAPOS network, each end node has a unique HDLC address. As shown in Figure 1, the address length is 8 bits. The LSB is always 1 which indicates the end of the field. When a SONET switch receives an HDLC frame, it forwards the frame based on the address in the frame header. In unicast, MSB is 0 and the rest of the bits are the port number to which a node is connected. Since the LSB is always 1, the minimum and maximum addresses are 0x01 and 0x7F, respectively. Address 0x01 is reserved and is assigned to the control processor in a SONET switch. In broadcast, MSB is 1 and the rest of the bits are all 1s. In multicast, MSB is 1 and the rest of the bits, except for the LSB, indicate the group address. +-------------+-+ | | | | | | | | | | |port number|1| +-+-----------+-+ ^ ^ | | | +------- EA bit (always 1) | 1 : broadcast, multicast 0 : unicast Figure 1 Address format 2.2 Address in multi-switch environment In a multi-switch environment, variable-length subnet addressing is used. Each switch has a switch number that is unique within the system. Subnetted node addresses consist of the switch number and the port number to which a node is connected. The address format is "01" for a unicast address, "all 1" for the broadcast address, and "1 1" for a multicast address. The address 0x01 is reserved and is assigned to the control processor in the "local" switch. That is, it indicates the switch itself to which the node is connected. The addresses of the form "0 1" are reserved, and indicates the control processor of the switch designated by the switch number. In Figure 2, the switch numbers are two bits long. Node N1 is connected to port 0x3 of switch S1 numbered 0x1 (01 in binary). Thus, Murakami & Maruyama Informational
