A MAPOS version 1 Extension - Node Switch Protocol (RFC2173)

Network Working Group K. Murakami Request for Comments: 2173 M. Maruyama Category: Informational NTT Laboratories June 1997

A MAPOS version 1 Extension - Node Switch 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 document describes a MAPOS extension, Node Switch Protocol, for automatic node address assignment. MAPOS is a multiple access protocol for transmission of network-protocol datagrams, encapsulated in High-Level Data Link Control (HDLC) frames, over SONET/SDH. NSP automates the HDLC address configuration of each node. Using NSP, a node retrieves its HDLC address from the switch to which it is connected.

1. Introduction

MAPOS[1], Multiple Access Protocol over SONET(Synchronous Optical Network)/SDH(Synchronous Digital Hierarchy)[2][3][4][5], is a protocol for transmission of HDLC frames over SONET/SDH. A SONET switch provides multiple access capability to each node. In MAPOS, each node has a unique HDLC address within a switch. The address is equivalent to the port number of the switch to which the node is connected. This document describes an extension to MAPOS, Node Switch Protocol, which enable automatic HDLC address assignment. First, it explains the addressing of MAPOS. Then, it describes the NSP protocol for automatic HDLC node address assignment.

2. Node Address Format

This section describes MAPOS Version 1 address format in single and multiple switch environment.

Murakami & Maruyama Informational [Page 1]

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 "0 <switch number> <node number> 1" for a unicast address, "all 1" for the broadcast address, and "1 <group address> 1" for a multicast address.

The address 0x01 is re...