MAPOS 16 - Multiple Access Protocol over SONET/SDH with 16 Bit Addressing
RFC 2175
Document | Type |
RFC - Informational
(June 1997; No errata)
Was draft-rfced-info-murakami2 (individual)
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Authors | Mitsuru Maruyama , Ken-ichiro Murakami | ||
Last updated | 2013-03-02 | ||
Stream | Legacy | ||
Formats | plain text html pdf htmlized bibtex | ||
Stream | Legacy state | (None) | |
Consensus Boilerplate | Unknown | ||
RFC Editor Note | (None) | ||
IESG | IESG state | RFC 2175 (Informational) | |
Telechat date | |||
Responsible AD | (None) | ||
Send notices to | (None) |
Network Working Group K. Murakami Request for Comments: 2175 M. Maruyama Category: Informational NTT Laboratories June 1997 MAPOS 16 - Multiple Access Protocol over SONET/SDH with 16 Bit Addressing 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. Authors' note This memo documents MAPOS 16, a multiple access protocol for transmission of network-protocol datagrams, encapsulated in HDLC frames with 16 bit addressing, over SONET/SDH. The primary difference with MAPOS version 1 is that it has 16 bit address field that offers significant wide address space. This document is NOT the product of an IETF working group nor is it a standards track document. It has not necessarily benefited from the widespread and in depth community review that standards track documents receive. Abstract This document describes the protocol MAPOS 16, Multiple Access Protocol over SONET/SDH with 16 Bit Addressing, for transmitting network-protocol datagrams over SONET/SDH. The primary difference with MAPOS version 1 is that it has 16 bit address field that offers significant wide address space. It first describes the major differences between MAPOS and MAPOS 16 briefly. Then, it explains the header format and its 16 bit address format. 1. Introduction MAPOS is a multiple access protocol for transmission of High-level Datalink Control (HDLC) frames over the Synchronous Optical Network / Synchronous Digital Hierarchy(SONET/SDH)[1][2][3][4]. It provides multiple access capability to SONET/SDH, an inherently point-to-point link. MAPOS version 1[5] focuses on the frame format compatibility with the conventional PPP[6], resulting with its narrow 8 bit address field. In contrast to MAPOS version 1, MAPOS 16 has a 16 bit address space. Murakami & Maruyama Informational [Page 1] RFC 2175 MAPOS 16 June 1997 In this document, header format and its 16 bit format are described. It also explains that 16 bit addressing has minimal influence on the conventional MAPOS protocol family such as Node-Switch Protocol[7] and Switch-Switch Protocol[8]. 2. MAPOS 16 Frame Format Like MAPOS version 1, MAPOS 16 framing is based on the HDLC-like framing used in PPP-over-SONET/SDH, described in RFC-1662[6]. However, the address field is extended to 16 bits, and the control field in the MAPOS version 1 is omitted for maintain the 32bit alignment of the header. Figure 2 shows the MAPOS 16 frame format. Logical Link Control (LLC), and Sublayer/Sub-Network Access Protocol (SNAP) are not used. It does not include the bytes for transparency. The fields are transmitted from left to right. +----------+---------------------+----------+ | | | | | Flag | Address | Protocol | | 01111110 | 16bits | 16 bits | +----------+---------------------+----------+ +-------------+------------+----------+----------- | | | | Inter-frame | Information | FCS | Flag | fill or next | | 16/32 bits | 01111110 | address +-------------+------------+----------+------------ Figure 2. Frame format Flag Sequence Flag sequence is used for frame synchronization. Each frame begins and ends with a flag sequence 01111110 (0x7E). If a frame immediately follows another, one flag sequence may be treated as the end of the preceding frame and the beginning of the immediately following frame. When the line is idle, the flag sequence is to be transmitted continuously on the line. Address The address field contains the destination HDLC address. A frame is forwarded by a switch based on this field. It is 16 bits wide. The LSB of the first byte indicates the continuation of this field, and must always be 0. The LSB of the second byte indicates the end of this field, and must always be 1. The MSB of the first byte is Murakami & Maruyama Informational [Page 2] RFC 2175 MAPOS 16 June 1997 used to indicate if the frame is a unicast or multicast frame. The MSB of 0 means unicast, with the remaining thirteen bits indicating the destination node address including two E/A bits. MSB of 1 means multicast, with the remaining thirteen bits indicating the groupShow full document text