IPv4 over MAPOS Version 1
RFC 2176
Document | Type |
RFC - Informational
(June 1997; No errata)
Updated by RFC 5494
Was draft-rfced-info-maruyama (individual)
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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 2176 (Informational) | |
Telechat date | |||
Responsible AD | (None) | ||
Send notices to | (None) |
Network Working Group K. Murakami Request for Comments: 2176 M. Maruyama Category: Informational NTT Laboratories June 1997 IPv4 over MAPOS Version 1 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 a mechanism for supporting Version 4 of the Internet Protocol (IPv4) on Version 1 of the Multiple Access Protocol over SONET/SDH. 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 a protocol for transmission of the Internet Protocol Version 4 (IPv4) over Multiple Access Over SONET/SDH (MAPOS) version 1. MAPOS is a link layer protocol and provides multiple access capability over SONET/SDH links. IP runs on top of MAPOS. This document explains IP datagram encapsulation in HDLC frame of MAPOS, and the Address Resolution Protocol (ARP). 1. Introduction Multiple Access Protocol over SONET/SDH (MAPOS) [1] is a high-speed link-layer protocol that provides multiple access capability over SONET/SDH. Its frame format is based on the HDLC-like framing [2] for PPP. A component called "Frame Switch" [1] allows multiple nodes to be connected together in a star topology to form a LAN. Using long haul SONET/SDH links, the nodes on such a "SONET-LAN" can span over a wide geographical area. The Internet Protocol (IP) [3] datagrams are transmitted in MAPOS HDLC frames [1]. This document describes a protocol for transmission of IP datagrams over MAPOS version 1 [1]. It explains IP datagram encapsulation in HDLC frame of MAPOS, and ARP (Address Resolution Protocol) for mapping between IP address and HDLC address. Murakami & Maruyama Informational [Page 1] RFC 2176 MAPOS June 1997 2. Frame Format for Encapsulating IP Datagrams An IP datagram is transmitted in a MAPOS HDLC frame. The protocol field of the frame must contain the value 0x0021 (hexadecimal) as defined by the "MAPOS Version 1 Assigned Numbers" [4]. The information field contains the IP datagram. The information field may be one to 65,280 octets in length; the MTU(Maximum Transmission Unit) of MAPOS is 65,280 octets. Although the large MTU size can suppress the overhead of IP header processing, it may cause fragmentation anywhere along the path from the source to the destination and result in performance degradation. To cope with the issue, Path MTU discovery [5] may be used. 3. Address Mapping This section explains MAPOS ARP and the mapping of special addresses. 3.1 ARP cache Each node on a MAPOS network maintains an "ARP cache" that maps destination IP addresses to their corresponding 8-bit HDLC addresses. Entries are added to this cache either manually or by the Address Resolution Protocol described below. Entries are removed from this cache manually, by the UNARP mechanism, or by ARP cache validation mechanism. An implementation must provide a mechanism for manually adding or removing arbitrary ARP cache entries. 3.2 Address Resolution Protocol (ARP) This subsection describes MAPOS ARP protocol and its packet format. 3.2.1 Overview The MAPOS ARP is similar to that for ethernet. Prior to sending an IP datagram, the node must know the destination HDLC address corresponding to the destination IP address. When its ARP cache does not contain the corresponding entry, it uses ARP to translate the IP address to the HDLC address. That is, it broadcasts an ARP request containing the destination IP address. In response to the request, the node which has the IP address sends an ARP reply containing the HDLC address. The returned HDLC address is stored in the ARP cache. 3.2.2 ARP Frame Format The protocol field for an ARP frame must contain 0xFE01 (hexadecimal) as defined by the "MAPOS Version 1 Assigned Numbers" [4]. The information field contains the ARP packet as shown below. Murakami & Maruyama Informational [Page 2] RFC 2176 MAPOS June 1997 +-------------------------+------------------------+ | Hardware Address Space | Protocol Address Space | | (25:MAPOS) | (2048 in Dec) | | 16 bits | 16 bits | +------------+------------+------------------------+Show full document text