Inverse Address Resolution Protocol
RFC 2390
Document | Type |
RFC - Draft Standard
(September 1998; No errata)
Obsoletes RFC 1293
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Authors | Andy Malis , Caralyn Brown , Terry Bradley | ||
Last updated | 2013-03-02 | ||
Stream | IETF | ||
Formats | plain text html pdf htmlized bibtex | ||
Stream | WG state | (None) | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 2390 (Draft Standard) | |
Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | (None) | ||
Send notices to | (None) |
Network Working Group T. Bradley Request for Comments: 2390 Avici Systems, Inc. Obsoletes: 1293 C. Brown Category: Standards Track Consultant A. Malis Ascend Communications, Inc. September 1998 Inverse Address Resolution Protocol Status of this Memo This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited. Copyright Notice Copyright (C) The Internet Society (1998). All Rights Reserved. 2. Abstract This memo describes additions to ARP that will allow a station to request a protocol address corresponding to a given hardware address. Specifically, this applies to Frame Relay stations that may have a Data Link Connection Identifier (DLCI), the Frame Relay equivalent of a hardware address, associated with an established Permanent Virtual Circuit (PVC), but do not know the protocol address of the station on the other side of this connection. It will also apply to other networks with similar circumstances. This memo replaces RFC 1293. The changes from RFC 1293 are minor changes to formalize the language, the additions of a packet diagram and an example in section 7.2, and a new security section. 3. Conventions The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD, SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this document, are to be interpreted as described in [5]. Bradley, et. al. Standards Track [Page 1] RFC 2390 Inverse Address Resolution Protocol September 1998 4. Introduction This document will rely heavily on Frame Relay as an example of how the Inverse Address Resolution Protocol (InARP) can be useful. It is not, however, intended that InARP be used exclusively with Frame Relay. InARP may be used in any network that provides destination hardware addresses without indicating corresponding protocol addresses. 5. Motivation The motivation for the development of Inverse ARP is a result of the desire to make dynamic address resolution within Frame Relay both possible and efficient. Permanent virtual circuits (PVCs) and eventually switched virtual circuits (SVCs) are identified by a Data Link Connection Identifier (DLCI). These DLCIs define a single virtual connection through the wide area network (WAN) and may be thought of as the Frame Relay equivalent to a hardware address. Periodically, through the exchange of signaling messages, a network may announce a new virtual circuit with its corresponding DLCI. Unfortunately, protocol addressing is not included in the announcement. The station receiving such an indication will learn of the new connection, but will not be able to address the other side. Without a new configuration or a mechanism for discovering the protocol address of the other side, this new virtual circuit is unusable. Other resolution methods were considered to solve the problems, but were rejected. Reverse ARP [4], for example, seemed like a good candidate, but the response to a request is the protocol address of the requesting station, not the station receiving the request. IP specific mechanisms were limiting since they would not allow resolution of other protocols other than IP. For this reason, the ARP protocol was expanded. Inverse Address Resolution Protocol (InARP) will allow a Frame Relay station to discover the protocol address of a station associated with the virtual circuit. It is more efficient than sending ARP messages on every VC for every address the system wants to resolve and it is more flexible than relying on static configuration. Bradley, et. al. Standards Track [Page 2] RFC 2390 Inverse Address Resolution Protocol September 1998 6. Packet Format Inverse ARP is an extension of the existing ARP. Therefore, it has the same format as standard ARP. ar$hrd 16 bits Hardware type ar$pro 16 bits Protocol type ar$hln 8 bits Byte length of each hardware address (n) ar$pln 8 bits Byte length of each protocol address (m) ar$op 16 bits Operation code ar$sha nbytes source hardware address ar$spa mbytes source protocol address ar$tha nbytes target hardware addressShow full document text