NBMA Next Hop Resolution Protocol (NHRP)
RFC 2332
Document | Type |
RFC - Proposed Standard
(April 1998; No errata)
Was draft-ietf-rolc-nhrp (ion WG)
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Authors | Bruce Cole , Naganand Doraswamy , Dave Katz , James Luciani , David Piscitello | ||
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 2332 (Proposed Standard) | |
Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | (None) | ||
Send notices to | (None) |
Network Working Group J. Luciani Request for Comments: 2332 Bay Networks Category: Standards Track D. Katz cisco Systems D. Piscitello Core Competence, Inc. B. Cole Juniper Networks N. Doraswamy Bay Networks April 1998 NBMA Next Hop Resolution Protocol (NHRP) 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. Abstract This document describes the NBMA Next Hop Resolution Protocol (NHRP). NHRP can be used by a source station (host or router) connected to a Non-Broadcast, Multi-Access (NBMA) subnetwork to determine the internetworking layer address and NBMA subnetwork addresses of the "NBMA next hop" towards a destination station. If the destination is connected to the NBMA subnetwork, then the NBMA next hop is the destination station itself. Otherwise, the NBMA next hop is the egress router from the NBMA subnetwork that is "nearest" to the destination station. NHRP is intended for use in a multiprotocol internetworking layer environment over NBMA subnetworks. Note that while this protocol was developed for use with NBMA subnetworks, it is possible, if not likely, that it will be applied to BMA subnetworks as well. However, this usage of NHRP is for further study. This document is intended to be a functional superset of the NBMA Address Resolution Protocol (NARP) documented in [1]. Luciani, et. al. Standards Track [Page 1] RFC 2332 NBMA NHRP April 1998 Operation of NHRP as a means of establishing a transit path across an NBMA subnetwork between two routers will be addressed in a separate document (see [13]). 1. Introduction 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 [15]. The NBMA Next Hop Resolution Protocol (NHRP) allows a source station (a host or router), wishing to communicate over a Non-Broadcast, Multi-Access (NBMA) subnetwork, to determine the internetworking layer addresses and NBMA addresses of suitable "NBMA next hops" toward a destination station. A subnetwork can be non-broadcast either because it technically doesn't support broadcasting (e.g., an X.25 subnetwork) or because broadcasting is not feasible for one reason or another (e.g., an SMDS multicast group or an extended Ethernet would be too large). If the destination is connected to the NBMA subnetwork, then the NBMA next hop is the destination station itself. Otherwise, the NBMA next hop is the egress router from the NBMA subnetwork that is "nearest" to the destination station. One way to model an NBMA network is by using the notion of logically independent IP subnets (LISs). LISs, as defined in [3] and [4], have the following properties: 1) All members of a LIS have the same IP network/subnet number and address mask. 2) All members of a LIS are directly connected to the same NBMA subnetwork. 3) All hosts and routers outside of the LIS are accessed via a router. 4) All members of a LIS access each other directly (without routers). Address resolution as described in [3] and [4] only resolves the next hop address if the destination station is a member of the same LIS as the source station; otherwise, the source station must forward packets to a router that is a member of multiple LIS's. In multi-LIS Luciani, et. al. Standards Track [Page 2] RFC 2332 NBMA NHRP April 1998 configurations, hop-by-hop address resolution may not be sufficient to resolve the "NBMA next hop" toward the destination station, and IP packets may have multiple IP hops through the NBMA subnetwork. Another way to model NBMA is by using the notion of Local AddressShow full document text