IPv6 over Non-Broadcast Multiple Access (NBMA) networks
RFC 2491
| Document | Type |
RFC - Proposed Standard
(January 1999; No errata)
Updated by RFC 8064
Was draft-ietf-ion-ipv6 (ion WG)
|
|
|---|---|---|---|
| Last updated | 2013-03-02 | ||
| Stream | IETF | ||
| Formats | plain text pdf html bibtex | ||
| Stream | WG state | (None) | |
| Document shepherd | No shepherd assigned | ||
| IESG | IESG state | RFC 2491 (Proposed Standard) | |
| Consensus Boilerplate | Unknown | ||
| Telechat date | |||
| Responsible AD | (None) | ||
| Send notices to | (None) | ||
Network Working Group G. Armitage
Request for Comments: 2491 Lucent Technologies
Category: Standards Track P. Schulter
Bright Tiger Technologies
M. Jork
Digital Equipment GmbH
G. Harter
Compaq
January 1999
IPv6 over Non-Broadcast Multiple Access (NBMA) networks
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 (1999). All Rights Reserved.
Abstract
This document describes a general architecture for IPv6 over NBMA
networks. It forms the basis for subsidiary companion documents that
describe details for various specific NBMA technologies (such as ATM
or Frame Relay). The IPv6 over NBMA architecture allows conventional
host-side operation of the IPv6 Neighbor Discovery protocol, while
also supporting the establishment of 'shortcut' NBMA forwarding paths
when dynamically signaled NBMA links are available. Operations over
administratively configured Point to Point NBMA links are also
described.
Dynamic NBMA shortcuts are achieved through the use of IPv6 Neighbor
Discovery protocol operation within Logical Links, and inter-router
NHRP for the discovery of off-Link NBMA destinations. Both flow-
triggered and explicitly source-triggered shortcuts are supported.
1. Introduction.
Non Broadcast Multiple Access (NBMA) networks may be utilized in a
variety of ways. At one extreme, they can be used to simply provide
administratively configurable point to point service, sufficient to
interconnect IPv6 routers (and even IPv6 hosts, in certain
Armitage, et. al. Standards Track [Page 1]
RFC 2491 IPv6 over NBMA networks January 1999
situations). At the other extreme, NBMA networks that support dynamic
establishment and teardown of Virtual Circuits (or functional
equivalents) may be used to emulate the service provided to the IPv6
layer by conventional broadcast media such as Ethernet. Typically
this emulation requires complex convergence protocols, particularly
to support IPv6 multicast.
This document describes a general architecture for IPv6 over NBMA
networks. It forms the basis for companion documents that provide
details specific to various NBMA technologies (for example, ATM [17]
or Frame Relay). The IPv6 over NBMA architecture allows conventional
host-side operation of the IPv6 Neighbor Discovery protocol, while
also supporting the establishment of 'shortcut' NBMA forwarding paths
(when dynamically signaled NBMA links are available).
The majority of this document focuses on the use of dynamically
managed point to point and point to multipoint calls between
interfaces on an NBMA network. These will be generically referred to
as "SVCs" in the rest of the document. The use of administratively
configured point to point calls will also be discussed. Such calls
will be generically referred to as "PVCs". Depending on context,
either may be shortened to "VC".
Certain NBMA networks may provide a form of connectionless service
(e.g. SMDS). In these cases, a "call" or "VC" shall be considered to
implicitly exist if the sender has an NBMA destination address to
which it can transmit packets whenever it desires.
1.1 Neighbor Discovery.
A key difference between this architecture and previous IP over NBMA
protocols is its mechanism for supporting IPv6 Neighbor Discovery.
The IPv4 world evolved an approach to address resolution that
depended on the operation of an auxiliary protocol operating at the
'link layer' - starting with Ethernet ARP (RFC 826 [14]). In the
world of NBMA (Non Broadcast, Multiple Access) networks ARP has been
applied to IPv4 over SMDS (RFC 1209 [13]) and IPv4 over ATM (RFC 1577
[3]). More recently the ION working group has developed NHRP (Next
Hop Resolution Protocol [8]), a general protocol for performing
intra-subnet and inter-subnet address resolution applicable to a
range of NBMA network technologies.
IPv6 developers opted to migrate away from a link layer specific
approach, chosing to combine a number of tasks into a protocol known
as Neighbor Discovery [7], intended to be non-specific across a
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