IPv6 Router Alert Option (RFC2711)
Original Publication Date: 1999-Oct-01
Included in the Prior Art Database: 2019-Feb-10
Internet Society Requests For Comment (RFCs)
C. Partridge: AUTHOR [+1]
This memo describes a new IPv6 Hop-by-Hop Option type that alerts transit routers to more closely examine the contents of an IP datagram. [STANDARDS-TRACK]
Network Working Group C. Partridge Request for Comments: 2711 BBN Category: Standards Track A. Jackson BBN October 1999
IPv6 Router Alert Option
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 (C) The Internet Society (1999). All Rights Reserved.
This memo describes a new IPv6 Hop-by-Hop Option type that alerts transit routers to more closely examine the contents of an IP datagram. This option is useful for situations where a datagram addressed to a particular destination contains information that may require special processing by routers along the path.
New protocols, such as RSVP, use control datagrams which, while addressed to a particular destination, contain information that needs to be examined, and in some case updated, by routers along the path between the source and destination. It is desirable to forward regular datagrams as rapidly as possible, while ensuring that the router processes these special control datagrams appropriately. Currently, however, the only way for a router to determine if it needs to examine a datagram is to at least partially parse upper layer data in all datagrams. This parsing is expensive and slow. This situation is undesirable.
This document defines a new option within the IPv6 Hop-by-Hop Header. The presence of this option in an IPv6 datagram informs the router that the contents of this datagram is of interest to the router and to handle any control data accordingly. The absence of this option in an IPv6 datagram informs the router that the datagram does not contain information needed by the router and hence can be safely
Partridge & Jackson Standards Track [Page 1]
RFC 2711 IPv6 Router Alert Option October 1999
routed without further datagram parsing. Hosts originating IPv6 datagrams are required to include this option in certain circumstances.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC-2119].
The goal is to provide an efficient mechanism whereby routers can know when to intercept datagrams not addressed to them without having to extensively examine every datagram. The described solution is to define a new IPv6 Hop-by-Hop Header option having the semantic "routers should examine this datagram more closely" and require protocols such as RSVP to use this option. This approach incurs little or no performance penalty on the forwarding of normal datagrams. Not including this option tells the router that there is no need to closely examine the contents of the datagram.
The router alert opti...