Neighbor Unreachability Detection Is Too Impatient (RFC7048)
Original Publication Date: 2014-Jan-01
Included in the Prior Art Database: 2014-Jan-09
Internet Society Requests For Comment (RFCs)
E. Nordmark: AUTHOR [+1]
IPv6 Neighbor Discovery [RFC4861] includes Neighbor Unreachability Detection (NUD), which detects when a neighbor is no longer reachable. The timeouts specified for NUD are very short (by default, three transmissions spaced one second apart). These short timeouts can be appropriate when there are alternative neighbors to which the packets can be sent -- for example, if a host has multiple default routers in its Default Router List or if the host has a Neighbor Cache Entry (NCE) created by a Redirect message. In those cases, when NUD fails, the host will try the alternative neighbor by redoing the next-hop selection. That implies picking the next router in the Default Router List or discarding the NCE created by a Redirect message, respectively.
Internet Engineering Task Force (IETF) E. Nordmark Request for Comments: 7048 Arista Networks Updates: 4861 I. Gashinsky Category: Standards Track Yahoo! ISSN: 2070-1721 January 2014
Neighbor Unreachability Detection Is Too Impatient
IPv6 Neighbor Discovery includes Neighbor Unreachability Detection. That function is very useful when a host has an alternative neighbor -- for instance, when there are multiple default routers -- since it allows the host to switch to the alternative neighbor in a short time. By default, this time is 3 seconds after the node starts probing. However, if there are no alternative neighbors, this timeout behavior is far too impatient. This document specifies relaxed rules for Neighbor Discovery retransmissions that allow an implementation to choose different timeout behavior based on whether or not there are alternative neighbors. This document updates RFC 4861.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc7048.
Gashinsky Standards Track [Page 1]
RFC 7048 NUD Is Too Impatient January 2014
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Table of Contents
1. Introduction ...................................................