Subject: Consensus action: ACCEPT [LL8] Is additional Routing Considerations text needed?

From: Erik Guttman <[email-masked]>
Date: Mon, 17 Feb 2003 17:58:32 +0100

RESULT:	Accept

ACTION:	Add a new routing considerations section with text:

  	The link local address block (169.254/16) MUST NOT be
  	included as a reachable prefix in any dynamic routing protocol.
  	Subnets of that address block (which should not exist - see sect
  	N.M) MUST NOT be included either.

NOTE:	Alex Zinin has not gotten back to us regarding his comment.
  	If he has additional concerns or does not approve of the text
	above, we will open a new issue.

NOTE2:	Ted Lemon noted that autoconfigured hosts may not know what
	address a router has, so all the statements regarding not
	forwarding to a router do not make sense.
	
---------------------------
If anyone agrees with the below, please submit a new issue
requesting the change:

	Thomas Narten suggested that in order to address this concern
	it might make sense to improve this text with the following
	additional terminology:

Thomas Narten <[email-masked]> wrote:
 > This document might find it useful to define "non-local" or
 > some term to indicate addresses that are connected to the same link as
 > the sender. Maybe on-link and off-link are the best terms, given that
 > IPv6 uses them. Then, one could say.
 >
 > Definitions (stolen from 2460):
 >
    router - a node that forwards packets not explicitly addressed to
                  itself.

    on-link destination - a destination that is attached to the same
		         link as the sender. Packets for on-link
		         destinations are sent directly to that
		         destination (e.g., by first ARPing for the
		         destination to determine its link-layer
		         address)

    off-link destination - Destination addresses that are not on the
		         same link as the sender.  Packets to off-link
		         destinations must be forwarded through a
		         router.

 > note: "routable" might also be useful to define more formally (there
 > is a definition in the document):
 >
 >   This document uses the term "routable address" to refer to all
 >   unicast addresses outside the 169.254/16 prefix, including global
 >   addresses and private addresses such as Net 10/8 [RFC 1918], all of
 >   which may be forwarded via routers.

 > Routable is a bad term (it's been cited as confusing on the
 > list). Might be better to talk about scopes, which is the real issue.
 >			
 > then change:

 >> 	The link local address block (169.254/16) MUST NOT be
 >> 	included as a reachable prefix in any dynamic routing protocol.
 >> 	Subnets of that address block (which should not exist - see sect
 >> 	N.M) MUST NOT be included either.

 > to

  	The link local address block (169.254/16) is reserved for
  	addresses that are on-link. Thus, it makes no sense to
  	advertise the prefix in routing protocols. The link-local
  	address block (and any addresses within the block) MUST NOT be
  	included as a reachable prefix in any dynamic routing
  	protocol. It SHOULD be ignored when received in messages from
  	routing protocols.

Erik
ZEROCONF WG chair