Subject: link local packet forwarding -- it was RE: draft-ipngwg-default -addr-select-00.txt

From: [email-masked]
Date: Thu, 4 Nov 1999 00:09:51 -0500

Steve,

>Alex,
>
>I disagree with your characterization of the issue.

Your message points even more to the need of a document, or an explanation
or conceptual model with details of how these mechanisms fit together.
Otherwise the potential for missinterpretations and disagreements will
perpetuate.

If the mechanism that you envisaged and will document, works, and is
universal, this is all beautiful and I WILL BE HAPPIER than I was with any
other mechanisms.

The concept of link-local packet forwarding is at the border of possible
interpretations.
Link-Local addresses are designed to be used for addressing on a single
link for purposes such as auto-address configuration, neighbor discovery,
or when no routers are present.
A router receiving a link-local packet should act like a host:  if it is
not the host to which the packet is sent to, then it should discard the
packet

With the hope that you take this constructively, architecturally, in
regarding scoped addresses, IMO, IPv6 should be consistent with the unicast
forwarding as we know it. If a unicast packet has IP topology information
then it is
forwarded, otherwise it is not. Hence, a "link" is a "zone" with zero (NO)
IP forwarding, (but of course with link specific forwarding/switching),
while a "site" is a "zone" with IP forwarding. Otherwise, IMO, a convincing
case for link-local forwarding is still to be made, and furthermore, the
issues and side effects of inadvertent packet duplication, and forwarding
are still to be resolved.

I would urge you to make the information available to the list even in
pieces, since the document, if it were an I-D, didn't make the 46th meeting
dead-line, and a presentation in a WG, like in previous cases, still may
leave  room for assumptions,  or speculations, which one is still too many,
for building solid, deployable, forwarding engines. Thanks.

>[...]

>>1. both models achieve over-all the same packet delivery functions.
>
>No, I don't think your model handles all the site-local cases.

Yes. It does. While a node can be on several sites, an interface is ON or
OFF a site, i.e. it is supposed to be attached to not more than one site
(draft-ietf-ipngwg-site-prefixes-03.txt,draft-ietf-ipngwg-scoped-routing-01
.txt).

>>2. MODEL I is simpler and cheaper than MODEL II because it consists of
ONE
>>MECHANISM.
>
>No, my model consists of one mechanism.  Your model...

No. I am sorry! Model I is not mine. I'm sorry MODEL I is not mine.
Regarding the NO forwarding of link-local packets, I think it is
everybody's model, since it is so widely implemented.

>...consists of one
>mechanism plus special-case handling of link-locals, which is effectively
>a second mechanism.

No. NO FORWARDING is in programming language a "return", which is the END
of
a protocol engine mechanism, and NOT A SECOND mechanism.

>>3. the restriction of MODEL I in regards of link-local forwarding,
applies
>>to a very low frequency occurrence, and it can be circumvented by site,
or
>>global address use.
>
>No, we don't know that link-local communication will be low frequency in
>all cases.  There may be scenarios (e.g., home networks) where there is
>significant link-local communication (e.g., audio packets from a stereo
>to some speakers).

No. I refer to link-local forwarding, NOT link-local communication.
YES. A node with two or more interfaces on the same link, and therefore
Link-local forwarding, is a low frequency occurence (you mentioned it in a
previous message).

Alex

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