Subject: I-D Action: draft-ietf-rtgwg-dst-src-routing-06.txt

From: [email-masked]
Date: Mon, 30 Oct 2017 13:01:08 -0700

A New Internet-Draft is available from the on-line Internet-Drafts directories.
This draft is a work item of the Routing Area Working Group WG of the IETF.

        Title           : Destination/Source Routing
        Authors         : David Lamparter
                          Anton Smirnov
	Filename        : draft-ietf-rtgwg-dst-src-routing-06.txt
	Pages           : 21
	Date            : 2017-10-30

Abstract:
   This note specifies using packets' source addresses in route lookups
   as additional qualifier to be used in hop-by-hop routing decisions.
   This applies to IPv6 [RFC2460] in general with specific
   considerations for routing protocol left for separate documents.
   There is nothing precluding similar operation in IPv4, but this is
   not in scope of this document.

   Note that destination/source routing, source/destination routing,
   SADR, source-specific routing, source-sensitive routing, S/D routing
   and D/S routing are all used synonymously.

The IETF datatracker status page for this draft is:
https://datatracker.ietf.org/doc/draft-ietf-rtgwg-dst-src-routing/

There are also htmlized versions available at:
https://tools.ietf.org/html/draft-ietf-rtgwg-dst-src-routing-06
https://datatracker.ietf.org/doc/html/draft-ietf-rtgwg-dst-src-routing-06

A diff from the previous version is available at:
https://www.ietf.org/rfcdiff?url2=draft-ietf-rtgwg-dst-src-routing-06

Please note that it may take a couple of minutes from the time of submission
until the htmlized version and diff are available at tools.ietf.org.

Internet-Drafts are also available by anonymous FTP at:
ftp://ftp.ietf.org/internet-drafts/

---

From: Brian E Carpenter <[email-masked]>
Date: Tue, 31 Oct 2017 11:25:53 +1300

Hi,

>    Both IPv4 [RFC0791] and IPv6 [RFC2460] architectures specify that
>    determination of the outgoing next-hop for packet forwarding is based
>    solely on the destination address contained in the packet header.

1) RFC8200 obsoleted RFC2460 recently.

2) I can't find any statement in RFC8200 to justify "solely". In fact,
as far as I can see the document says nothing about the destination address
except that it's "the address of the intended recipient".

https://tools.ietf.org/html/draft-ietf-v6ops-ipv6rtr-reqs-00#section-2.4
is quite explicit that source-address-based routing is allowed.

I'm not sure that RFC791 justifies the "solely" either. There's only one
very oblique statement, hidden in the discussion of loose source routes
("the routing is to be based on the destination address field"). If
there's any such restriction for IPv4, it must be hidden in RFC1812.
I couldn't find it, though.

It's fair to say that in practice, we have based forwarding solely
on the destination address. But I don't believe it's specified.

(Apart from that, I'm all for the draft, fwiw.)

Regards
   Brian