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

Brian E Carpenter <brian.e.carpenter@gmail.com> Mon, 30 October 2017 22:25 UTC

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Subject: Re: I-D Action: draft-ietf-rtgwg-dst-src-routing-06.txt
To: draft-ietf-rtgwg-dst-src-routing@ietf.org, rtgwg@ietf.org
References: <150939366833.7831.6538202571946834662@ietfa.amsl.com>
From: Brian E Carpenter <brian.e.carpenter@gmail.com>
Organization: University of Auckland
Message-ID: <3f046755-d2ee-7b74-33df-890b9effaec2@gmail.com>
Date: Tue, 31 Oct 2017 11:25:53 +1300
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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