Re: [v6ops] draft-ietf-v6ops-multihoming-without-nat66 WGLC

----- Original Message -----
From: "Fred Baker" <fred@cisco.com>
To: "savolainen teemu" <teemu.savolainen@nokia.com>; "Randy Bush"
<randy@psg.com>
Sent: Monday, February 28, 2011 10:02 PM

> On Feb 28, 2011, at 12:19 PM, <teemu.savolainen@nokia.com> wrote:
>
> > For what I know multihoming is very commonly used to describe a scenario
where a host has simultaneously multiple uplink ISP connections active.
>
> There are 185 RFCs and I-don't-know-how-many Internet Drafts (that may or may
not ever become RFCs) that discuss multihoming. And five IENs.
>
> The oldest use of the term I could find is in IEN 110, dated 1979. It uses the
term without definition (it must have been in the air at the time), but states
that
>
>    3.  Hosts which are deliberately multihomed on distinct networks
>    should be able to recover from interface failures, but by mechanisms
>    above the TCP/internet layer, not within them.
>
> So, clearly the expectation there was that "multihomed" implied "[multiple]
distinct networks" and the ability for a host to recover from failures.
>
> IEN 178 has a section with that title. It's introductory comment is that
>
>              A subscriber  may want to have multiple  connections to a
>         communication  system  for reliability or performance reasons.
>
> It goes on to describe having multiple addresses, the ability to use any of
them, and the ability to optimize its use of them, among other things.
>
> The first definition I find that can be described as a "definition" is in RFC
1122; RFC 1123 continues the discussion.

Fred

Prior to RFC1122, I find a definition of multi-homing in RFC791, which is what I
usually use as a reference.

Tom Petch

>          A host is generally said to be multihomed if it has more than
>          one interface to the same or to different networks.  See
>          Section 1.1.3 on "Terminology".
>
> And by the way has a second 3.3.4 on "local multihoming". Since RFC 1122 is
"host" requirements, it doesn't discuss the multihoming of a network. What it
addresses (no pun intended) is a host that is part of two or more subnets,
whether that means two or more interfaces or one interface with multiple
subnets.
>
> RFC 1127, which is Bob Braden's "Perspective on the Host Requirements RFCs",
goes on to discuss "AS Multihoming", which he defines as
>
>    multihomed AS: an AS that has more than one connection to other ASs,
>       but refuses to carry transit traffic.
>
>
>
>
> Bringing this back to the draft in question, my understanding is that the
authors are working from the model in which:
>
> a) a residential/SOHO/other-edge-network has multiple upstreams
> b) said network has at least one CPE
> c) the multiple upstreams provide a prefix each
> d) as a result, the residential/SOHO/other-edge-network has multiple prefixes
overlaid in it.
>
> Every host, by RFC 1122's definition, is multihomed (it has more than one
subnet, regardless of physical connectivity), and the network is multihomed (it
has more than one upstream.
>
>
> Did I miss something? Randy's description of multihomed networks he runes is
perfectly accurate. But BGP is not a requirement for multihoming; what is a
requirement is "multiple addresses" or "multiple upstreams".
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