Subject: Re: I-D Action: draft-foglar-ipv6-ull-routing-00.txt

From: Brian E Carpenter <[email-masked]>
Date: Fri, 15 Sep 2017 17:29:22 +1200

Hello,

Re https://tools.ietf.org/html/draft-foglar-ipv6-ull-routing-00

"One of the goals of IPv6 was to have a sufficiently long address
to allow grouping in fields to simplify routing decisions."

What makes you believe that? I don't recall such a goal in the IPng
process, and I can't see any trace of it in RFC1752 or RFC1726.

I do find some rather different considerations in RFC1726:

> 5.1 Scale
> 
>    CRITERION
>       The IPng Protocol must scale to allow the identification and
>       addressing of at least 10**12 end systems (and preferably much
>       more).  The IPng Protocol, and its associated routing protocols
>       and architecture must allow for at least 10**9 individual networks
>       (and preferably more).  The routing schemes must scale at a rate
>       that is less than the square root of the number of constituent
>       networks

which means that routing via a binary tree of addresses was not
considered OK.

...
> 5.2 Topological Flexibility
> 
>    CRITERION
>       The routing architecture and protocols of IPng must allow for many
>       different network topologies.  The routing architecture and
>       protocols must not assume that the network's physical structure is
>       a tree.

ditto.

So regardless of where we are today, I believe your assertion quoted
above is not true. In fact the exact opposite was the case when IPv6
was designed.

Now, if I ignore the stranger aspects of your proposal, you are 
proposing to subnet a /64 using something like a binary tree. It might
even work, at the price of replacing a great deal of existing software
and hardware. However, is there really a need for cut-through routing
in sensor networks, which seems to be your target scenario?

Regards
   Brian Carpenter

---

From: Bob Hinden <[email-masked]>
Date: Fri, 15 Sep 2017 10:49:24 +0300

Brian,

> On Sep 15, 2017, at 8:29 AM, Brian E Carpenter <[email-masked]> wrote:
> 
> Hello,
> 

I agree, I don’t remember anything like the goal written above.

Bob

> --------------------------------------------------------------------
> IETF IPv6 working group mailing list
> [email-masked]
> Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6
> --------------------------------------------------------------------

---

From: Mikael Abrahamsson <[email-masked]>
Date: Fri, 15 Sep 2017 09:56:52 +0200 (CEST)

On Fri, 15 Sep 2017, Brian E Carpenter wrote:

> "One of the goals of IPv6 was to have a sufficiently long address to 
> allow grouping in fields to simplify routing decisions."

Well, it's certainly used that way. If you go to an RIR you can ask for a 
lot more address-space than you can in IPv4 "to simplify routing".

So if I say "this device only sends /50 to the network, it has 48 ports, 
each port gets /56, that means I am never using a /52 out of this /50", 
then that's typically fine.

https://www.ripe.net/publications/docs/ripe-552#3

"3.4. Aggregation

Wherever possible, address space should be distributed in a hierarchical 
manner, according to the topology of network infrastructure. This is 
necessary to permit the aggregation of routing information by ISPs and to 
limit the expansion of Internet routing tables.

This goal is particularly important in IPv6 addressing, where the size of 
the total address pool creates significant implications for both internal 
and external routing.

IPv6 address policies should seek to avoid fragmentation of address 
ranges.

Further, RIRs should apply practices that maximise the potential for 
subsequent allocations to be made contiguous with past allocations 
currently held. However, there can be no guarantee of contiguous 
allocation."

-- 
Mikael Abrahamsson    email: [email-masked]

---

From: Ole Troan <[email-masked]>
Date: Fri, 15 Sep 2017 10:10:39 +0200

> process, and I can't see any trace of it in RFC1752 or RFC1726.

“Addressing can follow topology or topology can follow addressing; choose one” - Y Rekhter

Goal or no goal, we know of no other way to make the routing system scale.

Ole

---

From: Brian E Carpenter <[email-masked]>
Date: Sat, 16 Sep 2017 11:31:45 +1200

> Goal or no goal, we know of no other way to make the routing system scale.

Sure. I agree with that and with the RIPE policy that Mikael cited. Believe
me, everybody in the IPng discussion was acutely aware of the tension between
PA and PI addressing and the benefits of aggregation when possible. But that
is very different from the quoted "goal", which simply wasn't there. Allowing
topological aggregation was a goal, of course, but that's always been a
matter of prefix assignment policy, not of the protocol design.

Please note that I did not say that their idea will not work. It's the
"alternative fact" that I'm concerned about.

    Brian

---

From: Mark Smith <[email-masked]>
Date: Sat, 16 Sep 2017 11:06:35 +1000

>From what I've read in Christian Huitema's IPv6 book, at one stage
there was a thought of swapping the source and destination address
fields so that the DA field was first, to facilitate this sort of
cut-through forwarding. From memory, the explanation was that it was
decided against was because fields other than the just the DA address
have to be processed during layer 3 forwarding.

Regards,
Mark.