From: "Margaret Wasserman" <email@example.com>
Date: June 28, 2006 5:17:16 PM EDT
Cc: "'Tony Hain'" <firstname.lastname@example.org>, "'Tim Chown'"
<email@example.com>, "'Radia Perlman'" <Radia.Perlman@sun.com>,
"'Alex Zinin'" <firstname.lastname@example.org>, "'Erik Nordmark'"
<email@example.com>, <Donald.Eastlake@motorola.com>, "'Dave
Oran'" <firstname.lastname@example.org>, "'Bill Fenner'" <email@example.com>,
"'Jari Arkko'" <firstname.lastname@example.org>, <email@example.com>
Subject: RE: Review of draft-ietf-v6ops-nap-02.txt
As I understand it, there is a current proposal in the v6ops WG (in
draft-ietf-v6ops-nap-03-draft0.txt) to publish the following
There are other possible scenarios for the extreme situation when a
network manager also wishes to fully conceal the internal IPv6
topology. In these cases the goal in replacing the IPv4 NAT
is to make all of the topology hidden nodes appear from the outside
to exist at the edge of the network, just as they would when
o One could use explicit host routes and remove the correlation
between location and IPv6 address. In the figure below the
would be allocated prefixes from one or more logical subnets,
would inject host routes to internally identify their real
attachment point. This solution does however show severe
scalability issues and should be limited to uses with
substantially fewer than the maximum number of routes that
can support (generally about 50,000).
| Simple Gateway | Logical subnet
| or Home Agent |-+-+-+-+-+-+-+-+--
+------------------+ for topology
| hidden nodes
Real internal -------------+-
topology | |
The more I think about this proposal, the more questions arise,
(1) Do we really mean that the router in this picture would be a
gateway or home agent"? I don't think that is consistent with the
it could handle 50,000 routes. Or that it would run an IGP, for that
(2) What mechanism would hosts use to inject host routes into the
is that secured?
(3) How will local nodes know to use topology-specific ULA
local communication? What happens if they don't? Could this
result in a
large amount of internal traffic bouncing off of the "simple
gateway or home
(4) How does this interact with multicast traffic and ND. Can a
node on the
"logical subnet" send a link-local multicast packet on the logical
and safely assume that it will reach all of the nodes on that
subnet and no
one else? If not, how does this interact with ND?
(5) Would autoconfiguration be used on the logical subnet, or would
expected to get those addresses through other means?
(6) What advantages (if any) does this approach have over using a
subnet internally and using L2 switches and VLANs to handle
delivery? What disadvantages does it have when compared to that
(7) How does this proposal relate to the work currently underway in
If we decide that we actually want to make this recommendation, I'd
that we remove it from this document and make this recommendation in a
separate document that covers the scalability issues, the answers my
questions above, and any other factors that may affect the
From: Fred Baker [mailto:firstname.lastname@example.org]
Sent: Wednesday, June 28, 2006 4:00 PM
To: Margaret Wasserman; Dave Oran; email@example.com
Cc: 'Tony Hain'; 'Tim Chown'; firstname.lastname@example.org
Subject: Re: Review of draft-ietf-v6ops-nap-02.txt
Radia and Dave:
There is a dispute going on regarding the scalability of
topology hiding by what amounts to IS-IS level 1 routing
(identifying hosts in a multi-LAN network by their host
identifier and using a common subnet ID for the domain). Do
you know of available documentation of IS-IS level 1 routing
and its tested scalability?
As Radia knows, this question is also being looked at in IEEE
802.1, which presumes that there is only a single
multi-LAN-LAN, and that MAC addresses are used to route within it.
On Jun 28, 2006, at 12:40 PM, Margaret Wasserman wrote:
50K is an order of magnitude higher than the analysis in
presentation would seem to indicate. His presentation
routing will only scale to something on the order of 1K nodes.
free to check with Alex, though, as he certainly has more
understanding of IGP scaling than I do.
If this document is going to recommend doing flat routing
hiding, I think that the WG needs to do the analysis to
this is a valid and scalable technique.