Subject: RE: Draft of updated WG charter

From: "Ayyasamy, Senthilkumar \(UMKC-Student\)" <[email-masked]>
Date: Fri, 9 Jan 2004 19:17:47 -0600

> I think address selection & path selection shouldn't be on the end 
> system side of the line, so an architecture which causes every end 
> system in every multi-homed network to do those jobs seems broken 
> to me
 
you mean the folks who are selling/using the route control products[1]
(which allows to select the first hop of the best route) are stupids? 
I was of the thought that *provider* selection (or path/address
selection) should be done by users and not *providers*. 
 
[1] http://www.nanog.org/mtg-0206/smart.html

---

From: Jay Ford <[email-masked]>
Date: Fri, 9 Jan 2004 23:52:40 -0600 (CST)

> selection) should be done by users and not *providers*.

The meaning of "user" & "provider" apparently vary with context.

Here's the structure in my piece of the net:
   host: end system with associated end user(s);
      knowledge of general Internet: almost none
   core routers: routers inside my AS which directly connect to user nets &
      to border routers;
      knowledge of general Internet: subset of whole net, subject to border
      routers
   border routers: routers at boundary of my AS, talking to core routers
      inside & other ASes outside;
      knowledge of general Internet: as much as my BGP peers tell them modulo
      the policy I impose based on what I know about links, providers...

The hosts & associated end users are not up to the job of doing anything
resembling intelligent path selection.  A scheme in which the
source/destination addresses selected by a host dictates a path seems
unlikely to work well.

The core routers know enough to make a good choice among the border routers.

The border routers know the correct next hop for all destinations.

This is a good split of complexity & responsibility, with the hosts not
having to do any of it.

________________________________________________________________________
Jay Ford, Network Engineering Group, Information Technology Services
University of Iowa, Iowa City, IA 52242
email: [email-masked], phone: 319-335-5555, fax: 319-335-2951

---

From: Iljitsch van Beijnum <[email-masked]>
Date: Sat, 10 Jan 2004 14:30:21 +0100

> The border routers know the correct next hop for all destinations.

I'm sorry, but I have to disagree. The only thing that border routers 
know, is  that _if_ something is reachable, what the next hop is. 
Whether or not something is indeed reachable is burried beneath layers 
of aggregation. Even if we can make the information for all sites 
available without aggregation (which I don't think we can, re the need 
for route flap dampening in the late 1990s when we already had 
aggregation), there is no way we can make routers keep track of the 
reachability status of individual hosts. However, it shouldn't be too 
hard to make hosts keep track of the reachability status of (the 
different addresses of) the hosts they're actively communicating with. 
TCP already does this in single-address fashion for the purpose of 
congestion control.

> This is a good split of complexity & responsibility, with the hosts not

I'm sure this model can accommodate some situations, such as carefully 
managed networks. However, many networks aren't managed to any 
noticeable degree (home networks), or the network only consists of a 
number of hosts that happen to be in each other's vicinity for a while. 
In these cases, hosts must step up to the challenge.

It occurs to me that IPsec tunneling in VPN boxes vs running SSL on the 
end-hosts has many similarities to what we're discussing here. Is there 
anything we can learn here?