Subject: [Tsvwg] Are IP routers transparent to UDP Lite ?

From: Straub Gilles <[email-masked]>
Date: Mon, 14 Jun 2004 15:39:55 +0200

Hello All,

I am trying to evaluate UDP Lite technique. I had a look to the 2003 draft
on this matter.
I had a question regarding UDB checksum processing in IP routers : although,
in principle a transport layer is processed in end to end (in source and
destination), I wanted to check that no CRC check is performed in IP routers
: is anybody aware of IP routers where UDP or TCP checksum computation
(check & discard) is or can be enabled ? 

If UDP checksum computation is always done in the host only, then UDP lite
applications can be developped on existing internet, otherwise, this would
require router modifications.
Thanks in advance for any feedback I would get on this topic

Best Regards

Gilles STRAUB
[email-masked]
THOMSON

_______________________________________________
tsvwg mailing list
[email-masked]
https://www1.ietf.org/mailman/listinfo/tsvwg

---

From: Joe Touch <[email-masked]>
Date: Mon, 14 Jun 2004 12:16:41 -0700

> (check & discard) is or can be enabled ? 

That would kill IPsec'd packets... a protection that would defeat IPsec 
isn't very protective ;-(

> require router modifications.

Any router that performed that sort of delayed fill-in or check is 
basically performing as a host anyway. It would need to be updated as 
any host would, if the transport protocols supported changed.

Joe

---

From: Gorry Fairhurst <[email-masked]>
Date: Tue, 15 Jun 2004 19:56:34 +0100

Two devices that do recompute transport checksums are:

     Network Address Translation (NAT) Midboxes
     and gateways that do some sort of connection splitting

I don't count these as IP routers, although these functions can be 
performed on router hardware platforms... Note that UDP-Lite has a 
different IP protocol type, so these devices will anyway treat the IP 
packets carrying UDP-Lite in a different manner to that of TCP, UDP, etc.

A "normal" router should pass transport checksums as-is.

Gorry Dairhurst