Subject: draft-mahalingam-dutt-dcops-vxlan-00

From: Anton Ivanov <[email-masked]>
Date: Thu, 20 Oct 2011 08:52:10 +0100

Hi list,

Some comments:

Section 5 - UDP checksumming

If the outer UDP is correctly checksummed the virtual switch MAY trust 
the checksum and instruct locally connected endpoints not to checksum 
the inner frame.

Rationale - if traffic starts locally and terminates locally in a 
datacenter inner checksum has to be computed fully in software by the 
sending/receiving VMs. That is extra overhead which is not really 
necessary if the sending and the receiving host have computed the outer 
checksum in hardware on the physical ethernet interface (or in software 
in the ethernet driver).

Unless I am mistaken, this is similar to the case where checksums are 
being turned off on tap for local to local traffic. In this case we are 
simply extending it from one virtual switch to another.

-- 
     Humans are allergic to change. They love to say, "We've always
done it this way." I try to fight that. That's why I have a clock
on my wall that runs counter-clockwise.   -- R.A. Grace Hopper

A. R. Ivanov
E-mail:  [email-masked]