Re: State of play with Shim6 documents

[Brian E Carpenter <brc@zurich.ibm.com>]

On 2007-01-24 19:06, Henderson, Thomas R wrote:
> > -----Original Message-----

...
> >      * TCP Checksum Failure
> >
> >            Its not clear what the WG want to do on this. Suggestions?
>
> I would vote to align the checksum with the locators, under the
> assumption that defining an alternate probing mechanism to discover
> these problems is more cumbersome.  If you care strongly enough about
> using the transport checksum to detect incorrect address rewriting in
> certain error scenarios, that may argue for putting better error
> detection in the shim proper, but I'm not sure it is a high enough
> probability event.

I have the opposite view. I think we should keep rock solid
on the notion that shim6 preserves the end to end model as far
as upper layers are concerned. Fixing the TCP checksum twice,
on the way in and out of the shim, would be an ugly hack on
that model, and also the first step towards inserting all
sorts of ALG functionality in the shim to compensate for
misbehaving middleboxes.

Before taking any other decision, I'd want to see firm
observational evidence that there is a real problem. TCP
checksums are no business of middleboxes, except for the
TCP relay case which would probably need to be shim6-aware.

    Brian