option 212 for 6RD

Mikael Abrahamsson swmike at swm.pp.se
Tue Jan 15 09:08:14 CET 2013

On Tue, 15 Jan 2013, Tore Anderson wrote:

> So the RA LAN MTU trick really only helps TCP, correct? What is gained 
> from lowering the LAN MTU by means of RA, rather than rewriting the TCP 
> MSS field as we've "always" done in IPv4?

Because I have not seen IPv6 TCP MSS REWRITE on the CPEs I've looked at.

> TCP MSS clamping, on the other hand, could be done by the 6RD BR, and 
> yield beneficial results for all the subscribers (regardless of their 
> HGWs implementing the RA LAN MTU trick or not).

Well, that is a problem because some of the best 6RD platforms are 
completely stateless and don't do MSS rewrite. You have to look into every 
packet to do this, consuming resources.

Doing the RA trick or doing MSS clamping in the CPE is a more distributed 
way that is fine by me.

Mikael Abrahamsson    email: swmike at swm.pp.se

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