[c-nsp] IPv6 in IP overhead and ip tcp adjust-mss

[Tom Storey]

IPv6 headers are 40 bytes, twice that of IPv4.

Add 20 bytes for TCP headers, just as you would with IPv4, which gives  
you 60 bytes total for TCP/IPv6.

If using PPPoE you'd probably want an MSS of 1432 for IPv6.

However, IPv4 headers can vary in length to greater than 20 bytes,  
but, IPv6 has a fixed IP header length so it should be predictable.  
Unless youre doing something fancy, 1452 should suffice for IPv4 in  
most deployments (at least going by experience).

Tom

On 19/03/2008, at 8:45 PM, Kevin Barrass wrote:

>
> Hi
>
> I'm playing with a IPv6 tunnel broker on my home ADSL/Cisco 1701 for
> testing as we are deploying IPv6 at work over a long period.
> On my ADSL router I have ip tcp adjust-mss 1452 to account for the ppp
> over atm encapsulation overhead im assuming 1452 is correct as ive had
> varying recommendations. Does anyone know what the overhead for IPv6  
> in
> IP is as I would like to adjust the MSS on traffic over the IPv6  
> tunnel.
>
> Kind Regards
>
> Kev
> _______________________________________________
> cisco-nsp mailing list  cisco-nsp at puck.nether.net
> https://puck.nether.net/mailman/listinfo/cisco-nsp
> archive at http://puck.nether.net/pipermail/cisco-nsp/