[LARTC] TCP MSS clampage

[LARTC] TCP MSS clampage

[Tim Carr]

Hey,

My internet is provided via ADSL using PPPoE. When I take a look at 
ifconfig's output, I see that eth0 has an MTU of 1500, and ppp0 has an MTU 
of 1492. I don't _think_ that rp-pppoe (my pppoe util) is clamping the MSS. 
I am noticing some latency when there's a lot of bandwidth in use (but not 
 >90%). What should I clamp, eth0/ppp0? How much? And what with, rp-pppoe, 
or tc/iproute2/etc ?  I guess I don't really understand clamping MSS, can 
someone explain it in laymans terms? I have read the lartc-FAQ, and the only 
time I see clamping-MSS mentioned is section 15.7, which doesn't really 
explain why you'd do it.

Apologies if M$ makes this email look squonky in any way.

Thanks,

Tim Carr

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Re: [LARTC] TCP MSS clampage

[bert hubert]

On Thu, Feb 28, 2002 at 04:02:54PM +0000, Tim Carr wrote:
> Hey,
> 
> My internet is provided via ADSL using PPPoE. When I take a look at 
> ifconfig's output, I see that eth0 has an MTU of 1500, and ppp0 has an MTU 
> of 1492. I don't _think_ that rp-pppoe (my pppoe util) is clamping the MSS. 
> I am noticing some latency when there's a lot of bandwidth in use (but not 

Don't think, meassure :-)

>  >90%). What should I clamp, eth0/ppp0? How much? And what with, rp-pppoe, 
> or tc/iproute2/etc ?  I guess I don't really understand clamping MSS, can 
> someone explain it in laymans terms? I have read the lartc-FAQ, and the only 
> time I see clamping-MSS mentioned is section 15.7, which doesn't really 
> explain why you'd do it.

If you don't experience any problems then by all means do not tcp clamp.
rp-pppoe comes with wonderful documentation, I suggest you read it :-)

Regards,

bert

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