Re: Network Performance Issues.

[Alan Chandler <alan@chandlerfamily.org.uk>]

On Sunday 15 April 2007 16:20, Alan Chandler wrote:

> Firstly the case of direct downloading from my gateway.  This is a
> summary of a three protocol exchanges using wireshark
>
> youtube->me  http continuation seq 189688 next seq 191136
> youtube->me  http continuation seq 191136 next seq 192584
> me->youtube tcp ack seq no 192584
> youtube->me  http continuation seq 192584 next seq 194032
>
> Now when I look at a similar exchange when I am using the gateway
> machine just as a hop and there is a machine behind the gateway I get
> a different pattern
>
> youtube->me http cont seq 4344 next seq 5792
> me->youtube tcp ack seq 5792
> youtube->me http cont seq 7240 next seq 8688
> me->youtube dup ack seq 5792
> youtube->me http cont seq 10136 next seq 11584
> me->youtube dup ack seq 5792
> youtube->me http cont seq 5790 next seq 7240
> me->youtube tcp ack seq 8688
> youtube->me http cont seq 8688 next seq 10136
>
>
> As you can see, in this case, it appears that some packets are being
> lost and have to repeated via a dup ack.
>

It appears to be frameing errors at the ethernet level.  I am not sure 
why forwarding packets causes the problem, but the wan interface shows 
approx 1% of all packets have frameing errors.

Does anyone know what causes them


-- 
Alan Chandler
http://www.chandlerfamily.org.uk