[c-nsp] Effect of simultaneous TCP sessions on bandwidth

[Youssef Bengelloun-Zahr]

Le 11 nov. 2013 à 04:22, Randy <randy_94108 at yahoo.com> a écrit :

> 
> 
>>>>      - TCP traffic hits some kind of limit and isn't able to achieve more
>>>> than 40-60 Mbits/s in average      <=== That's the problem we are facing
> 
> what happens if you do this - 
> 
> 
> a transfer from host A(fra) to host B(ham) and another transfer at the same time from host D(ham) to host C(fra)? Do still avg at 90M for each transfer or do both drop to the 40M avg? If you pull off 90M it would eliminate the link. If not; since you have enabled high performance options, tcp timestamping used to calculate RTT perceives congenstion(with the increase of traffic across link) and initiates slowstart.

Hello,

Funny you mention this :

a- first, we start transfer from A (FRA) to B (HAM), we achieve BW close to 90 mbits/s,

b- second, we start transfer from B to A (while first transfer is running) and BW for first transfer collapses.


> 
> if what you are seeing only applies for simultanours transfers:
> 
> A To B and B to A, It would seem to imply A and B are the bottlenecks.

Hello, seems very unlikely to me :

- At location A, we have a Brocade CER-RT acting as a PE delivering Layer 2 service to the customer.

Customer server is directly connected using a GigE port.

- At location B, we have some kind of Alcatel CPE provided by LL provider.

Customer server is directly connected using a FE port.

Thanks.



> 
> hth,
> ./Randy
>