Re: [ledbat] list of reasons for needing multiple TCP connections

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Kartik Chandrayana (karchand) wrote:
> Joe,
> 
>   I am also not aware if parallelization of network code is implemented
> in OSes. However, I think it would be reasonable to expect that tcpcb
> lookups are done in a centralized fashion and once that is done,
> multiple tcp's can be processed in different cpus. Even the lookups can
> be distributed as they are only a read operation.

Parallelizing TCP includes dealing with not only the TCP code, but also
the IP input queue access, timers, etc. I am not as sure that there's a
one TCP per core mapping in current OS's - though I'd be glad to hear
someone *confirm* it.

Joe

> -----Original Message-----
> From: Joe Touch [mailto:touch@ISI.EDU] 
> Sent: Thursday, November 20, 2008 2:44 PM
> To: Kartik Chandrayana (karchand)
> Cc: Andrew G. Malis; ledbat@ietf.org
> Subject: Re: [ledbat] list of reasons for needing multiple TCP
> connections
> 
> 
> 
> Kartik Chandrayana (karchand) wrote:
>> Andy, Joe:
> 
>> One reason I can think of using multiple TCP connections is to 
>> overcome the non-negotiation of window-scale parameter on most boxes. 
>> With default window scale parameters, i.e 0, the congestion window is 
>> limited to 64KB only and thus for any pipe with 
>> bandwidth-delay-product greater than 64KB, a single TCP connection 
>> cannot keep the pipe full. In such a case, it would be beneficial to
> have multiple TCP connections.
>> Also, since TCP design was mostly with single cpu in mind, I think 
>> multiple TCP connections can harness the multi-cpu architectures 
>> better than a single lean fast TCP.
> 
> That presumes that the OS implements parallelization in the network
> code; I don't know if that's recently offered, but it has been the
> sticking point in the past.
> 
> Joe
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