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

"Kartik Chandrayana (karchand)" <karchand@cisco.com> Thu, 20 November 2008 20:54 UTC

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Thread-Topic: [ledbat] list of reasons for needing multiple TCP connections
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From: "Kartik Chandrayana (karchand)" <karchand@cisco.com>
To: Joe Touch <touch@ISI.EDU>
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Subject: Re: [ledbat] list of reasons for needing multiple TCP connections
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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.

Thanks,
-Kartik

-----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

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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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