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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: Performance of iSCSI, FCIP and iFCPI am more hopeful on the point of adapting the algorithm as environments change. The TCP gurus are conservative but not totally inflexible. -----Original Message----- From: Victor Firoiu [mailto:vfiroiu@nortelnetworks.com] Sent: Thursday, January 18, 2001 1:34 PM To: somesh_gupta Cc: IPS Reflector Subject: Re: Performance of iSCSI, FCIP and iFCP Somesh, I was looking more at the comparison between the FCIP case of multiple FC connections (all connections between two FCIP gateways) per TCP connection and the iFCP case of one/few TCP connections per FC connection (thus multiple TCP connections per pair of iFCP gateways). I think that, in general, one TCP connection per storage connection is closer to "one/two TCP connections per user" model, and thus easier to defend as being "fair", compared to multiple TCP connections per storage connection. I agree, this is quite a fuzzy quantification, but is as precise as RFC 2914 and 2309 get in this matter. Regarding modifing TCP congestion control as you suggest, I am again very skeptical. Victor Somesh Gupta wrote: > > Victor, > > I just assumed that you were familiar with the iSCSI specification > of multiple connections per session - which is essentially as you > describe in the second last paragraph - there is one big "flow" > between the initiator and the target (called an iSCSI session) > which is then striped across multiple TCP connections - and I > think people assumed that your statements were in support of > such a proposal. > > Having said that, the math still holds. And also the fact that > fundamental limits to the throughput of a single TCP connection > really do require a change to TCP congestion avoidance (esp when > mistaking link error for congestion) formulae. > > If the link error rate is such that errors occur faster than time > to recover (or of that order), TCP will have to accomodate that > somehow. I don't think the TCP gurus are inflexible in this area > - PAWS, window scaling, and SACK are all example of TCP accomodating > the characteristics of the underlying network. > > Somesh >
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