RE: An IPS Transport Protocol (was A Transport Protocol Without ACK)

[Black_David@emc.com]

> Now the solution. In the IPS protocol breaks down the 1MB data into 25
> 20K-sequences.  Each sequence has ten 2K segments.  Each sequence will be
> acknowledged individually.  We define a Delay Constant between the
transfer
> of two consecutive sequences.  On a not-so-busy network, the delay should
be
> zero.  Hence, the sender sends all 25 sequences or 500 segments without
> delay.  Using a 1 Gb adapter, the whole 1 MB of data goes out in 10 msec.
> 25 msec later they arrive at the destination.  Each sequence is
acknowledged
> individually.  25 msec later, all 25 ACKs come back to the sender.  The
> whole one 1 MB is transferred in 60 msec, not 1.6 sec.  

Sorry, that doesn't achieve the goal of complying with RFC 2581.  If the
"Delay
Constant" is set incorrectly for the network, the result is disastrous - the
whole
point of slow start is to set and adjust parameters like the "Delay
Constant"
automatically in a fashion independent of network conditions.  Also see the
discussion in RFC 2581 about initial window size.

> Personally, I will never implement an iSCSI provider using TCP
> stream oriented protocol.  I will implement the aforementioned congestion
> management in a fibre channel adapter today as an IPS provider.  As long
as
> an IPS provider deals with the PDU's correctly, it should always
> interoperate with another node which uses TCP stream oriented protocol.

In other words, change the TCP protocol to make it go faster for your
traffic
without changing the TCP header format.  Not only is this not a good idea,
but the approved WG charter specifically PROHIBITS the WG from working
on this, unless the argument can be made that the changes are required for
storage traffic.  I believe the current WG consensus is that TCP congestion
control is good enough for storage traffic, and hence would like to put an
end
to this thread.

--David

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David L. Black, Senior Technologist
EMC Corporation, 42 South St., Hopkinton, MA  01748
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