RE: FCIP/iFCP : Guarantee In-Order delivery for FC N/NL_ports

["Y P Cheng" <ycheng@advansys.com>]

> It is not only the desire to inter-operate with legacy FC devices
> that drives this requirement.
> This is a mandatory requirement, since FC-FLA Table 3 mandates
> that N/NL_Ports originating FLOGI SHALL request in-order delivery in
> the FLOGI.  (by setting the "Sequential Delivery" bit in their class
> specific parameters for class 2 & 3 to 1.).
> - Santosh

If in-order-delivery is a MUST, the next question is "How many open
sequences?"  On a 10 Gb/sec network with long latency, we need many open
sequences to fill the pipeline.  This is the same problem as TCP window size
of iSCSI.  To keep all open sequences in order, in the worst case, there
will be a huge holding buffer in an iFCP and FCIP device.  We have just
moved the TCP window problem from an end-point into a bridge or gateway
device.  Hence, by just changing the protocol, the problem does not go away.

Y.P. Cheng, ConnectCom Solutions