RE: iFCP: iFCP -06 comments

[Black_David@emc.com]

> > > > 10.4 b) What happens when the broadcast frame exceeds the MTU size?

[... snip ...]

> We had intended to use IP datagram fragmentation

Oh ... I'm not sure that's a real good idea.  Using IP fragmentation is
one of the few ways to make UDP datagram delivery even less reliable
than it already is.  This puts FC broadcast at the mercy of code that
doesn't
fragment correctly at both iFCP and network nodes (infrequently used code
paths are subject to bit rot) and systems in the network that can't or
don't want to deal with IP fragments (e.g., firewalls and NAT/NAPT boxes)
and hence drop rather than fragment.  For source fragmentation, discovering
the MTU to fragment to may also be a problem area.

While I'm not going to put my foot down yet, I would advise thinking about
using TCP to deliver FC broadcast frames over iFCP.  If FC broadcasts are
infrequent and not performance critical, perhaps iSNS could provide the
FC broadcast forwarding service?  This would also clean up any issues around
whether an iFCP gateway knows about all the other gateways in the fabric,
as the iSNS server always knows this.

Thanks,
--David

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