Subject: [Tsvwg] M3UA: SIF max

From: "Brian F. G. Bidulock" <[email-masked]>
Date: Sat, 10 Nov 2001 19:57:26 -0600

Greg,

It has come up on TSV that SCTP is incapable of fragmenting
messages until the complete message has arrived.  This has
a significant latency impact on M3UA interworking into SS7
where SS7 has an SIF max (e.g. MTP-3b) which is larger that
the path MTU of the SCTP association (e.g., Ethernet).
As a result, MTP-Users at the ASP should not send MSUs that
are larger than the path MTU (minus tax) and this artificial
SIF max should be communicated to ASP MTP-Users in the same
fashion as it is done for normal MTP-Users.

M3UA needs to address this with a SHOULD somewhere in the
text, something like:

   The ASP (or IPSP) SHOULD NOT send DATA messages representing
   MSUs that are greater that the SIF maximum, which is calculated
   as the lesser of the SIF maximum provided by the SG for the
   specific route, or the path MTU minus SCTP message and Chunk
   tax.

TCP transport need not impose this requirement.  It only
applies to SCTP to address SCTP's deficiency in this regard.

--brian

-- 
Brian F. G. Bidulock
[email-masked]
http://www.openss7.org/

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