Subject: [Megaco] StreamIds in SCTP as transport

From: "Rashim Anand" <[email-masked]>
Date: Tue, 22 Jul 2003 18:10:33 -0700

Hi,

In H.248 annex H (transport over SCTP), section H.7, a recommendation is
given -

It is recommended that transactions related to one context are transported
over the same stream.

Now suppose the following sequence of messages is exchanged ->

   MGC  ------STR 1-----------> MG
          T=1 { C=$ ... }

   MGC  <---------------------- MG
          Reply=1 { C=5 ... }

   MGC  ------STR 2-----------> MG
          T=2 { C=5 ... }

   MGC  ------STR 2-----------> MG
          T=3 { C=5 ... }

   MGC  ------STR 2-----------> MG
          T=4 { C=5 ... }

where, "T=[0-9]* { C=... }" refers to transaction requests while,
"Reply=[0-9]* { C=... }" refers to transaction replies,
"C" stands for ContextId and
STR1, STR2 refer to the outgoing stream identifiers used by the MGC.

The question is - does having STR2 different from STR1 violate the
philosophy behind the H.7 recommendation?

IMHO, it does not since the context id 5 becomes known to the MGC only after
getting a reply from the MG. Without the assigned context id, the MGC can
not send any transactions related to that context and so can not cause any
head of line blocking to transactions related to other contexts.

Please let me know your opinion?

Thanks,
Rashim Anand

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