On TD26 - Fast TCS and M/S negotiation in H.323v4

Paul Long Plong at SMITHMICRO.COM
Wed Jun 7 23:50:28 EDT 2000


Paul,

While you're at it, I would like to propose these (hopefully)
uncontroversial corrections and a clarification to TD-26a. Here are my
recommendations.

1. However rare, an EP may have a valid reason to reject TCS or MSD.
Therefore, we cannot require that the called EP always respond with TCSAck
and MSDAck. Replace this passage:

"... it shall include the fastStart element and the h245Control element
including both the TerminalCapabilitySetAck for the calling endpoint, the
TerminalCapabilitySet for the called endpoint and the
MasterSlaveDeterminationAck in the same H.225.0 message."

with this:

"... it shall encode the fastStart element and the h245Control element in
the same call-signalling message. This h245Control element shall contain the
TerminalCapabilitySet for the called endpoint and the called endpoint's
responses to the calling endpoint's TerminalCapabilitySet and
MasterSlaveDetermination."

2. Likewise, replace this:

"If the h245Control element with the TerminalCapabilitySetAck for the
calling endpoint, the TerminalCapabilitySet for the called endpoint and
MasterSlaveDeterminationAck are not received in the same message as
fastStart (e.g., because the called endpoint is pre-H.323v4), the fast start
procedures shall be completed, but not the Terminal Capability Set
negotiation and the Master/Slave Determination procedures."

with this:

"If the h245Control element with the called endpoint's TerminalCapabilitySet
and the called endpoint's responses to the calling endpoint's
TerminalCapabilitySet and MasterSlaveDetermination are not received in the
same message as fastStart (e.g., because the called endpoint is
pre-H.323v4), the fast start procedures shall be completed, but not the
Terminal Capability Set negotiation and the Master/Slave Determination
procedures."

3. It's not a big deal, but I'd like to make the disposition of the MSD and
TCS procedures clearer by adding this to the end of the above sentence:

", as if they had never been initiated by the calling endpoint"

Paul Long
Smith Micro Software, Inc.
"Primum non nocere"

-----Original Message-----
From: Paul E. Jones [mailto:paulej at PACKETIZER.COM]
Sent: Wednesday, June 07, 2000 2:59 AM
To: ITU-SG16 at MAILBAG.INTEL.COM
Subject: Re: On TD26 - Fast TCS and M/S negotiation in H.323v4


Jane,

I suspect that TD-26 has the procedural issues addressed-- it will just
be a
matter of specifying the usage of a different field.

I'll have to review what is written there, but the most obvious way to
prevent race conditions is to specify that channels may not be opened
via
H.245 until Fast Connect is accepted, explicitly refused, or implicitly
refused by not receiving a fastStart element up to and including
CONNECT.

Paul

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