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

[Paul Long]

Paul,

A couple of other things regarding TD-26a.

1. We need to say something about the H.245 timers for the Setup-tunneled
TCS and MSD messages. Since the responses could be delayed well beyond the
normal H.245 timers or not even received at all, we need to effectively
disable the timers for these messages. Otherwise, the H.245 procedures could
require the calling EP to declare a protocol error. This just cleans up some
loose ends. How about adding the following sentence to the end of 8.2.1?

"For the TerminalCapabilitySet and MasterSlaveDetermination messages
tunneled in Setup, the corresponding H.245 timers, T101 and T106, shall not
expire."

Note that the behavior associated with the H.245 MSDSE N100 counter stays
the same. I guess we don't need to mention this, though.

2. Besides rewording, replace "it is recommended" in the following sentence
with "should."

Before:
"In order to expedite the Terminal Capability Set negotiation and
Master/Slave Determination, it is recommended to tunnel the H.245
TerminalCapabilitySet and MasterSlaveDetermination in the Setup message in
h245Control."

After:
"The calling endpoint should tunnel the H.245 messages,
TerminalCapabilitySet and MasterSlaveDetermination, in the Setup message. If
the called endpoint acknowledges these H.245 messages, the H.245 session can
be available to the calling endpoint one round-trip delay sooner than if the
calling endpoint did not tunnel these messages."

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


-----Original Message-----
From: Paul Long [mailto:Plong at smithmicro.com]
Sent: Wednesday, June 07, 2000 10:50 PM
To: ITU-SG16 at MAILBAG.INTEL.COM
Subject: Re: On TD26 - Fast TCS and M/S negotiation in H.323v4


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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