Fast Connect & Bi Directional channels

Sasha Ruditsky sasha at
Mon Dec 11 08:04:54 EST 2000


It looks like there is yet another bug in the fast start procedure.
It is related to bi-directional channels establishment.

Standard says that in each bi-directional channel proposal there should be
unique forwardLogicalChannelNumber.
Standard says nothing about the value of this field in the accepted
bi-directional OLC.

It is known that bi-directional channels need 2 logical channel numbers
(forward and reverse).
I see 2 options for the value of forwardLogicalChannelNumber field in the
accepted bi-directional OLC:

1. It may be the same value as the forwardLogicalChannelNumber in the
corresponding proposal.
In this case we do not have the logical channel number for the reverse
This works OK till we are in fast start, but after H.245 connection
it will be impossible to perform H.245 actions on the reverse direction of
the channel.

2. It may be the unique logical channel number that is provided by calling
party and 
identifies the channel -- the reverseLogicalChannelNumber.
The problem with this is that caller does not know to which proposal this
channel belongs.
BTW The same problem exists with the unidirectional channels from callee to
caller and the solution 
is just to find the corresponding proposal, using different channel

I personally prefer the second option because it is more correct from the
H.245 point of view.
But, In any case it should be decided which is the standard one .


Alexander(Sasha) Ruditsky 
RADVision Ltd.
24 Raul Wallenberg St.   
Tel Aviv 69719  Israel           

Tel:       +972-3-645-5220
Fax:       +972-3-644-2903
Direct:    +972-3-645-5273
sasha at

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