[imtch323implementors] Conflict resolution for symmetrical OL Cs - which is the preferred mode?

Lyons, Terry TLyons at SONUSNET.COM
Thu Nov 1 16:09:38 EST 2001


Paul,

>From B.2.2.2/H.245v7 again:
simultaneousCapabilities is a set of AlternativeCapabilitySet. It is used to
list the simultaneous capabilities of the terminal.
An AlternativeCapabilitySet is a sequence of CapabilityTableEntryNumbers.
Only those CapabilityTableEntrys that have been defined shall be present in
an AlternativeCapabilitySet, although it is possible to define
CapabilityTableEntrys and refer to them in the same TerminalCapabilitySet.
If a terminal has a preference for the mode it would like to transmit or
receive, and wishes to express this when transmitting its capabilities, it
may do so by listing elements in AlternativeCapabilitySets in order of
decreasing preference.

So I think you mean to refer to the order in AlternativeCapabilitySet.

The question remains: how to compare capabilities that are listed in
different AlternativeCapabilitySets.
These AlternativeCapabilitySets may occur in different elements of
simultaneousCapabilities (unlikely)
or in different CapabilityDescriptors (more likely).

Would you agree that the preference between two capabilities is structured
as follows?

        1. compare descriptor numbers - lowest is preferred
        2. else compare simultaneousCapability element index - lowest is
preferred
        3. else compare AlternativeCapabilitySet element index - lowest is
preferred

There is text in B.2.2.2 to support #1 and #3 of the above.  Nothing is said
about #2.
And since other permutations of logic are possible, some clarification would
help.

- TLyons at sonusnet.com  +1 732 625-3003 ext 212


-----Original Message-----
From: Paul Long [mailto:plong at IPDIALOG.COM]
Sent: Thursday, November 01, 2001 3:04 PM
To: ITU-SG16 at mailbag.cps.INTEL.COM
Subject: Re: [imtch323implementors] Conflict resolution for symmetrical
OLCs - which is the preferred mode?


Terry,

B.2.2.2 refers to capabilityDescriptors, which are numbered according to
preference, whereas C.4.1.3 refers to simultaneousCapabilities, which are
arranged in order of preference. There is no conflict.

Paul Long
ipDialog, Inc.

-----Original Message-----
From: Lyons, Terry [mailto:TLyons at sonusnet.com]
Sent: Thursday, November 01, 2001 10:41 AM
To: ITU-SG16 at mailbag.cps.INTEL.COM
Cc: 'imtch323implementors at mail.imtc.org'; Lyons, Terry
Subject: [imtch323implementors] Conflict resolution for symmetrical OLCs
- which is the preferred mode?


Please consider these two extracts from RECOMMENDATION H.245 - VERSION 7

B.2.2.2 Capability Descriptors

If a terminal has a preference for the mode it would like to transmit or
receive, and wishes to express this when transmitting its capabilities, it
may do so by giving CapabilityDescriptors that relate to its preferred mode
or modes small values of capabilityDescriptorNumber.

C.4.1.3 Conflict resolution

When the master and the slave have indicated choices of receive capabilities
for a particular media type, the slave should attempt to open a logical
channel for the master's most preferred capability for which it has
capability, as given by the order the master has expressed its capabilities;
and the master should attempt to open a logical channel for its most
preferred capability for which the slave has capability, as given by the
order it has expressed its capabilities.

---------------------------------------

The new wording "the order the master has expressed its capabilities" is
insufficiently defined to act on and seems to conflict with the old
definition of prefered mode.

As explained in section B.2.1, a terminal's total capabilities may be
expressed over an extended period of time, not in a single message
(Terminals may dynamically add capabilities during a communication session
by issuing additional CapabilityDescriptor structures, or remove
capabilities by sending revised CapabilityDescriptor structures).
And the capability table entries by themselves are incomplete without
accompanying descriptors
(The terminal's total capabilities are described by a set of
CapabilityDescriptor structures).
Both capabililty table entries and capability descriptors are already
numbered.
Is the Order of Expression an additional attribute that needs to be inferred
when processing the pieces of a received Terminal Capability Set?

It seems that some clarification is needed.  Preferrably, C.4.1.3 should
refer back to B.2.2.2 for an operational definition.

- TLyons at sonusnet.com  +1 732 625-3003 ext 212

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