Conflict resolution for symmetrical OLCs - which is the preferred mode?

Lyons, Terry TLyons at SONUSNET.COM
Thu Nov 1 11:40:41 EST 2001

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
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  +1 732 625-3003 ext 212

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