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<DIV><FONT face=Arial>Folks,</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial>Since we're raising issues with coding Q.931 IEs, I
thought that it would be appropriate to post this message I received some time
back. (I removed the person's name and such, in case they preferred not to
share this with the world.)</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial>Is this a change that we should consider?</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial>Paul</FONT></DIV>
<DIV> </DIV>
<DIV style="FONT: 10pt arial">----- Original Message (modified) ----- </DIV>
<DIV> </DIV>
<DIV><FONT size=2>During recent H323 interoperability testing in Portland the
problem detailed below was identified. I could not find an existing Implementors
Guide or draft recommendation that covers this issue. Could you take a look at
this and let me know if there is an existing decision (or update) on this
item.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=2>Affected recommendation:</FONT></DIV>
<DIV><FONT size=2>H225</FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=2>Summary:</FONT></DIV>
<DIV><FONT size=2>Q931 and H225 descriptions of Bearer Capability IE octet 4 are
not consistent</FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=2>Description:</FONT></DIV>
<DIV><FONT size=2>In Q931 Section 4.5.5 Bearer Capability IE octet 4 always has
the extension bit set. The existence of octet 4.1 is determined based on the
contents of octet 4. This is shown in Figure 4-11/Q.931 and elaborated on by
Note 1 below the table.</FONT><FONT size=2> In H225 Section 7.2.2.1 Bearer
Capability IE octet 4 extension bit "Shall be set to '0' if the information
transfer rate is set to multirate". However the same section says that the
information element is encoded according to Figure 4-11/Q.931.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=2>Suggested resolution:</FONT></DIV>
<DIV><FONT size=2>Document (in H225) this bit as working as documented in Q931.
Add a note that implementations should not rely upon this bit and should not use
it as an indication that octet 4.1 exists (instead should check for multirate
setting). This solution will have a low level of impact on existing systems and
retains interoperability with Q931 ISDN equipment.</FONT></DIV>
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