About alias: H.323 ID

Days earlier, ran into an issue which was H.323 ID related when conferencing with CISCO and LIFESIZE endpoints.

Normally we got used to set the H.323 ID with any charactors we want. But seems some manufacturors like CISCO and
LIFESIZE don’t think it appropriate, because they are adapting some rules in the naming of H.323 ID.

Here was the issue:
When trying to start a call, if the peer endpoint’s H.323 ID is named with {DIGIT}.{DIGIT}, such as 123.456, both CISCO’s and LIFESIZE’ endpoints will not to send ARQ to the registered GK to start the call.

The first thought was DOT is not allowed in H.323 ID to CISCO and LIFESIZE, then made more tries with different combinations, turned out an H.323 ID with {ALPHA}.{DIGIT} just worked fine.

Then turned to the ITU/T H.323 series of documents, trying to find a detail naming rule for H.323 ID, but got no luck but a simple description:

The H.323 ID consists of a string of ISO/IEC 10646 characters as defined in Rec. ITU-T H.225.0. It
may be a user name, conference name, e-mail name, or other identifier.

To my understanding of this phrase, DOT should not be an invalid character, but why this happened???

BTW: Tested HUAWEI(TEx0) and POLYCOM(PVX8.0.2) endpoints,  a H.323 ID named with {DIGIT}.{DIGIT} rule is allowed to them.