New draft of H.245

Mike Nilsson mike.nilsson at BT-SYS.BT.CO.UK
Fri Sep 19 12:58:31 EDT 1997


In the meantime I found the H.225 section telling about basic aligned
variant of X.691 to be used for H.225.0 User-user information element
ASN.1 encoding.

The same of course shall apply for H.450 Supplementary service APDUs
(which are carried in User-user information element)

Karl Klaghofer
Siemens AG

From:  Klaghofer, Karl        PN M BT
Sent:  Thursday, September 18, 1997 6:15 PM
To:  'itu-sg16List'
Subject:  Octet-aligned encoding for H.450.x ?
Importance:  High

The H.450 Supplementary Services make use of the Packed Encoding Rules
(PER) according to X.691 (inline with H.225, H.245).

X.691 specifies four encoding rules:
BASIC-PER, CANONICAL-PER, both in two variants the ALIGNED variant, and
the UNALIGNED variant.

Are all of these encodings mandatory in H.323 (H.225, H.245) to support ?

Should we limit the X.691 variants in H.450.x (clause 9 of H.450.1) to
ALIGNED only   ?

Karl Klaghofer
Siemens AG
karl.klaghofer at

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