The purpose of the High layer compatibility information element is to provide a means which should be used by the remote user for compatibility checking. See Annex B.
The High layer compatibility information element is coded as shown in Figure 4-23 and Table 4-15.
The High layer compatibility information element can be repeated in the SETUP message to indicate dual high layer capabilities for selection. By default, if the High layer compatibility information element is repeated without the Repeat indicator information element, it shall be interpreted as increasing order of priority.
The maximum length of this information element is five octets.
Note - The High layer compatibility information element is transported transparently by an ISDN between a call originating entity, e.g. a calling user and the addressed entity, e.g. a remote user or a high layer function network node addressed by the call originating entity. However, if explicitly requested by the user (at subscription time), a network which provides some capabilities to realize teleservices may interpret this information to provide a particular service.
Bits |
||||||||
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
Octets |
High layer compatibility Information element identifier |
||||||||
0 |
1 |
1 |
1 |
1 |
1 |
0 |
1 |
1 |
Length of high layer compatibility contents |
2 |
|||||||
1 ext. |
Coding standard |
Interpretation |
Presentation method of protocol profile |
3 |
||||
0/1 ext. |
High layer characteristics identification |
4 |
||||||
1 ext. |
Extended high layer characteristics identification |
4a* |
||||||
1 ext. |
Extended videotelephony characteristics identification |
4a* |
||||||
Note 1- This octet may be present when octet 4 indicates Maintenance or Management. Note 2 – This octet may be present when octet 4 indicates audio visual. |
||||||||
High layer compatibility information element
High layer compatibility information element
Coding standard (octet 3) |
|
Bits |
|
7 6 |
|
0 0 |
CCITT standardized coding, as described below |
0 1 |
ISO/IEC standard (Note 1) |
1 0 |
National standard (Note 1) |
1 1 |
Standard defined for the network (either public or private) present on the network side of the interface (Note 1) |
Note 1 - These other coding standards should only be used only when the desired high layer compatibility cannot be represented by CCITT standardized coding. |
|
Interpretation (octet 3) |
|
Bits |
|
5 4 3 |
|
1 0 0 |
First (primary or only) high layer characteristics identification (in octet 4) to be used in the call |
All other values are reserved. |
|
Note 2 - "Interpretation" indicates how the "High layer characteristics identification" (in octet 4) should be interpreted. Note 3 - Currently, "Interpretation" has only a single value. However, "Interpretation", when enhanced, will be able to indicate how the "High layer characteristics identification" in the same information element shall be interpreted when multiple "High layer characteristics identifications" are used and exact relationship among them needs to be indicated (e.g. sequential usage, alternative list, simultaneous usage). Such enhancements in conjunction with the possible negotiation procedures are left for further study. |
|
Presentation method of protocol profile (octet 3) |
|
Bits |
|
2 1 |
|
0 1 |
High layer protocol profile (without specification of attributes) |
All other values are reserved. |
|
Note 4 - Currently, "Presentation method of protocol profile" has only a single value, i.e. a "profile value" is used to indicate a service to be supported by high layer protocols as required. Necessity of other presentation methods, e.g. service indications in the forum of layer-by-layer indication of protocols to be used in high layers, is left for further study. |
|
High layer characteristics identification (octet 4) |
|
Bits |
|
7 6 5 4 3 2 1 |
|
0 0 0 0 0 0 1 |
Telephony |
0 0 0 0 1 0 0 |
Facsimile Group 2/3 (Recommendation F.182 [68]) |
0 1 0 0 0 0 1 |
Facsimile Group 4 Class I (Recommendation F.184 [69]) |
0 1 0 0 1 0 0 |
|
0 1 0 1 0 0 0 |
(Note 7) |
0 1 1 0 0 0 1 |
(Note 7) |
0 1 1 0 0 1 0 |
Syntax based Videotex (Recommendations F.300 [73] and T.102 [74]) |
0 1 1 0 0 1 1 |
|
0 1 1 0 1 0 1 |
Telex service (Recommendation F.60 [76]) |
0 1 1 1 0 0 0 |
Message Handling Systems (MHS) (X.400 - Series Recommendations [77]) |
1 0 0 0 0 0 1 |
OSI application (Note 2) (X.200 - Series Recommendations [78]) |
1 0 0 0 0 1 0 |
FTAM application (ISO 8571) |
1 0 1 1 1 1 0 |
Reserved for maintenance (Note 8) |
1 0 1 1 1 1 1 |
Reserved for management (Note 8) |
1 1 0 0 0 0 0 |
Videotelephony (Recommendations F.720 [91] and F.721 [79]) and F.731 profile 1a) (Note 9) |
1 1 0 0 0 0 1 |
Videoconferencing Recommendation F.702 [94] and F.731 [97] Profile 1b (Note 9) |
1 1 0 0 0 1 0 |
Audiographic conferencing Recommendations F.702 [94] and F.731 [97] (including at least profile 2a2 and optionally 2a1, 2a3, 2b1, 2b2, and 2bc) (Notes 9 and 10) |
1 1 0 0 0 1 1 |
Reserved for audiovisual services (F.700 - Recommendations Series [80]) |
1 1 0 1 0 0 0 |
Multimedia services F.700-series Recommendations [80] (Note 9) |
1 1 0 0 0 1 1 |
Reserved for audiovisual services (F.700-series Recommendations [80]) |
1 1 1 1 1 1 1 |
Reserved |
All other values are reserved. |
|
Extended high layer characteristics identification (octet 4a for maintenance or management) |
|
Bits |
|
7 6 5 4 3 2 1 |
|
0 0 0 0 0 0 1 |
Telephony |
0 0 0 0 1 0 0 |
Facsimile Group 2/3 (Recommendation F.182) |
0 1 0 0 0 0 1 |
Facsimile Group 4 Class I (Recommendation F.184) |
0 1 0 0 1 0 0 |
Facsimile service Group 4, Classes II and III (Recommendation F.184) |
0 1 0 1 0 0 0 |
(Note 11) |
0 1 1 0 0 0 1 |
(Note 11) |
0 1 1 0 0 1 0 |
Syntax based Videotex (Recommendations F.300 and T.102) |
0 1 1 0 0 1 1 |
International Videotex interworking via gateways or interworking units (Recommendations F.300 and T.101) |
0 1 1 0 1 0 1 |
Telex service (Recommendation F.60) |
0 1 1 1 0 0 0 |
Message Handling Systems (MHS) (X.400 - Series Recommendations) |
1 0 0 0 0 0 1 |
OSI application (Note 2) (X.200 - Series Recommendations) |
1 0 0 0 0 1 0 |
FTAM application (ISO 8571) |
1 0 1 1 1 1 0 |
Not available for assignment |
1 0 1 1 1 1 1 |
Not available for assignment |
1 1 0 0 0 0 0 |
Videotelephony (Recommendations F.720 [91] and F.721 [79] and F.731, profile 1a) |
1 1 0 0 0 0 1 |
Videoconferencing Recommendations F.702 [94] and F.731 [97], profile 1b |
1 1 0 0 0 1 0 |
Audiographic conferencing Recommendations F.702 [94] and F.731 [97] (including at least profile 2a2 and optionally 2a1, 2a3, 2b1, 2b2 and 2bc) |
1 1 0 0 0 1 1 |
Reserved for audiovisual services (F.700-series Recommendations [80]) |
1 1 0 1 0 0 0 |
Multimedia services (F.700-series Recommendations [80]) |
1 1 0 1 0 0 1 |
Reserved for audiovisual services (F.700-series Recommendations [80]) |
1 1 1 1 1 1 1 |
Reserved |
All other values are reserved. |
|
Extended audiovisual characteristics identification (octet 4a for videotelephony) |
|
Bits |
|
7 6 5 4 3 2 1 |
|
0 0 0 0 0 0 1 |
Capability set of initial channel of H.221 |
0 0 0 0 0 1 0 |
Capability set of subsequent channel of H.221 |
0 1 0 0 0 0 1 |
Capability set of initial channel associated with an active 3.1 kHz audio or speech call. |
Note 5 – The coding above applies in case of "Coding standard" = "ITU-T Standard" and "Presentation method of protocol profile" = "High layer protocol profile". Note 6 – Further compatibility checking will be executed by the OSI high layer protocol. Note 7 – Codepoints are added only to those services for which ITU-T Recommendations are available. See also the I.241-series of Recommendations [34]. Note 8 – When this coding is included, octet 4 may be followed by octet 4a. Note 9 – When this coding is used, octet 4 may be followed by octet 4a. Note 10 – The multimedia services identified by this codepoint mush have a mandatory common core functionality of speech that will ensure a minimum capability to communicate. Note 11 – This codepoint was previously allocated for an F.200-series Recommendation that has been deleted. |
|