0x2751 High Layer Compatibility
(Interworking Only)

Used in:
0x0033 NPDI Universal ICB

Byte | Description
0, 1 | Tag 0x2751
2, 3 | Value[0] Length
4, 5 | Value[1] Coding Standard 0x00 CCITT Standardized Coding 0x01 ISO/IEC Standard 0x02 National Standard 0x03 Standard specific to identified location
6 | Value[2] Interpretation 0x04 First (primary or only) high layer characteristic identification to be used in the call. All other values are reserved.
7 | Value[3] Presentation Method of the Protocol Profile 0x01 High layer protocol profile. All other values are reserved.
8 | Value[4] High layer characteristics identification 0x01 Telephony 0x04 Facsimile Group 2/3 (Recommendation F.182) 0x21 Facsimile Group 4 Class I (Recommendation F.184) 0x24 Teletex service, basic and mixed mode of operation (Recommendation F.230 and facsimile service group 4, Classes II and III (Recommendation F.184) 0x28 Teletex service, basic and processable mode of operation (Recommendation F.220 [71]). 0x31 Teletex service, basic mode of operation. (Recommendation F.200 [72]). 0x32 Syntax based Videotex. (Recommendations F.300 [73] and T.102 [74]). 0x33 International Videotex Interworking via gateways or Interworking units (Recommendations F.300 and T.101 [75]). 0x35 Telex service (Recommendation F.60 [76]). 0x38 Message Handling Systems (MHS) (X.400 Series Recommendations [77]). 0x41 OSI Application (X.200 Series Recommendations [78]). 0x60 Audio Visual (Recommendation F.721 [79]) All the other values are reserved
9 | Value[5] Extended high layer characteristics identification 0x01 Telephony 0x04 Facsimile Group 2/3 (Recommendation F.182) 0x21 Facsimile Group 4 Class I (Recommendation F.184) 0x24 Teletex service, basic and mixed mode of operation (Recommendation F.230 and facsimile service group 4, Classes II and III (Recommendation F.184) 0x28 Teletex service, basic and processable mode of operation (Recommendation F.220 [71]). 0x31 Teletex service, basic mode of operation. (Recommendation F.200 [72]). 0x32 Syntax based Videotex. (Recommendations F.300 [73] and T.102 [74]). 0x33 International Videotex Interworking via gateways or Interworking units (Recommendations F.300 and T.101 [75]). 0x35 Telex service (Recommendation F.60 [76]). 0x38 Message Handling Systems (MHS) (X.400 Series Recommendations [77]). 0x41 OSI Application (X.200 Series Recommendations [78]). 0x60 Audio Visual (Recommendation F.721 [79]) All the other values are reserved
10 | Value[6] Optional bytes For future enhancements in protocol. Also can be used to customize the protocol with other information with this packet.

Network Protocol Data Intelligence. Also called “Interworking,” it is a software product that operates within Excel’s Call Control (Layer 4) and Services (Layer 5) call processing layers. NPDI is meant to enhance Excel’s call processing product offering by allowing call processing layers (specifically Layers 4 and 5) to perform advanced analysis, generation, and conversion of Network Signaling (NS) Layer 3 information.
See Information Control Block.
Comité Consultatif Internationale de Telephonique et Telegraphique (now ITU)
International Standards Organization
Interworking is a software feature within the Excel platform call control layer that enables protocol conversion by analyzing and converting Network Signaling (NS) Layer 3 information.
Open System Interconnection model