0x2756 Low Layer Compatibility Layer 2 Information
(Interworking Only)

Used in:
0x0033 NPDI Universal ICB

Byte | Description
0, 1 | Tag 0x2756
2, 3 | Length Variable
4, 5 | Value[0,1] User information layer 2 protocol 0x01 Basic mode ISO 1745 [36] 0x02 Recommendation Q.921 (I.441) [3] 0x06 Recommendation X.25 [5], link layer 0x0f Recommendation X.25 Multi link 0x08 Extended LAP-B for half duplex operation (T.71[37]) 0x09 HDLC ARM (ISO 4335)[38] 0x0a HDLC NRM (ISO 4335) 0x0b HDLC ABM (ISO 4335) 0x0c LAN logical link control (ISO 8802/2) 0x0d Recommendation X.75 [40]. Single link procedure (SLP). 0x0e Recommendation Q.922 0x0f Core aspects of recommendations Q.922 0x10 User specified 0x11 ISO 7776 DTE-DTE operation. All the other values are reserved.
6, 7 | Value[2,3] Mode Mode of Operation: 0001 Normal mode of operation. 0010 Extended mode of operation. All the other values are reserved. Q.933 Use: 0000 For use when the coding defined in recommendation Q.933 is not used. All the other values are reserved.
: | Value[4] User information layer 2 information This field is user defined. 0xFF is reserved.
: | Value[5] Window size 1-127 All other values are reserved.

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.
International Standards Organization
Packet Data Protocol (CCITT)
Link Access Procedure
Local Area Network
Data Terminal Equipment. According to the RS-232-C standard, DTE devices are typically personal computers or data terminals. See DCE.