0x2757 Low Layer Compatibility Layer 3 Information

Used in:
0x0033 NPDI Universal ICB

Byte | Description
0, 1 | Tag 0x2757
2, 3 | Length Variable
4 | Value[1] User information layer 3 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.
5 | Value[2] Mode 0x02 Recommendation Q.931 0x06 Recommendation X.25, packet layer 0x07 ISO/IEC 8208 [41] 0x08 CCITT Recommendation X.223 0x09 ISO/IEC 8473 [43] 0x0a Recommendation T.70 [32] 0x0b ISO/IEC TR 9577[82] 0x10 User specified All the other values are reserved.
| Value[3] Optional layer 3 information This field is user defined. 0xFF is reserved.
| Value[4] Default packet size 0x04 Default packet size 16 octets 0x05 Default packet size 32 octets 0x06 Default packet size 64 octets 0x07 Default packet size 128 octets 0x08 Default packet size 256 octets 0x09 Default packet size 512 octets 0x0a Default packet size 1024 octets 0x0b Default packet size 2048 octets 0x0c Default packet size 4096 octets All the other values are reserved.
| Value[5] Packet 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.
Call signaling protocol for setup and termination of calls.
Comité Consultatif Internationale de Telephonique et Telegraphique (now ITU)