Byte

Description

0, 1

Tag 0x2756

2, 3

Length Variable

4, 5

Value[0] 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[1] 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[2] User information layer 2 information

This field is user defined.

0xFF is reserved.

:

Value[3] Window size

1-127

All other values are reserved.