V120 Layer 2

V120 frame structure: fields

The structure of frame is that specified in Q921:

bits 8 _ _ _ _ _ _ 1 field
octet 1 Address (High order octet)
octet 2 Address (Low order octet)
octet 3 Control
octets 4-n Information

The structure of Information field is:

bits 8 _ _ _ _ _ _ 1 Information field
octet 1 H: terminal adaption Header
octet 2 CS: optional header extension for control state information
octets 3-n V120 Information

Address field

- Octet 1:
bits 8-3 LLI0 (bits 13-8 of LLI logical link identifier)
bit 2 C/R: Command/Response
bit 1 Address field extension (0)
- Octet 2:
bits 8-2 LLI1 (bits 7-1 of LLI logical link identifier)
bit 1 Address field extension (1)
LLI value Logical link identifier
0 In channel Signalling
1-255 Reserved for future standardization
256 Default LLI
257-2047 For LLI assignment
2048-8190 Reserved for future standardization
8191 In channel layer management
C/R value Meaning
0 Command
1 Response

Control field

As Q921 frame structure: control field.

 

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updated:  27-Feb-04