LAPD message group

位置：Abis-interface [BTS-BSC]的Layer 2

[前言]
LAPD是Link Access Protocol on D channel的縮寫，定義在CCITT (ITU-T)的Q.921.原本使用於N-ISDN，GSM時代使用於BSC與BTS之間的傳輸，在E1或T1的上層。

LAPD的訊息如下：
Disconnect(DISC)frame ______________--> CF
Disconnect mode(DM)frame ___________<-- RF
Frame reject(FRMR)frame ____________<-- RF
Information(I)frame ________________--> CF
Receiver not ready (RNR)frame ______<-> CF and RF
Receiver ready(RR)frame ____________<-> CF and RF
Reject(REJ)frame ___________________<-> CF and RF
SABME frame ________________________--> CF
Unnumbered acknowledgement(UA)frame <-- RF
Unnumbered information (UI) frame __--> CF
(共10個)
CF:Command-Frame
RF:Response-Frame

Ref:
[1] NetHawk GSM Analyser v7.9 HELP
[2] Gunnar Heine, GSM Networks: Protocols, Terminology, and Implementation, Artech House Publishers.1998.

070616r1版本