LAP-D is the ISDN set of second layer protocol, which is almost the same as the X.25 LAP-B protocol. The three logical digital communication channels of ISDN perform as follows:
B channel - transmit user business information includes digital data, video, voice; D channel - signaling and data packets between users and networks; H Channel - Performing with the same function but its running rate exceeds DS-0 ( 64 kbps).
LAP-D completion of the ISDN link establishment process is as follows:
Terminal Endpoint (TE) and Network Switching Receive Prepare Frame (RR), waiting to initialize a connection. Terminal Endpoint (TE) sends an unligated information (UI) frame, where the value of SAPI (service access point identification) is 63 (management protocol, query network), TEI (terminal end point identification) value is 127 (establishing broadcast link). Network allocation One can use TEI (range 64-126). TE sends a SABME frame with a SAPI value of 0 (call control), and the network allocates a TEI value. The network issues an unknown response (UA), SAPI = 0, and assigned a TEI value.
For more information, please visit the following page: 中文 版: http://www.networkDictionary.com/chinese/protocols/lapd.php English version: http://www.networkDictionary.com/protocols/LAPD.PHP
