The Avaya TN771DP maintenance test circuit pack performs maintenance functions. These functions includ packet bus reconfiguration that allows diagnostics and correction of recoverable packet bus failures before the link access procedure on the D-channel (LAPD) links fail.
LAPD is a link-layer protocol on the ISDN-BRI and ISDN-PRI data link layer (level 2). LAPD provides data transfer between two devices and error and flow control on multiple logical links. LAPD swaps spare leads with the malfunctioning leads to recover packet bus failures involving up to three malfunctioning leads (1 or 2 data or parity leads and one control lead).
Other maintenance functions include ISDN-PRI testing that originates and terminates loopback tests on ISDN facilities. The testing provides bit and block error rate information indicating ISDN facility quality.
The TN771DP circuit pack can be updated using the firmware download feature, which requires use of the TN799 C-LAN circuit pack interface.
A TN771 DP circuit pack is required for:
A maximum of one TN771DP circuit pack is allowed in any port network. A TN771DP is never used with the S8100 Media Server.