Avaya Configuring OSI Services Manual de usuario descargar pdf (Pagina 51)

OSI Overview

303535-A Rev 00

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Loop Detection

To prevent TARP storms and recursive loops in a looped topology, TARP

maintains a loop detection buffer (LDB) that keeps a record of the last sequence

number received from a particular NSAP. It checks each TARP protocol data unit

(PDU) that it receives against any corresponding entry in the loop detection

buffer.

If it finds no match:

• It processes the packet and adds a new entry to the loop detection buffer.

• It checks the tar_seq field. If the value is 0, it starts a timer set to the value of

the TARP LDB timer. When this timer expires, the entry is removed.

If there is a match, TARP compares the tar_seq value in the received packet with

the value in the LDB entry.

• If the packet’s tar_seq value is nonzero and is lower than the value in the

buffer, it discards the packet.

• If the packet’s tar_seq value is greater than the value in the buffer, TARP

processes the packet and assigns this tar_seq value to the buffer.

• If the packet’s tar_seq value is 0 and the TARP LDB timer is running, TARP

discards the packet. If the timer is not running, the tar_seq remains 0 and the

TARP LDB timer is started.

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Avaya Configuring OSI Services Manual de usuario Pagina 51