Cisco Systems ONS 15600 manual Tarp Loop Detection Buffer, Default Range Timer Description Seconds

Chapter 9 Management Network Connectivity

9.7.5 TARP

•Type— Indicates whether the TARP PDU was created through the TARP propagation process (dynamic) or manually created (static).

Provisionable timers, shown in Table 9-12, control TARP processing.

Table 9-12	TARP Timers
		Default	Range
Timer	Description	(seconds)	(seconds)
T1	Waiting for response to TARP Type 1 Request PDU	15	0–3600
T2	Waiting for response to TARP Type 2 Request PDU	25	0–3600
T3	Waiting for response to address resolution request	40	0–3600
T4	Timer starts when T2 expires (used during error recovery)	20	0–3600

Table 9-13shows the main TARP processes and the general sequence of events that occurs in each process.

Table 9-13 TARP Processing Flow

Process	General TARP Flow
Find a NET that	1.	TARP checks its TDC for a match. If a match is found, TARP returns the
matches a TID		result to the requesting application.
	2.	If no match is found, a TARP Type 1 PDU is generated and Timer T1 is
		started.
	3.	If Timer T1 expires before a match if found, a Type 2 PDU is generated and
		Timer T2 is started.
	4.	If Timer T2 expires before a match is found, Timer T4 is started.
	5.	If Timer T4 expires before a match is found, a Type 2 PDU is generated and
		Timer T2 is started.
Find a TID that	A Type 5 PDU is generated. Timer T3 is used. However, if the timer expires, no
matches a NET	error recovery procedure occurs, and a status message is provided to indicate
	that the TID cannot be found.
Send a notification	TARP generates a Type 4 PDU in which the tar-ttg field contains the NE’s TID
of TID or protocol	value that existed prior to the change of TID or protocol address. Confirmation
address change	that other NEs successfully received the address change is not sent.

9.7.5.2 TARP Loop Detection Buffer

The TARP loop detection buffer (LDB) can be enabled to prevent duplicate TARP PDUs from entering the TDC. When a TARP Type 1, 2, or 4 PDU arrives, TARP checks its LDB for a NET address (tar-por) of the PDU originator match. If no match is found, TARP processes the PDU and assigns a tar-por, tar-seq (sequence) entry for the PDU to the LDB. If the tar-seq is zero, a timer associated with the LDB entry is started using the provisionable LDB entry timer on the node view OSI > TARP > Config tab. If a match exists, the tar-seq is compared to the LDB entry. If the tar-seq is not zero and is less than or equal to the LDB entry, the PDU is discarded. If the tar-seq is greater than the LDB entry, the PDU is processed and the tar-seq field in the LDB entry is updated with the new value. The ONS 15600 LDB holds approximately 500 entries. The LDB is flushed periodically based on the time set in the LDB Flush timer on the node view OSI > TARP > Config tab.

Cisco ONS 15600 Reference Manual, R7.2

9-35