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Chapter 13
Management Network Connectivity
Table 13-12
Process
Find a NET that
matches a TID
Find a TID that
matches a NET
Send a notification
of TID or protocol
address change
13.6.5.2 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 Cisco ONS 15454 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.
13.6.5.3 Manual TARP Adjacencies
TARP adjacencies can be manually provisioned in networks where ONS 15454s must communicate
across routers or non-SONET NEs that lack TARP capability. In CTC, manual TARP adjacencies are
provisioned on the node view Provisioning > OSI > TARP > MAT (Manual Area Table) subtab. The
manual adjacency causes a TARP request to hop through the general router or non-SONET NE, as shown
in
Figure
78-18106-01
TARP Processing Flow
General TARP Flow
1.
TARP checks its TDC for a match. If a match is found, TARP returns the
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.
If Timer T2 expires before a match is found, Timer T4 is started.
4.
5.
If Timer T4 expires before a match is found, a Type 2 PDU is generated and
Timer T2 is started.
A Type 5 PDU is generated. Timer T3 is used. However, if the timer expires, no
error recovery procedure occurs, and a status message is provided to indicate
that the TID cannot be found.
TARP generates a Type 4 PDU in which the tar-ttg field contains the NE TID
value that existed prior to the change of TID or protocol address. Confirmation
that other NEs successfully received the address change is not sent.
13-23.
Cisco ONS 15454 Reference Manual, R8.5
13.6.5 TARP
13-39
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