OS and WaveStar® CIT users access remote Alcatel-Lucent 1850 TSS-5s equipped to operate as SONET/SDH network elements, using the remote Alcatel-Lucent 1850 TSS-5 Target Identifier (TID, name). However, remote Alcatel-Lucent 1850 TSS-5s are addressed on the DCC using Network Service Access Point Address (NSAP). Therefore, a method to provide TID-to-NSAP (name-to-address) and NSAP-to-TID (address-to-name) translations is necessary. Target Identifier Address Resolution Protocol (TARP) provides this capability.
For SONET NEs that support TCP/IP and TL1 OS interfaces, TARP is the de facto directory services standard to support multi-vendor OI compatibility. TARP is specified in Telcordia ® GR-253-CORE, SONET Transport Systems: Common Criteria.
Each NE in a network must be provisioned with a unique TID. The Alcatel-Lucent 1850 TSS-5's default TID is "ALU-TSS-5". The terms TID and source identifier (SID) are generally used interchangeably.
Important!
Some vendor NEs require that all TIDs start with an alphabetic character, or that each TID consist of specified minimum number of characters.
To be compatible with WaveStar® products, Alcatel-Lucent 1850 TSS-5 TIDs should not include special characters "%" and "#". Alcatel-Lucent 1850 TSS-5 TID provisioning allows special characters, but T1.245 SONET Directory Services (SDS) does not support special characters.
By default, each Alcatel-Lucent 1850 TSS-5 has a unique Network Service Access Point (NSAP) address, thus no NSAP provisioning is necessary in small networks. If the network size exceeds 50 OSI nodes, NSAP provisioning is required.
Although TARP functions automatically without any user provisioning, using standard default values, Alcatel-Lucent 1850 TSS-5 allows provisioning of the following TARP parameters. All TARP parameters are provisionable:
Lifetime
Manual Adjacency
Timers
Loop Detection Buffer (LDB) Flush Timer
TARP Data Cache (TDC) Enable/Disable
TDC TID-NSAP Entries.
It is recommended that the TARP default values always be used.
The three operations that depend on TARP TID-to-NSAP translations are:
When a TL1 TCP/IP or TL1 Gateway Network Element (GNE) receives a TL1 login request for a TL1-RNE, the TL1 login request includes the TL1-RNE's TID. The TL1-GNE relies on TARP to determine the TL1-RNE's NSAP. The TL1-GNE needs the NSAP to establish an OSI association with the TL1-RNE. The TL1 login request is forwarded to the TL1-RNE over that OSI association.
The local Alcatel-Lucent 1850 TSS-5 serves as a TL1-GNE and uses TARP as described above for WaveStar® CIT access via Alcatel-Lucent 1850 TSS-5's serial ports or TCP/IP. When accessing Alcatel-Lucent 1850 TSS-5 via OSI LAN, the WaveStar® CIT (or OS) performs the TL1-GNE function and uses TARP in a similar manner, also. The local Alcatel-Lucent 1850 TSS-5 uses TARP as described above to support remote Install Program/Copy Program.
The first time a TL1-GNE (or local Alcatel-Lucent 1850 TSS-5) requires a TARP TID-to-NSAP translation for each remote NE, the TL1-GNE originates a TARP query. The TARP query is propagated to all NEs in the same OSI routing area, and if no response is received from within the area, up to two additional TARP queries are propagated throughout the OSI domain. Each NE forwards the TARP queries to each of its neighboring OSI nodes (that is, adjacencies), except the neighbor from which the TARP query was received.
When the TARP query reaches the remote NE with the requested TID, that remote NE responds to the originating NE with the remote NE's NSAP address. If there is no response to any of the TARP queries for a TID, after the third query times out, an error response (for example, TL1- GNE unknown TID or TID not found) is returned to the originating NE.
When an Alcatel-Lucent 1850 TSS-5 is commanded to perform this translation, it knows the NSAPs of the remote NEs to be included in the responses but relies on TARP to determine the corresponding TIDs.
To ensure that the responses to these commands always include the most up-to-date network information, real-time TARP queries are originated instead of relying on the TARP Data Cache or TDC (although the TDC is updated, as appropriate, based on the responses to these NSAP-to-TID queries).
Because the NSAPs are known, these TARP queries are addressed directly to each remote NE (TARP propagation is not necessary). Each remote NE responds to the originating NE with the remote NE's TID.
In order to reduce the frequency of TARP propagation, and to improve the performance of the affected operations, Alcatel-Lucent 1850 TSS-5 supports a TDC option. By default, the TDC is enabled.
Each Alcatel-Lucent 1850 TSS-5 maintains its own TDC, independently. The TDC consists of TID-NSAP translations. Each Alcatel-Lucent 1850 TSS-5 automatically updates its own TDC based on the responses to previous TARP queries. The TDC may also be updated upon receipt of an unsolicited, automatic notification from another NE in the same OSI domain of a TID or NSAP change. The TDC has a maximum number of 16 entries; up to 15 entries may be manually entered. A circular buffer is used for the dynamic entries in the TARP Data Cache.
Alcatel-Lucent 1850 TSS-5 checks its TDC to see if it already has a required TID-to-NSAP translation before originating a TARP query. If a translation is not found in the TDC, the response to that TARP query is used to update the originating TDC. Alcatel-Lucent 1850 TSS-5 assures that its TDC maintains only one TID-NSAP translation for each unique TID. Alcatel-Lucent 1850 TSS-5 supports TDC sizes of up to 110 TID-NSAP translations. If the TDC is disabled or Alcatel-Lucent 1850 TSS-5's system controller is reset, the contents of the TDC are deleted.
In the unlikely event that a TDC includes an inaccurate TID-to-NSAP translation, Alcatel-Lucent 1850 TSS-5 confirms that both the NSAP and TID of the remote Alcatel-Lucent 1850 TSS-5 are correct before a remote operation proceeds. If there is a mismatch, an error response (for example, TL1-RNE unknown TID, Inconsistent TID, or Association Setup Failure) is returned to the originating NE.
To correct such a situation, delete the subject TID (L4tdctid) from the TDC, then re-request the remote operation for the subject TID. The subsequent TARP query results in an accurate TID-to-NSAP translation, and the TDC is updated accordingly. A broader solution is to disable and re-enable the TDC in which case all TDC entries are deleted.
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