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Cisco ONS 15454 Reference Manual, R7.0
78-17191-01
Chapter 13 Management Network Connectivity
13.7 13.7.5 TARP
13.7.5 TARP
TARP is used when TL1 target identifiers (TIDs) must be translated to NSAP addresses. The
TID-to-NSAP translation occurs by mapping TIDs to the NETs, then deriving NSAPs from the NETs by
using the NSAP selector values (Table 13-11 on page 13-32).
TARP uses a selective PDU propagation methodology in conjunction with a distributed database (that
resides within the NEs) of TID-to-NET mappings. TARP allows NEs to translate between TID and NET
by automatically exchanging mapping information with other NEs. The TARP PDU is carried by the
standard CLNP Data PDU. TARP PDU fields are shown in Table 13-12.
Table 13-13 shows the TARP PDUs types that govern TARP interaction and routing.
Table 13-12 TARP PDU Fields
Field Abbreviation Size (bytes) Description
TARP Lifetime tar-lif 2 The TARP time-to-live in hops.
TARP Sequence
Number
tar-seq 2 The TARP sequence number used for loop detection.
Protocol
Address Type
tar-pro 1 Used to identify the type of protocol address that the
TID must be mapped to. The value FE is used to
identify the CLNP address type.
TARP Type
Code
tar-tcd 1 The TARP Type Code identifies the TARP type of
PDU. Five TARP types, shown in Table 13-13, are
defined.
TID Target
Length
tar-tln 1 The number of octets that are in the tar-ttg field.
TID Originator
Length
tar-oln 1 The number of octets that are in the tar-tor field.
Protocol
Address Length
tar-pln 1 The number of octets that are in the tar-por field.
TID of Target tar-ttg n = 0, 1, 2... TID value for the target NE.
TID of
Originator
tar-tor n = 0, 1, 2... TID value of the TARP PDU originator.
Protocol
Address of
Originator
tar-por n = 0, 1, 2... Protocol address (for the protocol type identified in the
tar-pro field) of the TARP PDU originator. When the
tar-pro field is set to FE (hex), tar-por will contain a
CLNP address (that is, the NET).
Table 13-13 TARP PDU Types
Type Description Actions
1 Sent when a device has a TID for which
it has no matching NSAP.
After an NE originates a TARP Type 1 PDU, the PDU
is sent to all adjacent NEs within the NE routing area.
2 Sent when a device has a TID for which
it has no matching NSAP and no
response was received from the Type 1
PDU.
After an NE originates a TARP Type 2 PDU, the PDU
is sent to all Level 1 and Level 2 neighbors.