TID - Network addresses mappings are stored in a cache, implemented as a hash table. A cache entry can be created dynamically when a router hears from another TARP device (e.g. as a result of a query addressed to the router), or statically via TARP "map" commands. All dynamically created TARP cache entries (i.e. those that are not static or flagged as "LOCAL") are aged out. The time out value is configurable.

Configure the amount of time that the router waits to receive a response from a Type 1 PDU, a Type 2 PDU, and a Type 5 PDU and also configure the lifetime of the PDU based on the number of hops.

Set timers that control how long dynamically created TARP entries remain in the TID cache, and how long the system ID-to-sequence number mapping entry remains in the loop detection buffer table. The loop detection buffer table prevents TARP PDUs from looping.

TARP will maintain a list of useful counters, and will increment the relevant counter. There will also be extensive debugging support that will facilitate troubleshooting

The OSI network address is referred to as a network service access point (NSAP). The NSAP is assigned to the end system (ES) or intermediate system (IS) device. Unlike in IP, which has an address for every network interface, the OSI network device receives only one address, the NSAP address. The NSAP address has two parts, the Initial Domain Part (IDP) and Domain Specific Part (DSP).

Addresses in the ISO network architecture are referred to as network service access point (NSAP)addresses and network entity titles (NETs). Each node in an OSI network has one or more NETs. In addition, each node has many NSAP addresses. Each NSAP address differs from one of the NETs for that node in only the last byte. This byte is called the N-selector. Its function is similar to the port number in other protocol suites.

Our implementation supports all NSAP address formats that are defined by ISO 8348/Ad2; however, Cisco provides ISO Interior Gateway Routing Protocol (IGRP) or Intermediate System-to-Intermediate System (IS-IS) dynamic routing only for NSAP addresses that conform to the address constraints defined in the ISO standard for IS-IS (ISO 10589).

An NSAP address consists of the following two major fields, as shown in Figure 1:

• The initial domain part (IDP) is made up of 1-byte authority and format identifier (AFI) and a variable-length initial domain identifier (IDI). The length of the IDI and the encoding format for the domain specific part (DSP) are based on the value of the AFI.

• The DSP is made up of a High Order DSP (HO-DSP), an area identifier, a system identifier, and a 1-byte N-selector (labeled S).

Assign addresses or NETs for your domains and areas. The domain address uniquely identifies the routing domain. All routers within a given domain are given the same domain address. Within each routing domain, you can set up one or more areas, as shown in Figure 2. Determine which routers are to be assigned to which areas. The area address uniquely identifies the routing area and the system ID identifies each node.

The key difference between the ISO IGRP and IS-IS NSAP addressing schemes is in the definition of area addresses. Both use the system ID for Level 1 routing (routing within an area). However, they differ in the way addresses are specified for area routing. An ISO IGRP NSAP address includes three separate fields for routing: the domain, area, and system ID. An IS-IS address includes two fields: a single continuous area field (comprising the domain and area fields) and the system ID .

TARP must be explicitly enabled before the TARP functionality becomes available, and the router must have a TID assigned. Also, before TARP packets can be sent out on an interface, each interface must have TARP enabled and the interface must be able to propagate TARP PDUs.

The router will use the CLNS capability to send and receive TARP PDUs. If the router is configured as an IS, the router must be running IS-IS. If the router is configured as an ES, the router must be running ES-IS.

To turn on the TARP functionality, use the following commands in global configuration mode:

To enable TARP on one or more interfaces, use the following command in interface configuration mode

The following example shows how to enable TARP on the router and Ethernet interface 0. The router is assigned the TID name.

interface GigabitEthernet0/2/5
ip address 172.16.1.2 255.240.0.0 àip address for gig
ip router isis 1 -- to enable the isis configured under gig
negotiation auto
clns router isis 1 --- to assign it to clns
isis circuit-type level-1 --- isis level type
tarp enable

The following example shows how to enable TARP on the SDCC interface. The router is assigned the TID name.

interface SDCC0/3/3
ip address 192.168.10.7 255.255.0.0
encapsulation lapd
lapd t200 200
lapd role user 
‘lapd role network’ by default
clns mtu 512
clns router isis 1
isis circuit-type level-1
no isis hello padding
isis retransmit-interval 10
isis lsp-interval 512
tarp enable

tunnel source GigabitEthernet0/4/7
interface GigabitEthernet0/4/7
ip address 172.16.1.1 255.240.0.0
negotiation auto

Router#sh run | sec Tunnel1
interface Tunnel1
ip address 172.16.2.2 255.240.0.0
ip router isis 1
tunnel source GigabitEthernet0/4/7
tunnel destination 192.168.1.2
clns router isis 1
isis circuit-type level-1
tarp enable

For more information on SDCC, Configuring Data Communication Channel

The following example shows how to enable TARP on the router and Ethernet interface 0. The router is assigned the TID myname.

clns routing
 tarp run
 tarp tid myname

 interface ethernet 0
  tarp enable

To configure TARP on the router, perform the tasks in the following sections. Only the first task is required; all other tasks are optional.