ADTRAN T200 FNID Specifications download pdf (Page 26)

A-2 61184002L3-5B

Connectionless Network Service (CLNS),

which on the router includes ISO Transport

Class 4 and TL1.

LINK STATE ROUTING

One of the most important tasks a router has to

perform consists of detecting its immediate neighbors

and memorizing this relationship in a database.

Detection of neighbor end systems relies on the ES-IS

protocol operation. An ES periodically sends hello

(ESH) packets to its neighbors.

Detection of neighbor intermediate systems relies on

the IS-IS protocol operation. An IS periodically sends

hello (ISH) packets to its neighbors.

Each IS spreads knowledge of its direct connectivity

(e.g. its neighbors) to all other ISs. Level 1 routers

advertise all of their neighbors to all other ISs in the

area. Level 2 routers advertise all their Level 2

neighbors to all Level 2 routers in the domain along

with their own area Ids.

As a result, each Level 1 IS forms a complete picture

of the area, as a set of links. Likewise, each Level 2

IS forms a complete picture of the set of links that can

be used to join areas together into a routing domain.

Importantly, every IS in an area or domain has

precisely the same picture of the area or domain, once

the topology has stabilized and the routing

information has been disseminated.

Using this picture, each IS traverses the entire graph

using Dijkstra’s Shortest Path First (SPF) algorithm.

It finds, for each destination, the next hop to use on

the best path to that destination. Level 1 ISs also find

the shortest path to the nearest Level 2 IS. For Level

1 routing, the destination is a system ID; for Level 2

routing the destination is an area address.

It is necessary for all ISs in the area (for Level 1) or

domain (for Level 2) to have the same picture of the

area or domain. Otherwise, routing loops can occur

because two ISs may each think that the other is on

the shortest path to the destination sending packets

back and forth between each other until the packet

lifetime expires.

DCC SPECIFICATIONS

This section specifies the characteristics of the

SONET DCC as implemented in the Total Access

RMC and WMC products.

7-layer OSI stack

• Physical Layer

1 SONET section DCC, a 192 Kbps channel

carried in 3 section overhead bytes (D1, D2,

and D3) of the first STS-1

2 A separate stack exists per OCM; the DCC is

protected bidirectionally – active TL1

sessions (with corresponding transport

connections) will be lost if a fault occurs and

the protection switch results in the idle DCC

becoming active.

• Data Link Layer

1. The protocol is the Link Access Protocol on

the D-channel (LAPD) as specified in ITU-T

Recommendation Q.921, ISDN user-network

interface – Data link layer specification.

2. Acknowledged information transfer service

(AITS) is supported. Unacknowledged

information transfer service (UITS) is not

supported.

3. The Command/Response value is user

definable. The default is set to “User”.

• Network Layer

1. NSAP address as defined in GR-253-CORE

2. The NSAP area address is user-definable and

must match other NEs in the routing area. No

default value is provided.

3. The system ID is user definable and must be

unique for each NE in the routing area. No

default value is provided.

4. The Globally Unique Network Layer Quality

of Service (QoS) parameter is not supported.

5. Maximum packet size is not definable and is

fixed at 512 octets.

• Transport Layer

1. Supports both end system (ES) and

intermediate system (IS).

• Session Layer

1. Standard implementation.

• Presentation Layer

1. Standard implementation.

• Application Layer

1. TL1 is supported.

2. ACSE, ROSE/CMISE, FTAM, Name/Address

Translation Services are not supported.

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ADTRAN T200 FNID Specifications Page 26

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