ADTRAN Total Access OC-3 L3, Установка и эксплуатация

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61181031L3-5A A-1
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ABSTRACT
This appendix contains information regarding commu-
nications over the SONET Section Data Communica-
tions Channel (SDCC) and its implementation on the
ADTRAN Total Access 3000/3010 shelf. Background
information regarding the OSI stack and detailed infor-
mation for configuring the SONET Multiplexer boards
has been provided.
NOTE
This Practice assumes the reader is familiar
with the SCU Craft Interface.
BACKGROUND
In order to exchange TL1 messages, end-to-end connec-
tivity between an operations system (OS) and a network
element (NE) requires two separate connections to be
established between:
• An OS and the Gateway NE (GNE) over an X.25
virtual connection (SVC or PVC); a Fujitsu
FLM-150 or Lucent DDM 2000 are examples of a
GNE.
• The GNE and the target NE over the SONET DCC;
the Total Access 3000/3010 is an example of a
target NE.
OVERVIEW OF OSI ROUTING
A routing area is the smallest grouping of systems for
routing purposes. It is a neighborhood of interconnected
systems often called a “Level 1 Area.”
A routing domain is a collection of routing areas, all of
which must follow the same routing policies. It is often
called a “Level 2 Area.” All systems within the domain
must have the same system ID length. All routers within
the domain must follow the same identical policies, and
must not treat any systems in the area preferentially to
others.
OSI networks consist of two types of systems:
• End systems (ES)
• Intermediate systems (IS).
Intermediate Systems perform the relay function where
as End Systems do not.
There are two types of Intermediate Systems:
• A Level 1 IS routes packets to a destination within
an area or to the nearest Level 2 IS for destinations
outside the area.
• A Level 2 IS routes packets between two areas; it
also performs Level 1 routing for its current area.
All routing is based on the Network Service Access
Point (NSAP) Address. For the purposes of routing, an
NSAP is divided into an area address, a system ID, and
an N-selector.
The area address identifies an area within the routing
domain. The system ID identifies an ES in the area. The
N-selector is used by the ES to distinguish between
multiple users of the Connectionless Network Service
(CLNS), which on the router includes ISO Transport
Class 4 and TL1.
LINK STATE ROUTING
One of the most important tasks an IS 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. ESs periodically send hello
(ESH) packets to their neighbors.
Detection of neighbor Intermediate Systems relies on
the IS-IS protocol operation. ISs periodically send hello
(ISH) packets to their 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 has a complete picture of the
area, in the form of a set of links. Likewise, each Level
2 IS has a complete picture of the set of links that can be
used to join areas together into a routing domain. Impor-
tantly, every IS in an area or domain has precisely the
same picture of the area or domain, once the topology
Appendix A
Total Access 3000/3010 SONET SDCC Operation