6 - 8
ForeRunner ATM Switch Network Configuration Manual
ATM Forum PNNI
6.3.2.1.3
Levels
Each areas has a level associated with it. Levels are used to control the flow of reachability
information in a multi-level routing hierarchy (which is discussed in the next section). An
N-level hierarchy has N discrete values of levels associated with it, namely, L
1
, L
2
,..., L
N
. Each
of the areas in the hierarchy has one of these N values as its level. Numerical values are
assigned to levels in order from the lowest to the highest; i.e., L
1
< L
2
< L
3
< L
N,
so L
N
is the
highest level.
An area of level L
i
can adjoin any number of areas at level L
i-1
, but can only adjoin at most one
area at level L
i+1
or higher. This means that on a given switch, there can never be areas config-
ured that belong to more than two distinct levels. Furthermore, there can only be one area that
belongs to the higher level.
6.3.2.2 Domains
A domain is a group of areas that are configured to dynamically exchange reachability infor-
mation with one another. This allows connectivity between end systems belonging to different
areas without configuring static routes between areas. However, reachability information is
exchanged between domains only if routes are statically configured between the two domains.
Figure 6.4 shows an example of how a static route can connect two domains.
Figure 6.4 -
Static Route Connecting Two Domains
FT-PNNI node
PNNI node
Area A
Area B
Area C
Area D
Switch S1
Switch S2
Switch S4
Domain 1
Domain 2
Switch S3
IISP link
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Страница 16: ...TOC 10 ForeRunner ATM Switch Network Configuration Manual Table of Contents ...
Страница 20: ...LOF 4 ForeRunner ATM Switch Network Configuration Manual List of Figures ...
Страница 22: ...LOT 2 ForeRunner ATM Switch Network Configuration Manual List of Tables ...
Страница 30: ...viii ForeRunner ATM Switch Network Configuration Manual Preface ...
Страница 144: ...3 58 ForeRunner ATM Switch Network Configuration Manual Configuring an Emulated LAN ...
Страница 180: ...6 12 ForeRunner ATM Switch Network Configuration Manual ATM Forum PNNI ...
Страница 220: ...9 6 ForeRunner ATM Switch Network Configuration Manual Configuring Timing ...
Страница 300: ...D 24 ForeRunner ATM Switch Network Configuration Manual Configuring FramePlus Modules ...
Страница 308: ...Acronyms 8 ForeRunner ATM Switch Network Configuration Manual Acronyms ...
Страница 346: ...Glossary 38 ForeRunner ATM Switch Network Configuration Manual Glossary ...
Страница 352: ...Index 6 ForeRunner ATM Switch Network Configuration Manual Index ...