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area
|
A group of contiguous networks and their attached hosts. Area
boundaries are normally assigned by a network administrator.
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complete sequence number PDU (CSNP)
|
PDU sent by designated router to ensure database synchronization
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Connectionless Network Protocol (CLNP)
|
An OSI network layer protocol used by CLNS to handle data at
the transport layer; the OSI equivalent of IP
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Connectionless Network Service
Protocol (CLNS)
|
An OSI network layer service that enables data transmission
without establishing a circuit and that routes messages independently
of any other messages.
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end system (ES)
|
Any nonrouting network node or host
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intermediate system (IS)
|
A router
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level
1 routing
|
- Routing within an area
- Level 1 routers (or intermediate systems) track all the
individual links, routers, and end systems within a level 1 area.
- Level 1 routers do not know the identity of routers or
destinations outside their area.
- A level 1 router forwards all traffic for destinations
outside its area to the nearest level 2 router within its area.
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|
level
2 routing
|
- Routing between areas
- Level 2 routers know the level 2 topology and know which
addresses are reachable via each level 2 router.
- Level 2 routers track the location of each level 1 area.
- Level 2 routers are not concerned with the topology within
any level 1 area (for example, the details internal to each level
1 area).
- Level 2 routers can identify when a level 2 router is
also a level 1 router within the same area.
- Only a level 2 router can exchange packets with external
routers located outside its routing domain.
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|
link-state PDU (LSP)
|
PDU broadcast by link-state protocols that contains information
about neighbors and path costs; used to maintain routing tables; also
known as link-state advertisement
|
|
network entity title (NET)
|
ISO network addresses used by CLNS networks; an identifier of
a network entity in an end system or intermediate system. A NET consists
of an area address (routing domain), system identifier, and selector.
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|
network service access point (NSAP)
|
Hierarchical network address that specifies the point at which
network services are made available to a transport layer entity in
the OSI reference model. A valid NSAP address is unique and unambiguously
identifies a single system.
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|
partial sequence number PDU (PSNP)
|
PDU sent by designated router to acknowledge and request link-state
information
|
|
protocol data unit (PDU)
|
OSI term equivalent to packet, containing protocol control information
and, possibly, user data. This chapter uses the term packet interchangeably
with PDU.
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|
route tag
|
A numeric value assigned to the IP addresses on an IS-IS route
before the route is propagated to other routers in an IS-IS domain.
You can use this tag to control IS-IS route redistribution, route
leaking, or route summarization by referencing it in a route map.
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|
routing
domain
|
A collection of connected areas that provide full connectivity
to all end systems located within them. A routing domain is partitioned
into areas.
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|
system identifier
|
Uniquely identifies a system within an area
|
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table map
|
A mechanism for applying a route map to an IS-IS route as a
way to filter and manipulate route attributes before the route is
added to the routing table.
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