Verilink 9000 Series (34-00271) Product Manual - Manual (Page 311)

Definitions of Commonly Used Terms 289
Hardware multicast capabilities are also used where possible to deliver link-status
messages. OSPF areas are connected by the backbone area, the area with identifier
0.0.0.0. All areas must be logically contiguous and the backbone is no exception.
To permit maximum flexibility, OSPF allows the configuration of virtual links to
enable the backbone area to appear contiguous despite the physical reality.
Also, all OSPF protocol exchanges are authenticated. Authentication guarantees
that routing information is only imported from trusted routers, to protect the
Internet and its users. A variety of authentication schemes can be used but a single
scheme must be configured for each area. This enables some areas to use much
stricter authentication than others.
Definitions of
Commonly Used
Terms The following frequently used terms are defined below.
Adjacency
(OSPF only)
A relationship formed between selected neighboring routers for the purpose of
exchanging routing information. Not every pair of neighboring routers become
adjacent.
Autonomous
System
(OSPF only)
A group of routers exchanging routing information via a common routing protocol.
Abbreviated as AS.
Circuit or
Interface
The connection between a router and one of its attached networks. An interface has
state information associated with it, which is obtained from the underlying lower
level protocols and the routing protocol itself. An interface to a network has
associated with it a single IP address and mask (unless the network is an
unnumbered point-to-point network). An interface is sometimes also referred to as
a link.
Designated
Router
(OSPF only)
Each multi-access network that has at least two attached routers has a designated
router. The designated router generates a link state advertisement for the
multi-access network and has other special responsibilities in the running of the
protocol. The designated router is elected by the Hello Protocol. The router
concept enables a reduction in the number of adjacencies required on a
multi-access network. This in turn reduces the amount of routing protocol traffic
and the size of the topological database.
Hello Protocol
(OSPF only)
The part of the OSPF protocol used to establish and maintain neighbor
relationships. On multi-access networks the Hello Protocol can also dynamically
discover neighboring routers.
Interior Gateway
Protocol
The routing protocol spoken by the routers belonging to an Autonomous system.
Abbreviated as IGP. Each Autonomous System has a single IGP. Separate
Autonomous Systems may be running different IGPs.