Open Shortest Path First (Ospf); Open Shortest Path First - Bay Networks NauticaRS Reference Manual

Open Shortest Path First (OSPF)

117237-E Rev.00
A call that has been made for data transfer will not be kept open
by routing updates, because these are not included in the idle
calculation for that call. All routing updates received while the
connection is closed are copied to the local routing table(s), and
the table information is transferred automatically when the next
call is made.
These mechanisms, specifically related to ISDN connectivity,
combine to ensure that unnecessary calls are not made by Nautica
routers and that call duration is kept to a minimum.
The Bay Networks Nautica 4000 and Bay Networks Nautica
Marlin support OSPF, a protocol designed to remove some of the
restrictions of RIP in large networks, especially in the IP
environment.
While RIP is a distance-based protocol which uses hop count as
its only decision criteria and sends out routing updates every 30
seconds, ignoring network changes, OSPF is a Link State
Shortest Path First Protocol which records the state of an
interface and any changes to that interface. Such changes then
cause a routing update message to be sent. This greatly reduces
the number of messages on the internetwork. OSPF update
messages are also smaller in size, carrying only the changes to the
routing environment, rather than the whole routing table as in RIP.
This means a significant bandwidth saving on the internetwork.
However, OSPF routers need a more powerful Central Processing
Unit (CPU) and more memory to process the greater amount of
information generated. The Nautica series is ideal for OSPF due
to its use of RISC-based processors, which can be scaled up
easily to handle both medium and large network topologies.
Introduction to Protocols and Routing
1-19