Dynamic Routing - D-Link DFL-1600 User Manual

72 Chapter 10. Routing
simply drop the packet. Therefore, static routing is often used to make the
minimal set of routes to reach directly connected networks only.
10.3.2

Dynamic Routing

Complementing to static routing algorithm, Dynamic Routing adapts to
changes of network topology or traffic loads automatically. It learns all the
directly connected networks first, and gets further routes information from
other routers that are running the same algorithm. The algorithm then
sorts the routes it collected, selects the most suitable route for a destination
it has learned, appends the route into its routing table, and distributes this
information to other routers.
Dynamic routing responses to routing updates on the fly and is more
susceptible to problems such as routing loops. In the Internet, two types of
dynamic routing algorithm are typically used: a Distance Vector(DV)
algorithm & a Link State(LS) algorithm. How it decides the "best" route
and shares the update information with other routers depends on the type
of the algorithm applied.
Distance vector algorithm
Distance vector (DV) algorithm is a decentralized routing algorithm,
computing the "best" path in a distributed manner. Each router computes
the costs of its own attached links, and shares the route information only
with its neighbor routers. The router gradually learns the least-cost path
by iterative computation and knowledge exchange with its neighbors.
The Routing Information Protocol(RIP) is a well-known DV algorithm.
RIP sends update message regularly, and reflects the routing changes in the
routing table. Its path determination is based on the length of the path –
the number of intermediate routers, or the so-called hops. After updating
its own routing table, the router immediately begins transmitting its entire
routing table to its neighbor routers to inform the change.
Link state algorithm
Different from the DV algorithms, Link state (LS) algorithm enables the
routers to keep routing tables that reflect the topology of the entire
network, a global view of the routing information. As defined in this
algorithm, each router broadcasts its attached links and link costs to all the
other routers in the network. A router, upon receiving broadcasts from the
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