Routing Algorithms; Static Routing - D-Link DFL-1600 User Manual

10.3. Routing Algorithms

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world.
Routers inside an AS run the same routing algorithm and they only need to
know the topology of the area. There are special gateway routers in the
ASs that are responsible for routing packets from internal area to various
outside ASs. Gateway routers run inter-AS routing algorithm to determine
the paths toward the destinations locating in other ASs. Intra-AS routers
all maintain relationships with the gateway router to route packets out.
The most prevalent intra-AS(interior gateway) routing algorithms are
covered in the next section.
10.3 Routing Algorithms
A routing algorithm is an operator of the routing table. In the
internetworking environment, there are typically several paths between two
communication entities. The task of the routing algorithm is that given a
set of intermediate routing devices with different links connecting them, the
algorithm calculates a "best" path for two ends to communicate and
appends the path into the table.
In case of a device failure (a down link) in a selected path or other problems
that make the path unreachable, the algorithm selects the next best route
and updates the routing table to maintain the content of the table correct.
Many routing algorithms have been proposed and each features different
design for different goals. The most widely implemented algorithms can be
categorized into two classes: Static Routing & Dynamic Routing.
10.3.1

Static Routing

Static routing is a term used to refer to the manually configuration of the
routing table. The network administrators need to plan the routing table,
and manually add every necessary route and related information into the
table for successful packet forwarding. Any change on one path would
require the administrator to update the information in every affected
router.
As a result, the administration work in a large scale network environment
can be very cumbersome and error prone. In the case that a route is not
properly configured into the routing table, the router looks up in the table
to make path determination and no suitable route can be found, it will
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