- The usage of the re-configurable logic has been
increasing day by day both in scope as well as number.

- Re-configurable computing
combines both the hardware speed and the flexibility of the software.

- This is
the result of the combination of the highspeed computing and
re-configurability.

- Tough requirements are posed up on the routing in a network
by the increased QoS i.e., the quality of service.

- This increase in the
complexity of the computational capabilities bears an exponential relation with
the increased QoS.

- However, additional computational resources are needed for
achieving a network performance level that is acceptable.

- Re-configurable
computing offers a promising solution to the issues of the computations in the
routing process.

__There are 3 major aspects of the shortest path routing as mentioned below:__
Ø

**Path selection:**This involves the various algorithms such as the Dijkstra’s and bellman – ford algorithms and shortest path and minimum – hop routing.
Ø

**Topology change:**Changes in the topology are detected using the beacons.
Ø

**Routing protocols:**This involves routing protocols such as the link state routing protocols and distance vector protocols.
- Forwarding and routing are two different things.

- In
forwarding, the data packet is directed towards an outgoing link and an
individual router is used that also maintains a forwarding table.

- Routing
computes the paths that have to be followed by the packets.

- Routers exchange
the path information between themselves and the forwarding table is created by
each and every router in the chain.

__Routing is important for the following three main reasons:__**Ø**

**End-to-end performance:**The user performance is affected by the path quality, throughput, packet loss and delay in propagation.

**Ø**

**Use of the network resources:**The traffic has to be balanced between the several links and routers. The traffic is directed towards the links that are lightly loaded for avoiding the congestion.

**Ø**

**Transient disruptions during changes:**These disruptions include the load balancing problems, maintenance, failures etc. the packet loss as well as the delay has to be limited while the changes take effect.

- Shortest path routing is based up on a path
selection model that gives more preference to the destination.

- This type of
routing is insensitive to load as in it involves the static link weights.

- Here, either the sum of the link weights or the minimum hope is considered.

**-**

**In a shortest path problem,**the link costs are given for a network topology.

- For example,
C(x,y) denotes the cost of the node x to node y.

- If the two nodes x and y are
not adjacent to each other the cost is taken to be infinity.

- The least cost
paths linking all the nodes are computed from a node taken as the source.

**- Dijkstra’s shortest path algorithm is one of the algorithms used in the shortest path routing.**

- A central role is played by the problems involving finding the
shortest paths in the designing and the analyzation of the networks.

- A majority
of the routing problems can be taken as the shortest path problems and solved
if each link in the network has appropriate cost assigned to it.

- This cost even
reflects the bandwidth as well as the bit error ratio if required. - A number of
algorithms are available for computing the shortest path.

- But these algorithms
are applicable only if a single non – negative additive metric characterizes
every edge in the network.

- Out of these algorithms, the Dijkstra’s algorithm is
the most famous one.

- This algorithm find its use in the OSPF (open shortest path
first) routing procedure of the internet.

**- In this algorithm the number of operations carried out are proportional to the number of nodes in the network and the iteration is carried for n-1 times.**

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