Routing
o A Router is a process of selecting path along which the data can be transferred
from source to the destination. Routing is performed by a special device known as
a router.
o A Router works at the network layer in the OSI model and internet layer in TCP/IP
model
o A router is a networking device that forwards the packet based on the information
available in the packet header and forwarding table.
o The routing algorithms are used for routing the packets. The routing algorithm is
nothing but a software responsible for deciding the optimal path through which
packet can be transmitted.
o The routing protocols use the metric to determine the best path for the packet
delivery. The metric is the standard of measurement such as hop count, bandwidth,
delay, current load on the path, etc. used by the routing algorithm to determine
the optimal path to the destination.
o The routing algorithm initializes and maintains the routing table for the process of
path determination.
Routing Metrics and Costs
Routing metrics and costs are used for determining the best route to the destination. The
factors used by the protocols to determine the shortest path, these factors are known as
a metric.
Metrics are the network variables used to determine the best route to the destination. For
some protocols use the static metrics means that their value cannot be changed and for
some other routing protocols use the dynamic metrics means that their value can be
assigned by the system administrator.
The most common metric values are given below:
o Hop count: Hop count is defined as a metric that specifies the number of passes
through internetworking devices such as a router, a packet must travel in a route
to move from source to the destination. If the routing protocol considers the hop
as a primary metric value, then the path with the least hop count will be considered
as the best path to move from source to the destination.
