Difference between Dynamic Routing and Static Routing
Routing algorithms in the context of networking can be
classified variously. The prior classification is based on the building and
modification of a routing table. This can be done in two manners statically or
dynamically. More precisely these are known as static and dynamic routing
respectively.
In the Static routing, the table is set up and modified
manually whereas in the dynamic routing the table is built automatically with
the help of the routing protocols. Dynamic routing is preferred over static
routing because of the major issue in static routing where in case of link/node
failure the system cannot recover. The dynamic routing overcomes from the
static routing limitations.
Routing is the process of transferring the packets from
one network to another network and delivering the packets to the hosts. The
traffic is routed to all the networks in the internet work by the routers. In the routing
process a router must know following things:
·
Destination device address.
·
Neighbor routers for learning about
remote networks.
·
Possible routes to all remote
networks.
·
The best route with the shortest
path to each remote network.
·
How the routing information can be
verified and maintained.
1. Definition of Static Routing
Static routing does not
involve any change in routing table unless the network administrator changes or
modify them manually. Static routing algorithms function well where the network
traffic is predictable. This is simple to design and easy to implement. There
is no requirement of complex routing protocols.
The routing decisions are not made by current topology
or traffic because the static routing systems can not react to network changes
hence it doesn’t require extra resources to learn the changes. That is the
reason, static routing is considered as inappropriate for large and constantly
changing networks.
Static routing is also known as non-adaptive routing
which enables a pre-computed route to be fed into the routers offline. The
administrative distance is a metric to measure the trustworthiness of the
information received from a router. The default administrative distance for
static route is 1, consequently the static routes will only be covered in the
routing table when there is a direct connection to that network. Static routes
can be considered as an efficient method for a small and simple network that
does not change frequently.
2. Definition of Dynamic Routing
Dynamic routing is a
superior routing technique which alters the routing information according to
the altering network circumstances by examining the arriving routing update
messages. When the network change occurs, it sends out a message to the router
to specify that change, then the routes are recalculated and sent as a new
routing update message. These messages pervade the network, enabling the router
to change their routing tables correspondingly.
The technique uses routing protocols to disseminate
knowledge such as RIP, OSPF, BGP, etc. Unlike static routing, it does not
require manual updating instead its automatic in manner and updates the routing
table information periodically relying upon network conditions. For doing so,
it requires extra resources for storing the information.
Dynamic routing or otherwise called as adaptive
routing. The routing decisions are altered in these algorithms to
mirror the changes in the topology or traffic. There are various adaptive
algorithms which can be classified according to the source of information (from
where router get the information, adjacent routers or from all routers), change
in routes (whether the route is changing when load changes or when topology
changes), optimization metrics used (distance, number of hops, residual bandwidth).
The routes on which dynamic routing is performed are
known as dynamic routes where the information is responsive to changes in the
network so that it is consistently being updated. Though, there is always a
slack between the period that a network changes and when all the routers are
informed about the change. The router tries to match the network change, and it
causes a delay which is also known as convergence time.
The convergence time must be shorter. The larger network requires dynamic
routing because with static routing larger networks could not be manageable and
result in loss of connectivity.
There are several protocols that
can be used for dynamic routing. Routing
Information Protocol (RIP) is a distance-vector
routing protocols that prevents routing loops by
implementing a limit on the number of hops allowed
in a path from source to destination. Open Shortest Path
First (OSPF) uses a link state routing
(LSR) algorithm and falls into the group of interior gateway
protocols (IGPs). Intermediate
System to Intermediate System (IS-IS) determines the best route for data through a packet-switched
network. Interior
Gateway Routing Protocol (IGRP) and its advanced form Enhanced
Interior Gateway Routing Protocol (EIGRP) are used by routers to
exchange routing data within an autonomous
system.
3. Advantages and Disadvantages Static Routing
Advantages
·
Easily implemented in a small
network.
·
No overheads are produced on router
CPU.
·
Secure because the routes are
managed statically.
·
It is predictable as the route to
the destination is fixed.
·
Extra resources (such as CPU and
memory) are not required as update mechanisms
are not needed.
·
Bandwidth usage is not required
between routers.
Disadvantages
·
Unsuitable for complex topologies
and large networks.
·
Large networks increase
configuration complexity and time consumption.
·
Link failure can hinder traffic
rerouting.
·
The administrator must be extra
careful while configuring the routes.
4.
Advantages and Disadvantages of Dynamic Routing
Advantages
·
Suitable for all the topologies.
·
Network size doesn’t affect the
router operations.
·
Topologies are adapted
automatically to reroute the traffic.
Disadvantages
·
Initially, it could be complicated
to implement.
·
The broadcasting and multicasting
of routing updates make it less secure.
·
Routes rely on current topologies.
·
Additional resources are required
such as CPU, memory and link bandwidth.
5. Conclusion
Routing is one of most important operation of computer
networking in which the data packet is moved from source to destination using
an optimized path with a low delay; the path is elected with the help of
routing techniques. The difference between static and dynamic routing lies in
the table entries updating. In static routing, the routing information is
manually updated while in dynamic routing the information is automatically
updated using protocols.
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