Routing in Computer Network

Routing is a mechanism that selects a way for data to be transmitted from the source to the destination. Router is a specific device that does routing.

A router operates at the network layer of the OSI model and at the internet layer of the TCP/IP model. It is a networking device that forwards packets depending on the data in the packet header and forwarding table.

Routing algorithms are used to route packets. The routing algorithm is just a piece of software that determines the best path by which a packet may be sent.

The measure is used by routing systems to identify the optimum path for packet delivery. The metric is the unit of measurement utilised by the routing algorithm to identify the best way to the destination, such as hop count, bandwidth, latency, current load on the network, and so on.

The routing algorithm creates and maintains the routing table for the path decision process.

Metrics of Routing:

There are many different metrics used to define and measure the efficiency of routing. Some of them are as follows:

1. Hop Count:

A hop count is a statistic that describes the number of trips through internetworking devices such as routers that a packet must make in order to go from source to destination.

If the routing protocol uses hop count as a major metric value, the path with the fewest hops will be deemed the optimal way to take from source to destination.

2. Delay:

It is the amount of time it takes a router to process, queue, and transmit a datagram to an interface.

This measure is used by protocols to calculate the delay values for all links along the path from beginning to finish.

The path with the shortest delay will be deemed the best path.

3. Bandwidth:

The bandwidth of the link is the capacity of the link.

Bits per second are used to measure bandwidth.

A link with a greater transfer rate, such as gigabit, is chosen over a link with a lesser capacity, such as 56 kb.

The protocol will assess the bandwidth capacity of each connection along the way, and the route with the highest total bandwidth will be regarded as the optimal route.

4. Load:

Load refers to how busy a network resource, such as a router or network link, is. It may be calculated in a number of ways, including CPU usage and packets processed per second.

If the volume of traffic grows, so will the load value.

The load value varies in response to variations in traffic.

5. Reliability:

Reliability is a metric factor that might have a set value. It is determined by the network links, and its value is calculated dynamically. Some networks fail more frequently than others. Some network links recover more easily than others after a network breakdown.

Any dependability factor can be used to provide reliability ratings, which are typically quantitative values assigned by the system administrator.

Types of Routing:

1. Static Routing:

Nonadaptive Routing is another name for static routing. It is a method in which an administrator manually enters routes into a routing database. The packets for the destination can be sent by a Router following the path set by the administrator.

This method does not make routing decisions based on network state or topology.

Advantages:

• No Overhead: There is no overhead on the router’s CPU use. As a result, the less expensive router may be utilised to get static routing.
• Bandwidth consumption: There is no bandwidth usage between the routers.
• Security: It offers security since the system administrator is only authorised to regulate routing to a certain network.

Disadvantages:

• Adding each route manually to the routing database becomes quite complex in a big network. To manually create each route, the system administrator should be well-versed in topology.

2. Default Routing:

Default Routing is a routing strategy in which a router is set to deliver all packets to the same hop device, regardless of whether it belongs to a specific network or not. A packet is sent to the device for which default routing is enabled.

When networks have a single exit point, default routing is utilised. It is also beneficial when a large number of transmission networks must send data to the same HP device.

When a specific route is listed in the routing table, the router will take that route instead of the default route. When a specific route is not listed in the routing table, the default route is used.

3. Dynamic Routing:

It is sometimes referred to as Adaptive Routing. It is a technique in which a router creates a new route in the routing table for each packet in response to changes in the network’s condition or topology.

Dynamic protocols are utilised to find new paths to the goal. RIP and OSPF are the protocols used in Dynamic Routing to discover new routes.

If any of the routes fails, an automated modification will be performed to get to the destination.

Requirements for Dynamic Routing:

To exchange routes, all routers must use the same dynamic routing protocol. If the router detects a change in the condition or topology, it broadcasts this information to all other routers.

Advantages:

• It is simpler to set up.
• It is more successful in determining the optimum path in response to changes in the condition or topology.

Disadvantages:

• In terms of CPU and bandwidth use, it is more costly.
• It is less secure than default and static routing.

4. Unicast Routing:

The majority of internet and intranet traffic, known as unicast data or unicast traffic, is transmitted to a specific destination. Unicast routing refers to the transmission of unicast data across the internet. Because the destination is already known, it is the simplest kind of routing. As a result, the router just needs to look up the routing table and send the packet to the next step.

5. Broadcast Routing:

Broadcast packets are not routed and transmitted by routers on any network by default. The Broadcast domains are created by routers. However, in some instances, it can be set to forward broadcasts. A broadcast message is sent to every network device.

Broadcast routing can be accomplished in one of two methods (algorithms):

A router generates a data packet and transmits it one by one to each host. In this scenario, the router duplicates a single data packet with different destination addresses. All packets are sent unicast, but because they are sent to everyone, it appears like the router is broadcasting. This approach uses a lot of bandwidth, and the router must know the destination address of each node.

Second, when a router gets a broadcast packet, it simply floods that packet out of all interfaces. All routers are set up in the same way.

This technique is light on the router’s CPU, however it may result in duplicate packets received from peer routers.

Reverse path forwarding is a technique in which the router knows ahead of time where it should receive broadcasts from its predecessor. This method is used to discover and eliminate duplicates.

6. Multicast Routing:

Multicast routing is a subset of broadcast routing with distinct advantages and disadvantages. Packets are transmitted to all nodes, even if they do not wish to receive them, under broadcast routing. However, with Multicast routing, data is only transmitted to nodes that wish to receive the packets.

The router must be aware that there are nodes that want to receive multicast packets (or streams), and only then should it forward. To avoid looping, multicast routing employs the spanning tree protocol.

To detect and reject duplicates and loops, multicast routing employs the reverse path Forwarding method.

7. Anycast Routing:

Anycast packet forwarding is a technique that allows several hosts with the same logical address to communicate with each other. When a packet with this logical address is received, it is routed to the host that is closest in the routing topology.

Anycast routing is accomplished with the assistance of a DNS server. When an Anycast packet is received, DNS is queried to determine where it should be sent. DNS returns the IP address of the closest IP address specified on it.

Summary:

In this article, we looked at the concept of routing in computer networks. We looked at the different metrics used to evaluate different routing methods. Static, Default and Dynamic routing were also explained, along with a brief look at Unicast, Broadcast, Multicast and Anycast Routing.