What is routing?

You have most likely heard of the word routing or router. We are going to look at this concept in this shot in a simplified manner, but first, let’s whet our appetite. To avoid any confusion, let’s do a background refresher.

Networking

Networking is the process of making two or more computing devices communicate and share resources. Networking can be done through a wired or wireless medium. There are very smallpersonal area network, home area network, etc., mediumcampus or corporate area network, local area network, metropolitan area network, etc., and very largewide area network; the internet is an example of this) sized networks. But this is usually for the purpose of classification, because in the technical sense when a network contains a router, it is automatically a WAN that is a big network (an inter-network).

Networking models

Networking models are basically frameworks and packs of protocols after and with which a network is modeled and built. Although there are also new emerging and proprietary types, these models are basically/generally of two types:

• OSI model
• TCP/IP suite

The OSI model is a seven-layered model or architecture for network operations, with each layer responsible for different functions in a network. The names and functions of these layers are a discussion for another day, but let’s take note of layer three, the network layer.

TCP/IP protocol suite is the most practical and widely used model, although it is basically a suite of protocols or rules that guide the operations of a network. It bundled the seven layers of the OSI model into four layers. Our interest will be on layer three; the internet layer.

# Why the focus on layer three?

At this layer, networking happens. This is not possible without the use of a router that does routing. This now takes us straight to:

What is routing?

Just as the name implies, routing basically involves directions and directing to a specified location. Imagine going on a tour. Your tour guide with their map and other directional equipment could be called the router, and then they do the location-finding (routing).

Simply defined, routing is the function of the router at the network layer of the OSI model which is the process or act of moving packetsinformation groups from source to destination, using layer three informationthe IP address of the source and destination in an inter-network of computing devices. There are two primary concerns of the routing function:

• Optimal paths determination.
• The eventual movement of packets through the inter-network.

Optimal path determination

Have you ever wondered how your internet packets (request and replies) get to you, and what the processes involved are?

Path determination is an essential function of the router, whereby it chooses the best and most efficient route through which to send packets using a preset routing algorithm. You may ask, “Why should this be difficult, why not just pass the packet through?”

It is not as easy as that, and it is quite a difficult task for the router. Just like how getting to your favorite supermarket can be achieved via several routes, you always make the choice of a particular route that is most efficient at the time. This also happens during routing. The router checks all possible routes to the destination and, based on some conditions like hop countnumber of routers it would encounter, delay on a path, and others according to the algorithm used, it would choose the best paths to transmit packets.

Because routers are intelligent, they keep a record of the different paths they have used and will refer to it again in case they need to send packets once more for the same host. These are the set of events that occur any time there is a packet to be sent because a path that is efficient now might become faulty in a couple of seconds. The process continues as long there is a packet to be sent.

Packets transmission

Earlier, we mentioned layer three information. This is what packets transmission refers to. For a successful routing, the packets sent must reach the receiver successfully, or the receiver must send information of being contacted for cases of dropped packets.

For this to happen, the sender must have details of the receiver’s location, as well as the receiver of the sender. These location details are the IP address of both devices, and they can be found at the network layer, hence the name “layer three information.” With this, the router can communicate to the next router using its MAC address. If it does not know how it drops the packet. And if it does, the transmission continues via the best path chosen until it gets to the network of the destination host, and then to the intended host.

Notes

• Routers alone do the routing. Bridges don’t, because they only extend a network segment and communicate using layer two informationMAC address, while routers create different network segments and transmit using IP/ logical addresses.
• There are different algorithms and processes that the router uses to make successful path determination and packet transmission. These can all be set by the network administrator.
• Routing is concerned with two basic tasks: path determination and packet movement.