What are the different Methods of routing and routing protocols

Certification: Cisco CCNA Routing and Switching - Cisco Certified Network Associate Routing and Switching

Routing means communicating data from one router to another.Routing also means picking the best path to communicate data from one side to the other out of thousands of routers. Routing is the traffic officer of the internet. Can you imagine how the internet, that immeasurable agglomeration of data and nodes would possibly communicate? How those little boxes we call hardware exchange little bursts of electricity and somehow images appear of screens and sound comes out of them? Routing is one of the most important aspects of networking and data sharing. However you can’t have them communicate with one another freely without rules. It doesn’t need that much imagination to guess what a hacker could do with an un-governed internet. Networks need security, so they need rules. Thankfully, these rules are built in the networks themselves, through routing protocols.

Nodes and delivery

In case you didn’t already know, the internet is made out of nodes, usually routers, which all connect to one another, and information is passed through each one of them at a time. A router is a hardware device, usually specialized even if a computer would also work at increased costs. There are small networks within big networks, and each network has its own rules and type. Your own little home network, which usually compromises of a Wi-Fi router, a PC and other media devices (phone/console/laptop/smart-pad) connects to a larger network, usually around your zip code, then to an even bigger one, usually an AS, then to the internet. Within that, there are already thousands of nodes the data you send from your PC in the shape of a cat picture must pass through to be uploaded on the net. Among those other notes there are firewalls, gateways and switches.

There are two types of routing that come in place there. Static routing, and Dynamic routing. The internet itself is dependent on dynamic routing. That means that the pathways from point A to point B in a network is generated automatically,  through the constant sharing of network information amongst routers, rather than being manually configured by a technician. However both methods are used in symbiosis as they do not mutually exclude each other. Sometimes static routing is preferred because it is more secure, and it takes up less bandwidth.

Within a closed network, there are also different types of delivering the data, based on who needs what. Those are unicast, the delivery of data from one node to just one other, broadcast, the delivery of data from one node to all others in the network, multicast, the delivery of data from one node to multiple other nodes that expressed a an interest in receiving that data, anycast, the delivery of data from one point to any other, usually the closest, and geocast, which is the delivery of data towards a regional/geographic region. The internet itself is predominantly unicast driven, but there are some other types used as well in lesser weight.

Useful names to remember

Autonomous systems (AS) are a collection of Internet Protocols routing prefixes, administered by one group/company. These typically include internet providers or very large companies with a clear routing policy. Autonomous systems use Exterior Gateway Routing Protocols to communicate between each other. The last count of the total number of unique autonomous systems as recorded in 2014 was over 47,000. Each AS is accorded a specific identification number called autonomous system number which it uses to communicate with other ASes.

Routing tables are an “internal address book” inside each router in which it keeps particular network destinations. In some cases, such as the distance-vector protocols, the distance to that destination is also registered. The table contains information about the immediate network of the router.

Routing is sometimes confused with bridging because, it appears to do the exact same thing, but the difference is that bridging happens only in the first two layers of a network.

Routing protocols

Routing protocols, or routing policy, are “the rules” by which routers communicate with one another. At first, a lone router knows information only about its neighbors, the routers communicate what neighbors it can connect to first with them, and then with the entire network. That way, the routers can draw a map of their network.

There are 2 main types of protocols Interior Gateway and External Gateway. The most common Interior gateway protocols are: Link-state routing protocols which operate by “Open short path first” or “Immediate system to intermediate system” and Distance-vector routing protocols, protocols used to calculate long distance paths using algorithms such as the Bellman-Ford, Ford-Fulkerson or Dual FSM (Cisco)these protocols assign distance values to each connecting router and then sends the information towards the destination by the least value neighbor. Exterior gateway protocols are also used.Examples of exterior gate protocols are the EGB and BGB.

Interior gateway protocols are used by gateways in order to exchange routing information within an autonomous system (like a corporate private network). There are also Enhanced Interior Gateway protocols, that combine the utility of the Link-state routing protocols with the capabilities of the “Distance-vector routing protocols”.

Exterior gateway protocols are used by autonomous systems to exchange routing information between them. This type of protocol is instrumental for the internet. Search engine providers such as Google or Bing couldn’t operate without these protocols.

Another notable protocol is the Routing Information Protocol, a protocol which measures the distance from a router to its destination by counting “hops”. This protocol is used primarily to eliminate loops in the network by setting a maximum of 15 “hops” towards a destination. The downside of this protocol is that any destination that takes 16 or more “hops” is deemed unreachable, not mattering whether it’s just 16 “hops” or 100 “hops”.

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