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In order to be able to communicate with each other, routers use protocols. Through these protocols, changes are reported and routers share information about the whole network. Thus, the network itself adapts to changes in a dynamic way.

A protocol is also a formula that the router uses in order to appropriately determine the path that data must be sent on from one router to another.

As internet data is sent over TCP/IP, one of the most commonly used protocols by routers is OSPF. OSPF stands for Open Shortest Path First and is part of what is called the Interior Gateway Protocol (IGP). OSPF determines shortest paths between two points and was designed to replace RIP, which was much more bandwidth consuming. The main difference between OSPF and RIP is that OSPF provides only the most critical information between routers in order to determine the shortest path.

Although replaced by OSPF, some routers still use RIP – Routing Information Protocol. RIP determines the shortest possible route from origin to destination which is also part of the TCP/IP protocol suite. As RIP is constantly communicating routers with their neighbouring routers to determine shortest paths, it has the disadvantage of wasting bandwidth.

Apart from routing protocols, perhaps one of the most important protocols used by routers is CIDR. CIDR stands for Classless Interdomain Routing and has been able to support the massive expansion of the internet over the last few years. As more and more users connect to the internet, more and more IP addresses are necessary. IP routes increased from 2,000 in 1990 to 30,000 in 1995 and vendors and ISPs were faced with the challenge that the finite number of IP addresses would at some point be used up. As a consequence, CIDR was developed. CIDR is a method developed to create additional IP addresses that are then given to ISPs, which in turn give it to their users. What CIDR basically does is aggregate routers, resulting in the fact that one IP address can represent thousands of IP addresses that are serviced by major backbone companies, like Verizon Business or Sprint. Thus, all information sent through any of these addresses is sent to the backbone service provider.

As the next generation of data transmission is becoming a reality, making VoIP and real-time video transmission possible, more protocols are being developed in order to properly support new internet technologies. One such protocol developed in the last two years is MPLS – Multiprotocol Label Switching. When packets of data are sent over the internet, each packet is labelled by the first router with information such as destination and other type of forwarding information. The following routers can then analyze the label and forward it much faster than having to look up addresses in routing tables, making seamless data transmission possible for normal high speed connections.