Routers are the devices that make the Internet possible. Routers are connected to two or more networks at crossing points. When they receive a packet of information, they decide which way they should send the packet to ensure that it gets to its destination quickly and efficiently. For example, say you want to send an e-mail to your friend. The e-mail message will first be broken up into small packets. Each packet will contain the IP Address of the destination computer. Then, your computer will ship all the packets to the nearest router, which will be connected to many networks. The router then decides which network it should send the packet to in order to best reach your friend's computer!
Interior Gateway Protocols:
There are different types of routers for local-area networks and wide-area networks. Interior Gateway Protocols (IGP) are the protocols that manage routers within a small LAN, for example, a network in a small business. There are two main types of IGP protocols:
This is not only a pretty simple and straightforward IGP protocol, but it is also the most widely used. In the Routing Information Protocol, every router has a database, where it keeps all the information of the fastest route from one point to another.
Then, there is a "refresh" mechanism. Every router will send a copy of the information stored in its database to all of the routers that are near it. It shares its information about the quickest, most efficient way to get information from one IP Address to another. Some routers do this every 30 seconds to ensure that all of the other routers have the most up-to-date information! Say one of the routers receiving the information finds a shorter way to get from one point to another. Then, it will update its own database to incorporate the new route!
RIP is very efficient, and is widely used!
2. Open Shortest Path First (OSPF):
This protocol, although not as simple as RIP, is very fast. They are generally used more in larger local-area-networks.
As you know, routers in the RIP protocol only keep track of the routers that are closest to itself. In OSPF, the routers keep track of ALL of the routers in the network.
Another major difference between RIP and OSPF is that when RIP "refreshes," the router sends its whole database to the neighboring routers. On the other hand, OSPF only sends the paths that have been changed. Also, RIP might refresh every 30 seconds. OSPF only sends data when there has been a change.
Exterior Gateway Protocols:
The Exterior Gateway Protocols (EGP) form the backbone of the Internet. They can be used to link multiple LANs to create a wide-area network. The most commonly used EGP is the Border Gateway Protocol (BGP)
The Border Gateway Protocol forms the backbone of the Internet. It ensures
that the information you send to another computer will reach its destination,
even if problems, like if a network connection goes down arise. The BGP protocol is kind of similar to the RIP protocol. When a BGP router
is first connected to the Internet, it will connect to the other BGP routers
near it. BGP routers send four types of messages to its neighboring routers: 2. Update: These messages contain information about routes and paths;
such as if there is a newer, quicker path between two computers, etc. There
are two types of update messages:
3. Notification: These messages include any type of error that might come
up. 4. Keepalive: Sent about every 30 seconds, these messages notify neighboring
BGP routers that the sending router is still up and running. If a router
does not get a Keepalive message in a certain amount of time, it will close
the connection with that router.
Border Gateway Protocol:
1. Open: This opens a connection with a neighboring router.
· Withdrawn Routes: These contain the IP Addresses of computers that
the router can no longer reach.
· Paths: These messages send information about quicker paths between
two IP Addresses.
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