How routers really work.

This assignment required us to listen to the How Stuff Works Podcast: "How routers work".  The hosts did a good job of providing a general overview of routers and associated protocols. Unfortunately it is hard for me to pay attention to podcasts... so after listening to it three times I have a decent understanding of their discussion.  I hope to overcome the shortfall of all audio podcast by providing pictures to keep you interested.

The hosts focused on three layers of the OSI model. For those of you that don't live in your parents basement OSI stands for open systems interconnection (I didn't know what OSI meant either) and is the backbone of the modern network. In the most basic sense the OSI model is set of definitions to help create the ideal network. .  

Layer one is the 'bit' or physical layer. The actual physical elements of a single communication device such as the internal configuration of the device (pins, bit rate, encoding) or other elements like the voltage needed to transmit data.

Layer two concerns communication between devices within a LAN (local area network).  Which contrary to the title of the post, a router is not needed to allow communication within a LAN, only a switch.

A router is needed when you need to communicate with another network. The network of networks (Layer 3 - internet) is when routers really come into play.  "The router controls the information moving from a local area network to the internet.... and without a router... global communication would not be possible."

Routers transmit pieces of information called packets. Many packets are used to send or request a piece of information. Packets also come with instructions on where the data is to be delivered. Routers help packets reach their final destination by automatically selecting the fastest path to the destination server.  A router uses a routing table to help it send packets.  Routing tables contain a list of dynamic rules that are constantly updating by routers communicating with each other to help select the best paths for packets to be sent.

Routers constantly communicate with each other to determine the path of least resistance.

Routers essentially calculate the cost of transmitting a piece of data to its destination.  For example, one packet may be sent from router A to router B to router C to router D.  Typically routers look for a path with the fewest hops and if a packet has been through too many hops the router may think the packet is lost or has already reached its destination and is loitering on the network.

Bunnies all over the world are tasked with delivering your Wikipedia searches to and from routers. 

MAC addresses are associated with each device on a local network.  Once a bunny has reached the router with the requested information it looks to see which MAC addressed requested the information and delivers the wikipedia search for Miss Piggy to my laptop. 

Ten points if you can spot what is wrong with this picture.

Sometimes we may receive packets from evil malicious bunnies that are carrying data that is harmful to our computers and network.  That is why it is important to have a firewall.  Thankfully, most routers have firewalls built into them.  Firewalls have a set of rules they use to filter out bad packets from ever entering our local networks.

I like to think of my firewall as being Mr. T

I only scratched the surface on how routers work.  If you have any questions please comment and I will try to answer your question as concisely as possible accompanied with an appropriately funny image.