Data Networking: Physical vs. Protocol
Now that you have learned a little about myself from my about me post, let’s dive into our first topic in my on-going series as a student of IT (that’s also my twitter handle btw @StudentOf_IT).
Physical and Protocol Networking
I believe students often forget with networking the physical medium, and the protocol used to transport the data are independent from each other. For example, my education curriculum or program focuses mostly on Transmission Control Protocol (TCP) Internet Protocol (IP) over Ethernet. Although, there is a relationship between the two, and both a physical medium and protocol are required to transport any data, IP is not reliant on Ethernet, and Ethernet is not reliant on IP.
Rules of the Road (or Network)
Confused yet? I was when I was trying to understand this. Picture the physical medium as a road. By itself, this road is meaningless, and dangerous without rules and control protocols. There is a clear path from one place to another, but the cars are driving at various speeds, sides of the road, and have little care for the cars around them. This is because a road by itself does not have rules. Have you ever been behind a group of people walking really slow taking up an entire hallway? This is because that hallway by itself has no rules. The people walking in the hallway make the rules or follow an established protocol.
Let us add the type of physical network cable into the equation now. For this example, we are going to use 1Gb Ethernet (e.g. 1GbE), however this applies to any type of optical or electrical cable (not to mention wireless). Ethernet is our rules on the road or physical medium. We have a speed limit of 1Gb (one billion bits per second), we must drive in given direction on a certain side (transmit or receive path) of the road, and any vehicle on the road must meet certain standards (Ethernet frame).
The next logical assumption is the protocol are the vehicles on the road right? Well half right, and this was the part I had the most trouble understanding. The vehicle itself is irrelevant. The cargo inside determines the protocol used. The protocol is providing you directions to how to reach your destination, and standards of how to handle the cargo.
Bring IT (The Network) Together
Let us put the two together now. The cargo will be using IP protocol, and the road will be Ethernet. You bought a shirt at Target that is too small for you. Because of this you want to return the shirt, and buy a new one. The shirt in this case is your cargo/IP packet (remember, this applies to any type of protocol). The shirt has determined you are going to Target, and because of the road (any physical medium), and the rules put in place on the road (ethernet) we know how to get there safely.
What if you do not have any cargo/requesting data?
This would be handled in the same way as the above example. The car might be empty now, but we were told how to handle the future cargo, and are already following the standards of how to transport it.
Wrap up
IP is not solely reliant on Ethernet, and Ethernet is not solely reliant on IP. In other words the road is not reliant on only one set of rules, and the rules can apply to more than one kind of road. If IP was implemented on a Fiber Channel network (as it was in the past), the road itself would be changed, but the rules would stay the same, like going from a paved to a gravel road. The rules on the road can be changed as well. Fiber Channel over Ethernet (FCoE) can be implemented on an Ethernet network instead of IP. This would change how we drive on the road. Britain driving on the left side of a paved road, instead of the right.
That is enough from me for now, check back soon to read my continuing series of experiences as a student of IT. 😛
Cory Peden – Student of IT
StudentofIT 