Chasing the “Ah-ha!” Moments

Image courtesy of Wikipedia

Whenever I talk to people who are just getting started in networking, there’s a part of me that wishes I was in their shoes. I say that because I know several of the things they are going to learn or figure out in the next couple of years and I remember having to go through the same process. Before I understood variable length subnet masks(VLSM), the numbers in the subnet mask field of a workstation’s TCP/IP settings didn’t really mean a whole lot to me. If someone used slash notation(ie /24, /16, /27), I had no idea what that meant. Like a lot of people, I relied on someone to tell me what the subnet mask was. However, once I learned about VLSM, it was as if a whole new world opened up. That was one of my absolute favorite “Ah-ha!” moments. You’ve had those yourself haven’t you? It is the point in time in which a certain technical concept just clicks in your head. You go from not really understanding it, to comprehending it. In fact, it’s almost as if that concept is only represented in binary inside your head. You go from a 0 to a 1 with no in between.

As you progress along in networking, more and more of these “Ah-ha” moments come. Unfortunately, over time they become fewer and fewer. That’s not to say that they go away completely. They don’t. They are just harder to come by. I’ve found that I am able to keep a steady stream of these “Ah-ha” moments coming as long as I look at technology without taking anything for granted. What I mean by that is that I don’t assume anything when it comes to trying to understand a protocol or technology. What I “think” I know might actually be wrong. My understanding might only be partial. I have to continually ask “why/what/how/when/where” when dealing with technology.

Let me give you a personal example. I have known for many years that a T-1 is 1.544Mbps in terms of bandwidth. It is comprised of 24 64kb channels. The only problem is that 24×64,000 is 1536000 and not 1544000. Oops. Where did the other 8k go? To further drive this home, a “show interface” on a serial link that is configured as a full T-1 shows the interface bandwidth to be 1536kbps. Why the discrepancy? I could have just moved on and ignored the reason behind the discrepancy. However, by researching the issue and figuring out what the issue with this discrepancy was, I learned a whole lot more about T-1’s. I learned how alarms over the circuit get propagated. I learned what the extended super frame(ESF) actually was. In other words, had I not been curious as to why the math didn’t add up when it came to T-1 bandwidth, I would be far more deficient in the inner workings of the T-1.

In the spirit of chasing the “Ah-ha” moments, take a look at the 4 questions below. Go find the answers if you don’t already know them.

1. Why is MPLS faster than conventional IP based routing?
2. What are the differences between a multi-layer switch and a router?
3. Why do you need different antennas for wireless access points and where would you use each antenna type? Sure, this is rather open ended, but what I am getting at is the radiation pattern of each antenna.
4. How does traceroute really work? Not just the TTL mechanics, but look at the various ICMP type codes as well.

Can you remember the last “Ah-ha” moment you had? If not, why? If so, does it make you want to go out and find more of those moments?