Is Bandwidth A Precious Resource?


During a recent episode of the Packet Pushers Podcast, Greg and Drew talked about the fact that bandwidth just keeps increasing and we live in a world where the solution to most problems is to just increase the pipeline to the data center or to the Internet. I came into networking after the heady days of ISDN lines everywhere and trying to do traffic shaping on slow frame relay links. But I also believe that we’re going to quickly find ourselves in a pickle when it comes to bandwidth.

Too Depressing

My grandparents were alive during the Great Depression. They remember what it was like to have to struggle to find food or make ends meet. That one singular experience transformed the way they lived their lives. If you have a relative or know of someone that lived through that time, you probably have noticed they have some interesting habits. They may keep lots of cash on hand stored in various places around the house. They may do things like peel labels from jelly jars and use them as cups. They may even go to great lengths to preserve as much as they can for reuse later “just in case”.

It’s not uncommon for this to happen in the IT world as well. People that have been marked by crazy circumstance develop defense mechanisms against. Maybe it’s making a second commit to a configuration to ensure it’s correct before being deployed. Maybe it’s always taking a text backup of a switchport before shutting it down in case an old bug wipes it clean. Or, as it relates to the topic above, maybe it’s a network engineer that grew up on slow ISDN circuits trying to optimize links for traffic when there is absolutely no need to do so.

People will work with what they’re familiar with. If they treat every link as slow and prone to congestion they’ll configure they QoS policies and other shaping features like they were necessary to keep a 128k link alive with a massive traffic load. Even if the link has so much bandwidth that it will never even trigger the congestion features.

Rational Exuberance

The flip side of the Great Depression grandparent is the relative that grew up during a time when everything was perfect and there was nothing to worry about. The term coined by Alan Greenspan to define this phenomenon was Irrational Exuberance, which is the idea that the stock market of 1996 was overvalued. It also has the connotation of meaning that people will believe that everything is perfectly fine and dandy when all is well right up to the point when the rug gets pulled out from underneath them.

Going back to our bandwidth example, think about a network engineer that has only ever known a world like we have today where bandwidth is plentiful and easily available. I can remember installing phone systems for a school that had gigabit fiber connectivity between sites. QoS policies were non-existent for them because they weren’t needed. When you have all the pipeline you can use you don’t worry about restraining yourself. You have a plethora of bandwidth capabilities.

However, you also have an issue with budgeting. Turns out that there’s no such thing as truly unlimited bandwidth. You’re always going to hit a cap somewhere. It could be the uplink from the server to the switch. Maybe it’s the uplink between switches on the leaf-spine fabric. It could even be the WAN circuit that connects you to the Internet and the public cloud. You’re going to hit a roadblock somewhere. And if you haven’t planned for that you’re going to be in trouble. Because you’re going to realize that you should have been planning for the day when your options ran out.

Building For Today

If you’re looking at a modern enterprise, you need to understand some truths.

  1. Bandwidth is plentiful. Until it isn’t. You can always buy bigger switches. Run more fiber. Create cross-connects to increase bandwidth between east-west traffic. But once you hit the wall of running out of switch ports or places to pull fiber you’re going to be done no matter what.
  2. No Matter How Much You Have, It Won’t Be Enough. I learned this one at IBM back in 2001. We had a T3 that ran the entire campus in Minnesota. They were starting to get constrained on bandwidth so they paid a ridiculous amount of money to have another one installed to increase the bandwidth for users. We saturated it in just a couple of months. No matter how big the circuit or how many you install, you’re eventually going to run out of room. And if you don’t plan for that you’re going to be in a world of trouble.
  3. Plan For A Rainy Day. If you read the above, you know you’re going to need to have a plan in place when the day comes that you run out of unlimited bandwidth. You need to have QoS policies ready to go. Application inspection engines can be deployed in monitor mode and ready at a moment’s notice to be enabled in hopes of restricting usage and prioritizing important traffic. Remember that QoS doesn’t magically create bandwidth from nothing. Instead, it optimizes what you have and ensures that it can be used properly by the applications that need it. So you have to know what’s critical and what can be left to best effort. That means you have to do the groundwork ahead of time so there are no surprises. You have to be vigilant too. Who would have expected last year that video conference traffic would be as important as it is today?

Tom’s Take

Bandwidth is just like any other resource. It’s not infinite. It’s not unlimited. It only appears that way because we haven’t found a way to fill up that pipe yet. For every protocol that tries to be a good steward and not waste bandwidth like OSPF, you have a newer protocol like Open/R that has never known the harsh tundra of an ISDN line. We can make the bandwidth look effectively limitless but only by virtue of putting smart limits in place early and understanding how to make things work more smoothly when the time comes. Bandwidth is precious and you can make it work for you with the right outlook.

2 thoughts on “Is Bandwidth A Precious Resource?

  1. I feel the same way about computer memory in general. I come from the era where software engineers had so much constraints hardware wise on their computers that saving 10kb of ram could be seen as imperative. You could not expect anyone to have more room than a floppy drive. Virtually no one had a hard drive.

    In contrast, applications like the games of today frequently come with 50GB to 100GB of textures and the general public just shrugs it off like it’s a normal thing. One has to wonder if this is lazy programming? Are we teaching our programmers that resources are plentiful? The programmers of today clearly never had to experience the harsh constraints of 640kb of RAM and a floppy drive. I wonder what the senior programmers that had those constraints would think of such a resource budget and what they would accomplish with it.

  2. There’s also what I call the pressure cooker effect. If you’ve been holding demand down with limited capacity, then projections of future consumption may be falsely low. Which leads to if you build it it will (maybe) get used. (I first saw this with an office photocopier, which was overworked. Budget and predictive stats only allowed expanding capacity 10% a year. It took something like 10 years to get it to the right capacity.)

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