Don't forget the cables

An architectural approach to cable management

Don't forget the cables

Before deciding to pursue a career in network engineering, I studied and graduated in the more traditional field of mechanical engineering. As such, I learned that the Second Law of Thermodynamics states that the natural tendency of isolated systems is to degenerate into disorder and chaos.

Since moving into network engineering, I believe I have found the best metaphor to describe this tendency - server rooms and their comms racks. It seems that no matter the effort and energy input to the system, the gradual decay into absolute chaos is inevitable.

Design Comes First

Despite its inevitability, we must hold off the disorder for at least the lifespan of the server room equipment, which is likely to be upwards of 5 years. Cables and devices should be easily identifiable and easy to maintain. It should be easy for first-line engineers to install or remove devices and more importantly, it should be easy for them to see and understand how and why the rack is designed and built the way it is so that they can follow suit in their day-to-day maintenance tasks. This is only possible by thinking about cable management and rack layout during the design and architecture phase of network design. If your network design / new site procedures do not include cable management from the very start and instead you tend to let your engineers figure it out on install day, then the usability and functionality of the project is entirely resting on the competency and experience of your engineers.

If you address rack layout and cable runs as part of your architecture and design, you will have an understanding of the length of cables required, how many of each colour you may need, where the cable management infrastructure should be installed, etc. You can then supply your engineer with the correct number of each length and colour of cable and dictate where each should go - giving the on-site engineer the best chance of success. And don’t forget that the department or customer holding the purse strings cannot see the extra special Software Defined Networking technology that you are using, or even understand the razor-sharp cutting edge security. When they open the server room door and look at a rat’s nest a week after install, they are going to wonder if the state of the installation reflects the setup of rest of their new systems.

During your design phase, make sure you understand the physical devices and layouts. Do you have any bulky or heavy devices in the rack, and can they be installed at the bottom to make it easier for the engineer? Do you have any devices that have particularly dense network cabling and require a lot of connections, can this device be moved closer to the switch it is connecting to? Have you got the correct cable management tools for that rack/install, and have you got enough of it? Finally, do you understand where each cable will need to run, how long those cables need to be, and what colour you would like it to be? Using a rack management tool can be very helpful at this stage to allow you to drag and drop devices around virtually. It may even give you some automatic assumptions of cable run lengths, power input required and heat output. You should have a good understanding of what the rack will look like before any devices are ordered.

A Recent Installation

We had a challenge recently for one of our customers and their new office in Leeds. For various reasons, we were restricted to one comms rack in the server room. This resulted in the device density being higher than we would usually allow and put particular demands on cable management. With a higher device density, we had a much higher cable density and without proper planning, it would have been impossible to manage from day one.

Collapsed Core Stack - Partially cabled

By allowing for these density demands from the start, we were able to play around with the rack layouts and make sure we could fit everything in, while still having a functional comms cabinet. We sourced some small 20cm pre-made patch cables specifically for this install so that we could have the shortest cable runs as possible at the densest parts of the rack. When we were happy with the design and had an understanding of cable runs at the front, we then did the same for the power distribution at the back of the rack to ensure we had multiple sources of power that were easy to identify. We had a full understanding of the layout and cable runs before we ordered any hardware.

During the install, the devices with longer cable runs were installed first, cable managed and assessed to ensure it matched up with the design. We could then layer up devices on top of that, until the full rack was complete. We tried to keep cables a tight as possible by installing all cables to a single device at the same time – running the cables and managing them as a bundle rather than individuals. As with all our installs, each cable is labelled at both ends so we were able to bundle cables up, run them properly and still ensure they ended up in the correct place.

Access layer flood cabled with 20cm pre-made cables

In Conclusion

You do have to invest slightly more time (although not as much as you would think) during the design and install phases, but you easily make back your time over the lifespan of the infrastructure. This should be easy to maintain for many years – although perhaps I might pop into the office and see how the onsite engineers have been treating it…