meaning of "diverse" in computer networking

Factual Questions
1

In a video about networking in a datacenter, they used the phrase “we run those cables up onto the trays and take the most diverse route possible to …”. I can’t think of a single meaning for diverse that matches a single cable run. Immediately after this line they talk about running two cables if a customer “need(s) to be diverse specifically”.

I know enough about networking to understand they’re using “diverse” to mean physically separated so a single incident (e.g. fire, water damage, axe-throwing aficionado) is less likely to sever all your network connections. However, that’s not possible with a single physical cable. The way they’re describing these links it sounds like the customer is responsible for everything above the physical layer.

Here’s the video (at time of this comment), for context: A DAY in the LIFE of the DATA CENTRE | NETWORK TOUR with ASH & JAMES! - YouTube .

2

Never heard ‘diverse’ used that way. I think he was talking redundant cabling, but it’s not clear. He may just be another tech guy with limited verbal skills.

3

In the networking cabling sense, “diverse” means that the cable runs are not all in the same physical space, where they could all be interrupted at once. (Rather like guidance on backing up your computer data: having a backup on a second hard drive in your computer protects you against a drive filure, but does nothing if a thief steals the computer! ‘Diverse backup’ means storing a backup copy in a different physical location (like keeping a backup copy at work.)

An old story to illustrate the virtues of “diverse” network cabling:
Way back when, in the early days of the internet, all the internet network connections in the state of Minnesota came through one network center, in a single building just east of the University of Minnesota campus, alongside the Mississippi River. Now this center had been well designed; the network servers were on an upper floor, they were redundant, parallel systems, with separate, duplicate power supplies, and 2 phone company lines, coming in from opposite sides of the building, one coming in from University Avenue, and the other along Washington Avenue.

But as it turned out, both those phone company lines eventually ran alongside each other in conduits on the underside of the Washington Ave bridge over the Mississippi. And the abutment where that bridge meets the riverbank is a quiet, private space, very sheltered from the wind, rain, & snow. An ideal spot for a homeless person to set up a makeshift home. But when winter comes to Minnesota, you need some source of heat, so making a campfire there is advisable. What’s not advisable is drinking until you fall asleep, and having the campfire get out of control, and spread to your cardboard/plywood ‘walls’, and become a bigger fire. Especially if the fire damages all the phone cables running above you under the bridge deck!

All of Minnesota was cut off from the internet for a day or so, until the phone company could run emergency temporary connections. (Back then, this was far less serious than it would be now. Most disturbed were various academic researchers.) This illustrates what engineers mean when they talk about “a single point of failure”.

When those lines were repaired, the network center made sure that they now had 2 diverse phone links, one going west to Minneapolis, and a different one going east to St. Paul. And they verified that each link left the state in a different direction.

4

If the tray permits you to route a cable to the left or the right, you shouldn’t route them all to the left, because a mishap on the left could take out all your customers.

5

I think that the point has been made perfectly above but as I work in telecoms, I can’t let this rare opportunity go past :slight_smile:

Clearly, one cable can’t be diverse from itself. I think he was implying that there would be a 2nd cable to be diverse from. HMS Irruncible makes the good point, that you might just run half via one route and half via a 2nd.

Out of the DC, diversity is important for larger companies. This might encompass not only geographic routing but also different pops to the Internet, diferent supplier or cloud DC’s or indeed different Telecoms vendors.

when you get intercontinental, it can be more tricky because of the more limited number of undersea routes (see here https://www.submarinecablemap.com/ ) .

Lastly the trickiest thing is finding exact routes in hard-to-get-at places. No-one has fibre everywhere, so quite often you rely on a 3rd party or even a 4th and 5th party for routes and diversity confirmations.

6

He’s standing in front of a cabinet with multiple fiber cables in it as he speaks. And he’s talking about laying fiber in the overhead racks. I think he just means that when laying multiple fibers in the overhead racks, to a cabinet, they try to spread them around as much as possible.

And then, if you pay more, you can have routing from multiple ingress points, under floor routing, and routing from multiple carriers.

7

Yep - he’s talking about customers who have multiple (presumably redundant) fibre connections into their rack - so rather than running all those fibres along the same route, you choose a different route for each one - any incident that damages something in one place (for example accidental damage during maintenance) is less likely to take the whole service down