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Why submarine cable, why not satellite?

Why submarine/subsea cables rather than satellite. Story between my friend who is from finance background and myself.

Today, one of my friends who is totally foreigner to our industry, visited me at home. It was a family dinner actually and as I said, He is not a network engineer but just a curios person.

I was talking about telecom companies with him, I said that 99% of our Internet data (Not only data, voice and video traffic too) is carried through undersea cables (Often we call as submarine or subsea cables) and He asked a clever set of questions. I was not expecting to be honest. Not because He is not smart ? But He is a finance guy !! He is not supposed to ask those, you will see.

First He said that, it is really old fashion that we still have a physical cables, why still we see the cables going through the air.

My response was, actually we are talking about subsea cables, we don't see them. Even at the shore, cables are buried, so we don't see them.

Even the aerial fiber is generally not seen at the public places but maybe in the datacenters which you don't have an access ?

What you see probably is an electric cables.

Then he said, why subsea cables then, wouldn't it be too costly ? Why not just a satellite? Wouldn't it be too install and use faster than subsea cable ?

I suspected that He is studying network engineering with this question ?

He has some points here actually.

Yes subsea cables are really costly, depends on distance , transmission equipments , fiber types , physical subsea routes , number of repeaters (It might be repeaterless submarine cable though) and so on.

Building a communication satellite , launching it, operating and having a frequency license etc, is not cheap either. If you are leasing a capacity from the Satellite Provider that is a different case and for sure would be much cheaper.

But as you might know, there are two main problems with communication satellite.

First one is latency (delay) and second one is available bandwidth.

Of course, while I was explaining these terms to him, I didn't use technical jargon.

Instead, for the latency I just said, first problem is ; when you try to open Youtube, how long you will wait website to be loaded.

For the bandwidth, I said, if you and your wife try to watch a HD video at the same time, with satellite it will be a problem but with subsea fiber , you will watch without buffering.

Those who have an experience with satellite networking know that I am talking about GEO (36000 km above the earth) satellites, that's why we have this latency. Other satellites which are orbiting at the LEO and MEO spaces have less latency due to altitude. But let's not make this post deep dive satellite post.

Wouldn't it be faster to install satellite than a submarine cable ?

If we are not talking about building a satellite, launching it, waiting at the orbit for tests and taking it into an operation, then yes. As with the other wireless deployments, having satellite communication link is much faster than deploying submarine cables (In some cases take years).

Although I didn't talk about the reliability and the security aspect with my friend who is from finance background, submarine cables, in fact, almost all wire (copper, fiber, coaxial) connections are more reliable than wireless (Satellite is a wireless technology which uses RF spectrum).In summary, fiber provides unlimited bandwidth (Shannon's capacity Limit) and very low latency compare to satellite communication. Day by day, more bandwidth is demanding from the networks and even with very low latency satellite systems, submarine cable will be a primary method to carry the data between countries and the continents for a long time.

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Orhan Ergun

Orhan Ergun, CCIE/CCDE Trainer, Author of Many Networking Books, Network Design Advisor, and Cisco Champion 2019/2020/2021

He created OrhanErgun.Net 10 years ago and has been serving the IT industry with his renowned and awarded training.

Wrote many books, mostly on Network Design, joined many IETF RFCs, gave Public talks at many Forums, and mentored thousands of his students.  

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