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Yesterday I visited the offices of RailTel - a public company in India that provides communication backbone to the Indian Railways, they had a very sophisticated setup of Optical Fiber cables for data transmission. They said that this is a private network for internal use only.

Then when I was in the Exchange Office - the main communication office, a place where they actually use those communication channels. They said that we could connect to the Intranet and as well as the Internet!

My question is, that how is this possible? How can privately laid optical fibers connect globally? On google, I picked up the term internet exhange? But this has got me confused further, why would a private network want to go to this exchange? Please explain me in very simple terms, how does this all work? If this is just a connection of wires, then why charge so much for little bandwidth?

Thanks.

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    This question appears to be off-topic because it is about "explain some topic I don't know anything about to me". Server Fault is a site for pro sysadmins to ask questions about actual technical problems they have, not for anyone coming to ask about something technology related they don't know about. Please read our help center.
    – Sven
    Jun 30, 2013 at 15:08
  • I am sorry, there is no other place I could post something like this.
    – user24454
    Jun 30, 2013 at 15:44
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    Then you are out of luck because this isn't a place to post this either.
    – Sven
    Jun 30, 2013 at 16:05

2 Answers 2

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It connects the same way any network connects to the Internet.

There's nothing special about fiber, it connects to the Internet the same way as copper. It's all Ethernet (for the most part), so the medium doesn't matter.

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  • I want to know how any network connects to the internet, suppose I lay some optical fibers around my society to provide them with optical fiber connections, i.e act as an ISP, then how can I connect this intranet to the internet?
    – user24454
    Jun 30, 2013 at 15:39
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    If you have to ask that question, then you're nowhere near ready to act as an ISP. You should take some network engineering courses and get a job in the field.
    – MDMarra
    Jun 30, 2013 at 15:54
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    Do you think this course will do, coursera.org/course/comnetworks?
    – user24454
    Jun 30, 2013 at 17:22
  • @user24454 That's a great place to start. The quality of classroom education in technical fields, particularly in India, is often quite poor, because people who really know their stuff can make a lot more money by doing networking than they can by teaching it. Studying online via institutions like Coursera, EdX, and Udacity is a very good idea in my opinion.
    – Skyhawk
    Jun 30, 2013 at 19:07
  • Ok, thanks, I agree and can verify that quality of education in India is very very poor, most of the institutions here are fraud.
    – user24454
    Jul 1, 2013 at 5:21
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Here's what happens: at that office, or at least somewhere on the private network, there's a firewall that has an Internet connection. With a basic configuration, such a firewall would route traffic from the private network to the Internet, and it would block unauthorized connections from the Internet to the private network. It also would provide IPv4 Network Address Translation (NAT).

Incidentally, private fiber-optic networks belonging to public utilities, like the one that you have described, are almost always severely underutilized. It is common in the United States for a portion of the unused capacity to be leased to private-sector Internet Service Providers (ISPs). Selling excess network capacity to ISPs, both to enhance capacity between major cities and to extend high-speed internet access into rural areas, is a potential revenue source for organizations like the Indian Railways.

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  • Oh ok, I think I got the first part. Now if they leave the line to private ISP, what use will it be to the private ISP? Its like a very fast waterfall (OFC) falling into a thin tube (private ISP).
    – user24454
    Jun 30, 2013 at 15:42
  • Not necessarily. The private ISP connection could be fiber as well, although you are correct that internal networks are often faster than ISP connections. As @MDMarra said, it is fundamentally no different from how other business networks are connected to the Internet.
    – Skyhawk
    Jun 30, 2013 at 16:13
  • I wish I could get a clearer picture about all this.
    – user24454
    Jun 30, 2013 at 17:23

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