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Who Provides Internet Service for My Internet Service Provider?

2012-09-04_105842

You pay your Internet Service Provider (ISP) for internet access, and they turn on the sweet, sweet, fire hose of data for you. But who provides the flow for your ISP? Read on to learn the ins and outs of global data delivery.

Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-drive grouping of Q&A web sites.

The Question

SuperUser reader KronoS poses the question many geeks have asked at one point:

I’ve been wondering recently about how the infrastructure of the Internet really works.

I know that I have an Internet Service Provider (ISP) that supplies my connection to the Internet.

But what I don’t know is: Who provides the Internet to the ISP? And who supplies it to them? Is there a never-ending loop that eventually connects us all together?

Who indeed? It’s networks all the way down, but not all of them are immediately visible to the end user.

The Answer

Courtesy of SuperUser contributor Tom Wijsman, we’re treated to a detailed peek at how we can determine who specifically is providing internet access to our ISP and what it means to be part of the provider-to-the-providers network.

How do I figure out the Internet’s infastructure?

Let’s suppose we don’t know about the history of the Internet, nor do we have access to any online resources that explains us this. Then, the only way to learn how the Internet infrastructure is built is to go back to the roots. Using existing protocols to discover how our Internet is built.

Specifically, the Internet Control Message Protocol or ICMP defines the Echo request and the Echo reply. By increasing the Time To Live of an IP packets by 1 each iteration, you can find each next hop on the path to your target. This allows you to get a list of hops between you and your target, the classical traceroute.

On Windows, you can use tracert; on Linux and Mac OS X, you can use traceroute.

So, let’s do a traceroute from Belgium to the United States; Stack Exchange looks like a good target.

Tracing route to stackexchange.com [64.34.119.12] over a maximum of 30 hops:

  ... redacted ...

  5    10 ms    12 ms    12 ms  te-3-3.car2.Brussels1.Level3.net [212.3.237.53]
  6    11 ms    11 ms    15 ms  ae-0-11.bar2.Brussels1.Level3.net [4.69.148.178]
  7    20 ms    13 ms    15 ms  ae-7-7.ebr1.London1.Level3.net [4.69.148.182]
  8    16 ms    16 ms    18 ms  vlan101.ebr2.London1.Level3.net [4.69.143.86]
  9    83 ms    84 ms    87 ms  ae-44-44.ebr1.NewYork1.Level3.net [4.69.137.78]
 10    84 ms    93 ms    97 ms  ae-71-71.csw2.NewYork1.Level3.net [4.69.134.70]
 11    87 ms    96 ms    83 ms  ae-2-70.edge1.NewYork1.Level3.net [4.69.155.78]
 12    84 ms    93 ms    84 ms  gig2-0.nyc-gsr-b.peer1.net [216.187.123.5]
 13    87 ms    84 ms    85 ms  gwny01.stackoverflow.com [64.34.41.58]
 14    87 ms    82 ms    87 ms  stackoverflow.com [64.34.119.12]

Interesting, we now know that Belgium, London and New York are all connected to Level3. Level3 can be seen as an ISP to ISPs, they simply interconnect multiple ISPs. Here is a picture of how it’s connected:

2012-09-04_110537

Let’s go the opposite direction, China! The first thing I could find is the search engine Baidu.

Tracing route to baidu.com [123.125.114.144] over a maximum of 30 hops:

  ... redacted ...

  5    12 ms    10 ms    12 ms  ae0.anr11.ip4.tinet.net [77.67.65.177]
  6   167 ms   167 ms   167 ms  xe-5-1-0.sjc10.ip4.tinet.net [89.149.185.161]
  7   390 ms   388 ms   388 ms  as4837.ip4.tinet.net [77.67.79.150]
  8   397 ms   393 ms   397 ms  219.158.30.41
  9   892 ms     *      392 ms  219.158.97.13
 10   407 ms   403 ms   403 ms  219.158.11.197
 11   452 ms   451 ms   452 ms  219.158.15.5
 12     *      434 ms   434 ms  123.126.0.66
 13   449 ms   450 ms   450 ms  61.148.3.34
 14   432 ms   433 ms   431 ms  202.106.43.66
 15   435 ms   435 ms   436 ms  123.125.114.144

Well, not much information about the Chinese ISPs there but we at least found Tinet. Here is a nice picture of their site that shows how they connect with the various ISPs:

2012-09-04_110636

They simply have a cloud of hops spread about the relevant part of the world they serve, and at the end points they connect to the ISPs. The reason they have a cloud of hops is for reliability, for when some hops fall out.

If you repeat this a few times, you can get an idea of how everything is connected.

2012-09-04_111016

So, What Network Tiers Are There?

The huge networks we found through trace-routing are known as Tier 1 networks.

Although there is no authority that defines tiers of networks participating in the Internet, the most common definition of a tier 1 network is one that can reach every other network on the Internet without purchasing IP transit or paying settlements.

By this definition, a tier 1 network is a transit-free network that peers with every other tier-1 network. But not all transit-free networks are tier 1 networks. It is possible to become transit-free by paying for peering or agreeing to settlements.

Common definitions of tier 2 and tier 3 networks:

  • Tier 2: A network that peers with some networks, but still purchases IP transit or pays settlements to reach at least some portion of the Internet.

  • Tier 3: A network that solely purchases transit from other networks to reach the Internet.

If you click through to Tier 1 networks from the Internet Backbone page you get to a list of the current Tier 1 networks:

  • AT&T from USA
  • Centurylink (formerly Qwest and Savvis) from USA
  • Deutsche Telekom AG from Germany
  • Inteliquent (formerly Tinet) from USA
  • Verizon Business (formerly UUNET) from USA
  • Sprint from USA
  • TeliaSonera International Carrier from Sweden
  • NTT Communications from Japan
  • Level 3 Communications from USA
  • Tata Communications from India

It is not known if AOL Transit Data Network (ATDN) is still a Tier 1 network.

Wait, what… What is Peering?

These networks connect to each other through a process known as ‘peering’. Most traffic needs to go over at least 2 different top tier networks in order to reach its destination, and the networks are bridged with peering arrangements. The way this usually works is that each party to the agreement will commit to routing x amount of traffic for the other party on their network, and vice-verse. There is usually no money exchanged in these arrangements, unless one side is sending or receiving a lot more data than the other sides.

Large companies can also go out and arrange their own peering relationships. For example Netflix has arranged its own peering and network infrastructure directly with multiple tier-1 networks so that its traffic is both cheaper and closer to end users on each of the popular US broadband ISP’s.

See this Wikipedia page on Peering.

There’s a lot more to read at those pages; this answer gives a general idea, discovering all the details are left as an exercise to the reader.


Have something to add to the explanation? Sound off in the the comments. Want to read more answers from other tech-savvy Stack Exchange users? Check out the full discussion thread here.

Jason Fitzpatrick is warranty-voiding DIYer and all around geek. When he's not documenting mods and hacks he's doing his best to make sure a generation of college students graduate knowing they should put their pants on one leg at a time and go on to greatness, just like Bruce Dickinson. You can follow him on if you'd like.

  • Published 09/4/12

Comments (9)

  1. r

    so it doesn’t come from The Network Fairy? –magic of the internets

  2. TheFu

    If you wanted to snoop on almost all internet traffic, that’s the list of suppliers that a government would need to contact. That number seems much smaller than one would hope.

  3. vipin kumar

    I didn’t get it, can u explain who is providing internet connectivity to ISP..

  4. cwcarlson

    To vipin kumar:

    I think the answer to your question depends on the ISP and where in the world you are located. For example, COX is a large ISP that is in a number of states in the U.S. In California, using traceroute, I learned that the Internet provider for COX is Charter. COX might connect to someone else in Nebraska.

    When I worked for SGI, they were connected directly to Sprint with a T1 line (which was a fairly large pipe to the Internet in that day). You can see by the explanation above that Sprint is a Tier 1 company.

  5. Loser

    3 33 ms 31 ms 32 ms 219.148.65.97
    4 * * * 请求超时。
    5 35 ms 34 ms 37 ms 202.97.80.125
    6 35 ms 36 ms 36 ms 202.97.53.106
    7 111 ms 112 ms 112 ms 202.97.53.250
    8 458 ms 459 ms 460 ms 202.97.51.70
    9 381 ms 411 ms 386 ms 202.97.50.62
    10 375 ms 376 ms 369 ms xe-0-6-0-2.r06.snjsca04.us.bb.
    0.9.29]
    11 468 ms * * ae2.bbr01.eq01.sjc02.networkla
    9.206]
    12 527 ms 528 ms 533 ms ae0.bbr02.cs01.den01.networkla
    .149]
    13 545 ms 545 ms 546 ms ae0.bbr02.eq01.chi01.networkla
    .130]
    14 550 ms 548 ms 535 ms ae0.bbr02.eq01.wdc02.networkla
    .154]
    15 548 ms 552 ms 557 ms ae1.dar01.sr01.wdc01.networkla
    .193]
    16 447 ms 455 ms 444 ms po1.fcr01.sr01.wdc01.networkla
    .134]
    17 557 ms 555 ms 555 ms howtogeek.com [208.43.115.82]

  6. steve.lim

    Halfway through tracing “request timed out”…

  7. Ushindi

    It’s actually pretty simple – I send AT&T money every month and they send me the internet…see?

  8. Naruto

    IANA and ICANN are both merged

    ICANN – maintains the 13 root servers

    IANA-provides internet through optic fibres(which is a US army or navy based, i don’t remember correctly)

    ex: In India, TIER 2 ISP providers are Reliance and BSNL, these TIER 2 people will pay to TIER 1 ISP’s which is of US, now TIER 2 people will provide to TIER 3 people like SIFY, TATA, etc,…

    US is the backbone, IANA+ICANN-INTERNET

    correct me if i’m wrong, i shared what i know, please don’t take it in a wrong way
    thanks, and i’m a regular reader of howtogeek

  9. Zyfer

    probably the best idea of how its set up…

    large spider webs are solder/welded/super glued to other large spider webs.. and that forms the base level.

    then there are medium sized spider webs and they are super glued on to the larger ones and have to pay a fee to the large spider web masters!

    and then there are itsy bitsy spider webs and they pay rent to the medium webbers… now the ppl they use the internet would probably be the “flies” here and they get eaten by the medium and tiny spiders but a large amount goes to the Large spider master.

    After all its called the interwebs for a reason.

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