People often define the internet as a network of networks but this is wrong. If I connected two LANs together that wouldn't nesecarilly be on or part of the internet. In class we learned about ATM, and how it's not part of the internet. If the internet is just the joining of networks, how can one possibly say a network protocol isn't part of the internet?

For example, to be part of the internet, must TCP/IP suite be used? Must Ethernet be used, or can Token ring be used? For every layer of the OSI model must a certain technology be used to be part of the internet?


3 Answers 3


An internet (lower-case "i") is a network of networks. The Internet (upper-case "I") is what you mean. The Internet is the largest internet (network of networks). The networks comprising the Internet connect to each other by agreement of the network owners using BGP as the routing protocol. Since BGP is based on TCP, TCP/IP is a requirement. After all, IP stands for Internet Protocol.

Layer 3 of the OSI model (IP) is the lowest layer that the Internet cares about. That means that any layer-1 or layer-2 protocols (ethernet, token-ring, FDDI, arcnet, ATM, frame relay, etc.) may be used (or required) on or between any of the individual networks, so ethernet is not an Internet requirement.

Any network could use a different layer-3 protocol, as long as the layer-3 protocol connecting the networks is IP. This used to be common when IPX networks were first connecting to the Internet through an IP gateway before they were converted from IPX to IP.


IP is the common ground that ties the Internet together. IP can run on top of many different underlying network technologies and many different higher level protocols can run on top of IP. Parts of the Internet certainly do run on top of ATM networks. Ethernet is becoming the dominent technology but it's by no means the only technology.

Being "on the Internet" means being able to reach all or at least the vast majority of other hosts "on the Internet". That means interconnecting with other networks.

There are two main types of relationship, peering and transit (and also various intermediate possibilities).

In a transit relationship, a customer pays a provider to deliver traffic to and from the "Internet in general". The provider will almost certainly charge the customer for this service. It will almost certainly run over a private link.

In a peering relationship, two networks interconnect so that each network and it's customers can talk to the other nework and it's customers. The agreement may be "settlement free" or it may be paid depending on the relative negotiating positions of the two proviers.

At the top of the pile are transit free providers (sometimes called "teir 1", but the traditional definition of "teir 1" required settlement free peering while it's possible to become transit free using paid peering). These all peer with each other.

P.S. It is exactly because IP is the common ground that the process of upgrading from IPv4 to IPv6 is so painful. Essentially there are now two seperate Internets, the IPv4 internet and the IPv6 internet. They run on top of the same infrastructure and there are some limited transition mechanisms but they are essentially seperate networks.


Nodes reachable via a global IP address are on the Internet.

Internet Protocol (IP) is short for the DoD Standard Internet Protocol, RFC 791. The IANA assigns global IP addresses.

Note: being on the Web and being on the Internet are two different concepts.

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