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What are the other computer communication protocols except for TCP/IP?

I know about only this and in interview they asked me about Can two PC's communicate without TCP/IP protocol suite and I did not have any answer.

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closed as too broad by psusi, MariusMatutiae, DavidPostill, Kevin Panko, Raystafarian Jun 15 '15 at 17:47

There are either too many possible answers, or good answers would be too long for this format. Please add details to narrow the answer set or to isolate an issue that can be answered in a few paragraphs.If this question can be reworded to fit the rules in the help center, please edit the question. ? – nos May 31 '11 at 19:13
up vote 6 down vote accepted

There is as many protocols as you want. And they differ of level.

Try to lookup OSI model on wikipedia. The navigation frame at the left present you many protocols with their layers.

You'll also see that IP is a protocol and TCP is another protocol that uses IP.

And yes computers can communicate without TCP and even without IP.

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TCP/IP has taken over most communication duties, but there were a few other methods before TCP/IP took over everything.

Netware used to rule Windows file sharing before NT came around. It had it's own protocol suite with NCP IPX and SPX. NT took over this space and Netware is hard to come by now.

There used to be NetBIOS/NetBEUI. This was file sharing on Windows 3.1 and NT4 somewhat. I think this isn't supported anymore. It's been supplanted by NetBIOS over TCP/IP.

There's also AppleTalk, which at one point could have been used, but even Apple is discontinuing Appletalk in favor of TCP/IP. Rendezvous/Bonjour fills in some of the holes in TCP/IP that AppleTalk used to handle.

Before TCP/IP UNIX machines used to use UUCP. This is a store and forward protocol, works over modems too.

Mainframe machines used to use BITNET, but I think it never was used on Windows machines, though would be a good trivia answer.

Communicate how? For simple file transfer you could use a serial protocol like kermit.

These are all theoretical. What could you actually use? NetBEUI, AppleTalk, NetWare are probably all non-starters. Kermit and UUCP are probably both possible, with uucp harder to set up

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IPX/SPX, anyone? – Sathya May 21 '11 at 15:37
This is awesome bro. Thanks. – narayanpatra May 23 '11 at 9:14

TCP is a communication protocol working on the so-called "Transport Layer", layer 4 of the ISO/OSI Stack. This basically means that it is a protocol defined to carry any arbitrary data over another protocol.

In the ISO/OSI stack, basically, it works like this: Data from the application layer (7) is encapsuled in protocols from lower layers (6 and 5, but mostly layer 4) and then sent over a protocol on a lower level (mostly layer 3). Layer 2 and 1 will take care of the physical transmission.

As an example, data could be sent over HTTP (let's say a website). This is layer 7. The HTTP data will be encapsuled in TCP (layer 4). The TCP data again is encapsuled within IP, which is a protocol of the "Network Layer", layer 3 (and therefore can carry any other data from above layers).

But: There are several other protocols, you could even define your own. A well-known counterpart to TCP is UDP, which is targeted towards non-reliable communication and realtime applications like video conferencing or gaming.

IP is very dominant, but still there could be an arbitrary number of other protocols. For example ICMP is famous for being used in the ping command.

So, to summarize: Two machines do not need to communicate over TCP/IP. In a practical situation they could use, for example, UDP. IP could be replaced too, but that's probably too hard to implement as all current operating systems' networking functions are all based on TCP/IP communication.

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UDP is part of the TCP/IP protocol suite. You would be communicating with TCP/IP which is not allowed from the question. I'm not sure why you bring up layer 4 with TCP, it's confusing. TCP/IP doesn't even follow the OSI layers. – Rich Homolka May 20 '11 at 22:35
@Rich I know that UDP is part of the TCP/IP model, but I nowhere mentioned that I was talking about it. I was talking about the ISO/OSI stack and never even mentioned the TCP/IP suite. Maybe it is just a bit ambiguous to talk about TCP/IP and "sending TCP over IP". – slhck May 21 '11 at 0:53

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