Which of the following protocols can use multiple TCP connections between the same client and the server?

Question

In one of the pairs of protocols given below , both the protocols can use multiple TCP connections between the same client and the server. Which one is that?

1. HTTP, FTP
2. HTTP, TELNET
3. FTP, SMTP
4. HTTP, SMTP

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My attempt:

SMTP: only one TCP connection

Telnet: only one TCP connection

HTTP: Multiple connections can be used for each resource

FTP: FTP uses Telnet protocol for Control info on a TCP connection and another TCP connection for data exchange

HTTP may use different TCP connection for different objects of a webpage if non-persistent connections are used. FTP uses two TCP connections, one for data and another control.

So , option (1) is true .

Can you explain it in a formal way, please?

Answer 1

First it's not clear what "client" (and "server") means. A machine/hardware or software?

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Anyway, any protocol (or at least any of the listed in your question) can use multiple TCP connections between the same client and the server.

Even if "client" means "software":

• HTTP - obviously, any browser can have the same page/server in multiple tabs

• FTP - most FTP clients have ability to run a transfer queue with multiple parallel transfers

• Telnet - tabbed terminal client

• SMTP - Probably not commonly used, but what prevents an e-mail client from dispatching multiple emails at the same time using separate connections?

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Unless it is meant that the multiple connection are used for the same "session".

In what case, your answer (HTTP + FTP) is the correct one, and the question is badly asked.