How the data transfer between routers

Now a days most of the traffic is TCP/IP but there are some crucial services that are transfered in UDP like DNS, TFTP, etc.

Regards.

Thameem,

There are many different network protocols associated with different network applications and implementations. Jooker is right, most traffic is TCP and UDP, but there are a whole slew of other protocols that have other purposes:

ARP - Address Resolution Protocol (Maps MAC addresses to IP addresses)
ICMP - Internet Control Message Protocol (Most of the time determines accessibility of other network resources, like ping)
FTP - File Transfer Protocol (Transfers Files from one computer to another across a network)
DNS - Domain Name Service (Translates www.[].com to an IP address)
SMB - Server Message Block (Allows you to see other devices on your network in most cases, esp. Windows devices)

There are many more than that but that is just an example of the various types of data encapsulation for networking.

It is also important to understand that network data is not sent in any specific format. These protocols add information to the outside edges of the actual data so that networks and systems know what to do with them when they arrive. It's like sending something through the mail. The letter itself is the data that you care about, but you've got to put it in an envelope first with a specific set of information about where the letter is going and where it's from before you can send it. The envelope is equivalent to these various network protocols. I hope this makes sense.