Ccna routing and Switching Complete Study Guide

The Host-to-Host or Transport Layer Protocols

The main purpose of the Host-to-Host layer is to shield the upper-layer applications from 

the complexities of the network. This layer says to the upper layer, “Just give me your data 

stream, with any instructions, and I’ll begin the process of getting your information ready 

to send.”

Coming up, I’ll introduce you to the two protocols at this layer:

 

■

Transmission Control Protocol (TCP)

 

■

User Datagram Protocol (UDP)

In addition, we’ll look at some of the key host-to-host protocol concepts, as well as the 

port numbers.

Remember, this is still considered layer 4, and Cisco really likes the way 

layer 4 can use acknowledgments, sequencing, and flow control.