Peer-to-Peer Communication

Peer-to-Peer Communication

During the process of peer-to-peer communication, the protocols at each layer exchange packets of information called protocol data units (PDUs) between peer layers.

The PDU should go through OSI layers start from Application to Physical layer. When PDU  goes to Transport layer , transport layer adds its own header depending of protocol is in use ,and  PDU is called SEGMENT .So segment is PDU that transport layer adds its header to it . Then transport layer send the packet to network layer , the netwotk adds its own header , now the PDU is called  packet . Then network layer sends packet to data link layer , data link layer adds its own header and PDU at the data link layer is called FRAME . 

So the hierarchical level is like this:

DATA= Application+Presentation+Session layers

Segment= Transport layer

Packet= Network Layer

Frame= Data link layer

Bytes= Physical layer