Peer-to-peer communication is the exchange of data and information between equal or equivalent entities within a network architecture, with each entity acting as a sender and a receiver.
"Peer-to-peer" means sharing information between the same layers on communicating hosts in layered communication. Although each layer interacts with the layers above and below it, the passed data is intended for the matching levels on the receiving host. This is known as horizontal communication.
Furthermore, data flows through the stack, being adjusted by processing at each layer to ensure successful transmission. Horizontal communication requires vertical communication, often known as transferring data up and down the stack.
As you can see from the image above, as the data traverses the protocol stack, its designation shifts along with its name, with the overarching term being a protocol data unit (PDU) irrespective of its stack location. PDUs are named differently based on their stack position:
- Data: An application layer PDU.
- Segment: A transport layer PDU.
- Packet: An internet layer PDU.
- Frame: A link layer PDU.
Peer-to-Peer Communication Overview
Encapsulation and de-encapsulation are networking operations that require transforming data for transmission and reception. As data flows down the stack, encapsulation bundles it with particular headers at each layer, ensuring proper handling by intermediate devices.
At the receiving end, de-encapsulation requires stripping these headers in reverse order, allowing layers to interact correctly. These procedures facilitate horizontal communication inside the protocol stack by allowing effective communication between corresponding levels on different hosts.
The following steps are involved in the encapsulation process:
- The application layer receives user data and adds its header, creating a data unit.
- To build a segment, the transport layer adds its own header that identifies the source application.
- The Internet layer adds its own header, resulting in a packet with routing information for network delivery.
- The Link layer creates a frame by adding a header and a trailer or Frame Check Sequence (FCM). The trailer aids in error checking, and the frame is turned into a physical signal for network transmission.
The following steps are involved in the de-encapsulation process:
- The link layer first analyzes the frame header and trailer for faults and discards erroneous frames. If the frame header is error-free, it reads it, removes the header and trailer, and sends data to the Internet layer.
- The internet layer evaluates the packet header to determine if it should be processed at the internet layer or passed to the transport layer. Before proceeding, it eliminates the packet header.
- To determine the application protocol, the transport layer examines the segment header. It removes the segment header and passes the data to the proper protocol.
- The application layer protocol eliminates the data header before processing and transferring the data to the user application.