Full form of PPP, Work, Format, Different Phases, Point-to-Point Protocol

The PPP stands for Point-to-Point Protocol, which helps in the communication between the two devices. It can be used in different types of physical networks, such as serial cables, phone lines, cell phones, fiber optic links, etc. For example, if you are accessing the internet from home, the PPP protocol will be used.

The PPP protocol can be used on a synchronous link like ISDN and, further, on an asynchronous link like dial-up. Internet service providers use the PPP protocol to provide dial-up access to the internet. The full form of PPP signifies point-to-point communication, which means the communications move from one computer or device to another within a predefined network boundary.

In this article, we provide details about PPP, its framework, services, and applications to help users understand its significance in communication technology. 

How Does PPP Work?

PPP protocols are designed to bridge the gap between physical connections and more abstract network protocols like the Transmission Control Protocol and Internet Protocol (TCP/IP). Again, PPP encapsulates the individual units of data called "datagrams" produced by other network protocols. Further, these datagrams first travel over a point-to-point link and are then converted back to standard TCP/IP data packs for travel across traditional networks. A common example is a dial-up Internet connection.

Services Provided by PPP

• This protocol decides how two devices can authenticate with each other. For example, it decides how the password will be exchanged between two devices. 
• PPP protocol defines the format of a frame through which transmission occurs. 

• It defines the data exchange process and also the rate of the exchange.
• The PPP protocol defines how the two devices can negotiate the link establishment for the exchange of data.  
• It allows multiple network communication protocols to use the same physical communication line.
• This protocol also provides connection over multiple links. 

Format of PPP Protocol

The frame format of the PPP protocol consists of the following fields:

• Flag: The PPP frame starts and ends with a field called Flag. It indicates the start and end of the frame. The flag field is a 1-byte field that appears at the beginning and the ending of the frame and has a bit pattern such as 01111110.
• Address: It is a 1-byte field after the opening flag field that contains the constant value of 11111111. These 8 ones represent a broadcast message.
• Control: It is a field that is set through the constant value of 11000000. It is not a required field as PPP does not support flow control and has a very limited error control mechanism. 
• Protocol: This field defines what is being carried in the data field. It can either be user information or other information. By default, this field is 2 bytes long.
• Payload: This field carries either user data or other information and is negotiated between the endpoints of communication. The maximum length of the payload field is 1500 bytes.
• FCS: It is a 2-byte or 4-byte standard CRC (Cyclic redundancy check) for error detection.

Components of PPP

There are three components to the PPP protocol, and these are as follows:

• Link Control Protocol

This protocol is responsible for first establishing, then configuring, and finally maintaining the links. It also provides the negotiation mechanism to set the options between the two endpoints and establish the link.

• Authentication Protocol

This protocol plays a very important role in the verification of user identity in PPP protocol over the dial-up links. In other words, this protocol is used to authenticate the endpoints for the use of services. There are two protocols for authentication:

1. Password Authentication Protocol
2. Challenge handshake authentication Protocol

• Network Control Protocol

After the establishment of the link and authentication, this protocol is used for negotiating the parameters and facilitating the encapsulation of data.

Application of PPP

• It is widely used in broadband communications through the internet which requires plenty of data transmission with high speed.
• It is used for multiprotocol data transfer between two connected computers. In other words, it is used in point-to-point devices, such as routers. Routers are point-to-point connected devices where the PPP protocol is widely used as it supports Wide Area Network (WAN), not a simple Local Area Network (LAN) protocol.
• A PPP connection is applicable when two systems physically connect through a telephone line. For example, an established PPP connection between a branch office and a central office helps the mutual transfer of data through the network.
• PPP can be used on a variety of physical media, including twisted-pair copper wire, fiber optic lines, or satellite links.
• PPP is used to establish IP or other networks to transfer data between two directly connected nodes over a physical connection or a direct link.
• PPP can provide services over multiple mediums, such as dial-up modems and virtual private networks (VPN)

Different Phases of PPP

The PPP protocol has to go through various phases, as follows:

• Dead: It is the inactive phase when no communication takes place and the link is quiet.
• Establish: It is the phase when any one of the points starts communication. Firstly, the connection goes into the established phase and then, the options are negotiated between the two points. After a successful negotiation, the system goes into the authenticate phase. However, if there is a requirement for authentication the system goes into the network phase.
• Authenticate: During the establishment phase, the two nodes may proceed with the authentication by sending several authentication signals. Further, if the authentication becomes successful then the connection goes into the networking phase otherwise goes into the termination phase.
• Network: The PPP protocol specifies that the two nodes establish an agreement before the exchange of the data. To clarify, PPP supports multiple protocols at the network layer. Therefore, the receiving node needs to know which protocol will receive the data.
• Open: In this phase the data transfer takes place. As soon as the connection reaches this phase, the exchange of data packets is initiated. Further, the Connection remains in this phase until one of the endpoints in the communication terminates the connection.
• Terminate: It is the phase when the connection is terminated. In other words, the exchange of several data packets between two ends and the link is closed.

Conclusion

PPP is a traditional communications protocol originally designed to provide connectivity over serial hardware channels. This protocol is still widely used for embedded systems due to its simplicity and affordability as compared to the newer hardware systems. It has advanced features designed to ensure quality, security, and performance.

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