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Table of contents
1.
Introduction
2.
What is the point to point protocol?
3.
Components of Point to Point Protocol  
4.
Point to Point Protocol Frame Format 
5.
Transition phases of Point to Point protocol
6.
Services Provided by Point to Point Protocol
7.
Services  not provided by Point to Point Protocol
8.
Working of Point to Point Protocol
9.
Advantages of Point to Point Protocol
10.
What is PPP Stack?
11.
Frequently Asked Questions 
11.1.
What is point to point protocol multiplexing?
11.2.
Which device is used in point-to-point protocol?
11.3.
What is Point to Point Protocol Encapsulation?
12.
Conclusion
Last Updated: Mar 27, 2024
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Point to Point Protocol (PPP)

Author Vidhi Singh
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Introduction

Point to Point Protocol, in short, is commonly referred to as PPP. It is used for access in point-to-point. The PPP stands for Point-to-Point protocol.

Point to Point Protocol

It is a data link layer protocol that resides in the Data Link Layer of the OSI model. It is used to encapsulate the Network Layer protocols and all the information present in the payload in order to be transmitted across the serial links. 

What is the point to point protocol?

Point to Point Protocol is one of the communication protocols of the Data Link Layer which transmits multiprotocol data between two directly connected computers. It is a byte-oriented protocol that is widely employed in broadband communications having quite heavy loads and high speeds. The data is commnicated in frames. It is also known as RFC 1661.

As the data link layer protocol is used to identify from where the transmission starts and ends, so Internet Service Provider(ISP) uses the Point to Point Protocol that offers dial-up access to the internet. 

It is the most widely used protocol for Point to Point access. Suppose a user wants to access the internet through his home, the Point Point Protocol will be used. 

Recommended Topic, Basic Networking Commands and Computer Network.

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Components of Point to Point Protocol  

The basic components of Point to Point Protocol are as follows: 

  • Link Control Protocols (LCP) − It establishes, configures, tests maintains, and terminates links for transmission. It also imparts negotiation for the set up of options and use of features by the two endpoints of the links. Few LCP options provided by Point to Point Protocol are −
    • Authentication:  Peer routers exchange authentication messages. Two authentication choices are Challenge Handshake Authentication Protocol (CHAP) and Password Authentication Protocol (PAP).
    • Compression:  It increases the effective throughput on Point to Point Protocol connections by decreasing the data in the frame that should go across the link. The protocol then decompresses the frame at the destination. 
    • Error Detection: This identifies fault conditions.
    • Multilink: It offers load balancing several interfaces used by Point to Point Protocol through Multilink Point to Point Protocol.

 

  • Encapsulation Component − This component encapsulates the datagram so that they can be transmitted over the specified physical layer.

 

  • Network Control Protocols (NCPs) − These protocols negotiate the parameters and facilities for the network layer. For every higher-layer protocol supported by Point to Point Protocol, one NCP is there. Some of the NCPs of Point to Point Protocol is −
    • IPCP(Internet Protocol Control Protocol) 
    • OSINLCP(OSI Network Layer Control Protocol) 
    • IPXCP(Internetwork Packet Exchange Control Protocol)
    • DNCP(DECnet Phase IV Control Protocol)
    • NBFCP(NetBIOS Frames Control Protocol)
    • IPV6CP(IPv6 Control Protocol) 

source 

There is one more component, but that is not considered is the more prominent one: 
 

Authentication Protocols (AP) − These protocols are responsible for authenticating endpoints for service usage. The authentication protocols of Point to Point Protocol are −

  • PAP(Password Authentication Protocol) (PAP)
  • CHAP(Challenge Handshake Authentication Protocol)  


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Point to Point Protocol Frame Format 

The fields of the Pint to Point Protocol Frame are as follows:
 

  1. Flag Field
    The Flag Field marks the starting and the ending of the frame. The flag field has a size of 1-byte. It is somehow similar to the HDLC flag.
     
  2. Address Field
    The Address field is basically a broadcast address. It has a size of 1-byte and stores a constant value that is, 11111111. These eight 1s represent a broadcast message. 
     
  3. Control Field
    The control field is a compulsory field where protocol supports flow and error control mechanisms. This field basically uses the format of U-frame i.e., Unnumbered frame in HDLC. In Point to Point Protocol, this field is set to 1 byte i.e., 00000011 binary value. 
     
  4. Protocol Field
    It defines what is to be carried out in the data field. This field basically identifies the network protocol of the datagram. It usually identifies the sort of packet in the data field i.e., what exactly is being carried in the data field. This field has a size of 1 or 2 bytes.
     
  5. Data Field
    It usually stores the upper layer datagram. The Network layer datagram is particularly encapsulated in this field for regular PPP data frames. The length of this field varies.
     
  6. FCS Field
    This field usually stores the checksum simply for the identification of errors. It can be either 2 or 4 bytes in size. It is also calculated with address, control, protocol, and even information fields. Characters are added to the frame for control and handling of errors. 
     

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Transition phases of Point to Point protocol

The Point-to-Point Protocol (PPP) undergoes several distinct phases during establishment.

It starts with the Initialization Phase, transitioning from the "dead" state to the "establishment" phase upon detecting a carrier signal. 

The Authentication Phase follows, where peers authenticate using protocols like PAP or CHAP. Next is the Network Layer Protocol Phase, negotiating the protocols to be used (e.g., IP, IPv6). 

The Link Configuration Phase allows for additional options like compression and error detection. In the Link Maintenance Phase, the link is actively used for data transfer. When no longer needed, the link moves into the Termination Phase, leading to Link Disconnection and a return to the "dead" state.

Services Provided by Point to Point Protocol

The prominent services offered by Point to Point Protocol are −

  • Defining the data frame format of the data to be transmitted.
  • Defining the procedure of establishing a link between two points and exchange of data. 
  • Stating authentication rules of the communicating devices.
  • Stating the method of encapsulating the network layer data in the frame.
  • Providing connections over multiple links.
  • Providing an address for network communication.
  • Supporting several network layer protocols by providing a range of services.

Services  not provided by Point to Point Protocol

The services not provided by Point to Point Protocol are:-

  • Routing: PPP lacks routing capabilities, relying on higher-layer protocols for determining data paths
  • Addressing: It doesn't handle network layer addressing, requiring protocols like IP for node identification
  • Error Correction: While it has basic error-checking, advanced error correction is not a native feature
  • Compression: PPP doesn't offer data compression; additional protocols are needed for this function
  • Multiplexing: Designed for point-to-point links, it doesn't support multiple data streams over one connection
  • Encryption: It doesn't provide in-transit data encryption; higher-layer protocols like IPsec handle this
  • Network Layer Services: PPP operates at the data link layer, lacking functions like addressing and routing, which are handled by higher-layer protocols like IP

Working of Point to Point Protocol

Point to Point Protocol together uses the three(3) components, namely LCP, NCP, and Encapsulation Component(described earlier in this article) to allow communication.

There are four main steps to establish, maintain and terminate a Point to Point Protocol session:

  • The initial step of setting up a Point to Point Protocol session between devices includes both testing purposes and sending LCP link-establishment frame for configuration. These frames also characterize which alternatives.
  • The next step uses LCP frames to test the link‘s nature. Assembled data can be used to evaluate if links are appropriate for dealing with different protocols on the upper layer.
  • In this step, NCP frames are sent over links to determine which Network Layer protocols need configuration. 
  • In the last step, while ending the Point to Point Protocol session, LCP link-termination frames are used to cut the connection. The third category of LCP frame (Link-Maintenance) is often employed for using and troubleshooting the Point to Point Protocol links. 

Advantages of Point to Point Protocol

A few benefits of Point to Point Protocol are:

  • It offers an extensible suite of protocols.
  • It bolsters authentication by CHAP and PAP.
  • It has a quality management feature for links that evaluates the quality of links. It takes down the links in case of too many errors.
  • It is kind of a sturdy process for managing link variables, including the maximum possible frame size. 
     

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What is PPP Stack?

A PPP (Point-to-Point Protocol) stack refers to the layered architecture of protocols used to establish and manage a point-to-point connection between two network nodes. It comprises several distinct layers, each responsible for specific functions in the communication process:

  • Physical Layer: This is the lowest layer in the stack and deals with the physical medium over which data is transmitted (e.g., copper wires, fiber optics). It defines the electrical, mechanical, and procedural aspects of data transmission.
  • Link Layer: Located above the physical layer, the link layer is responsible for framing data into discrete units (frames) for transmission, as well as error detection and correction. In PPP, the Link Control Protocol (LCP) operates at this layer, handling link establishment, configuration, and termination.
  • Network Layer: If necessary, a network layer protocol (like IP) is used for addressing and routing data between the two connected devices. This layer is responsible for logical addressing, packet forwarding, and network management.

Frequently Asked Questions 

What is point to point protocol multiplexing?

PPP multiplexing allows multiple network layer protocols (like IP, IPv6) to be transmitted over a single PPP link, enabling diverse communication.

Which device is used in point-to-point protocol?

A modem or network interface device is commonly used in point-to-point protocol to establish a direct connection between two nodes.

What is Point to Point Protocol Encapsulation?

Encapsulation is basically a process where the lower-layer protocol receives the data from the higher-layer protocol and places this data portion of its frame.

The Point to Point Protocol encapsulation is the process of enclosing one type of packing with help of other types of packets. The protocol generally offers encapsulation so that various protocols at the network get supported simultaneously.

Conclusion

This article extensively discusses Point to Point Protocol, its components, services offred, advantages and other aspects in detail.

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