Introduction
The three-way handshake is a fundamental process used in computer networking to establish a reliable connection between two devices. It is a key component of the Transmission Control Protocol (TCP), which is widely used for communication over the Internet.
This article provides an in-depth explanation of the three-way handshake process, its purpose, and the sequence of steps involved.
Step 1- Initial Connection Request SYN (Synchronize):
- The client (initiator) sends a TCP segment with the SYN (synchronize) flag set to the server (responder).
- This segment contains a sequence number (SYN sequence number) that the client chooses to start the communication. It also includes other TCP options, such as maximum segment size.
Step 2 - Server Response SYN-ACK (Synchronize-Acknowledge):
- Upon receiving the SYN segment, the server allocates the necessary resources for the connection and generates its own SYN sequence number.
- The server responds by sending a TCP segment with both the SYN and ACK (acknowledge) flags set to the client.
- This segment includes the server's SYN sequence number and acknowledges the client's SYN sequence number from Step 1.
Step 3- Client Acknowledgment ACK (Acknowledge):
- After receiving the SYN-ACK segment, the client acknowledges the server's response by sending an ACK segment.
- The ACK segment has the ACK flag set and confirms the server's SYN sequence number.
- At this point, both the client and server have exchanged their SYN sequence numbers and established a connection.
- They can now begin sending data using sequence numbers that have been synchronized.
Connection Establishment:
With the completion of the three-way handshake, both devices have exchanged initial sequence numbers, synchronized their communication settings, and established a reliable connection. Subsequent data transmission can now occur between the client and server using the agreed-upon sequence numbers and other parameters.
Connection Termination:
The three-way handshake is also used during connection termination. When a device wants to terminate the connection, it sends a TCP segment with the FIN (finish) flag set. The other device acknowledges the FIN segment, and both devices exchange FIN and ACK segments to close the connection gracefully.
Conclusion
The three-way handshake is a crucial process in TCP/IP networking, enabling reliable and orderly connection establishment and termination. It ensures that both communicating devices synchronize their initial sequence numbers and establish the necessary parameters for data transmission.
Understanding the three-way handshake is essential for network administrators and developers working with TCP-based applications, as it forms the foundation of secure and efficient communication over the Internet.
The three-way handshake ensures that both ends of the connection are ready and aware of each other's sequence numbers and communication parameters. It establishes a reliable and synchronized connection before data transmission begins, reducing the chances of data loss or corruption.
FAQs
Steps of a three-way handshake
How does a 3-way handshake work in TCP? ›
The TCP handshake
TCP uses a three-way handshake to establish a reliable connection. The connection is full duplex, and both sides synchronize (SYN) and acknowledge (ACK) each other. The exchange of these four flags is performed in three steps—SYN, SYN-ACK, and ACK—as shown in Figure 3.8.
What are the three messages of the TCP IP three-way handshake? ›
It involves three steps: SYN (Synchronize), SYN-ACK (Synchronize-Acknowledge), and ACK (Acknowledge).
What happens after the three-way handshake? ›
Once the TCP three-way handshake is made, the data segment is then passed to the Internet layer. At this layer, IP provides logical-addressing info, encloses data into a datagram, and provides routing to support delivery across the interconnected network.
What is the correct order of messages sent in a TCP handshake? ›
TCP 3-Way Handshake Process
- The client starts the process and sets the SYN flag to 1. The client sends the message to the server by setting the SYN flag to 1. ...
- The server replies with (SYN+ACK) ...
- The final acknowledgment from the client (ACK)
HTTP uses TCP as the transport protocol and before user data is sent, TCP 3-way handshake establishes the TCP connection. So, for each TCP connection, there are 3 packets exchanged and each packet is between 54 and 66 Bytes (notice the Len field).
Is TCP or UDP a three-way handshake? ›
TCP is connection-oriented while UDP is connectionless
The connection is established via a three-way handshake. The client sends a synchronization request, the server sends back an acknowledgment, and the client returns a synchronization acknowledgment in response. Comparatively, UDP is a connectionless protocol.
What are the benefits of a three-way handshake? ›
The 3-Way Handshake is necessary to establish a reliable connection, confirming that both communicating devices are ready to exchange data. It helps in preventing issues like data corruption, out-of-order delivery, and unauthorized access.
How TCP terminates the connection? ›
The TCP Connection Termination Process
Initiation of Termination: The party wishing to terminate the connection sends a TCP segment with the FIN (Finish) flag set to the other party. The FIN flag indicates that the sender has no more data to send.
What is the last phase of the TCP handshake? ›
This step is known as a synchronization acknowledgment or SYN ACK. Step 3: The final step of the handshake is the client acknowledging the connection with an ACK message.
People give and receive the same type of handshake regardless of gender. A handshake is held for about two to three seconds. Eye contact during the handshake. Exchange a brief verbal introduction or greeting during handshake.
What is the timeout for TCP 3 way handshake? ›
If the three-way TCP handshake does not complete in the timeout period, it is dropped. This option is selected by default. TCP Handshake Timeout (seconds): The maximum time a TCP handshake has to complete the connection. The default is 30 seconds.
How long does the 3 way handshake take to complete? ›
Setting up a TCP connection requires communicating a Three Way Handshake. In this phase, there are three packets that are transmitted sequentially (C->S, S->C, C->S again). This means that it takes 1.5 RTT (Round Trip Time) to set up a connection.
What is the correct process for the TCP three-way handshake? ›
This article provides an in-depth explanation of the three-way handshake process, its purpose, and the sequence of steps involved.
- Step 1- Initial Connection Request SYN (Synchronize): ...
- Step 2 - Server Response SYN-ACK (Synchronize-Acknowledge): ...
- Step 3- Client Acknowledgment ACK (Acknowledge):
Each handshake involves two students and contributes to the degree of two vertices. So, the sum of degrees is 2×25=50. According to the Handshaking Theorem, this sum is also equal to twice the number of handshakes. Therefore, 50=2×E, where E is the number of handshakes.
How to handshake between two servers? ›
To accomplish the two-way handshaking considering a client/server model, the client sends an SYN message to the server with a sequence number X. Then, the server should acknowledge (ACK) the SYN message, providing another sequence number Y and establishing the connection.
What is the mechanism of handshaking? ›
A handshake is a means of synchronization among communicating mechanisms. In its simplest form it involves two mechanisms connected by a pair of so-called links, one for sending signals and one for receiving signals.
How does TCP FIN work? ›
The TCP FIN flag is used to terminate a TCP connection by signaling the end of data transmission to the remote endpoint. The sender sends a FIN segment, which indicates that it has no more data to send and requests to close the connection.
Which field in the TCP header indicates the status of the three-way handshake process? ›
Expert-Verified Answer. The field in the TCP header that indicates the status of the three-way handshake process is the Flags field. The Flags field is 6 bits long and is used to control various aspects of the TCP connection. Within the Flags field, there are several individual bits that have specific meanings.
What is a three-way handshake in TCP quizlet? ›
A three-way-handshake is a method used in a TCP/IP network to create a connection between a local host/client and server. It is a three-step method that requires both the client and server to exchange SYN and ACK (acknowledgment) packets before actual data communication begins.
