• Subject Name : Computer Network

Packets Synchronization


Introduction: TCP 3-Way Handshake (SYN, SYN-ACK, ACK).


TCP message types.

Task 3.1: Using the packets captured and saved in the previous section, name and explain the core protocols involved in getting the web page of Brunel University (or any webpage for that matter).

Task 3.2.

What is the sequence number in the SYN segment?.

What is the sequence number in the SYNACK segment?.

What is the acknowledgment number in the SYNACK segment? How did the server determine this acknowledgement number?.

What time was the SYN segment sent? What time was the SYNACK segment received? What is the round trip time?



Introduction to TCP 3-Way Handshake (SYN, SYN-ACK, ACK)

The IPS is the design pattern and collection of networking protocols used across the Internet and related networks. The TCP / IP protocols are widely recognised as the Transmission Control Protocol (TCP) and the Internet Protocol (IP) as the basic protocols in the series. This was developed as a concept of the Defense Department (DoD), and was sponsored by the US Defense Department by DARPA for the implementation of the networking technique. The protocol stack is applied. One of the main protocols of the sequence of Internet protocols is the Transmission Control Protocol (TCP). That came in as the Internet Protocol (IP) was first introduced. The entire system is also generally called TCP / IP. TCP offers a stable, structured and error-controlled byte transfer between popular hosts applications. A contact interface is established at an intermediate point between the client system and the Internet network through the Transmission Control Protocol. TCP is a trustworthy stream distribution device that assures that any byte sent is similar to that sent. As packet transmissions across multiple networks are not efficient, TCP uses a strategy known as optimistic retransmission acceptance. Transmission Control Protocol recognizes, separates and attaches a TCP header forming a TCP line. Information from a network source. 

The Internet Protocol Suite offers end-to - end software processing defining how to load, username, send, route and receive data. The interface is divided into four levels of abstraction, which define all associated protocols through networking. Lowest to maximum, the connection layers include data transmission methods which stay on a network segment (link), the Internet layer, the internet networking structure between individual networks, the transportation layer, the host-to - host contact management, and the application layer that enables the data exchange from the user to the server for applications.

Three-Way Handshake

THREE-WAY HANDSHAKE or a TCP 3-way handshake is used to create a connection between the server and the client in a TCP / IP network. This is a three-stage procedure that involves the exchanging of syncing and acknowledgement packets to both client and server before the real data transmission operation occurs. Three-way hand-shake is built to help you create and discuss TCP socket contacts concurrently at both ends. This helps several TCP port links to be moved.

TCP Message Types

  • Syn: Used for communicating and initiating. This also lets you coordinate computer series numbers.
  • ACK: Confirms that it obtained SYN from the other hand.
  • SYS-ACK: Local system SYN communication and the previous packet ACK code.
  • FIN: Used to terminate a connection.

Following are the three step that take place during Three-way handshake

  • Step 1: The client connects to a server in the first stage. This sends a section with SYN and tells the server about the application beginning contact and the sequence number of the device.
  • Step 2: The SYN-ACK signal collection is used to respond to the client order. ACK allows you to show the answer from the obtained segment and SYN indicates which sequence number the segments will start with.
  • Step 3: During this final stage the server 's response is understood by the client and the client continues with the internal data transmission phase by establishing a secure link.

Task 3.1: Using the Packets Captured and Saved in The Previous Section, Name and Explain the Core Protocols Involved in Getting the Web Page of Brunel University (or Any Webpage for That Matter).

As we know that everything on internet has some protocols like (HTTP, IP, TCP, UDP) and more like them, so whenever we assess any site from internet or search engine it has few protocols that comes with it are given as follows: -

  • Source IP (
  • Destination IP address (
  • Used Protocol (TCP (transfer control protocol))
  • Src port: 58742
  • Dst port: 443

These are the basic protocols that come with site when we assess it, 

  • Source IP:

It is a type of id that is assigned to the site or anything assessable thing after the request in response. from where it is generated an IP is assigned to it and with this Destination id also attached so it reaches at exactly where it needed.

  •  Destination IP:

It is a types of id that is used to find the place or location from where the request was generated.

  • TCP:

Transmission Control Protocol (TCP) – a connection-oriented communications protocol that facilitates the exchange of messages between computing devices in a network. It is the most common protocol in networks that use the Internet Protocol (IP); together they are sometimes referred to as TCP/IP.

  • Port:

Port numbers are used by TCP (Transmission Control Protocol)

Task 3.2

Answer the following questions

What is the Sequence Number in the SYN Segment?

The sequence number is the byte number of data in the first byte (also known as the TCP segment) of the TCP file. The (relative) number of the series is zero (Seq=1), with flags used to establish SYN. It is the first sequence number if SYN flag is placed (1). This number plus 1 is the series number of the real first byte and the known amount of the corresponding ACK. If the SYN flag is explicitly set (0), the first data byte of that sector for the current session will be accrued in sequence number.

What is the sequence number in the SYNACK segment?

Also Seq=1 (relative sequence number)

What is the acknowledgment number in the SYNACK segment? How did the server determine this acknowledgement number?

The acknowledgement number is the sequence number of the next byte the receiver expects to receive

Acknowledgment number = 2 (relative acknowledgement number)

Since sync is 1 in this situation, SYNACK message will respond with the X + 1 accreditation number. The next sequence number predicted by the sender of the ACK would be the value in the field if the ACK flag is placed. This acknowledges that all bytes have been (if any) received. The first ACK transmitted at either end recognizes the original number at the other end, but not any details.

What time was the SYN segment sent? What time was the SYNACK segment received? What is the round trip time?

Sequence number sent = 1 sent at 4.799157

Acknowledgment number received at 5.660660

Round trip number is the difference b/w sequence send and received: - so = 0.86

Above is a screen shoot given of the wireshark that I have used for assignment solution.

Conclusion on Packets Synchronization

In the end, it can be concluded that it was a fun assignment and more informative, make students to learn how to operate different software’s like Wireshark, and how to deal with packets what’s is actually 3 way hand-shake process , and by doing practice now it is making more sense that how it all works how All the data is being assessed through internets from one source to destination and also I learned a lot about synchronization flags how it turns on and off. All that kind of things that will be more than sufficient for a networking to start.

References for Packets Synchronization

Chappell, L. (2012). Wireshark network analysis. PODBOOKS. COM, LLC.

Chappell, L. (2017). Wireshark 101: Essential Skills for Network Analysis-Wireshark Solution Series. Laura Chappell University, USA.

Sanders, C. (2017). Practical packet analysis: Using Wireshark to solve real-world network problems. No Starch Press.

Wang, S., Xu, D., & Yan, S. (2010, April). Analysis and application of Wireshark in TCP/IP protocol teaching. In 2010 International Conference on E-Health Networking Digital Ecosystems and Technologies (EDT) (Vol. 2, pp. 269-272). IEEE.

Remember, at the center of any academic work, lies clarity and evidence. Should you need further assistance, do look up to our Computer Science Assignment Help

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