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Wireshark Sequence Diagram

8/24/2021
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Have you ever wondered how your computer talks to other computers on your local LAN or to other systems on the internet?

Understanding the intricacies of how computers interact is an important part of networking and is of equal interest to a sysadmin as well as to a developer. In this article, we will make an attempt to discuss the concept of communication from the very basic fundamental level that needs to be understood by everybody.

TCP/IP PROTOCOL SUITE

Communications between computers on a network is done through protocol suits. The most widely used and most widely available protocol suite is TCP/IP protocol suite. A protocol suit consists of a layered architecture where each layer depicts some functionality which can be carried out by a protocol. Each layer usually has more than one protocol options to carry out the responsibility that the layer adheres to. TCP/IP is normally considered to be a 4 layer system. The 4 layers are as follows :

  1. Application layer
  2. Transport layer
  3. Network layer
  4. Data link layer

The following sequence diagram illustrates the 3-way handshake process And this is how the handshake is captured by wireshark During this handshake, the client and the server also declare their capabilities for each other to agree on the common connection parameters to be used between them. Wireshark: This lab uses Wireshark to capture or examine a packet trace. A packet trace is a record of traffic at some location on the network, as if a snapshot was taken of all the bits that passed across a particular wire. Include the following features on your diagram: The Sequence and ACK number, if present, on each segment.

1. Application layer

Answer: The lease time is the amount of time the DHCP server assigns an IP address to a client.During the lease time, the DHCP server will not assign the IP given to the client to another client, unless it is released by the client. Sequence diagram of a hospital management system. Technology has completely transformed the field of medicine, as it has with most industries. A hospital information system, also known as a hospital information system, helps doctors, administrators, and hospital staff managing all of the activities and information collected at a hospital, including checkups, prescriptions, appointments,. Generate sequence diagrams and call flow diagrams from Wireshark output The sequence diagrams provide a visual trace of the packet flow between different nodes: Generate sequence diagrams at IP address or port level Extract messages from GTP tunnels.

This is the top layer of TCP/IP protocol suite. This layer includes applications or processes that use transport layer protocols to deliver the data to destination computers.

At each layer there are certain protocol options to carry out the task designated to that particular layer. So, application layer also has various protocols that applications use to communicate with the second layer, the transport layer. Some of the popular application layer protocols are :

  • HTTP (Hypertext transfer protocol)
  • FTP (File transfer protocol)
  • SMTP (Simple mail transfer protocol)
  • SNMP (Simple network management protocol) etc

2. Transport Layer

This layer provides backbone to data flow between two hosts. This layer receives data from the application layer above it. There are many protocols that work at this layer but the two most commonly used protocols at transport layer are TCP and UDP.

TCP is used where a reliable connection is required while UDP is used in case of unreliable connections.

TCP divides the data(coming from the application layer) into proper sized chunks and then passes these chunks onto the network. It acknowledges received packets, waits for the acknowledgments of the packets it sent and sets timeout to resend the packets if acknowledgements are not received in time. The term ‘reliable connection’ is used where it is not desired to loose any information that is being transferred over the network through this connection. So, the protocol used for this type of connection must provide the mechanism to achieve this desired characteristic. For example, while downloading a file, it is not desired to loose any information(bytes) as it may lead to corruption of downloaded content.

UDP provides a comparatively simpler but unreliable service by sending packets from one host to another. UDP does not take any extra measures to ensure that the data sent is received by the target host or not. The term ‘unreliable connection’ are used where loss of some information does not hamper the task being fulfilled through this connection. For example while streaming a video, loss of few bytes of information due to some reason is acceptable as this does not harm the user experience much.

3. Network Layer

This layer is also known as Internet layer. The main purpose of this layer is to organize or handle the movement of data on network. By movement of data, we generally mean routing of data over the network. The main protocol used at this layer is IP. While ICMP(used by popular ‘ping’ command) and IGMP are also used at this layer.

4. Data Link Layer

Wireshark Sequence Diagram

This layer is also known as network interface layer. This layer normally consists of device drivers in the OS and the network interface card attached to the system. Both the device drivers and the network interface card take care of the communication details with the media being used to transfer the data over the network. In most of the cases, this media is in the form of cables. Some of the famous protocols that are used at this layer include ARP(Address resolution protocol), PPP(Point to point protocol) etc.

TCP/IP CONCEPT EXAMPLE

One thing which is worth taking note is that the interaction between two computers over the network through TCP/IP protocol suite takes place in the form of a client server architecture.

Wireshark generate sequence diagram

Client requests for a service while the server processes the request for client.

Now, since we have discussed the underlying layers which help that data flow from host to target over a network. Lets take a very simple example to make the concept more clear.

Consider the data flow when you open a website.

Wireshark Sequence Diagram

As seen in the above figure, the information flows downward through each layer on the host machine. At the first layer, since http protocol is being used, so an HTTP request is formed and sent to the transport layer.

Here the protocol TCP assigns some more information(like sequence number, source port number, destination port number etc) to the data coming from upper layer so that the communication remains reliable i.e, a track of sent data and received data could be maintained.

At the next lower layer, IP adds its own information over the data coming from transport layer. This information would help in packet travelling over the network. Lastly, the data link layer makes sure that the data transfer to/from the physical media is done properly. Here again the communication done at the data link layer can be reliable or unreliable.

This information travels on the physical media (like Ethernet) and reaches the target machine.

Now, at the target machine (which in our case is the machine at which the website is hosted) the same series of interactions happen, but in reverse order.

The packet is first received at the data link layer. At this layer the information (that was stuffed by the data link layer protocol of the host machine) is read and rest of the data is passed to the upper layer.

Similarly at the Network layer, the information set by the Network layer protocol of host machine is read and rest of the information is passed on the next upper layer. Same happens at the transport layer and finally the HTTP request sent by the host application(your browser) is received by the target application(Website server).

One would wonder what happens when information particular to each layer is read by the corresponding protocols at target machine or why is it required? Well, lets understand this by an example of TCP protocol present at transport layer. At the host machine this protocol adds information like sequence number to each packet sent by this layer.

At the target machine, when packet reaches at this layer, the TCP at this layer makes note of the sequence number of the packet and sends an acknowledgement (which is received seq number + 1).

Now, if the host TCP does not receive the acknowledgement within some specified time, it re sends the same packet. So this way TCP makes sure that no packet gets lost. So we see that protocol at every layer reads the information set by its counterpart to achieve the functionality of the layer it represents.

PORTS, SERVERS AND STANDARDS

On a particular machine, a port number coupled with the IP address of the machine is known as a socket. A combination of IP and port on both client and server is known as four tuple. This four tuple uniquely identifies a connection. In this section we will discuss how port numbers are chosen.

You already know that some of the very common services like FTP, telnet etc run on well known port numbers. While FTP server runs on port 21, Telent server runs on port 23. So, we see that some standard services that are provided by any implementation of TCP/IP have some standard ports on which they run. These standard port numbers are generally chosen from 1 to 1023. Football manager 2021 sur chromebook. The well known ports are managed by Internet Assigned Numbers Authority(IANA).

While most standard servers (that are provided by the implementation of TCP/IP suite) run on standard port numbers, clients do not require any standard port to run on.

Client port numbers are known as ephemeral ports. By ephemeral we mean short lived. This is because a client may connect to server, do its work and then disconnect. So we used the term ‘short lived’ and hence no standard ports are required for them.

Also, since clients need to know the port numbers of the servers to connect to them, so most standard servers run on standard port numbers.

The ports reserved for clients generally range from 1024 to 5000. Port number higher than 5000 are reserved for those servers which are not standard or well known.

If we look at the file ‘/etc/services’, you will find most of the standard servers and the port on which they run.

As you see from the /etc/services file, FTP has port number 21, telent has port number 23 etc. You can use ‘grep’ command on this file to find any server and its associated port.

As far as the standards are concerned, the following four organizations/groups manage the TCP/IP protocol suite. Both the IRTF and the IETF fall under the IAB.

  1. The Internet Society (ISOC)
  2. The Internet Architecture Board (IAB). The IAB falls under the ISOC.
  3. The Internet Engineering Task Force (IETF)
  4. The Internet Research Task Force (IRTF)

An interaction diagram is either a sequence diagram or a communication diagram, both of which show essentially the same information. These diagrams, along with class diagrams, are used in a use case realization, which is a way to achieve or accomplish a use case.

Wireshark generate sequence diagram

Sequence Diagrams

Sequence diagrams can illustrate a succession of interactions between classes or object instances over time. Sequence diagrams are often used to illustrate the processing described in use case scenarios. In practice, sequence diagrams are derived from use case analysis and are used in systems design to derive the interactions, relationships, and methods of the objects in the system. Sequence diagrams are used to show the overall pattern of the activities or interactions in a use case. Each use case scenario may create one sequence diagram, although sequence diagrams are not always created for minor scenarios.

Wireshark Sequence Diagram

The symbols used in sequence diagrams are shown in the figure below. Actors and classes or object instances are shown in boxes along the top of the diagram. The leftmost object is the starting object and may be a person (for which a use case actor symbol is used), window, dialog box, or other user interface. Some of the interactions are physical only, such as signing a contract. The top rectangles use indicators in the name to indicate whether the rectangle represents an object, a class, or a class and object.

objectName:A name with a colon after it represents an object.
:classA colon with a name after it represents a class.
objectName:classA name, followed by a colon and another name, represents an object in a class.

A vertical line represents the lifeline for the class or object, which corresponds to the time from when it is created through when it is destroyed. An X on the bottom of the lifeline represents when the object is destroyed. A lateral bar or vertical rectangle on the lifeline shows the focus of control when the object is busy doing things.

Wireshark Generate Sequence Diagram

Horizontal arrows show messages or signals that are sent between the classes. Messages belong to the receiving class. There are some variations in the message arrows. Solid arrowheads represent synchronous calls, which are the most common. These are used when the sending class waits for a response from the receiving class, and control is returned to the sending class when the class receiving the message finishes executing. Half (or open) arrowheads represent asynchronous calls, or those that are sent without an expectation of returning to the sending class. An example would be using a menu to run a program. A return is shown as an arrow, sometimes with a dashed line. Messages are labeled using one of the following formats:

  • The name of the message followed by empty parentheses: messageName().
  • The name of the message followed by parameters in parentheses:
    messageName(parameter1, parameter2 . . .).
  • The message name followed by the parameter type, parameter name, and any default value for the parameter in parentheses:
    messageName(parameterType:parameterName(defaultValue). Parameter types indicate the type of data, such as string, number, or date.
  • The message may be a stereotype, such as «Create», indicating that a new object is created as a result of the message.

Timing in the sequence diagram is displayed from top to bottom; the first interaction is drawn at the top of the diagram, and the interaction that occurs last is drawn at the bottom of the diagram. The interaction arrows begin at the bar of the actor or object that initiates the interaction, and they end pointing at the bar of the actor or object that receives the interaction request. The starting actor, class, or object is shown on the left. This may be the actor that initiates the activity or it may be a class representing the user interface.

Wireshark Network Sequence Diagram

Figure illustration below is a simplified example of a sequence diagram for a use case that admits a student to a university. On the left is the newStudentUserInterface class that is used to obtain student information. The initialize() message is sent to the Student class, which creates a new student record and returns the student number. To simplify the diagram, the parameters that are sent to the Student class have been omitted, but would include the student name, address, and so on. The next activity is to send a selectDorm message to the Dorm class. This message would include dorm selection information, such as a health dorm or other student requirements. The Dorm class returns the dorm name and room number. The third activity is to send a selectProgram message to the Program class, including the program name and other course of study information. The program advisor name is returned to the newStudentUserInterface class. A studentComplete message is sent to the Student class with the dorm, advisor name, and other information.

Sequence diagrams can be used to translate the use case scenario into a visual tool for systems analysis. The initial sequence diagram used in systems analysis shows the actors and classes in the system and the interactions between them for a specific process. You can use this version of the sequence diagram to verify processes with the business area experts who have assisted you in developing the system requirements. A sequence diagram emphasizes the time ordering (sequence) of messages.

During the systems design phase, the sequence diagrams are refined to derive the methods and interactions between classes. Messages from one class are used to identify class relationships. The actors in the earlier sequence diagrams are translated to interfaces, and class interactions are translated to class methods. Class methods used to create instances of other classes and to perform other internal system functions become apparent in the system design using sequence diagrams.

Communication Diagrams

Communication diagrams were introduced in UML 2.0. Their original name in UML 1.x was collaboration diagrams. Communication diagrams describe the interactions of two or more things in the system that perform a behavior that is more than any one of the things can do alone. For instance, a car can be broken down into several thousand individual parts. The parts are put together to form the major subsystems of the vehicle: the engine, the transmission, the brake system, and so forth. The individual parts of the car can be thought of as classes, because they have distinct attributes and functions. The individual parts of the engine form a collaboration, because they “communicate” with each other to make the engine run when the driver steps on the accelerator.

Wireshark network sequence diagram

A communication diagram is made up of three parts: objects (also called participants), the communication links, and the messages that can be passed along those links. Communication diagrams show the same information as a sequence diagram but may be more difficult to read. In order to show time ordering, you must indicate a sequence number and describe the message. A communication diagram emphasizes the organization of objects, whereas a sequence diagram emphasizes the time ordering of messages. A communication diagram will show a path to indicate how one object is linked to another.

Some UML modeling software, such as IBM’s Rational Rose, will automatically convert a sequence diagram to a communication diagram or a communication diagram to a sequence diagram with the click of a button. A communication diagram for the student admission example is illustrated in the figure below. Each rectangle represents an object or a class. Connecting lines show the classes that need to collaborate or work with each other. The messages sent from one class to another are shown along connecting lines. Messages are numbered to show the time sequence. Return values may also be included and numbered to indicate when they are returned within the time sequence.

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