Assignment 1 Mehdi Lebbar R1712D4147431 - Copie PDF

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Communication and security course...

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ASSIGNMENT 1

Contents 1.

2.

OSI Model.........................................................................................................................................................2 1.1.

Application layer, what is an application layer message ?......................................................................2

1.2.

Transport layer, what is a transport layer segment?................................................................................2

1.3.

Network Layer, what is a network layer datagram?................................................................................3

1.4.

Data link layer, what is a data link layer frame ?....................................................................................3

Advantages of optical fiber over coaxial cable and twisted-pair......................................................................3 2.1.

Coaxial cable...........................................................................................................................................3

2.2.

Dual coiled cable.....................................................................................................................................4

2.3.

Optical fiber.............................................................................................................................................4

2.4.

A comparison of the three types of cables...............................................................................................5

2.5.

Advantages of optical fiber.....................................................................................................................5

3.

Architectural generic components of a public communications network.........................................................6

4.

SHA-1 signature algorithm...............................................................................................................................7

5.

The impact of communication network applications on everyday life.............................................................7 5.1.

6.

The importance of the means of communication in our lives................................................................7

Why are standards important for protocols?.....................................................................................................8 6.1.

What is the definition of protocols?........................................................................................................8

6.2.

What is the difference between standard and protocol?..........................................................................8

6.3.

The importance of standards for communication between computers....................................................8

7.

TCP and UDP messages....................................................................................................................................9

8.

Network topologies, pros and cons...................................................................................................................9 8.1.

Bus topology............................................................................................................................................9

8.2.

Ring Topology.........................................................................................................................................9

8.3.

Star Topology........................................................................................................................................10

References...............................................................................................................................................................11

1. OSI Model The open systems connection form is ISO 7498, which is the technical standard developed by the ISO-Organization Standards International for network design. This model defines how the network protocols and equipment communicate and how they work together.

1.1.

Application layer, what is an application layer message ?

It is a layer that is directly responsible for dealing with the network user, its applications, and its platform, and it deals with the network from users in the networks. Application Layer adds a header, which is a piece of data used by the application layer in order to be understood on the other end of the line.

Figure 1: Representation of a message

Application layer protocols provide the ability for an application to communicate with Another app, regardless of hardware, OS, or any specifications. Others related to computer correspondence. Most of the applications, services, or protocols that are often included in IP / TCP are described as "Application Server / Client" applications this means that the application consists of two main parts, and it can be implemented on two different computers.

1.2.

Transport layer, what is a transport layer segment?

This layer configures the passage of data between the systems or hosts and defines the structure of the message. It translates the application layer packets it receives into transport layer messages, identified as transport-layer segment, figure 2 represents a transport-layer segment. This layer slices the message into pieces and attaches header to each piece/chunk, which is the sending and receiving application parts. Small numbers and serial numbers of those pieces and then send them. Among the protocols used in this layer are: UDP, TCP, IP / TCP. Before data transfer starts, both the sending and receiving applications inform the operating systems of those applications that a communication process will start and that both of them are ready. In this case, it can be said that the communication has started and that the data transmission can start.

Figure 2: Representation of a transport-layer segment

1.3.

Network Layer, what is a network layer datagram?

This layer defines the routing data protocols to ensure that information arrives from one station to another on the network. When data reaches the network layer, the source address and destination address of the data that each frame contains is checked to determine if the data has reached the final destination. A datagram is an elemental transfer unit associated with the network layer. Datagrams are initially composed with header and data sections. Datagrams offer a connectionless communication service across a packet-switched network. The network does not guarantee the delivery, arrival time, and order of arrival of datagrams.

1.4.

Data link layer, what is a data link layer frame ?

When receiving data from the physical layer, the data link layer checks the correctness and efficiency of the flow and efficiency of the data from the physical layer, checks for no errors, then encapsulates the bits in frames ( figure 3) . It addresses the data and regulates its flow. The data link layer is one of the three layers (Data link layer, network layer, transport layer) in charge for transferring data between equipment and devices by synchronizing data of blocks and controlling the flow of that data. According to The TCP/IP Guide, Frames are the outcome of the ending layer of encapsulation prior the data is sent through the physical layer. A frame is “the unit of transmission in a link layer protocol, and consists of a link layer header followed by a packet.”

Figure 3: Representation of a data link frame

2. Advantages of optical fiber over coaxial cable and twisted-pair 2.1.

Coaxial cable

Coaxial cable is a single wire habitually enveloped with copper in foam insulation, proportionally encircled in a laced interweaved metallic armor, and then covered with a plastic sheath. The coaxial cable can transmit measurement signals at a widespread range of frequencies because of its isolation property. It is thus widely used in feeder lines that link wireless transmitters and receivers to their antennas, digital audio, computer network communications, and cable television signal delivery.

Figure 4: Representation of coaxial cable

2.2.

Dual coiled cable

The Twisted Pair Cable is a type of wire in which two conductors are connected together in a single circuit. It comes in two versions: the twisted pair (STP) shielded and the twisted pair untied (UTP). STP is widely used in Ethernet Token Ring networks and UTP. For eg, for the 1000BASE-T (Gigabit Ethernet, or GbE) and 10 GBASE-T (10 Gigabit Ethernet, or 10 GbE) networks, Cat 7 twisted-pair cables are used. The image below shows a look at UTP (left) and STP (right).

Figure 5: Representation of dual coiled cable

2.3.

Optical fiber

Optical fibers are defined as flexible and transparent strands made of plastic, glass or silica with a diameter somewhat thicker than the diameter of a human hair, and these fibers are usually used to conduct light between two points and on a large scale in the field of communication to allow data transmission over long distances and at a high transmission rate compared to electrical cables , Where copper wires have been replaced by optical fibers due to their ability to transmit data with the lowest percentage of loss and because they are more resistant to electromagnetic interference. This technology has also been used for lighting and imaging purposes such as space photography.

Figure 6: Representation of optical fiber cable

2.4.

A comparison of the three types of cables

Coaxial cable can be mounted quickly, and is relatively resistant to intrusion. However, due to its high attenuation, it is bulky and suitable for short span spans. Long-distance data transmission would be expensive. In comparison, the twisted pair cable, simple to install and run, is the most versatile and cheapest of the three types of cable. But it has the issue of attenuation as well and offers relatively low bandwidth. It is however, subject to interference and noise. Optical fiber cable is compact and lightweight, one of the most common means for both new cable installations and improvements, including backbone, horizontal and even laptop applications. The fiber cable is resistant to electromagnetic interference, because the conductor is glass, which ensures that no electricity will pass through it. The main benefit of the fiber optic cable is that it can relay vast volumes of data over a long distance at high speed with low loss. However, complex installation skills are needed, which are difficult to operate and costly in the short term. (Walrand, 2002)

2.5. 

The advantages of optical fiber

Lower cost: Several kilometers of optical cable are less expensive than their equivalent copper cable.



Lack of thickness: the diameters of optical fibers are less than that of copper wires. High load



Capacity: optical fibers allow a larger number of telephone lines or channels to pass through, due to being less thick than copper wires, which allows placing a larger number of optical fiber bundles inside the cable.



Lack of signal degradation: optical fiber has less signal loss than copper wire.



The use of optical signals: Optical fibers use optical signals to transmit data through them, unlike the electrical signals used in copper wires, and these signals passing through one of the fibers do not collide with others in the neighboring fibers, which helps in greater clarity in telephone calls and television.



Less power consumed: Data transmitters used in optical fiber technology consume less energy compared to high voltage electrical transmitters used in copper wires, due to the less loss of signals transmitted through optical fibers.



Digital data transmission: Optical fibers are an ideal system for transmitting digital data especially in computer networks. Non-combustible: The optical fibers are considered non-flammable due to the lack of electricity passing through them.



Lightweight: Fiber optic cables are lighter than their copper counterpart and they take up less ground.



Flexibility: Optical fibers are used in digital cameras because they are flexible and able to transmit and receive light.

3. Architectural generic components of a public communications network Using four generic architectural components, a public telecommunications network can be described: •

Subscribers: The computers that connect to the network. It is still the case that telephones are the majority of subscribers to public telecommunications networks, but the percentage of data traffic is growing year by year.

•

Subscriber line: The relation, also mentioned to as the subscriber loop or local loop, between the subscriber and the network. Twisted-pair wire is used for almost all local loop links. Usually, the length of a local loop varies from a few kilometers to several tens of kilometers.

•

Exchanges: The network switching points. A switching center serving subscribers directly is known as an end office. Characteristically, an end office will support many thousands of subscribers in a localized area.

•

Trunks: Branches between exchanges. Using either FDM or synchronous TDM, trunks carry many voice frequencies circuits.

4. SHA-1 signature algorithm The preferred approach will be to use HMACs, as they are faster than using RSA computationally. This however, includes establishing a shared key with Bob before the message is transmitted. A type of message authentication code (CAM) or MAC (message authentication code), calculated using a cryptographic hash function in combination with a secret key, is an HMAC, standing for key-hash message authentication code. It can be used as with any CAM, to verify data integrity and message validity simultaneously. Any iterative hash function, such as MD5 or SHA-1, can be used in the calculation of an HMAC; the name of the resulting algorithm is HMAC-MD5 or HMAC-SHA-1. HMAC's cryptographic quality depends on the hash function's cryptographic quality and the size and quality of the key.

5. The impact of communication network applications on everyday life Communication is defined as the exchange of information between individuals through a shared system based on symbols, and this process may be between two or more persons, and thus communication consists of two components, namely, sending and receiving, as the party who sends the message is defined by the name of the sender, and whoever receives it is the receiver. And the messages exchanged and transmitted may include various contents of ideas, facts, concepts, opinions, instructions, emotions, beliefs, attitudes, etc., and this in turn made the means of communication an integral part of individuals' lives, it is almost impossible that one day passes without using them. It has been estimated that individuals' use of various means of communication occupies a large space in their lives more than any other activity, and this may be either writing, talking with friends, or through phone calls, etc. (Gordon, 1999)

5.1.

The importance of the means of communication in our lives

In our everyday and practical lives, the means of communication are of great importance. Some of the essential tasks that they accomplish are the following: A means of communicating truth, thoughts, knowledge and statistics, and of transmitting them. In work environments, they are used to inspire workers and control the way the workflow and the different activities between the departments of the company. (Grimsley) 

Consolidating the external partnerships of businesses with clients and suppliers.



Efficiency in doing business, which exposes the organization to the public in a positive way.



Contribute to educating people, widening their perspectives and horizons.



Helping to overcome language differences and the process of personal contact with people.

6. Why are standards important for protocols? 6.1.

What is the definition of protocols?

Protocols are known in English Protocols, and are sometimes known as communication standards. Network protocols are a collection of rules for coordinating network work, and protocols are essential for all network devices and computers, as the operation of these devices relies on a set of protocols to complete the communication process. Data exchange and various protocols represent the technology's conceptual principles.

6.2.

What is the difference between standard and protocol?

Standards are different from protocols. Standards are the way things should be, and the protocols used or that are applied may or may not constitute a standard. To simplify this, you can consider the standards as the theoretical basis, and not necessarily their full implementation on the ground, as for what is applied in reality is the protocols, and these protocols may be the implementation of the standards in full and thus become standards or that these protocols do not adhere to the standard and therefore it is called a protocol or It's called a standard.

6.3.

The importance of standards for communication between computers

It is essential to set standards, rules for all manufacturers of hardware and software to follow, and those are important for a number of reasons: 

Requirements define clearly and unambiguously how the information is transmitted.



Products of the manufacturer can work effectively with other products of the manufacturer if they all comply with the same requirements.



By establishing a set of specifications, you provide a structure through which all manufacturers can design new, successful products.



Standards break down complex concepts into smaller, more methodological, easier-tounderstand elements.

7. TCP and UDP messages Both TCP and UDP run on the Transport Layer as previously stated, the message transmitted by TCP is called connection-oriented and the one delivered by UDP is called connectionless or best-effort.

8. Network topologies, pros and cons In computer networks, topology means what a network is, or the way devices are connected to each other in a network. In the following, we look at the most important known network topologies. (Mitchell, 2019)

8.1.

Bus topology

The first type of computer network topology is linear topology or (bus topology) where all network devices are connected by a single cable. This type is typically used in small networks and is very simple and cheap, but if anything happens on the cable stage, the whole network fails, and it only supports a small number of devices and a limited flow of data that only flows on one side.

Figure 7: Representation of a bus topology

Capabilities

   

Not expensive. Used in small networks. Simple and easy to absorb. Easy to extend.

Limitations

 



A failure at the cable level causes failure of the entire network. If there is a large data flow...