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Introduction to Data Communications and Networking. Chapter 1 (Set 1). Dr. Ali Maqousi, Dr. Tatiana Balikhina [email protected] , [email protected] Department of Computer Networks Faculty of Information Technology Petra University. DATA COMMUNICATIONS.

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Introduction to Data Communications and Networking

Chapter 1 (Set 1)

Dr. Ali Maqousi, Dr. Tatiana Balikhina

[email protected] , [email protected]

Department of Computer Networks

Faculty of Information Technology

Petra University


  • The term telecommunication means communication at a distance.

  • The word data refers to information presented in whatever form is agreed upon by the parties creating and using the data.

  • Datacommunications are the exchange of data between two devices via some form of transmission medium such as a wire cable.

Characteristics that define effectiveness of data communications
Characteristics that define effectiveness of data communications

  • Delivery

  • Accuracy

  • Timeliness

  • Jitter

A data communications system must transmit data to the correct destination in an accurate and timely manner.

Components of data communication system
Components of Data Communication System communications

  • Message is the information (data) to be communicated (text, numbers, images, audio, and video).

  • Sender is the device that sends the data message (computer, mobile phone, video camera and so on).

  • Receiver is the device that receives the message.

  • Transmission medium is the physical path by which a message travels from sender to receiver (twisted-pare, coaxial, fiber-optic cables and radio waves).

  • Protocolis an agreement between the communicating devices on how communication is to proceed.

Data flow modes communications

Data flow modes
Data flow modes communications

  • Simplex as one-way street. Only one of the two devices on a link can transmit; the other can only transmit.

  • Half-duplex, each station can both transmit, but not at the same time.

  • Full-duplex (or duplex), both stations can transmit and receive simultaneously.

Networks communications

  • Computer Network is a collection of devices (nodes) interconnected by a single technology (transmission medium link).

  • Node can be a computer, printer, or any other device capable of sending and/or receiving data generated by other nodes on the network.

  • Interconnected computers are two or more computers that able to exchange information.

Networks communications

Computer network example

Networks communications

  • Internet is the network of networks(connection of two or more networks)

  • Intranet is a private business network.

  • Most networks use distributed processing, in which atask is divided among multiple computers.

  • Distributed System is a software system built on top of a network.

  • World Wide Web is a distributed system that runs on top of the Internet.

Networks criteria communications

  • Performance can be measured in many ways, including:

    1)Transit time (time required for a message to travel from one device to another);

    2) Response time (elapsed time between inquiry and response).

    Performance is often evaluated by two networking metrics:

    Throughput and delay.

    To enhance performance we need more throughput and less delay.

  • Reliability is measured by :

    1) accuracy of delivery;

    2)frequency of failure;

    3) time it takes a link recover from failure.

  • Security include:

    1) protecting data from unauthorized access;

    2) protecting data from damage;

    3) development recovery policies and procedures.

Benefits of Computer Networks I communications

  • Business Applications

  • Resource Sharing (printers, scanners, storage devices, and sharing information, (client-server model))

  • Communication Medium (E-mail)

  • Being ableto place orders in real time (Purchase)

  • - E-Commerce, M-Commerce

Business applications of networks
Business Applications of Networks communications

A network with two clients and one server.

Benefits of Computer Networks II communications

  • Home Network Applications

  • - Access to remote information (e.g. Google)

  • Person to person communication

  • Using social networks (e.g. Facebook)

  • - Interactive entertainment

  • - E- commerce, M-Commerce

Network attributes: communications1 - Types of connection

  • Point-to-point

  • Multipoint (or multidrop, e.g. broadcasting networks)

Network attributes: communications2 –Topology

The topology of the network is the geometric representation of the relationship of all the links and nodes to each other.

Categories of networks communications

  • The most common classification of networks is based on its physical size (scale).

Local Area Network communications (LAN)

  • LAN is a network within a single building or campus of up to a few kilometres in size.

  • LANs share the following characteristics:

  • - their transmission media

  • - their size (restricted small size)

  • - their topology (Bus, Ring, Star)

  • - their setting up cost is low

  • - Data transfer rate is high (10Mbps, 100Mbps, 10Gbps)

LAN topologies: Mesh (1) communications

A fully connected mesh topology (five devices)

We need n(n-1)/2 duplex-mode point-to-point links to connect n devices

LAN topologies: Mesh (2) communications

  • Advantages of mesh topology:

  • Eliminating traffic problem (each link is dedicated to pair of devices);

  • Robustness (break in one line does not lead to break of all network);

  • Privacy and security;

  • Fault identification and isolation is easy.

  • Disadvantages of mesh topology:

  • Large amount of cabling and I/O ports are required;

  • Wiring can be greater than available space;

  • It is expensive.

Mesh mainly is used to connect servers of a hybrid topology network that can include several other topologies.

LAN topologies: Star (1) communications

Star topology uses point-to-point connections (station-hub).

LAN topologies: Star (2) communications

  • In a Star topology, each station is directly connected to a central controller – hub.

  • The hub acts as exchange: device sends data to hub, which then relays the data to other device.

  • Advantages of star topology:

  • Less expensive than mesh;

  • Less cabling;

  • Easy maintenance.

  • Disadvantages of star topology:

  • One single point of failure – hub.

LAN topologies: Star (3) communications

An isolated LAN connecting 12 computers to a hub in a closet

LAN topologies: Bus (1) communications

Bus topology is multipoint. One large cable acts as a backbone to link all devices in a network.

LAN topologies: Bus (2) communications

  • In abustopology, all stations are attached to a liner transmission medium (bus) through appropriate hardware interface (tap).

  • Advantages of bus topology:

  • easy to install;

  • efficient use of wiring;

    • Disadvantages of bus topology:

    • One single point of failure – backbone cable.

    • Difficult maintenance.

    • IEEE 802.3 (Ethernet) is an example of bus topology.

    • (IEEE stands for Institute of Electrical and Electronics Engineers)

    LAN topologies: Ring (1) communications

    LAN topologies: Ring (2) communications

    • In a Ring topology, each station on the network is connected to two other stations, forming a loop or ring.

    • It uses token (signal circulating in a ring) to control transmission.

    • Advantages of ring topology:

    • To add or delete a device requires changing only two connections.

    • Fault isolation is simplified

    • No conflict in the transmission of data.

  • Disadvantages of ring topology:

    • - if one connection fails, the rest of the network will fail.

    • To avoid this a dual ring could be used.

    • IEEE 802.5 ( IBM Token Ring) & FDDI (Fiber Distributed Data Interface) are examples.

  • LAN topologies: Hybrid communications

    A hybrid topology: a star backbone with three bus networks

    Metropolitan communicationsArea Network (MAN) (1)

    • MANis a network with a size between a LAN and a

    • WAN. It normally covers a city.

    • Examples of a MAN:

    • 1) part of the telephone company network that can provide a high-speed DSL line to the customer;

    • 2) cable TV network.

    Metropolitan communicationsArea Network (MAN) (2)

    • MAN based on cable TV

    Wide Area Network (WAN) (1) communications

    Relation between hosts on LANs and the subnet.

    • The main differences between WAN and LAN are:

    • - LAN is fully controlled by the owner whilst the WAN needs the involvement of another authority like Telephone Company.

    • - The transfer rate of LAN is higher than the transfer rate of WAN.

    Wide Area Network (WAN) (2) communications

    • WAN network spans a large geographical area, it contains a collection of hosts that are connected by a communication subnet.

    • Host is a machine that is used to run user (i.e., application) program and is owned by the customers.

    • Subnet consists of transmission lines and switching elements, and its job is to carry messages from host to host.

    Wide Area Network (WAN) (3) communications

    A stream of packets from sender to receiver.

    Wide Area Network (WAN) (4) communications

    • Subnet is typically owned and operated by a telephone company or Internet service provider.

    • Transmission lines move bits between machines, they can be made of copper wire, optical fiber, or even radio links.

    • Switching elements are specialized computers that connect three or more transmission lines and they called Routers.

    Wireless Networks (1) communications

    • - Users have a dream to connect their notebooks to the network without having to be plugged into a telephone wall socket.

    • - To achieve a true mobility there is a need to use a radio (or infrared) signals for communication.

    • Three main categories:

    • 1- System interconnection

    • 2- Wireless LANs

    • 3- Wireless WANs

    Wireless Networks (2) communications

    (a) Bluetooth configuration

    (b) Wireless LAN

    Wireless Networks (3) communications

    • - System interconnection, it is about interconnecting the components of a computer using a short-range radio that uses the master-slave paradigm.

    • Example:

    • - Bluetooth is a short-range wireless network that allows digital components to connect to a computer by merely being brought within range.

    Wireless Networks (4) communications

    • - Wireless LAN, it is a system where every computer has a radio modem and antenna with which it can communicate with other systems.

    • - Wireless LANs are used in small offices, homes, older office building , conference rooms and other places.

    • - IEEE 802.11 (WiFi) is a standard for wireless LANs.

    Wireless Networks (5) communications

    • Wireless LAN

    Wireless Networks (6) communications

    • - Wireless WAN, it is similar to wireless LAN system, but with lower bandwidth and is used in a wide area systems.

    • - Three generations of Wireless WAN :

    • the first one was analog and for voice only

    • the second one was digital and for voice only

    • the third one is digital and for both voice and data

    • - IEEE 802.16 (WiMAX) is a standard for wireless WANs.

    Home Networks communications

    • - Every device in the home will be capable of communicating with every other device, and all of them will be accessible over the Internet.

    • - Examples of devices that are capable of being networked:

    • 1- Computers (PC, Notebook, PDA)

    • 2-Entertainment (TV, DVD, Camera...)

    • 3-Telecommunications (telephone, intercom...)

    • 4-Appliances (microwave, refrigerator, lights…)

    • 5- Telemetry (smoke alarm, thermostat, babycam…)

    Internetworks communications

    • Internetwork or internet is a collection of interconnected networks that provides universal service among heterogeneous communication networks.

    A heterogeneous network made of four WANs and two LANs

    The Internet (1) communications

    The Internet has revolutionized many aspects of our daily lives. It has affected the way we do business as well as the way we spend our leisure time. The Internet is a communication system that has brought a wealth of information to our fingertips and organized it for our use.

    History of Internet:

    Beginning in 1969. It was called ARPANET.

    • TCP/ IP is a protocol suite in the Internet.

    • The main Internet applications are:

    • E-mail, News, Remote Login, File transfer, World Wide Web (WWW)

    The Internet (2) communications

    Hierarchical organization of the Internet

    The Internet (3) communications

    - The Internet today is run by private companies, not the government.

    - The national Internet service providers are backbone networks created and maintained by specialized companies.

    - These backbone networks are connected by complex switching stations (normally run by a third party) called network access points (NAPs).

    - Local ISPs can be connected to a regional or national

    service provider.

    - Most end users are connected to the local ISPs.

    The Internet (4) communications

    Networking Standards (1) communications

    In this section, we define two widely used terms: protocols and standards. First, we define protocol, which is synonymous with rule. Then we discuss standards, which are agreed-upon rules.

    A protocol is a set of rules that governs data communication; the key elements of a protocol are syntax, semantics, and timing.

    - The term syntaxrefers to the structure or format of the data, meaning the order in which they are presented.

    - The word semanticsrefers to the meaning of each section of bits. How is a particular pattern to be interpreted, and what action is to be taken based on that interpretation?

    - The term timingrefers to two characteristics: when data should be sent and how fast they can be sent.

    Networking Standards (2) communications

    Standards are necessary to ensure that products from different manufacturers can work together as expected.

    • Advantages of standards

    • A standard assures that there will be a large market for a particular piece of equipment or software.

    • A standard allows products from multiple vendors to communicate.

    • Disadvantages of standards

    • A standard tends to freeze the technology.

    • There are multiple standards for the same thing.

    Networking Standards (3) communications

    Standards are developed through the cooperation of standards creation committees, forums, and government regulatory agencies.

    The ISO, ITU-T, ANSI, IEEE, and IETF are some of the organizations involved in standards creation.

    ISO - International Organization for Standardization

    ITU-T - International Telecommunication Union-Telecommunication Standards Sector

    ANSI - American National Standards Institute

    IEEE - Institute of Electrical and Electronics Engineers

    IETF - Internet Engineering Task Force

    - Forums are special-interest groups that quickly evaluate and standardize new technologies.

    - A Request for Comment (RFC) is an idea or concept that is a originator to an Internet standard.

    Networking Standards (4) communications

    The 802 working groups. The important ones are marked with *. The ones marked with  are hibernating. The one marked with † gave up.