Lecture 0: Course Overview

Lecturer Details Dr. Walid Khedr Web: Department of Information Technology

Course Info Course Name: Computer Networks Course Number: IT305 Course Group: Office Hours: 11 am – 12 pm, Thursday Tools: Cisco Packet Tracer 6 simulator, Wireshark 1.1 protocol analyzer Prerequisite: CS260 (Operating Systems) Course Materials: Text Book Lecture Notes

Grading Policy Your final grade will be calculated as follows: Term Work: Assignments / Homework / Quizzes / Midterm exam (20 points) Lab Exams (20 points) Oral Exam, Attendance and Participation (20 points) How to participate? Ask questions Answer questions Make comments Total is 150 points

Grading Rules 1. Final exam is cancelled if attendance < %75 2. If final exam grade is less than %30, your final grade will be just your final exam grade.

What is Computer Network A computer network or data network is a telecommunications network which allows computers to exchange data. In computer networks, networked computing devices exchange data with each other along network links (data connections). The connections between nodes are established using either cable media or wireless media. The best-known computer network is the Internet.

Why computer networks is important Among all of the essentials for human existence is the need to interact with others. Communication is almost as important to us as our reliance on air, water, food. The creation and interconnection of robust Data Networks is having a profound effect.

Why computer networks is important Current data networks have evolved to carry voice, video streams, text, and graphics between many different types of devices

Communication Before beginning to communicate with each other, we establish rules or agreements to govern the conversation. An identified sender and receiver Agreed upon method of communicating (face-to-face, telephone, letter) Common language and grammar

The Elements of Digital Communication Message sources devices that need to send a message to devices. A channel, consists of the media that provides the pathway over which the message can travel from source to destination. Messages can be sent across a network by first converting them into binary digits, or bits. These bits are then encoded into a signal that can be transmitted over the appropriate medium.

The Elements of Digital Communication

The Elements of a Network Devices These are used to communicate with one another Medium This is how the devices are connected together Messages Information that travels over the medium Rules Governs how messages flow across network

The Elements of a Network Network Hardware Network Software

Network Hardware Network edge: hosts: clients and servers servers often in data centers Network core: interconnected routers switches

Network Media Communication across a network is carried on a medium 3 types of Media: Metallic wires within cables Glass or plastic fibers (fiber optic cable) Wireless transmission

Network Hardware Networks can be classified by their scale: ScaleType VicinityPAN (Personal Area Network) » BuildingLAN (Local Area Network) » CityMAN (Metropolitan Area Network) » CountryWAN (Wide Area Network) » PlanetThe Internet (network of all networks)

Personal Area Network Connect devices over the range of a person Example of a Bluetooth (wireless) PAN:

Local Area Networks Connect devices in a home or office building Called enterprise network in a company Wireless LAN with Wired LAN with switched Ethernet

Metropolitan Area Networks Connect devices over a metropolitan area Example MAN based on cable TV:

Connect devices over a country Example WAN connecting three branch offices: Wide Area Networks (1)

Wide Area Networks (2) An ISP (Internet Service Provider) network is also a WAN. Customers buy connectivity from the ISP to use it.

Network Software Protocol layers » Service primitives » Relationship of services to protocols »

Rules that Govern Communications (Protocols) Communication in networks is governed by pre-defined rules called protocols. These protocols are implemented in software and hardware that is loaded on each host and network device Networking protocols suites describe processes such as: The format or structure of the message How and when error and system messages are passed between devices The setup and termination of data transfer sessions

Protocol Layers (1) Protocol layering is the main structuring method used to divide up network functionality. Each protocol instance talks virtually to its peer Each layer communicates only by using the one below Lower layer services are accessed by an interface At bottom, messages are carried by the medium

Protocol Layers (2) Example: the philosopher-translator-secretary architecture Each protocol at different layers serves a different purpose

Protocol Layers (3) Each lower layer adds its own header (with control inform- ation) to the message to transmit and removes it on receive

Why Using Layer Models To visualize the interaction between various protocols, it is common to use a layered model. Benefits of doing so: Helps break down network function. Create standard for equipment manufacturing. Allows vendors to focus in specialized areas of the network

Service Primitives (1) A service is provided to the layer above as primitives Hypothetical example of service primitives that may provide a reliable byte stream (connection-oriented) service:

Service Primitives (2) Hypothetical example of how these primitives may be used for a client-server interaction Client Server LISTEN (0) ACCEPT RECEIVE SEND (4) DISCONNECT (6) CONNECT (1) SEND RECEIVE DISCONNECT (5) Connect request Accept response Request for data Reply Disconnect (2) (3)

Relationship of Services to Protocols Recap: A layer provides a service to the one above[vertical] A layer talks to its peer using a protocol [horizontal]

Reference Models Reference models describe the layers in a network architecture OSI reference model » TCP/IP reference model » Model used for this text »

OSI Reference Model A principled, international standard, seven layer model to connect different systems – Provides functions needed by users – Converts different representations – Manages task dialogs – Provides end-to-end delivery – Sends packets over multiple links – Sends frames of information – Sends bits as signals

TCP/IP Reference Model A four layer model derived from experimentation; omits some OSI layers and uses the IP as the network layer. IP is the “narrow waist” of the Internet Protocols are shown in their respective layers

Model Used in this Book It is based on the TCP/IP model but we call out the physical layer and look beyond Internet protocols.

Protocol Data Units (PDU) and Encapsulation

The Process of Sending and Receiving (F )

Example Networks The Internet » 3G mobile phone networks » Wireless LANs » RFID and sensor networks »

Contents 1. Introduction presents the basics of communication and how networks have changed our lives. 2. Application Layer Functionality and Protocols introduces you to the top network model layer, the Application layer. 3. Transport Layer introduces you to the Transport Layer 4. Network Layer introduces the OSI Network layer.

CCNA1 : Network Fundamentals Contents 6. Data Link Layer discusses the services provided by Data Link layer 7. Physical Layer introduces the Physical layer

Offline Course Materials

Packet Tracer Simulation Tool A powerful network simulation program developed by Cisco that allows students to experiment with network behavior.

Wireshark 1.10 Wireshark is the world's foremost network protocol analyzer, and is the standard across many industries and educational institutions.

Reading Chapter 1 Download and study Packet Tracer 5.3

Next Lecture Chapter 1