Living in a Network Centric World IT 305

Living in a Network Centric World IT 305: Computer Networks – Chapter 1 © 2007 Cisco Systems, Inc. All rights reserved. Cisco Public 1

Course Info § Dr. Walid Khedr, Ph. D. –Email: khedrw@yahoo. com –Web: www. staff. zu. edu. eg/wkhedr –Department of Information Technology 2/46

Contents 1. Living in a Network-Centric World 2. Communicating over the Network 3. Application Layer Functionality and Protocols 4. OSI Transport Layer 5. OSI Network Layer 6. Addressing the Network IPv 4 7. Data Link Layer 8. OSI Physical Layer 9. Ethernet 10. Planning and Cabling Networks 11. Configuring and Testing Your Network 3/46

Introduction § 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. 11/46

Data Networks § Current data networks have evolved to carry voice, video streams, text, and graphics between many different types of devices 12/46

Communication § It can be in many forms and occurs in many environments § Before beginning to communicate with each other, we establish rules or agreements to govern the conversation. (Protocols) § Among the protocols that govern successful human communication are: – An identified sender and receiver – Agreed upon method of communicating (face-to-face, telephone, letter, photograph) – Common language and grammar – Speed and timing of delivery – Confirmation or acknowledgement requirements 13/46

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. 14/46

A Closer Look at Network Structure 15/46

Network Edge (End Devices) 16/46

The Network Core and Intermediary Devices 17/46

Network Core § Mesh of interconnected routers that connect the Internet’s end systems. § The fundamental question: how is data transferred through net? –Circuit Switching: dedicated circuit per call: telephone net –Packet-Switching: data sent thru net in discrete “chunks” 18/46

Network Core: Circuit Switching § A circuit-switched network is one that establishes a dedicated circuit (or channel) between nodes and terminals before the users may communicate. 19/46

Network Core: Circuit Switching § The four circuit switches are interconnected by four links. § Each of these links consists of n circuits, so that each link can support n simultaneous connections. 20/46

Multiplexing Circuit Switching § Frequency Spectrum: the difference between the highest and lowest frequencies available for network signals. § Frequency Division Multiplexing (FDM): The frequency spectrum of a link is shared among the connections established across the link. –The link dedicates a frequency band to each connection for the duration of the connection. § Time Division Multiplexing (TDM): Time is divided into frames of fixed duration and each frame is divided into a fixed number of time slots. –When the network establish a connection across a link, the network dedicates one time slot in every frame to the connection. 21/46

Multiplexing Circuit Switching Example: FDM 4 users frequency time TDM frequency time 22/46

Network Core: Packet Switching § Packet switching splits traffic data into packets that are routed over a shared network. § Packet-switching networks do not require a circuit to be established, and they allow many pairs of nodes to communicate over the same channel. 23/46

Multiplexing Packet Switching § STDM method analyzes statistics related to the typical workload of each input device (printer, fax, computer) and determines on-thefly how much time each device should be allocated for data transmission on the cable or line. 24/46

Four sources of packet delay transmission A B propagation nodal processing queueing dnodal = dproc + dqueue + dtrans + dprop dtrans: transmission delay: § L: packet length (bits) § R: link bandwidth (bps) § dtrans = L/R dtrans and dprop very different dprop: propagation delay: § d: length of physical link § s: propagation speed in medium (~2 x 108 m/sec) § dprop = d/s * Check out the Java applet for an interactive animation on trans vs. prop delay 25/46

Communicating Over Networks § All networks have four basic elements in common: – Rules or agreements to govern how the messages are sent, directed, received and interpreted – The messages or units of information that travel from one device to another – A means of interconnecting these devices - a medium that can transport the messages from one device to another – Devices on the network that exchange messages with each other 26/46

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 27/46

The Elements of a Network 28/46

The Elements of a Network § Network connections can be wired or wireless § Cable: UTP, Coaxial, Optic Fibers etc § Wireless: Bluetooth, laser, microwave etc 29/46

The Elements of a Network § Protocols are the rules that the networked devices use to communicate with each other. The industry standard in networking today is a set of protocols called TCP/IP (Transmission Control Protocol/Internet Protocol). § On the top of TCP/IP: 30/46

The Elements of a Network 31/46

The Elements of a Network 32/46

The Elements of a Network 33/46

The Elements of a Network 34/46

The Elements of a Network 35/46

The Elements of a Network 36/46

The Elements of a Network 37/46

Converged Networks § Traditional telephone, radio, television, and computer data networks each have their own individual versions of the four basic network elements. § In the past, every one of these services required a different technology to carry its particular communication signal. 38/46

Converged Networks § Technology advances are enabling us to consolidate these disparate networks onto one platform - a platform defined as a converged network. 39/46

Network Architecture Characteristics § There are 4 basic characteristics for networks in general to meet user expectations – Fault tolerance – Scalability – Quality of service (Qo. S) – Security 40/46

A Fault Tolerant Network Architecture § Fault tolerance is the ability for a network to recover from an error, such as the failure of a device or a link (a connection between two devices). § Fault tolerance is often achieved by having redundant devices or links, so that if one fails, messages can be re -routed around the failure through other devices or links. 41/46

A Fault Tolerant Network Architecture § Early network type: Circuit switched connectionoriented network 42/46

A Fault Tolerant Network Architecture § Packet switched networks, the data are broken up into many small packets that are sent independently through the network, each finding its own best route through the network. 43/46

A Scalable Network Architecture § Scalability means the ability to expand to meet new demands. § Most networks are designed in a hierarchical, layered approach so new devices and links can be added without interfering with existing networks. 44/46

Providing Quality of Service (Qo. S) § Quality of Service is a control mechanism that can provide different priority to different users or data flow or guarantee a certain level of performance to a data flow in accordance with request from the application program. 45/46

Providing Quality of Service (Qo. S) 46/46

Providing Quality of Service (Qo. S) 47/46

Providing Network Security § Unauthorized use of communication data might have serious consequences § 2 types of network security concerns that must be addressed to prevent serious consequences: – Network Infrastructure Security - physical securing of devices that provide network connectivity and preventing unauthorized access to the management software that resides on them – Content Security - protecting the information contained within the packets being transmitted over the network and the information stored on network attached devices 48/46

Providing Network Security § Security measures taken in a network should: – Prevent unauthorized disclosure or theft of information – Prevent unauthorized modification of information – Prevent Denial of Service § Means to achieve these goals include: – Ensuring confidentiality – Maintaining communication integrity – Ensuring availability 49/46

Summary 50/46

Reading § Chapter 1 - Living in a Network-Centric World § Packet Tracer Skills Integration Activity 1. 7. 1. 3 51/46

Next Lecture § Chapter 2: Communicating over the Network 52/46

Questions 53/46