Living in a Network Centric World IT305: Computer Networks – Chapter 1

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

Contents Living in a Network-Centric World Communicating over the Network Application Layer Functionality and Protocols OSI Transport Layer OSI Network Layer Addressing the Network IPv4 Data Link Layer OSI Physical Layer Ethernet Planning and Cabling Networks Configuring and Testing Your Network

Living in a Network Centric World This chapter provides the introduction to the course by showing how networking pervades everyday life.

Objectives Describe how networks impact our daily lives. Identify the key components of any data network. Identify converged networks. Describe the characteristics of network architectures: fault tolerance, scalability, quality of service and security.

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.

How Networks Impact Daily Life Early communication relies on face-to-face conversations. Nowadays, telephone, fax, interconnection of data networks etc. Early data networks were limited to exchanging character-based information between connected computer systems. Current networks have evolved to carry voice, video streams, text, and graphics between many different types of devices

Networks Supporting the Way We Learn Courses delivered using network or Internet resources are often called online learning experiences, or e-learning. Ex: Cisco Netacad Online courseware and delivery offer many benefits to businesses. Among the benefits are: Current and accurate training materials. Availability of training to a wide audience. Cost reduction

Networks Supporting the Way We Works Business networks evolved to enable the transmission of many different types of information services, including e-mail, video, messaging, and telephony

Networks Supporting the Way We Play The widespread adoption of the Internet by the entertainment and travel industries enhances the ability to enjoy and share many forms of entertainment, regardless of location.

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.

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

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

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.

A Closer Look at Network Structure

Network Edge (End Devices)

The Network Core and Intermediary Devices

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”

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.

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.

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.

Multiplexing Circuit Switching 4 users Example: FDM frequency time TDM frequency time

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.

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

Four sources of packet delay transmission A propagation B nodal processing queueing dnodal = dproc + dqueue + dtrans + dprop dtrans: transmission delay: L: packet length (bits) R: link bandwidth (bps) dtrans = L/R dprop: propagation delay: d: length of physical link s: propagation speed in medium (~2x108 m/sec) dprop = d/s dtrans and dprop very different * Check out the Java applet for an interactive animation on trans vs. prop delay 25

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

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

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

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:

The Elements of a Network

The Elements of a Network

The Elements of a Network

The Elements of a Network

The Elements of a Network

The Elements of a Network

The Elements of a Network

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.

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

Network Architecture Characteristics There are 4 basic characteristics for networks in general to meet user expectations Fault tolerance Scalability Quality of service (QoS) Security

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.

A Fault Tolerant Network Architecture Early network type: Circuit switched connection-oriented network

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.

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.

Providing Quality of Service (QoS) 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.

Providing Quality of Service (QoS)

Providing Quality of Service (QoS)

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

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

Summary

Reading Chapter 1 - Living in a Network-Centric World Packet Tracer Skills Integration Activity 1.7.1.3

Next Lecture Chapter 2: Communicating over the Network

Questions