1.1 Chapter 1 Introduction

HISTORY AND BACKGROUND  Networks used to be proprietary (software & hardware)  Technologies (components) were designed for a specific purpose in mind  Certain applications for certain type of networks  Different disjointed computer networks  Multiple terminals on desk for different uses  Application or network upgrade

HISTORY AND BACKGROUND  Big push to make networks “open”  “Open” means “non-proprietary”  All of the various vendors could design and manufacture network components that were compatible and interchangeable  Was it a good thing? Why?

HISTORY AND BACKGROUND  Benefits:  drives up computer usage  drives up software application purchases  drives up network usage  more efficiency for businesses, government, etc..  The idea behind having “open system”  have the ability to interconnect many different networks into a single network  Internetworking  Provides interconnection, protocols  Hides details of the underlying hardware

DATA COMMUNICATIONS  Where are the data communications?  Why data communications?  Telecommunication: communication at a distance.  Data: information presented in whatever form is agreed upon by the parties creating and using the data.  Data communications: the exchange of data between two devices via some form of transmission medium such as a wire cable.

1.6  What do we need? Hardware Software  Four fundamental characteristics: 1. Delivery: correct destination 2. Accuracy: correct data 3. Timeliness: fast enough 4. Jitter: uneven delay  Topics covered: 1. Components 2. Data representation 3. Data flow 1-1 DATA COMMUNICATIONS

1.7 Figure 1.1 Five components of data communication Components

1.8 Data Representation  Text , articles, etc Coding (Unicode, ASCII)  Numbers Direct conversion  Images Pixels, resolution, gray scale, RGB, YCM  Audio Continuous, signal conversion  Video Movie, continuous/discrete

1.9 Figure 1.2 Data flow (simplex, half-duplex, and full-duplex) Data Flow

NETWORKS A network is a set of devices (often referred to as nodes) connected by communication links. A node can be a computer, printer, or any other device capable of sending and/or receiving data generated by other nodes on the network. Network Criteria Physical Structures Network Models Categories of Networks Interconnection of Networks: Internetwork Topics discussed in this section:

1.11  Network criteria 1. Performance Transit time, response time. Throughput, delay. 2. Reliability Failure frequency, recovery time. 3. Security Protection. 1-2 NETWORKS

1.12 How to classify networks? By Scale Personal area network (PAN) Local Area Network (LAN) Campus Area Network (CAN) Metropolitan area network (MAN) Wide area network (WAN) By Connection Method Optical fiber Ethernet Wireless LAN HomePNA Power line communication By Network Topology Bus network Star network Ring network Mesh network

1.13 Figure 1.3 Types of connections: point-to-point and multipoint Type of Connections

1.14 Figure 1.4 Categories of physical topology Physical topology physical topology: design or layout of the network

1.15 Mesh Figure 1.5 A fully connected mesh topology (five devices) Example: telephone regional offices Advantages: no traffic problems Robust. No link failure no effect on others. Privacy security Easy to detect the abnormal situation. Disadvantages: Amount of cables, i/o ports Efficiency and effectiveness Space Cost

1.16 Star Figure 1.6 A star topology connecting four stations Less expensive. One link and I/o port connecting to the hub. No direct traffic between two devices. Advantages: Easy to install Less cables Maintain: add, move, delete Robustness Disadvantages; Hub is too important The hub represents a single source of failure

1.17 Bus Figure 1.7 A bus topology connecting three stations Multipoint Advantages: Easy to install Less cables Disadvantages: Hard to detect fault isolation. Bus cable is too important

1.18 Ring Figure 1.8 A ring topology connecting six stations Point to point with 2 devices on both sides Advantages: Easy to install Maintain: add move delete Fault isolation Disadvantages: Unidirectional traffic

1.19 Hybrid Figure 1.9 A hybrid topology: a star backbone with three bus networks

1.20 Network models  Local area network (LAN)  Wide area network (WAN)  Metropolitan area networks

1.21 Figure 1.10 An isolated LAN connecting 12 computers to a hub in a closet In a building, office, or school Share hardware, software and data Client-server, hub LAN normally uses only one type of transmission medium Bus, ring and star

1.22 Figure 1.11 WANs: a switched WAN and a point-to-point WAN

1.23 Figure 1.12 A heterogeneous network made of four WANs and two LANs

THE INTERNET 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. A Brief History The Internet Today (ISPs) Topics discussed in this section:

THE INTERNET  History of the Internet 1. ARPA ( Advanced research projects agency) 2. ARPANET 3. Transmission control Protocol (TCP) 4. Internetworking Protocol (IP)  Internet today  Internet service providers (ISPs)

PROTOCOLS AND STANDARDS  Protocols (rules) 1. Why do we need protocols? 2. Key elements of protocols a) Syntax: structure or format of the data b) Semantics : meaning of each section of bits c) Timing: when sent and how fast  Standards 1. De facto vs. De jure 2. Organizations 3. Internet standards (Internet draft & RFC)

PROTOCOLS AND STANDARDS Network Standards Organizations NNational Standards Organizations (Generally responsible for standards within a nation and usually participate in that nation’s international activity) American National Standards Institute (ANSI) British Standards Institute (BSI) French Association for Normalization (AFNOR) German Institute for Normalization (DIN) RRegional Standards Organizations ( Restrict their activity to a specific geographical region but generally influence standards outside their regions) Committee of European Posts and Telegraph (CEPT) European Committee for Standardization (CEN) European Computer Manufacturers’ Association (ECMA) IInternational Standards Organizations (Promote standards for worldwide use) International Standards Organization (ISO) International Telecommunications Union (ITU)consists of ITU-T, which is responsible for communications, interfaces, and other standards related to telecommunications; and ITU-R, which is responsible for allocating frequency bands in the electromagnetic spectrum for telecommunications, and for making recommendations relating to radio communications. (Note: ITU-T is the former CCITTConsultative Committee for International Telephony and Telegraphy.) IIndustry, Trade, and Professional Standards Organizations ( Restrict their activity to member interest areas but generally influence other areas) Electronic Industries Association (EIA) Telecommunications Industries Association (TIA) Institute for Electrical and Electronics Engineers (IEEE) Internet Engineering Task Force (IETF)

PROTOCOLS AND STANDARDS The Network Standardization Process PPlanning Phase Proposals submitted by vendors or organizations are examined. A determination is made whether there is a need to establish a standard. If a need is found, the development of a project is authorized and assigned to a technical committee. DDevelopment Phase Committee prepares a working paper describing the scope of the proposed work. Liaisons with other standards groups are established. A draft proposal of the standard is produced. Draft is voted on and all negative comments are addressed. Draft is submitted to parent organization for discussion and approval. AApproval Phase All members of the organization vote on draft. Draft is made available to the public for review. Draft is ultimately approved as a standard. PPublication Phase The new standard is published.

1.29 Summary  Data communications  Networks  The internet  Protocols and standards