1 Introduction and Internet Applications Chapter 1 & 2 Introduction and Overview updated: 8/26/142 Networking Seems Complex • The networking subject seems complex, because – Different technologies exist and each is adopted for a particular application • Each technology has features that distinguish it from the others – Companies create commercial network products and services • often by using technologies in new unconventional ways – Different technologies must be combined and interconnected in many ways • Computer networks can be especially confusing to a beginner because – No single underlying theory exists that explains the relationship among all parts – Multiple organizations have created computer networks standards – Various organizations have attempted to define conceptual models – The set of technologies is diverse and changes rapidly • The lack of consistency in the field has produced another challenge for beginners: – Multiple groups each attempt to create their own terminology – Computer networking jargon contains terms that are often abbreviated, misused, or associated with products1. Network Applications and Network Programming 2. Data Communications 3. Switching Networks (Packet Switching and Circuit Switching) Technologies 4. Internetworking with TCP/IP 5. Additional Networking Concepts and Technologies These are the course objectives! 3 The Five Key Aspects of NetworkingNetwork Applications and Network Programming • Network services are provided by an application software – an application on one computer communicates across a network with an application program running on another computer • Network applications span a wide range, such as: – email – file transfer – web browsing – voice telephone calls (VoIP) – distributed databases – audio/video teleconferencing • Each application offers a specific service to the user using a specific user interface – But all applications can communicate over a single, shared network • To write the application software one must learn about one interface to network 4 Network HW and Software are Separate from One another!Examples of Network Services voice mail Twitter e-mail instant messaging chat rooms newsgroups telephony videoconferencing collaboration groupware global positioning system (GPS)Computing, Datacom, Telecom Ref: Agilent TechnologiesData Communications: • Refers to the study of low-level mechanisms and technologies used to send information across a physical communication medium • Provides a foundation of concepts on which the rest of networking is built • Focuses on ways to use physical phenomena to transfer information – impacts the design of many protocol layers 7 Data Communication System Model Transmission System (media)Packet Switching and Networking Technologies • In 1960s, the packet switching concept revolutionized data communications • Early communication networks had evolved from telegraph and telephone systems – A physical pair of wires between two parties to form a dedicated circuit • Packet switching changed networking in a fundamental way – Packet switching divides data into small blocks, called packets • It includes an identification of the intended recipient in each packet • Devices throughout the network each have information about how to reach each possible destination – Packet switching allows multiple users to share a network – It provided the basis for the modern Internet 8Packet Switching and Networking Technologies - Basic Characteristics • Many designs for packet switching are possible – Depending on speed, distance, and economic cost • But there is a need for answers to basic questions: – How should a destination be identified? – How can a sender find the identification of a destination? – How large should a packet be? – How can a network recognize the end and beginning of one packet? – If a network is shared, then how can they coordinate to insure that each receives a fair opportunity to send? – How can network technologies be designed to meet various requirements for speed, distance, and economic cost? – How can packet switching be interfaced to other networks (e.g., wireless)? 9Internetworking with TCP/IP • In the 1970s, another revolution in computer networks arose: Internet – connecting multiple networks together • In 1973, Vinton Cerf and Robert Kahn – Proposed that a single packet switching technology cannot meets everyone’s needs – They explored interconnecting many packet switching technologies into a functioning whole – They proposed a set of standards to be developed for such an interconnection – The resulting standards became known as the TCP/IP Internet Protocol Suite (usually abbreviated TCP/IP) • TCP / IP takes a virtualization approach – Defining a network-independent packet and identification scheme 10 The success of TCP/IP lies in its tolerance of heterogeneity11 Public and Private Parts of the Internet • From ownership point of view, we can categorize networks – Public Networks – Private Networks • A public network is run as a service that is available to subscribers (Toll ways!) – Any individual or corporation who pays the subscription fee can use – A company that offers service is known as a service provider (ISP) – Public refers to the general availability of service, not to the data being transferred • A private network is controlled by one particular group – network use is restricted to one group – a private network can include circuits leased from a provider Read about Net Neutrality!ISP and its Services 12 ISP School ISP HomesPrivate Network • Network vendors generally divide private networks into four categories based on the size: – Consumer – Small Office / Home Office (SOHO) – Small-to-Medium Business (SMB) – Large Enterprise 13 Project Topic14 Networks, Interoperability, and Standards • All entities (e.g., TX & RX) in a network must agree on how information will be represented and communicated – Signal, hand shaking, format, etc. • An important issue is interoperability – it refers to the ability of two entities