Introduction and Overview Chapter 1 Introduction and Overview © Bobby Hoggard, Department of Computer Science, East Carolina University These slides may not be used or duplicated without permission

Creation of the Internet 1980: Birth of the Internet Started as a small research project with a few sites a few universities and the US Dept. of Defense Two major goals of the project: Create communication between different types of systems Create a system to allow parts of it to communicate, even when other parts fail

Why is Networking Complex? Must have ways to manage network traffic Must have ways to manage interference from outside sources Being able to recognize different parts Many technologies exists Many ways to combine and connect the parts Differing communication means (some standards incompatible with others) Lack of consistency Technical terms are often confused with names of products Misuse of terms (ex: server)

5 Key Aspects of Networking Network Applications and Programming Data Communications Packet Switching and Networking Technologies Internetworking with TCP/IP Additional Concepts and Technologies

Network Apps & Programming Network Application: application software that provides network services Applications include: email, file transfer, web browsing, voice telephone calls, distributed databases, teleconferencing An application program on one device communicates with an application program on another device Email Application Email Data Email Application Email Data

Network Apps & Programming Applications offer a specific service and interface, but share a single communication network Programmers only need to learn the network interface and some basic functions The same functions are used in all networking applications Application programs can be written without understanding the hardware/software that transfers the data however… Understanding the underlying network can help you write applications that are more reliable, correct and efficient

Data Communications The study of low-level technologies used to send data over a physical network How to use physical phenomena to transfer information Three major communication methods: Wires (uses electricity) Fiber optics (uses light) Wireless (uses radio waves)

Packet Switching Breaking data into smaller units for easier, and more reliable transmission, and more efficient use of the network Packet switching evolved from traditional telephone switching circuits Understanding how they work is vital to understanding how packet switching helps

Traditional Switching Telephones have a dedicated connection line to the telephone company central office Central offices are connected to each other through multiple connections and to bigger offices

Traditional Switching Each telephone co. office finds the best available circuit A dedicated connection is made between sender and receiver Once those connections have been made, they can’t be used to make other connections until this communication has finished

Packet Switching Data is divided into small packets and sent individually Packets can take various routes to get to the destination, and may arrive out of order H E L L O

Packet Switching Connections are not held for long periods of time As such, this frees the circuits so other devices can use them, making more efficient use of the circuits H E L L O J A V A

Internetworking with TCP/IP A set of protocols that govern communication across the Internet Adapts as it travels across different types of network Creates a “virtual” networking system Defines network independent packets and addressing Allows new technologies to be incorporated, without requiring the replacement of old technologies

Public vs. Private Networks The Internet consists of both Public networks A service available to subscribers Anyone paying for the service can have access A service provider provides access Private networks Controlled by one group of people Network use is restricted Private networks can include circuits leased from a public provider

Types of Private Networks Consumer Could be as simple as connecting a printer to a computer Small Office / Small Home (SOHO) Involves several devices usually confined to one small area/room Small-to-Medium Size Business (SMB) Several networks connected together throughout a building Large Enterprise Several buildings connected (each being a small/med business) Buildings can be geographically separated

Interoperability & Standards The ability of two devices to communicate without misunderstanding Standards (protocols) specify details of how to communicate How electrical signals are used to represent data How to initiate communication Format of the message What to do when an error occurs

Protocol Suites and Layers Protocols must be developed to ensure that the system is complete and works efficiently Protocols are designed in sets called families or suites Each protocol in a suite handles one aspect of communication

TCP/IP Protocol Suite Application Transport Internet Network Interface Layer 5 Application Layer 4 Transport Layer 3 Internet Layer 2 Network Interface Layer 1 Physical “All Time Is Nearly Passing”

TCP/IP Protocol Suite Data originates at the application level because one application wants to communicate with another Data is passed down through the layers Each layer adds a header to help the opposing layer identify and process the data Once data reaches the bottom, it is physically transmitted to the receiving device The received packet is passed back up through the layers, with each layer stripping off it’s header

Goal: Get the data from the sender application to the receiver application Transport Internet Network Interface Physical Application Transport Internet Network Interface Physical data data

Goal: Get the data from the sender application to the receiver application Transport Internet Network Interface Physical Application Transport Internet Network Interface Physical data data

Application Transport Internet Network Interface Physical Format of the message How applications interact with each other Transport How fast can the receiver receive data How to avoid network congestion Make sure packets arrive in correct order Internet Internet addressing structure Format of Internet packets Dividing large packets into smaller ones Error reporting Network Interface Hardware addressing Packet size for the specific physical network Protocols for the specific physical network Physical Electrical properties, Radio frequencies, etc. Signaling

7-Layer OSI Model Application Presentation Session Transport Network Data Link Layer 1 Physical “All People Seem To Need Data Processing”