1-1 Introduction to Computer Networks and Data Communications

1-2 Data Communications and Computer Networks The Language of Computer Networks Computer network - an interconnection of computers and computing equipment using either wires or radio waves over small or large geographic distances Local area network - networks that are small in geographic size spanning a room, building, or campus Metropolitan area network - networks that serve an area of 3 to 30 miles - approximately the area of a typical city

1-3 Data Communications and Computer Networks The Language of Computer Networks Wide area network - a large network that encompasses parts of states, multiple states, countries, and the world Personal area network – a network of a few meters, between wireless devices such as PDAs, laptops, and similar devices. Voice network - a network that transmits telephone signals Data network - a network that transmits computer data

1-4 Data Communications and Computer Networks The Language of Computer Networks Data communications - the transfer of digital or analog data using digital or analog signals Telecommunications - the study of telephones and the systems that transmit telephone signals Network management - the design, installation, and support of a network and its hardware and software

1-5 Data Communications and Computer Networks The Big Picture of Networks Networks are composed of many devices, including: workstations (computers and telephones) servers network hubs and switches (bridges) routers (LAN-WAN and WAN-WAN) telephone switching gear

1-6 Data Communications and Computer Networks

1-7 Data Communications and Computer Networks Network Architectures A reference model that describes the layers of hardware and software necessary to transmit data between two points or for multiple devices / applications to interoperate Reference models are necessary to increase the likelihood that different components from different manufacturers will converse There are two architectures that are required learning: The OSI Model, and the TCP/IP protocol suite

1-8 Data Communications and Computer Networks Network Architectures The OSI Model’s seven layers

1-9 Data Communications and Computer Networks Network Architectures Application layer - where the application using the network resides. Common network applications include remote login, file transfer, , and web page browsing. Presentation layer - performs a series of miscellaneous functions necessary for presenting the data package properly to the sender or receiver

1-10 Data Communications and Computer Networks Network Architectures Session layer - responsible for establishing sessions between users. Transport layer - provides an end-to-end error-free network connection. Makes sure the data arrives at the destination exactly as it left the source. Network layer - responsible for creating, maintaining and ending network connections. Transfers a data packet from node to node within the network.

1-11 Data Communications and Computer Networks Network Architectures Data link layer - responsible for taking the data and transforming it into a frame with header, control and address information, and error detection code. Physical layer - handles the transmission of bits over a communications channel. Includes voltage levels, connectors, media choice, modulation techniques.

1-12 Data Communications and Computer Networks

1-13 Data Communications and Computer Networks Network Architectures The TCP/IP protocol suite

1-14 Data Communications and Computer Networks Network Architectures Application layer - equivalent to the OSI’s presentation and application layers Transport layer - performs same function as OSI transport layer Network (Internet or internetwork) layer - roughly equivalent to the OSI’s network layer Network access (data link/physical) layer - equivalent to the OSI’s physical and data link layers

1-15 Data Communications and Computer Networks Network Architectures Logical and physical connections - A logical connection is one that exists only in the software, while a physical connection is one that exists in the hardware. Note that in a network architecture, only the lowest layer contains a physical connection, while all higher layers contain logical connections.

1-16 Data Communications and Computer Networks Network Architectures Logical and physical connections

1-17 Data Communications and Computer Networks Network Architectures Example of data flow through layers

1-18 Data Communications and Computer Networks Network Connections in Action

1-19 Data Communications and Computer Networks The TCP/IP Protocol Suite in Action Note the flow of data from user to web browser and back At each layer, information is either added or removed, depending on whether the data is leaving or arriving at a workstation The adding of information over pre-existing information is termed encapsulation

1-20 Data Communications and Computer Networks Chapter 1

1-21 Data Communications and Computer Networks Review Questions A user is sitting at work using a laptop computer with a wireless connection into the corporate LAN. The user is sending . What basic connections are being used? List the seven OSI layers with a quick description of each layer. List the TCP/IP layers with a quick description of each layer. What is the difference between a logical and a physical interface / connection?