WHY NEED NETWORKING? • Access to remote information • Person-to-person communication • Cooperative work online • Resource sharing
NETWORKING • 1) Communication methodology and protocols: • rules and conventions to be followedfor the communicating systems to “understand” each other • Topology and design: • The layout of the network • 3) Addressing: • How systems locate each other on the network • 4) Routing: • How the data path is established • 5) Reliability: • Making sure the received data are exactly what have been sent. • 6) Interoperability: • The degree to which products of different companies can network with each other • 7) Security: • Protection of all components of a network • 8) Standards.
A NETWORK comprises of: 1- PROTOCOL SOFTWARE: - encodes and formats data - detects and corrects problems 2- TRANSMISSION HARDWARE: - cables - satellites 3- SPECIAL-PURPOSE HARDWARE DEVICES: - Interconnect transmission media - Transmission control
POINT-TO-POINT COMPUTER TOPOLOGIES STAR RING BUS
NETWORKS AND LAYERS Networks are organized as series of LAYERS Each layer is built on the one below it The purpose of each layer is to offer services to the other layer The number and function of layers may vary among different networks.
COMMUNICATIONS PROTOCOL Communications protocols are rules established to govern the way data are transmitted in a computer network. THE PHYSICAL LAYER – Defines the manner in which nodes of a network are connected to one another SUBSEQUENT LAYERS – describe how messages are packaged for transmission - how messages are routed through the network - security procedures - the manner in which messages are displayed Example known: TCP/IP (Transmission control protocol/ Internet protocol) Application Transport Network 5 Layers of TCP/IP Data Link Physical
TYPES OF NETWORKS • Wide Area Network (WAN) • Metropolitan Area Network (MAN) • Local area Network (LAN): • connects nodes in close proximity LOCAL AREA NETWORKS • Valuable resources can be shared by all computers networked in LAN: • Applications software • Links to other LAN servers • Communication capabilities (lines or modem) • I/O devices (printers, scanners etc) • Storage devices • Add-on boards (video capture board etc)
LAN ACCESS METHODS 1) TOKEN ACCESS METHOD: an electronic “token” travels around a ring of nodes header specifies whether the token is “free” or carrying signals a sender node captures a free token and changes it to “busy” 2) ETHERNET: Nodes must contend for the right to send message. Node requests network service from the network software The request might return a “busy” signal or a “line free” signal operates much like conversation between “polite people” !!! Can transmit up to 1 GB per second
SERVERS ON LAN • A server is a component that can be shared by the users in LAN • File server: dedicated PC with high-capacity hard disk for storage • Print server: usually in the same PC as the file server; handles print jobs for LAN • Communications server: controls one or more modems in order to establish communications links external to LAN
LAN SOFTWARE NETWORK OPERATING SYSTEMS Is actually several pieces of software Certain requests within a LAN are redirected to the appropriate server EX: Windows NT Server APPLICATIONS SOFTWARE FOR LANs General purpose software EX: MS Office 2000 Workgroup applications EX: email; electronic conferencing
VIRTUAL LOCAL AREA NETWORKS Nodes are not physically connected by the same medium. Few people experience the rapid changes of today's business environment more than Information Technology (IT) managers. Employees move, business operations are restructured and new technologies emerge. All of these changes add pressure to networks already straining under the requirements of more users, more powerful workstations and more demanding applications. Virtual LANs (VLANs) can help IT managers adapt to these changes more easily and effectively, while increasing overall network performance. By offering a highly flexible means of segmenting a corporate network, VLANs reduce the performance bottlenecks that occur when traditional backbone routers can't meet the demands of fast, switched networks.
VLANs allow highly flexible, efficient network segmentation, enabling users and resources to be grouped logically, without regard to physical location. A VLAN is a group of PCs, servers and other network resources that behave as if they were connected to a single, network segment — even though they may not be. For example, all marketing personnel may be spread throughout a building. Yet if they are all assigned to a single VLAN, they can share resources and bandwidth as if they were connected to the same segment. The resources of other departments can be invisible to the marketing VLAN members, accessible to all, or accessible only to specified individuals, at the IT manager's discretion.
Basically, a VPN is a private network that uses a public network (usually the Internet) to connect remote sites or users together. Instead of using a dedicated, real-world connection such as leased line, a VPN uses "virtual" connections routed through the Internet from the company's private network to the remote site or employee.