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Transcript
NETWORKING 1) Communication methodology and protocols: rules and conventions to be followed for the communicating systems to “understand” each other WHY NEED NETWORKING? - 2) Topology and design: The layout of the network 3) Addressing: How systems locate each other on the network Access to remote information Person-to-person communication Cooperative work online Resource sharing 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. 1 2 NETWORK TOPOLOGY A NETWORK comprises of: 1- PROTOCOL SOFTWARE: - encodes and formats data - detects and corrects problems STAR 2- TRANSMISSION HARDWARE: - cables - satellites RING 3- SPECIAL-PURPOSE HARDWARE DEVICES: - Interconnect transmission media - Transmission control BUS 3 NETWORKS AND LAYERS 4 COMMUNICATION PROTOCOLS Networks are organized as series of LAYERS Communications protocols are rules established to govern the way data are transmitted in a computer network. Each layer is built on the one below it THE PHYSICAL LAYER – Defines the manner in which nodes of a network are connected to one another The purpose of each layer is to offer services to the other layer The number and function of layers may vary among different networks. 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 5 6 1 TYPES OF NETWORKS LAN ACCESS METHODS 1. Wide Area Network (WAN) 1) TOKEN ACCESS METHOD: an electronic “token” travels around a ring of nodes header specifies whether the token is “free” or carrying signals 2. Metropolitan Area Network (MAN) 3. Local area Network (LAN): connects nodes in close proximity a sender node captures a free token and changes it to “busy” LOCAL AREA NETWORKS 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 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) operates much like conversation between “polite people” !!! Can transmit up to 1 GB per second 7 8 LAN SOFTWARE SERVERS ON LAN NETWORK OPERATING SYSTEMS A server is a component that can be shared by the users in LAN 1) File server: dedicated PC with high-capacity hard disk for storage 2) Print server: usually in the same PC as the file server; handles print jobs for LAN 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 3) Communications server: controls one or more modems in order to establish communications links external to LAN General purpose software EX: MS Office 2000 Workgroup applications EX: email; electronic conferencing 9 VIRTUAL LOCAL AREA NETWORKS 10 VLANs allow highly flexible, efficient network segmentation, enabling users and resources to be grouped logically, without regard to physical location. 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. 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. All of these changes add pressure to networks already straining under the requirements of more users, more powerful workstations and more demanding applications. 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. 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. 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. 11 12 2 A typical VPN might have a main LAN at the corporate headquarters of a company, other LANs at remote offices or facilities and individual users connecting from out in the field. 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. 13 3