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Introduction to Computer Systems Networking Fundamentals Dr. E.C. Kulasekere University of Moratuwa IESL – Information Technology Part I Network Technology Connectivity to other computers. Expands the capability of a PC. Satisfies sharing of resources. Expands human communication. Increases security threats. Concurrency effects. Introduction to Computer Systems 2 Dr. E.C. Kulasekere IESL – Information Technology Part I Modem for Home Connectivity Most common mode of HAN connection. Some issues related to modems. Speed: maximum speed 56K Needs dial up for connection. Telephone line usage while on modem. Price is not to high compared to other services. Needs reconnection when the link dies. Introduction to Computer Systems 3 Dr. E.C. Kulasekere IESL – Information Technology Part I Other Methods of Connectivity Cable modem. DSL Wireless Satellite-based services. ISDN Leased Lines All of these are categorized as broadband. Data rates exceeding 128kbps. Introduction to Computer Systems 4 Dr. E.C. Kulasekere IESL – Information Technology Part I Home Connection Infrastructure Modem/NIC/DSL Modem interface. ISP/POTS. Switch/Router. Internet/PSTN Then the sequence is inverted. The links maybe digital or analog. Introduction to Computer Systems 5 Dr. E.C. Kulasekere IESL – Information Technology Part I Cable Modems (Using CATV Services) This is a piggyback on a cable TV service. Faster than ISDN (128 Kbps). Uses a crossover cable with RJ45 connector. The fiber-coax cable configuration (fig) Not found in Sri Lanka. Introduction to Computer Systems 6 Dr. E.C. Kulasekere IESL – Information Technology Part I Digital Subscriber Line (DSL) Uses existing POTS to provide a high speed connection. Low cost alternative to ISDN. The connection sharing is more efficient than cable modems. (fig19.2) Common types ADSL and SDSL. Advantageous and disadvantages of DSL/SDSL Low-pass filters are used to isolate the TP signal from DSL signal. ..\webDocs\DSL.htm Introduction to Computer Systems 7 Dr. E.C. Kulasekere IESL – Information Technology Part I Wireless Broadband Used for home users that are out of reach from POTS. Should not be confused with wireless internet services provided for PDAs and mobile phones. Uses microwaves (fig 19.3) Uses routers and modems (fig 19.4) Introduction to Computer Systems 8 Dr. E.C. Kulasekere IESL – Information Technology Part I Integrated Services Digital network (ISDN) Uses digital signals on the POTS. Mostly designed for leased lines. Configuration allows for multiple type of terminations (fig 19.7) Uses a terminal adapter (TA) for termination and it is not a modem. Costs more than DSL. Introduction to Computer Systems 9 Dr. E.C. Kulasekere IESL – Information Technology Part I Leased Lines For uses with high bandwidth requirements such as businesses. Leased line is 24 hour permanent connection which can only be changed by the TP company (what about DSL?) T1 line 1.5Mbps, T3 line 45Mbps. The BW is split among users by the ISP. Used for connection that has high utilization. Introduction to Computer Systems 10 Dr. E.C. Kulasekere IESL – Information Technology Part I Sharing Internet Connections One connection may not be enough for small-office and home (SOHO) systems. Windows 98SE, ME, 2K and XP have built in internet connection sharing (ICS) gateway software (fig 19.12) Routers can also be used for internet sharing (fig 19.13/14) Introduction to Computer Systems 11 Dr. E.C. Kulasekere IESL – Information Technology Part I Types of Networks LAN: The smallest office network is referred too as a LAN HAN: LAN in a home environment is called a HAN. Used for internet connection sharing. WAN: LANS at different places can be hooked by a WAN. The Internet: A network of LAN/WAN networks. Intranets: One or more LANs in a SOHO environment is called an intranet. Extranets: Intranets that share a part of the network with customers Introduction to Computer Systems 12 Dr. E.C. Kulasekere IESL – Information Technology Part I Requirements of a Network Physical cable or wireless connection. A common set of communication rules called network protocols. A software to enable transactions called a network operating system. Resources that can be shared. Software that enables computers to access other computers with shared resources: a network client. Introduction to Computer Systems 13 Dr. E.C. Kulasekere IESL – Information Technology Part I Components of a network Introduction to Computer Systems 14 Dr. E.C. Kulasekere IESL – Information Technology Part I Network Components Local area networks contain three basic hardware components Servers (also called hosts or host computers) Clients Circuits Clients and Servers typically work together in clientserver networks. Networks without servers are called peer-to-peer networks. Routers are specialized devices responsible for moving information between networks, are also a common network component. Server types: file servers, print servers, Web servers, e-mail and directory servers. Dr. E.C. Kulasekere Introduction to Computer Systems 15 IESL – Information Technology Part I Network Categorization According to Distance A common way of thinking about networks is by the scale of the network. 3 common network types are: Local Area Networks (LANs) which typically occupy a room or building, usually include a group of PCs that share a circuit. Backbone Networks, have a scale of a few hundred meters to a few kilometers. Include a high speed backbone linking the LANs at various locations. Metropolitan Area Networks (MANs) which typically have a scale of a few kilometers to a few tens of kilometers & connects LANs and BNs at different locations, often using leased lines or other commercial services to transmit data. Wide Area Networks (WANs) have a scale of hundreds or thousands of kilometers. Like MANs, leased circuits or other commercially available services are used to transmit data. Introduction to Computer Systems 16 Dr. E.C. Kulasekere IESL – Information Technology Part I Introduction to Computer Systems 17 Dr. E.C. Kulasekere IESL – Information Technology Part I LAN Topologies Introduction to Computer Systems 18 Dr. E.C. Kulasekere IESL – Information Technology Part I Bus Topology These are the earliest networks. Single cable (coaxial) is used with terminations at end. If some part of the cable malfunctioned, since the termination is lost the connections are lost. Adding a new computer was troublesome. Introduction to Computer Systems 19 Dr. E.C. Kulasekere IESL – Information Technology Part I Ring Topology This is a bus with the two ends connected. No termination necessary. Examples are fiber distributed data interface (FDDI) used for large high speed networks. Token ring (IBM) is another example. Is SeaMeWe an example? Signals go in a ring and get absorbed at the sender terminal. Malfunction of ring results in failure (solution: Fig 20.11) Introduction to Computer Systems 20 Dr. E.C. Kulasekere IESL – Information Technology Part I Star Topology Most popular type used today. Uses UTP cables to patch panel. Example implementation is a hub. Failure in one link is not catastrophic. For fast Ethernet this is the most commonly used type of configuration. CAT3 (10MB) or CAT5 (100MB) cables are used. Introduction to Computer Systems 21 Dr. E.C. Kulasekere IESL – Information Technology Part I Introduction to Computer Systems 22 Dr. E.C. Kulasekere IESL – Information Technology Part I High Speed Networking Switched Ethernet Fast Ethernet 100Base-T Gigabit Ethernet: Used with fiber optic cables. Can use CAT5 cable. Also referred to as 1000Base-T. ATM Introduction to Computer Systems 23 Dr. E.C. Kulasekere IESL – Information Technology Part I Switched Ethernet Switched Ethernet relies on centralized multiport switches to provide a physical link between multiple LAN segments The switch is intelligent and switches between segments with maximum BW allocation. It’s a cost-effective technique for increasing the overall network throughput and reducing congestion on a 10-Mbps network. The infrastructure is the same as usual. Introduction to Computer Systems 24 Dr. E.C. Kulasekere IESL – Information Technology Part I 100Base-T 100BASE-T retains the familiar CSMA/CD media access technique used in 10-Mbps Ethernet networks. Hence network management system need not be rewritten. Supports a broad range of cabling options. CAT5 UTP, Type 1 STP or duplex multimode fiber cable. It can easily be integrated into existing 10-Mbps Ethernet LANs, so your previous investment is saved Introduction to Computer Systems 25 Dr. E.C. Kulasekere IESL – Information Technology Part I Introduction to Computer Systems 26 Dr. E.C. Kulasekere IESL – Information Technology Part I Introduction to Computer Systems 27 Dr. E.C. Kulasekere IESL – Information Technology Part I ATM cell-based fast-packet communication technique that supports data-transfer rates ranging from sub-T1 speeds (less than 1.544 Mbps) up to 10 Gbps An ATM network can be treated as a single network, whether it connects points in a building or across the country The fixed cell length signaling method offers predictable performance. Can be integrated into the existing network. Introduction to Computer Systems 28 Dr. E.C. Kulasekere IESL – Information Technology Part I Gigabit Ethernet The Gigabit Ethernet standard was approved in June 1998, and its speed of 1 Gbps is a tenfold increase over Fast Ethernet. two basic types: shared and switched. Shared Gigabit Ethernet is a higher-speed version of 10/100BASE-T using CSMA/CD Medium Access Control Switched Gigabit Ethernet uses Logical Link Control (LLC) Its primary use is for backbones. The medium is fiber or Category 5e 100-ohm cable. Introduction to Computer Systems 29 Dr. E.C. Kulasekere IESL – Information Technology Part I More on Wireless Networking Advantages Flexibility in installing Flexibility in usage (movement of PCs) Disadvantages Security is not so good. Interference from other devices. Introduction to Computer Systems 30 Dr. E.C. Kulasekere IESL – Information Technology Part I Adhoc Wireless Networks Inexpensive and flexible. Each workstation relates on a peer-topeer basis with the other PCs. You can add a wireless router to gain access to the internet if required. Only suitable for small networks where security is not an issue. Introduction to Computer Systems 31 Dr. E.C. Kulasekere IESL – Information Technology Part I Adhoc Wireless network Introduction to Computer Systems 32 Dr. E.C. Kulasekere IESL – Information Technology Part I Infrastructure Mode Wireless Network Larger installations in larger buildings. Depends on access points connected together. Each workstation communicates with the access point rather than directly with another workstation. May not offer BW for networks with heavy traffic. Security is still a concern. Introduction to Computer Systems 33 Dr. E.C. Kulasekere IESL – Information Technology Part I Infrastructure mode wireless network Introduction to Computer Systems 34 Dr. E.C. Kulasekere IESL – Information Technology Part I Completely wired network Introduction to Computer Systems 35 Dr. E.C. Kulasekere IESL – Information Technology Part I Integrated Network Introduction to Computer Systems 36 Dr. E.C. Kulasekere IESL – Information Technology Part I Fiber Optic Networks Fiber optic cable is used in applications that require high BW, long distances, and complete immunity to electrical interference. A common application for fiber optic cable is as a network backbone Introduction to Computer Systems 37 Dr. E.C. Kulasekere IESL – Information Technology Part I Fiber Optic Networks (Cont …) Greater BW. Eg. two million telephone conversations have been simultaneously transmitted over a single fiber using Wavelength-Division Multiplexing (WDM). Low attenuation, longer distances: less repeaters are used so cost effective. Security:It’s very easy to monitor taps. If tapped, the cable leaks light, causing the entire system to fail. Immunity to interference. Introduction to Computer Systems 38 Dr. E.C. Kulasekere IESL – Information Technology Part I Introduction to Computer Systems 39 Dr. E.C. Kulasekere IESL – Information Technology Part I Cables Most commonly used are the (unshielded twisted pair) UTP cables. The need for better cabling is tied down to the increase in speeds and BW that is required for todays' applications. Introduction to Computer Systems 40 Dr. E.C. Kulasekere IESL – Information Technology Part I CAT5 Cabling Category 5 (CAT5) cabling is good, solid cable for 100-Mbps LANs Category 5 standard has been around since 1991 If you still have a lot of 10-Mbps equipment, CAT5 cabling will serve your needs. Also handles 100Mbps fast ethernet as well. If you are hitting the limit at 100Mpbs upgrade to CAT5e. Introduction to Computer Systems 41 Dr. E.C. Kulasekere IESL – Information Technology Part I CAT5e Cabling Enhanced Cat 5, was ratified in 1999. It’s an incremental improvement designed to enable cabling to support full-duplex Fast Ethernet operation and Gigabit Ethernet. CAT5e has stricter specifications for PSELFEXT (Power Sum Equal-Level FarEnd Crosstalk), NEXT (Near-End Crosstalk), Attenuation, and Return Loss (RL) than those for Category 5 This is also a 100MHz standard. Introduction to Computer Systems 42 Dr. E.C. Kulasekere IESL – Information Technology Part I CAT6 Cabling Features more stringent specifications for crosstalk and system noise. Ratified in 2002. to transmit according to CAT6 specs, jacks, patch cables, patch panels, crossconnects, and cabling must all meet CAT6 standards all CAT6 components must be backward compatible with CAT5e, CAT5, and Category 3. if CAT6 cable is used with CAT5e jacks, the channel will perform at a CAT5e level. Introduction to Computer Systems 43 Dr. E.C. Kulasekere IESL – Information Technology Part I Cable Standards Introduction to Computer Systems 44 Dr. E.C. Kulasekere IESL – Information Technology Part I Cabinets and Racks A cabinet is an enclosure with a door (or doors); a rack is an open frame An enclosed cabinet can be locked with a simple lock and key Fans are installed to cool. Built in power cabling. Cabling infrastructure provided. Introduction to Computer Systems 45 Dr. E.C. Kulasekere IESL – Information Technology Part I Connectors/Data Interfaces ..\webDocs\Connector Guide.htm Connectors are important for the cabling infrastructure. If two types of connectors are mixed. The lower speed one will set the limit of operation. ..\webDocs\Data Interfaces.htm Introduction to Computer Systems 46 Dr. E.C. Kulasekere IESL – Information Technology Part I LAN Hardware In traditional LANs, only one network node transmits data at a time while all other stations listen. This can lead to timing requirements not satisfied for video tx etc. bridges and routers process data packets on an individual basis, switches maintain multiple, simultaneous data conversions among attached LANs Switched circuits are better since they are dedicated connections. Introduction to Computer Systems 47 Dr. E.C. Kulasekere IESL – Information Technology Part I Introduction to Computer Systems 48 Dr. E.C. Kulasekere IESL – Information Technology Part I Switch Technologies The switch you have to buy for the LAN depends on the type of switching that have to be carried out. ..\webDocs\Layer 2, 3, and 4 Switching Overview.htm In depth analysis of such switches will be done next year. Introduction to Computer Systems 49 Dr. E.C. Kulasekere IESL – Information Technology Part I Routers and Bridges Routers and bridges link two or more individual Local Area Networks (LANs) to create an extended-network LAN or Wide Area Network (WAN). Introduction to Computer Systems 50 Dr. E.C. Kulasekere IESL – Information Technology Part I Routers Link networks using different network identities. Transmit only the data needed by the final destination across the LAN. Examine and rebuild packets without passing errors on to the next LAN. Routers are "smarter" than bridges, because they find the best route for all the data sent to them by the previous router or the end station of the LAN. Introduction to Computer Systems 51 Dr. E.C. Kulasekere IESL – Information Technology Part I Bridges Connect two parts of the same LAN network to make it larger. Unlike routers, every bridge builds an internal list of addresses of the attached network devices on both sides of it. If the destination address is on the opposite segment or if the bridge doesn't have the address logged, it forwards the information. Bridges operate on MAC-Layer addresses. They're protocol independent, so they transfer data between workstations without having to understand the protocol. Introduction to Computer Systems 52 Dr. E.C. Kulasekere IESL – Information Technology Part I Media Converters interconnects different cable types— twisted pair, fiber, and Thin or thick coax—within an existing network Introduction to Computer Systems 53 Dr. E.C. Kulasekere IESL – Information Technology Part I Media Converters (Cont …) Introduction to Computer Systems 54 Dr. E.C. Kulasekere IESL – Information Technology Part I Wiring Cable is cable, so buy the cheapest! – Follow this advice to fall in trouble. experts estimate that 70% of network failures are primarily caused by cable-related problems. So what’s a LAN manager to do? Introduction to Computer Systems 55 Dr. E.C. Kulasekere IESL – Information Technology Part I Backbone Wiring Main wiring between closet and floors. Star topology is used for backbone wiring. Starting point for horizonal wiring. Introduction to Computer Systems 56 Dr. E.C. Kulasekere IESL – Information Technology Part I Horizontal Wiring Introduction to Computer Systems 57 Dr. E.C. Kulasekere IESL – Information Technology Part I Horizontal Wiring (Cont…) encompasses all cable from a work-area wallplate or network connection to the telecommunications closet. The outlets, cable, and cross-connects in the closet are all part of the horizontal wiring, which gets its name because the cable typically runs horizontally above ceilings or along the floor. ..\webDocs\Premise Wiring.htm Introduction to Computer Systems 58 Dr. E.C. Kulasekere IESL – Information Technology Part I Other Devices ..\webDocs\Routers & Bridges.htm ..\webDocs\USB & FireWire.htm ..\webDocs\Video Connectors.htm Introduction to Computer Systems 59 Dr. E.C. Kulasekere