2What is a Network?A group of Computers and devices connected together for the purpose of sharing resources and services.It may be as simple as two computers or as complex as the Internet.
3Why Networking? Sharing information — eg. data communication Do you prefer these?Or this?
4Sharing hardware or software eg. print documentCentralize administration and supporteg. Internet-based, so everyone can access the same administrative or support application from their PCs
5What is a LAN? Local Area Network A group of computers in a single locationLimited by no. of computers and distance coveredExample: Our school network
6What is a WAN? Wide Area Network Two or more LANs connected together using a telecommunication serviceExample: NYC Dept. of Education
7Example of WAN: Broadband Cable Network Cable TV services have been extensively developed in most modern citiesCable TV companies try to make use of their coaxial cable installed (that are supposed to carry TV signals) to deliver broadband data servicesMany cable network wiring has been replaced with hybrid fiber-coax (HFC) ― i.e. use of fiber-optic cable to connect to the subscribers’ buildings, and then the original coaxial cable to connect to each household
8The connection is shared by a number of subscribers, hence may raise performance and security problemsPCTVFiber-optic cableCable DropCoaxialCableCable company
9What is a WLAN Wireless LAN This is a LAN that uses Radio Frequency technology to allow for communication among computers and devicesExample: wireless home network
10Role of Computers in a Network Client- computer or device that specializes in knowing how to ask for services in a network. Example: Workstation in a networkServer- Computer or device that specializes in knowing how to provide services in network. Example: Print Server in a networkPeer- Computer or device that may be able to be both a server or a client at the same time. Example: Workstation in a simple network (peer-to-peer network …. P2P Network)
11How many kinds of Networks? We can classify networks in different waysBased on network medium: Wired (twisted pair, coaxial cables, fiber-optic cables) and WirelessBased on network size: LAN and WANBased on management method: Peer-to-peer and Client/ServerBased on topology (connectivity): Bus, Star, Ring, Mesh
12What is the Network Medium? Cabled/WiredSTP – shielded twisted pairUTP – unshielded twisted pair(cat 5, 5E, 6, 7)CoaxialFiber Optic (single mode, Multi mode)
13WirelessMicrowave - Microwaves are electromagnetic waves with wavelengths ranging from as long as one meter to as short as one millimeterInfrared - Infrared radiation (IR) is electromagnetic radiation with a wavelength between 0.7 and 300 micrometersRadio - Radio waves transmit music, conversations, pictures and data invisibly through the air, often over millions of miles - wavelengths in the electromagnetic spectrum longer than infrared light
14Twisted-Pair CablesIf the pair of wires are not twisted, electromagnetic noises from, e.g., motors, will affect the closer wire more than the further one, thereby causing errors
15Unshielded Twisted-Pair (UTP) Typically wrapped inside a plastic cover (for mechanical protection)A sample UTP cable with 5 unshielded twisted pairs of wiresMetalInsulator
16Categories of UTP Cables UTP cables are classified according to the quality:Category 1 ― the lowest quality, only good for voice, mainly found in very old buildings, not recommended nowCategory 2 ― good for voice and low data rates (up to 4Mbps for low-speed token ring networks)Category 3 ― at least 3 twists per foot, for up to 10 Mbps (common in phone networks in residential buildings)Category 4 ― up to 16 Mbps (mainly for token rings)Category 5 (or 5e) ― up to 100 Mbps (common for networks targeted for high-speed data communications)Category 6 ― more twists than Cat 5, up to 1 Gbps
17Shielded Twisted-Pair (STP) STP cables are similar to UTP cables, except there is a metal foil or braided-metal-mesh cover that encases each pair of insulated wires
18Coaxial CablesIn general, coaxial cables, or coax, carry signals of higher frequency than UTP cablesOuter metallic wrapping serves both as a shield against noise and as the second conductor that completes the circuit
19Fiber-Optic CablesLight travels at 3108 ms-1 in free space and is the fastest possible speed in the UniverseAn optical fiber consists of a core (denser material) and a cladding (less dense material)Simplest one is a multimode step-index optical fiberMultimode = multiple paths, step-index = refractive index follows a step-function profile (i.e. an abrupt change of refractive index between the core and the cladding)Common light sources: LEDs and lasers
21Advantages of Peer-to-Peer Easy to install and configureMost Client OS already have the components required to set the computer as part of a peer to peer networkIndividual machines do not depend on the presence of a dedicated serverIndividual users control their own shared resourcesInexpensive to purchase and operateNeed no additional equipment or software beyond a suitable operating system.Best for networks with less than 10 users
22Disadvantages of Peer-to-Peer Security applies to a single resource at a timeUsers may be required to use as many passwords as there are shared resources.Each machine must be backed up individually to protect all shared data.The machine that shares resources suffers reduced performanceThere is no centralized organizational scheme to locate or control access to data
23Advantages of Client/Server Centralized User Accounts, Security, and access controls simplify network administrationMore powerful equipment means more efficient access to network resourcesA single password for network logon delivers access to all resourcesServer based networking makes the most sense for networks with 10 or more users or any network where resources are used heavily.
24Disadvantages of Client/Server Server failure renders the network unusable, or it results in loss of network resources.Special purpose server software requires allocation of expert staff, which increases expenses.Dedicate hardware and software add to the cost.
25What are ProtocolsSet of rules that allow computer to communicate with each other
26Network ProtocolsTCP/IP (Transmission Control Protocol/ Internet Protocol)Nwlink or IPX/SPXNetBEUI
27Network Software NOS (Network Operating System) Windows Server 2008 Novell Netware 6.5UnixLinux
28Network ServicesThe reason for setting up a network in the first place:File and PrintDHCP (Dynamic Host Configuration Protocol)DNS (Domain Naming Service)SecurityApplication or DatabaseWeb / ProxyMail/FTP/IM/ChatRAS (Remote Access Service)
29What are Topologies?The physical shape computers and devices create when connected togetherThe different topologies are:BUSSTARRINGMESHHYBRIDS
30Bus (not commonly found in LANs anymore) Needs terminationAdding devices disrupts the networkCable failure hard to find
34Topologies Ring Mesh No beginning and no end Uses token passing to communicateMeshAll computers areconnected to each otherMore Fault tolerant
35Variation of Major Topologies (Hybrids) Star-BusBackbone interconnect two or more hubsStar-RingPhysical Star, but logical ringThe way the IBM token ring Works.
36What are Networking Models? A model describes the different stages data needs to go through in order to go from one computer to another.When you send an how does it reach the destination?Examples are TCP/IP and the OSI models
37OSI Networking Model 7 Layers Application Presentation Session TransportNetworkData linkPhysical
38TCPI/IP Networking model 4 layersApplication LayerTransportInternet LayerNetwork Interface Layer
40Bluetooth an alternative wireless network technology standard supports a very short range (approximately 10 meters)relatively low bandwidth (1-3 Mbps)
41Computer/device ID/Addressing Every computer or device which is part of a network includes a network card.Every network card needs to have:Physical address (MAC address)Logical address (IP address)
42MAC address Media Access Control address a unique identifier assigned to most network adapters or NIC by the manufacturer for identificationa series of 6 groups of two digits, letters and numbers, separated by dashesExample: 00-1E-4F-A
43IP Addressing Supports 4.3 billion addresses 32 bit address (Dotted decimal)4 numbers (0 to 255) separated by dotsThe addresses are divided into Class A, B, C, D, E according to network size.
44Subnet Mask The subnet mask is used to identify the network address. The sending computer needs to know this in order to decide whether the packet is meant for the local network or for another network.
46Private vs. Public Addresses. Private addresses are only valid in a private networkPublic are valid in the InternetEx. Private address /8 , to , and /24
47IP addressing Network Class Number of Hosts Class A approximately 16,000,000Class Bapproximately 65,000Class C254
48IP address Class A Class A addresses range from 188.8.131.52 to 184.108.40.206 The Class A range has the possibility of 126 networksEach network has the capability of 16,777,214 unique hostsThe default subnet mask is
49IP address Class BClass B addresses range from toThe Class B range has the possibility of 16,384 networksEach network has the capability of 65,534 unique hostsThe default subnet mask is
50IP address Class CClass C addresses range from toThe Class C range has the possibility of 2,097,152 networksEach network has the capability of 254 unique hostsThe default subnet mask is
51IP Address Class DClass D addresses are used for multicasting to a number of different hosts.Class D addresses range from toHas the potential for 268,435,456 unique multicast groups.
52IP address Class EClass E is an experimental address block that is reserved for future useClass E addresses range from to
53Communication types Unicast (One to one) Broadcast (One to all) Multicast (One to a group)
54TCP/IP Protocols Application layer Transport Layer Internet Layer Telnet, FTP, HTTP, SMTPDHCP, DNS, TFTP, SNMPTransport LayerTCP, UDPInternet LayerICMP, ARP, RARP, IP
55Binary to decimal conversion 1286432168421Binary=This is equivalent toDecimal= =75