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Networking. What is a Network? A group of Computers and devices connected together for the purpose of sharing resources and services. It may be as simple.

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Presentation on theme: "Networking. What is a Network? A group of Computers and devices connected together for the purpose of sharing resources and services. It may be as simple."— Presentation transcript:

1 Networking

2 What 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.

3 3 Why Networking? Sharing information eg. data communication Do you prefer these? Or this?

4 4 Sharing hardware or software Centralize administration and support eg. print document eg. Internet-based, so everyone can access the same administrative or support application from their PCs

5 What is a LAN?LAN Local Area Network A group of computers in a single location Limited by no. of computers and distance covered Example: Our school network

6 What is a WAN?WAN Wide Area Network Two or more LANs connected together using a telecommunication service Example: NYC Dept. of Education

7 7 Example of WAN: Broadband Cable Network Cable TV services have been extensively developed in most modern cities Cable TV companies try to make use of their coaxial cable installed (that are supposed to carry TV signals) to deliver broadband data services Many 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

8 8 The connection is shared by a number of subscribers, hence may raise performance and security problems Fiber-optic cable Cable companyCoaxial Cable TV PC Cable Drop

9 What is a WLANWLAN Wireless LAN This is a LAN that uses Radio Frequency technology to allow for communication among computers and devices Example: wireless home network

10 Role 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 network Server- Computer or device that specializes in knowing how to provide services in network. Example: Print Server in a network Peer- 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)

11 11 How many kinds of Networks? We can classify networks in different ways Based on network medium: Wired (twisted pair, coaxial cables, fiber-optic cables) and Wireless Based on network size: LAN and WAN Based on management method: Peer-to-peer and Client/Server Based on topology (connectivity): Bus, Star, Ring, Mesh

12 What is the Network Medium? Cabled/Wired STP – shielded twisted pair UTP – unshielded twisted pair(cat 5, 5E, 6, 7) Coaxial Fiber Optic (single mode, Multi mode)

13 Wireless Microwave - Microwaves are electromagnetic waves with wavelengths ranging from as long as one meter to as short as one millimeter Infrared - Infrared radiation (IR) is electromagnetic radiation with a wavelength between 0.7 and 300 micrometers Radio - 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

14 14 If 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 Twisted-Pair Cables

15 15 Unshielded Twisted-Pair (UTP) Typically wrapped inside a plastic cover (for mechanical protection) A sample UTP cable with 5 unshielded twisted pairs of wires Metal Insulator

16 16 Categories 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 now Category 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

17 17 Shielded 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

18 18 Coaxial Cables In general, coaxial cables, or coax, carry signals of higher frequency than UTP cables Outer metallic wrapping serves both as a shield against noise and as the second conductor that completes the circuit

19 19 Fiber-Optic Cables Light travels at 3 10 8 ms -1 in free space and is the fastest possible speed in the Universe An optical fiber consists of a core (denser material) and a cladding (less dense material) Simplest one is a multimode step-index optical fiber Multimode = 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

20 Network Types Peer to peer Client/server

21 Advantages of Peer-to-Peer Easy to install and configure Most Client OS already have the components required to set the computer as part of a peer to peer network Individual machines do not depend on the presence of a dedicated server Individual users control their own shared resources Inexpensive to purchase and operate Need no additional equipment or software beyond a suitable operating system. Best for networks with less than 10 users

22 Disadvantages of Peer-to-Peer Security applies to a single resource at a time Users 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 performance There is no centralized organizational scheme to locate or control access to data

23 Advantages of Client/Server Centralized User Accounts, Security, and access controls simplify network administration More powerful equipment means more efficient access to network resources A single password for network logon delivers access to all resources Server based networking makes the most sense for networks with 10 or more users or any network where resources are used heavily.

24 Disadvantages 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.

25 What are ProtocolsProtocols Set of rules that allow computer to communicate with each other

26 Network Protocols TCP/IP (Transmission Control Protocol/ Internet Protocol) TCP/IP Nwlink or IPX/SPX NetBEUI

27 Network Software NOS (Network Operating System) NOS Windows Server 2008 Windows 2003 Server Novell Netware 6.5 Unix Linux

28 Network Services The reason for setting up a network in the first place: File and Print DHCP (Dynamic Host Configuration Protocol) DNS (Domain Naming Service) Security E-mail Application or Database Web / Proxy Mail/FTP/IM/Chat RAS (Remote Access Service)

29 What are Topologies?Topologies The physical shape computers and devices create when connected together The different topologies are: BUS STAR RING MESH HYBRIDS

30 Bus (not commonly found in LANs anymore) Needs termination Adding devices disrupts the network Cable failure hard to find

31 31 Bus Topology BNC T-Connector Coaxial cable Network Card

32 Star (Most common topology) Requires a hub/switch Easy to troubleshoot Requires more wiring

33 Star Topology

34 Topologies Ring No beginning and no end Uses token passing to communicate Mesh All computers are connected to each other More Fault tolerant

35 Variation of Major Topologies (Hybrids) Star-Bus Backbone interconnect two or more hubs Star-Ring Physical Star, but logical ring The way the IBM token ring Works.

36 What 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 e-mail how does it reach the destination? Examples are TCP/IP and the OSI models

37 OSI Networking Model 7 Layers Application Presentation Session Transport Network Data link Physical

38 TCPI/IP Networking model 4 layers Application Layer Transport Internet Layer Network Interface Layer

39 Networking standards IEEE 802.x Standards 802.3 Ethernet Networks 802.11 Wireless Networks 11a, 11b, 11g, 11n

40 Bluetooth an alternative wireless network technology standard supports a very short range (approximately 10 meters) relatively low bandwidth (1-3 Mbps)

41 Computer/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)

42 MAC address Media Access Control address a unique identifier assigned to most network adapters or NIC by the manufacturer for identification a series of 6 groups of two digits, letters and numbers, separated by dashes Example: 00-1E-4F-A0-61-69

43 IP Addressing Supports 4.3 billion addresses 32 bit address (Dotted decimal) 4 numbers (0 to 255) separated by dots The addresses are divided into Class A, B, C, D, E according to network size.

44 Subnet 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.

45 Default Subnet masks are: Class A 255.0.0.0 Class B 255.255.0.0 Class C 255.255.255.0

46 Private vs. Public Addresses. Private addresses are only valid in a private network Public are valid in the Internet Ex. Private address. 10.0.0.0/8, 172.16.0.0 to 172.31.0.0, and 192.168.0.0/24

47 IP addressing Network ClassNumber of Hosts Class Aapproximately 16,000,000 Class Bapproximately 65,000 Class C254

48 IP address Class A Class A addresses range from 1.0.0.0 to 126.0.0.0 The Class A range has the possibility of 126 networks Each network has the capability of 16,777,214 unique hosts The default subnet mask is 255.0.0.0

49 IP address Class B Class B addresses range from 128.0.0.0 to 191.255.0.0 The Class B range has the possibility of 16,384 networks Each network has the capability of 65,534 unique hosts The default subnet mask is 255.255.0.0

50 IP address Class C Class C addresses range from 192.0.1.0 to 223.255.255.0 The Class C range has the possibility of 2,097,152 networks Each network has the capability of 254 unique hosts The default subnet mask is 255.255.255.0

51 IP Address Class D Class D addresses are used for multicasting to a number of different hosts. Class D addresses range from 224.0.0.0 to 239.255.255.255 Has the potential for 268,435,456 unique multicast groups.

52 IP address Class E Class E is an experimental address block that is reserved for future use Class E addresses range from 240.0.0.0 to 254.255.255.255

53 Communication types Unicast (One to one) Broadcast (One to all) Multicast (One to a group)

54 TCP/IP Protocols Application layer Telnet, FTP, HTTP, SMTP DHCP, DNS, TFTP, SNMP Transport Layer TCP, UDP Internet Layer ICMP, ARP, RARP, IP

55 Binary to decimal conversion Binary= 01001011 This is equivalent to Decimal=64+8+2+1=75 1286432168421 01001011

56 Binary Conversion BinaryDecimal _____________________________________ 10000000128 11000000192 11100000224 11110000240 11111000248 11111100252 11111110254 11111111255


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