Networking

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

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

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

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

9. What is a WLAN • 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. 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. Twisted-Pair Cables 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

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

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. 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. 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. Fiber-Optic Cables • Light travels at 3108 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 Protocols Set of rules that allow computer to communicate with each other

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

27. Network Software • NOS (Network Operating System) • 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? 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. Bus Topology Coaxial cable BNC T-Connector 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

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