Chapter 5 Networks Communicating and Sharing Resources

Chapter objectives: Understand basic networking. Discuss the advantages and disadvantages of networks. Distinguish between Peer-to-Peer & client/server LAN. Define topology and understand how 3 LAN topologies differ. Explain the importance of protocols. Most widely used protocol & it’s versions. Identify the special components of wide area network (WAN) that differentiate from LAN.

Network Definition Set of technologies that connects computers to allow communication and collaboration between users. A group of two or more computer systems linked together to exchange data. Any device connect to the network referred to as a node. Any device has a unique logical address (name). Any device also has a unique physical address (MAC). A node need NIC to connect to network.

The Uses of a Network Simultaneous access to data Data files are shared Shared files stored on a server Software can be shared Shared peripheral device Printers and faxes are common shares Reduces the cost per user Devices can be connected to the network Teaching Tip Figure 9A.2 on page 342 visually describes the sharing process. It can be helpful to have students open a shared file that you control. Make a change then have the students open it again. Alternatively, share a document and allow your students to write in it. Then demonstrate how the shared document changes. Spend time discussing why application servers need to be so powerful.

The Uses of a Network Personal communication Email Conferencing Voice over IP Phone communication over network wires Easier data backup Backup copies data to removable media Server data backed up in one step Teaching tip It is fun if you can setup a teleconference in your classroom. Students get to learn how to join or create the conference. Additionally, they learn how to participate. Finally, students have fun, especially with shared whiteboards.

Sharing Data File server contains documents used by other computers.

Advantages and Disadvantages of Networking: Reduce hardware costs. Sharing application. Sharing information resources. Centralized data management. Connecting people. Disadvantages: Loss of autonomy. Lack of privacy. Security Threats. Loss of productivity.

Common Network Types LAN Protocol: Local Area Network (LAN) LAN interconnects devices in a limited area such as a home, school, or office building using network media. Contains printers, servers and computers. Systems are close to each other. Organizations often have several LANS. LANs Types Wired LAN Wireless LAN VLAN LAN Protocol: Standard or Rules specify how two dissimilar network components can establish a communication. Teaching tip Use a real world example to describe an organization with interconnected LANs.

Wired LAN Network Cables Unshielded Twisted Pair (UTP) Cable Shielded Twisted Pair (STP) Cable Coaxial Cable Fiber Optic Cable Ethernet: the most popular cabling technology in LAN. Ethernet uses a protocol called CSMA/CD Twisted Pair cable Coaxial cable Fiber Optic cable Rj-45 connector

Network Interface Card Connects node to the media Unique Machine Access Code (MAC) Insider Information The Xerox Corporation controls the assignment of Ethernet addresses to NIC manufacturers.

Wireless LANs Wifi standards and speeds Wi-Fi: wireless LAN standard that offers Ethernet speeds through the use of radio waves instead of wires. Wifi standards and speeds Standard Max Speed Typical Range 802.11a 54 Mbps 150 feet 802.11b 11 Mbps 300 feet 802.11g 802.11n 100 Mbps 300+ feet

Network layers

Types Of (LAN)Structure Types of LAN in terms of MEDIUM Wireless Wired Types of LAN in terms of Networking Model Peer-to-peer Client/Server Virtual private Network

Peer-to-Peer Network(P2P): Tend to slow down as the number of users increase. Keeping track of all the shared folders & files can be confusing. Security not strong because the lack of hierarchy. Nodes access resources on other nodes Each node controls its own resources Peer-to-Peer Network(P2P): All of the computers on the network are equals or peers and there is no file server but there is a file sharing in which each computer users decides which, if any, files will be accessible to other users on the network. Users also may choose to share entire directories or even disks, they can also choose to share peripherals such as printers. P2P networks are often used for home work or small business they don’t require a NOS (Network Operating System) and can be set with any operating system. P2P LAN are best used for simple networks connecting no more than 10 computers.

Client/Server network Nodes and servers share data roles Nodes are called clients Servers are used to control access Database software Access to data controlled by server Server is the most important computer Virtual Private Network (VPN) Operates a private network over the internet Client / Server Network: Includes one or more servers as well as clients . A client can be any type of computer ---- PC, Mac, desktop, notebook or handheld device that is connected to a network and contains the software that enables it to send requests to server. It can work with any size or physical layout of LAN and doesn’t tend to slow down with heavy use. Virtual Private Network (VPN): used by many business companies to provide their employees and customers with quick, secure access to the corporate information. A VPN operates a a private network over the internet making the data accessible to authorized users in remote locations through the use of secure, encrypted connection & software.

LAN Topologies Network Topology: the physical layout of the LAN. Bus Topology. Star Topology. Ring Topology. * Topology isn’t just arrangement of computers but provides solutions to the problem of contention which occurs when 2 computers try to access the LAN at the same time. *contention sometimes result into collisions which is the corruption of network data caused when 2 computers transmit simultaneously.

1- Bus Topology

1- Bus Topology One wire or cable connects all nodes. Terminator special connectors ends the circuit. Advantages Simple, reliable and easy to expand Easy to setup Small amount of wire Disadvantages: Only one node can transmit at a time. Slow & Easy to crash Used at home or small office. If more than one node transmit at the same time each node waits a small random amount of time before it attempts to retransmit again. Length restriction because of the lose of signal strength. Practical limit to the number of nodes attached to avoid contention. To resolve contention problems bus network uses some type of contention management a technique that specifies what happens when a collision occurs.

2- Star Topology

2- Star Topology Solves the expansion problems of the bus topology. All nodes connect to a hub Packets sent to hub Hub sends packet to destination Advantages Easy to setup and add users. One cable can not crash network Disadvantages Loss of hub crash down the entire network Uses lots of cable Most common topology used at office buildings, computer labs and WAN. * Hub: central wiring and simple broadcast device that does not manage traffic and usually results in frequent collision

3- Ring Topology

3- Ring Topology Nodes connected in a circle. Not in common used today. Special unit of data called Token travels around the ring and is used to transmit data Nodes can transmit only when it posses the token. Advantages Time to send data is known No data collisions Disadvantages Slow Lots of cable Well suited for use within a division of a company or on one floor of a multi floor building.

Wide Area Networks (WAN) Two or more LANs connected Over a large geographic area Typically use public or leased lines Phone lines Satellite The Internet is a WAN Teaching tip Blockbuster Video uses a WAN to connect it’s stores nationwide. Customers from Pittsburgh may rent videos in Hilton Head. Late fees will even be displayed!

WAN PROTOCOLS TCP/IP are open protocols that define how the Internet works. IP defines the internet addressing scheme. TCP defines how one computer can contact another to exchange control and confirmation messages. Circuit switching A protocol (method) used in a telephone systems with direct connection between the communicating devices. Packet switching A method used when no effort is made to create a single direct connection between the communicating devices. The internet protocols collectively called TCP/IP TCP/IP is an abbreviation for transmission control protocol(TCP)/internet protocol(IP) IP is the most fundamental of all internet protocol because it defines the internet addressing scheme which enables any internet-connected computer to be uniquely identified. IP address has for part which are separated by periods (such as 128.254.108.7) Circuit and packet switching WAN protocols are based on either circuit-or packet switching network technology, but most use packet switching packet switching is more efficient and less expensive than circuit switching With Circuit switching the method used in the public switched telephone system there is a direct connection between the communicating devices With packet switching the method used for computer communication no effect is made to create signal direct connection between the two communicating devices

Network Hardware Switches Hubs Replacement for hubs Only intended node receives transmission Fast and secure Center of a star network All nodes receive transmitted packets Slow and insecure

Network Hardware Gateway Router Bridge Connects two dissimilar networks Connects coax to twisted pair Most gateways contained in other devices Connects two or more LANs Packets sent to remote LAN cross Network is segmented by IP address Connect internal networks to the Internet Need configured before installation Connects two or more LANs together Packets sent to remote LAN cross ,other packets do not cross Segments the network on MAC addresses