NETWORK Computer and devices, connected by some type of media. Two computers to thousands of computers connected across the world via the Internet. Networks may link mainframe computers, desktop computers, printers, plotters, fax machines, and phone systems.
NETWORK (CONT.) Manage and administer resources on multiple computer from one location. Networks allow multiple users to share devices and resources such as: - printers - faxes - program and files
ADVANTAGES OF NETWORKING• File Sharing : The major advantage of a computer network is that is allows file sharing and remote file access. A person sitting at one workstation of a network can easily see the files present on the other workstation.• Resource Sharing : If there are four people in a family, each having their own computer, they will require four modems (for the Internet connection) and four printers, if they want to use the resources at the same time. A computer network, on the other hand, provides a cheaper alternative by the provision of resource sharing.
• Increased Storage Capacity : As there is more than one computer on a network which can easily share files, the issue of storage capacity gets resolved to a great extent. When many computers are on a network, memory of different computers can be used in such case. One can also design a storage server on the network in order to have a huge storage capacity.• Increased Cost Efficiency : There are many softwares available in the market which are costly and take time for installation. Computer networks resolve this issue as the software can be stored or installed on a system or a server and can be used by the different workstations.
TYPES OF NETWORK Peer-to-Peer Client / Server
PEER-TO-PEER NETWORKSPeer-to-peer networks : Resource sharing, processing, and communication controls are fully decentralized often called a workgroup. All clients are given equal importance in using the network resources and users are individually authenticated by workstations. No fixed clients and servers. Common with up to 12 computers Disadvantage – slow transmission
CLIENT / SERVER NETWORKSClient/server networks It is a network where the servers provide services to different clients. A centralized server provides client authentication services. Servers play a key role in managing several applications like access to shared files, printers, and hardware.
CLIENT-SERVERUsually high-powered servers. The types of servers are: - 12
CLIENT-SERVERAdvantages DisadvantagesSecurity and data sources are spending more costly for a servercontrolled by the serverAll components (client / network / need maintenance every time the server) work simultaneously rates are determined to ensure the effectiveness of the system.Sharing data and software applicatio Networking does not ns can be done work if something went wrong on the server. 13
LANS, MANS AND WANSThere are three main categories of networks:• Local Area Network (LAN) – is a relatively small network of computers, printers, and other devices in single building or floor.• Metropolitan Area Network (MAN) – is a high-speed internetwork of LANs across a metropolitan area.• Wide Area Network (WAN) – traditionally connects LANs using the PSTN(Public Switched Telephone Network) or more commonly the Internet. To provide connectivity over a large geographic area.
LOCAL AREA NETWORK (LAN)LAN characteristics: They are used within small areas ( such as in an office building). They offer high-speed communication-typically 100Mbps or faster. They provide access for many devices. They use LAN- specific equipment such as hub and NICs-usually no need router.
METROPOLITAN AREANETWORKMAN characteristics: Sites are dispersed across a city/large campus and perhaps the surrounding area as well. With the advent of MANs, historically slow connection (56Kbps-1.5Mbps) have given way to communication at hundreds of megabits per second and even gigabit speeds. They use devices such as routers, telephone switches, and microwave antennas as part of their communication infrastructure A MAN usually interconnects a number of (LANs) using a high-capacity backbone technology, such as fiber-optical links.
WIDE AREA NETWORKWAN characteristics : They can cover a very large geographic area even span the world. They usually communicate at slow speed (compared to LANs). They use devices such as routers, modems, and WAN switches, connectivity devices specific to LANs and used to connect to long-haul transmission media.
COMMON NETWORK ELEMENT Client A computer on the network that requesting resources or services. Server A computer on the network that manages network access and shared resources. Network Interface Card (NIC) A device inside a computer that connects a computer to the network media. Network Operating System(NOS) Server that enable a computer to control network access and manage resources. The most popular NOS are Microsoft Windows Server, Novell NetWare and UNIX. Host A device that provides resource sharing for other computers on the same network.
COMMON NETWORK ELEMENTS (CONT.)• Node A device such as, client, server, or other network equipment that is identified by a unique network address.• Topology The physical layout of a computer network. Network topology can be a ring, bus or star formation, or hybrid combinations.• Backbone The backbone of a network (Cable) that combines smaller network into a large network.• Transmission Media Media that carrying the network signal (cable/channel)• Connectivity Devices Modems, repeaters, bridges, routers, switch, hub and etc.• Segment It is a physical partitioning of network.
NETWORK TOPOLOGIES Network topology is the layout pattern of interconnections of the various elements (cable, nodes, etc.) of a computer network. Bus Ring Star Hybrid Mesh
Group Activities…Bus??? Hybrid??? Ring??? Star??? Mesh???
BUS Bayonet Neill–Concelman (BNC connector) Connect two or more computer using coaxial cable and BNC connector. Terminator are installed on both ends of the cable. Without the terminator, the electrical signal that represent the data would reached the end of cooper wire and bounce back, causing errors on the network. Advantages : inexpensive to install, can easily add more workstation. Disadvantages : If the cable break down, the network is down, access time and network performance degrade as devices are added to the network.
RING Computer are connected in a ring (circle). It has no beginning or end, so there is no need to terminate the cable. Every device have an equal advantage in accessing the media. Advantages : There are no collisions , no terminators are needed, easy to locate and correct problems with devices and cable. Disadvantages : requires more cable than a bus network, a break in the cable brings the entire network down.
STAR All computer are connected to a central point such as hub or switch The most common topology used today Data on a star topology passes through the hub or switch before continuing to its destination. Advantages : Cable failure will not disrupt the network. Disadvantages : Single point of failure.
HYBRID• Combination of any two or more different topologies.• The most commonly used topologies are Star-Bus or Star-Ring.• Advantages : If a computer fails, it will not affect the rest of the network• Disadvantages : If the central component, or hub, that attaches all computers in a star, fails, no computer will be able to communicate.
MESH All computer are connected to every other computer on the network Rarely used on a Local Area Network (LAN) The topology of the Internet. Advantages : Very redundant. No disruption when expanded. Disadvantages : Expensive. Requires a lot of cable and network interface cards.
ADVANTAGES & DISADVANTAGES OF TOPOLOGIESTopology Advantages DisadvantagesBus Less cable Easy to install Cable faulty, entire system down Network not working even Difficult to troubleshoot with 1 PC failed Least fault toleranceStar Inexpensive Easy to troubleshoot Low data rate Moderately difficult to install Easy to reconfigure Require more cablesRing Almost no loss in signal quality over network Failure of single connection can take down entire network Not that easy to install & troubleshootMesh Every PC connected to each other Large amount of cables Very expensive & difficult to Most fault tolerance manage 34
NETWORKING STANDARDS ORGANIZATIONSOrganizations that set standards for networking: American National Standards Institute (ANSI) Electronic Industries Alliance (EIA) and Telecommunication Industry Association (TIA) Institute of Electrical and Electronics Engineers (IEEE) International Organization for Standardization (ISO) International Telecommunication Union (ITU) Internet Society (ISOC) Internet Assigned Numbers Authority (IANA) and Internet Corporation for Assigned Names and Numbers (ICANN)
PRINCIPLES OF NETWORKINGSender• The first of these elements is the message source, or sender. It is the device which sends the data messages.• Message sources are people, or electronic devices, that need tocommunicate a message to other individuals or devices.Destination•The second element of communication is the destination, orreceiver, of the message.•The destination receives the message and interprets it.Source•A third element, called a channel, provides the pathway overwhich the message can travel from source to destination.
RULES OF COMMUNICATION IN NETWORKING Identification of sender and receiver (establish a link) Agreed-upon medium or channel (face-to-face, telephone, letter, photograph)-issue a command and command qualifier Appropriate communication mode (spoken, written, illustrated, interactive or one-way)-acknowledgement of command Common language Grammar and sentence structure - dissection message Error Control and correction Error detecting and recovering is one of the main functions of communication protocol. It ensures that data is transmitted without any error. It also solves the problem if an error is detected. Speed and timing of delivery-termination and transmission Ex:RS232 –handshaking concept
Protocols define the details of how the message istransmitted, and delivered. This includes issues of: Message format Message size Timing Encapsulation Encoding Standard message pattern
MESSAGE ENCODING•Encoding is the process of converting thoughts into the language,symbols, or sounds, for transmission. Decoding reverses this process inorder to interpret the thought. In computer communication Messages sent across the network are first converted into bits by the sending host. Each bit is encoded into a pattern of sounds, light waves, or electrical impulses depending on the network media over which the bits are transmitted. The destination host receives and decodes the signals in order to interpret the message.
Message formatting Message formats depend on the type of message and the channel that is used to deliver the message. Ex: The process of placing one message format (the letter) inside another message format (the envelope) is called encapsulation. De-encapsulation occurs when the process is reversed by the recipient and the letter is removed from the envelope.
MESSAGE FORMATTING(CONT.) Each computer message is encapsulated in a specific format, called a frame before it is send to network. A frame acts like an envelope; it provides the address of the intended destination and the address of the source host. The format and contents of a frame are determined by the type of message being sent and the channel over which it is communicated.
MESSAGE SIZE When long message is sent from one host to another over a network, it is necessary to break the message into smaller pieces. Each piece is encapsulated in a separate frame with the address information, and is sent over the network. At the receiving host, the messages are de- encapsulated and put back together to be processed and interpreted.
MESSAGE TIMING People use timing to determine when to speak, how fast or slow to talk, and how long to wait for a response. Rules: a) Access Method Access Method determines when someone is able to send a message. If two people talk at the same time, a collision of information occurs. Hosts on a network need an access method to know when to begin sending messages and how to respond when errors occur.
MESSAGE TIMING (CONT.) b) Flow Control Timing also effects how much information can be sent and the speed that it can be delivered. In network communication, a sending host can transmit messages at a faster rate than the destination host can receive and process. Source and destination hosts use flow control to negotiate correct timing for successful communication. c) Response Timeout Hosts on the network also have rules that specify how long to wait for responses and what action to take if a response timeout occurs.
MESSAGE PATTERN Unicast A one-to-one message pattern Only a single destination for the message. Multicast One-to-many pattern Multicasting is the delivery of the same message to a group of host destinations simultaneously. The most complex type of message because they require a means of identifying a set of specific devices to receive a message. Broadcast If all hosts on the network need to receive the message at the same time, a broadcast is used. One-to-all message pattern.
MESSAGE PATTERN(CONT.) Unicast: 1-to-1 Multicast: 1-to- many Broadcast: 1 to all48 Networking fundamentals
Ethernet card. 51From top tobottom:RJ-45, AUI(Attachment UnitInterface) , and BNCconnectors
LOCALTALK Ethernet Cards LocalTalkFast data transfer Slow data transfer(10 to 100 Mbps) (23 Mbps)Expensive - purchased Built into Macintoshseparately computersRequires computer slot No computer slot necessaryAvailable for most Works only oncomputers Macintosh computers 52