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Students completing this chapter should be able to: • Explain the importance of bandwidth in networking. • Use an analogy from their experience to explain bandwidth. • Explain the difference between bandwidth and throughput. • Calculate data transfer rates. • Explain why layered models are used to describe data communication. • Explain the development of the Open System Interconnection model (OSI). • List the advantages of a layered approach. • Identify each of the seven layers of the OSI model. • Identify the four layers of the TCP/IP model. • Describe the similarities and differences between the two models. • Briefly outline the history of networking. • Identify devices used in networking. • Understand the role of protocols in networking. • Define LAN, WAN, MAN, and SAN. • Explain VPNs and their advantages. • Describe the differences between intranets and extranets.
Local Area Networks (LAN) Businesses needed a solution that would successfully address the following three problems: • How to avoid duplication of equipment and resources • How to communicate efficiently • How to set up and manage a network
Wide-area networks (WANs) • A way for information to move efficiently and quickly • WANs could connect user networks over large geographic areas
Networking Devices • Equipment that connects directly to a network segment is referred to as a device. These devices are broken up into two classifications. • Network Devices • end-user devices
End user devices • End-user devices that provide users with a connection to the network are also referred to as hosts • These devices allow users to share, create, and obtain information. • Host devices are physically connected to the network media using a network interface card (NIC)
Network interface card(NIC) • A NIC is a printed circuit board that fits into the expansion slot of a bus on a computer motherboard, or it can be a peripheral device.
Network interface card(NIC) • Laptop or notebook computer NICs are usually the size of a PCMCIA card. • Each individual NIC carries a unique code, called a Media Access Control (MAC) address
Network devices • Network devices provide transport for the data that needs to be transferred between end-user devices. Network devices provide extension of cable connections, concentration of connections, conversion of data formats, and management of data transfers.
Repeater • A repeater is a network device used to regenerate a signal. Repeaters regenerate analog or digital signals distorted by transmission loss due to attenuation.
Bridges • convert network transmission data formats as well as perform basic data transmission management. • provide connections between LANs. • perform a check on the data to determine whether it should cross the bridge or not. This makes each part of the network more efficient
Switches • Workgroup switches add more intelligence to data transfer management. • They can determine whether data should remain on a LAN or not • They can transfer the data only to the connection that needs that data.
Routers Routers have all the capabilities listed above. • regenerate signals • concentrate multiple connections • convert data transmission formats, and manage data transfers • They can also connect to a WAN, which allows them to connect LANs that are separated by great distances
Network topology • Network topology defines the structure of the network. One part of the topology definition is the physical topology, which is the actual layout of the wire or media. The other part is the logical topology, which defines how the media is accessed by the hosts for sending data
Logical topology • The logical topology of a network is how the hosts communicate across the medium - broadcast Ethernet - token passing Token Ring Fiber Distributed Data Interface (FDDI)
A protocol • A protocol is a formal description of a set of rules and conventions that govern a particular aspect of how devices on a network communicate. • Protocols determine the format, timing, sequencing, and error control in data communication
Protocols Protocols control all aspects of data communication, which include the following: (IEEE, ANSI , TIA , EIA , ITU ) • How the physical network is built • How computers connect to the network • How the data is formatted for transmission • How that data is sent • How to deal with errors
LANs consist of the following components: Computers Network interface cards Peripheral devices Networking media Network devices Some common LAN technologies are: Ethernet Token Ring FDDI Local-area networks (LANs)
WANs interconnect LANs, which then provide access to computers or file servers in other locations. Some common WAN technologies are: Modems Integrated Services Digital Network (ISDN) Digital Subscriber Line (DSL) Frame Relay US (T) and Europe (E) Carrier Series – T1, E1, T3, E3 Synchronous Optical Network (SONET) Wide-area networks (WANs)
Metropolitan-area networks (MANs) • A MAN is a network that spans a metropolitan area such as a city or suburban area. A MAN usually consists of two or more LANs in a common geographic area .
Storage-area networks (SANs) A SAN is a dedicated, high-performance network used to move data between servers and storage resources SANs offer the following features: • Performance – SANs enable concurrent access of disk or tape arrays by two or more servers at high speeds. • Availability – SANs have disaster tolerance built in, because data can be mirrored using a SAN up to 10 kilometers (km) or 6.2 miles away. • Scalability – Like a LAN/WAN, it can use a variety of technologies. This allows easy relocation of backup data, operations, file migration, and data replication between systems.
Virtual private network (VPN) • A VPN is a private network that is constructed within a public network infrastructure such as the global Internet. Using VPN, a telecommuter can access the network of the company headquarters through the Internet by building a secure tunnel between the telecommuter’s PC and a VPN router in the headquarters
Types of VPNs • Access VPNs– Access VPNs provide remote access to a mobile worker and small office/home office (SOHO) to the headquarters of the Intranet or Extranet over a shared infrastructure. • Intranet VPNs – Intranet VPNs link regional and remote offices to the headquarters of the internal network over a shared infrastructure using dedicated connections • Extranet VPNs – Extranet VPNs link business partners to the headquarters of the network over a shared infrastructure using dedicated connections
Benefits of VPNs • A VPN is a service that offers secure, reliable connectivity over a shared public network infrastructure such as the Internet. • They are the most cost-effective method of establishing a point-to-point connection between remote users and an enterprise customer's network
Intranets and extranets • Intranets are designed to permit access by users who have access privileges to the internal LAN of the organization. • Extranets refer to applications and services that are Intranet based, and use extended, secure access to external users or enterprises.
Importance of bandwidth • Bandwidth is defined as the amount of information that can flow through a network connection in a given period of time.
Measurement • In digital systems, the basic unit of bandwidth is bits per second (bps). Bandwidth is the measure of how much information, or bits, can flow from one place to another in a given amount of time, or seconds.
Limitations • Bandwidth varies depending upon the type of media as well as the LAN and WAN technologies used. The physics of the media account for some of the difference. • The actual bandwidth of a network is determined by a combination of the physical media and the technologies chosen for signaling and detecting network signals.
Throughput • Throughput refers to actual measured bandwidth, at a specific time of day, using specific Internet routes, and while a specific set of data is transmitted on the network
Digital versus analog • Electromagnetic waves are called analog because they have the sameshapes as the light and sound waves produced by the transmitters • Analog bandwidth is measured by how much of the electromagnetic spectrum is occupied by each signal. The basic unit of analog bandwidth is hertz (Hz), or cycles per second. • In digital signaling all information is sent as bits, regardless of the kind of information it is. Voice, video, and data all become streams of bits when they are prepared for transmission over digital media. • Unlimited amounts of information can be sent over the smallest or lowest bandwidth digital channel.
Networking Models • The concept of layers is used to describe communication from one computer to another • As the data passes between layers, each layer adds additional information that enables effective communication with the corresponding layer on the other computer • The OSI and TCP/IP models have layers that explain how data is communicated from one computer to another.
Layer Communication • Layer 4 on the source computer communicates with Layer 4 on the destination computer. The rules and conventions used for this layer are known as Layer 4 protocols.
OSI layers The OSI reference model explains how packets travel through the various layers to another device on a network Dividing the network into seven layers provides the following advantages: • It breaks network communication into smaller, more manageable parts. • It standardizes network components to allow multiple vendor development and support. • It allows different types of network hardware and software to communicate with each other. • It prevents changes in one layer from affecting other layers. • It divides network communication into smaller parts to make learning it easier to understand.