Basics of Networking

Editor's Notes

• #2: Cisco Networking Academy Program IT Essentials: PC Hardware and Software v4.1 Chapter 8: Fundamental Networks
• #3: 8.1 Explain the principles of networking Websites that allow individuals to link to each other’s pages are called social networking sites. A set of related ideas can be called a conceptual network. The connections you have with all your friends can be called your personal network. Converged data networks can include general purpose computers, such as PCs and servers, as well as devices with more specific functions, including printers, phones, televisions, and game consoles. All data, voice, video, and converged networks share information and use various methods to direct how this information flows. The information on the network goes from one place to another, sometimes via different paths, to arrive at the appropriate destination. The public transportation system is similar to a data network. The cars, trucks, and other vehicles are like the messages that travel within the network. Each driver defines a starting point (source) and an ending point (destination). Within this system, there are rules such as stop signs and traffic lights that control the flow from the source to the destination. After completing this section, students will meet these objectives: Define computer networks Explain the benefits of networking Teaching Strategy: The mail system allows messages to travel between any place that can be reached. The telephone system allows worldwide voice, fax, and Internet connections. Public transportation moves people and packages from source to destination. Each of these has a way of getting into and out of the network and a means of directing traffic. It is much the same with computer networks.
• #4: 8.1.1 Define computer networks A host is any device that sends and receives information on the network. Peripherals are devices that are connected to hosts. Some devices can serve either as hosts or peripherals. Computer networks are used globally in businesses, homes, schools, and government agencies. Many of the networks are connected to each other through the Internet. Network devices include: Resources shared across networks include: Services, such as printing or scanning Storage space on removable devices, such as hard drives or optical drives Applications, such as databases Network uses include: Access information stored on other computers Print documents using shared printers Synchronize the calendar between your computer and your smart phone Different types of network media: Copper cabling uses electrical signals to transmit data between devices Fiber-optic cabling uses glass or plastic wire, also called fiber, to carry information as light pulses Wireless connection uses radio signals, infrared technology (laser), or satellite transmissions 8.1.2 Explain the benefits of networking The benefits of networking computers and other devices include lower costs and increased productivity. With networks, resources can be shared, which results in less duplication and corruption of data. Fewer peripherals needed – Printers, scanners, and backup devices can be shared among the network users. Increased communication capabilities - Collaboration tools facilitate communicate between users; Examples: e-mail, forums and chats, voice and video, and instant messaging Avoid file duplication and corruption - Servers store data and share it with network users. Confidential or sensitive data can be protected and shared with the users who have permission to access that data. Document tracking software can be used to prevent users from changing files that others are accessing at the same time. Lower cost licensing – The site license allows a group of people or an entire organization to use the application for a single fee. Centralized administration - Fewer people needed to manage the network. Lower cost to the company. Easier data backup to a central location. Conserve resources - Data processing is distributed across many computers to prevent overloading one computer with processing tasks. Student Activity: The student course content includes a matching activity, 8.1.2 Advantages and Disadvantages of Networking. To complete this activity, students will identify each phrase as an advantage or a disadvantage.
• #7: 8.2 Describe types of networks Data networks continue to evolve in complexity, use, and design. To communicate about networks, different types of networks are given different descriptive names. A computer network is identified by the following specific characteristics: The type of media used to connect the devices The type of networking devices used How the resources are managed How the network is organized How the data is stored The area it serves
• #8: 8.2.1 Describe a LAN Local Area Network (LAN) refers to a group of interconnected computers that is under the same administrative control. In the past, LANs were considered to be small networks that existed in a single physical location. Although LANs can be as small as a single local network installed in a home or small office, over time, the definition of LANs has evolved to include interconnected local networks consisting of many hundreds of hosts, installed in multiple buildings and locations. In this context, the word “Local” in Local Area Network refers to local consistent control rather than being physically close to each other. Devices in a LAN may be physically close, but it is not a requirement. 8.2.2 Describe a WAN A WAN covers a much larger area than a LAN. The most common example of a WAN is the Internet. The Internet is a large WAN that is comprised of millions of interconnected LANs. All of these networks are connected together using WAN connections, such as a phone company, cable company, or Internet Service Provider (ISP). Telecommunications service providers (TSP) are used to interconnect these LANs at different locations. 8.2.3 Describe a WLAN Traditionally, in a LAN, devices are connected together using copper cabling. In some environments, installing copper cabling may not be practical, desirable, or even possible. In these situations, wireless devices are used to transmit and receive data using radio waves. These networks are called wireless LANs, or WLANs. WLAN coverage can be limited to the area of a room or can have greater range. As with LANs, you can share resources such as files and printers, and access the Internet on a WLAN. Student Activity: The student course content includes a matching activity, 8.2.3 Network Types. To complete this activity, students will match each description to its network type.
• #9: 8.2.4 Explain peer-to-peer networks Individual users are responsible for their own resources and can decide which data and devices to share. There is no central point of control or administration in the network. Peer-to-peer networks work best in environments with ten or fewer computers. Peer-to-peer networks have several disadvantages: There is no centralized network administration which makes it difficult to determine who controls resources on the network. There is no centralized security. Each computer must use separate security measures for data protection. The network becomes more complex and difficult to manage as the number of computers on the network increases. There may be no centralized data storage. Separate data backups must be maintained. This responsibility falls on the individual users. Peer-to-peer networks still exist inside larger networks today. Even on a large client network, users can still share resources directly with other users without using a network server. In your home, if you have more than one computer, you can set up a peer-to-peer network. 8.2.5 Explain client/server networks Servers on a client/server network commonly perform some of the processing work for client machines; for example, sorting through a database before delivering only the records requested by the client. In a client/server model, the servers are maintained by network administrators. Data backups and security measures are implemented by the network administrator. The network administrator also controls user access to the network resources. All of the data on the network is stored on a centralized file server. Shared printers on the network are managed by a centralized print server. Network users with the proper permissions can access both the data and shared printers. Each user must provide an authorized username and password to gain access to network resources that they are permitted to use. A workgroup is a collection of workstations and servers on a LAN that are designed to communicate and exchange data with one another. Each workstation controls the user accounts, security information, and access to data and resources for that computer. A domain is a group of computers and electronic devices with a common set of rules and procedures administered as a unit. A domain does not refer to a single location or specific type of network configuration. The computers in a domain are a logical grouping of connected computers that can be located in different locations in the world. A specialized server called a domain controller manages all security-related aspects of users and network resources, centralizing security and administration. For data protection, an administrator performs a routine backup of all the files on the servers. If a computer crashes, or data is lost, the administrator can easily recover the data from a recent backup.
• #10: 8.3.1 Explain bandwidth and data transmission Data is sent in small chunks called packets. A packet has a header, containing the source and destination of the packet. A header has sequencing information so that the packets can be assembled at the destination. Bandwidth can be compared to highway traffic flow On a highway, cars represent the data. Number of lanes represents the number of cars that could travel on the highway at the same time. An eight-lane highway allows four times as many cars as a two-lane highway. The amount of time it takes data to travel from source to destination is called latency. Like a car traveling across town that encounters stop lights or detours, data is delayed by network devices and cable length. Network devices add latency when processing and forwarding data. When surfing the Web or downloading a file, latency does not normally cause problems. Time critical applications, such as Internet telephone calls, video, and gaming, can be significantly affected by latency. Data is transmitted in one of three modes: Simplex (Unidirectional transmission) is a single, one-way transmission. Example: The signal sent from a TV station to your TV. Half-duplex allows data to flow in one direction at a time. Simultaneous transmission in two directions is not allowed. Example: Two-way radios, police or emergency mobile radios Full-duplex allows data to flow in both directions at the same time. Bandwidth is measured in only one direction. 100 Mbps full-duplex means a bandwidth of 100 Mbps in each direction. A telephone conversation is an example of full-duplex communication. Both people can talk at the same time, and can still hear each other. Broadband technologies, such as digital subscriber line (DSL) and cable, operate in full-duplex mode. Broadband allows multiple signals to travel on the same wire simultaneously. Full-duplex networking technology increases network performance because data can be sent and received at the same time. Example: With DSL, users can download data and talk on the telephone at the same time.
• #11: 8.3.2 Describe IP addressing An IP address is a number that is used to identify a device on the network. Each device on a network has a unique IP address. A network device is referred to as a host or node. Each host must have an IP address within the same network to be able to communicate with each other. The IP address is similar to the mailing address of a person. It is known as a logical address because it is logically assigned based on the host location. The IP address, or network address, is based on the local network and is assigned to each host by a network administrator. This process is similar to the local government assigning a street address based on the logical description of the city or village and neighborhood. An IP address consists of a series of 32 binary bits (ones and zeros). The 32 bits are grouped into four 8-bit bytes called octets. Example: 10111110.01100100.00000101.00110110 An IP address is also represented in a dotted decimal format. Example: the binary IP address shown above is 190.100.5.54 When a host is configured with an IP address, it is entered as a dotted decimal number, such as 192.168.1.5. Imagine if you had to enter the 32-bit binary equivalent of this: 11000000101010000000000100000101. If just one bit were mistyped, the address would be different and the host may not be able to communicate on the network. Unique IP addresses on a network ensure that data can be sent to and received from the correct network device. The logical 32-bit IP address is hierarchical and is composed of two parts. The first part identifies the network and the second part identifies a host on that network. Both parts are required in an IP address. As an example, if a host has IP address 192.168.18.57, the first three octets, 192.168.18, identify the network portion of the address, and the last octet, 57 identifies the host. This is known as hierarchical addressing, because the network portion indicates the network on which each unique host address is located. Routers only need to know how to reach each network and not the location of each individual host. Class A - Large networks, implemented by large companies and some countries. First octet is from 1-127. 127.0.0.0 is a special network reserved for testing. 127.0.0.1 is a loopback address. Class B - Medium-sized networks, implemented by universities. First octet is from 128-191. Class C - Small networks, implemented by ISP for customer subscriptions. First octet is from 192-223. Class D - Special use for multicasting. First octet is from 224-240. Class E - Used for experimental testing
• #12: 8.3.2 Describe IP addressing If an organization owns one Class B network but needs to provide IP addresses for four LANs, the organization will subdivide the Class B network into four smaller parts by using subnetting, which is a logical division of a network. The subnet mask specifies how it is subdivided. An experienced network administrator typically performs subnetting. After the subnetting scheme has been created, the proper IP addresses and subnet masks can be configured on the hosts in the four subnetted LANs. These skills are taught in the Cisco Networking Academy courses related to CCNA level networking skills. Manual IP address configuration In a network with a small number of hosts, it is easy to manually configure each device with the proper IP address. A network administrator who understands IP addressing should assign the addresses and should know how to choose a valid address for a particular network. To manually enter an IP address on a host, go to the TCP/IP settings in the Properties window for the Network Interface Card (NIC). The NIC is the hardware that enables a computer to connect to a network. It has an address called the Media Access Control (MAC) address. Whereas the IP address is a logical address that is defined by the network administrator, a MAC address is "burned-in" or permanently programmed into the NIC when it is manufactured. The IP address of a NIC can be changed, but the MAC address never changes. The main difference between an IP address and a MAC address is that the MAC address is used to deliver frames on the LAN, while an IP address is used to transport frames outside the LAN. A frame is a data packet, along with address information added to the beginning and end of the packet before transmission over the network. Once a frame is delivered to the destination LAN, the MAC address is used to deliver the frame to the end host on that LAN. Dynamic IP address configuration If more than a few computers comprise the LAN, manually configuring IP addresses for every host on the network can be time-consuming and prone to errors. In this case, the use of a Dynamic Host Configuration Protocol (DHCP) server would automatically assign IP addresses and greatly simplify the addressing process. Student Activity: The student course content includes worksheet, 8.3.2 Identify IP Address Classes. To complete this worksheet, students will specify the IP Address Class for each given IP address and mask.
• #13: 8.3.3 Define DHCP Dynamic Host Configuration Protocol (DHCP) is a software utility used to dynamically assign IP addresses to network devices. This dynamic process eliminates the need for manually assigning IP addresses. A DHCP server can be set up and the hosts can be configured to automatically obtain an IP address. When a computer is set to obtain an IP address automatically, all of the other IP addressing configuration boxes are dimmed. The server maintains a list of IP addresses to assign, and manages the process so that every device on the network receives a unique IP address. Each address is held for a predetermined amount of time. When the time expires, the DHCP server can use this address for any computer that joins the network.
• #14: 8.3.3 Define DHCP The DHCP server receives a request from a host. The server then selects IP address information from a set of predefined addresses that are stored in a database. Once the IP address information is selected, the DHCP server offers these values to the requesting host on the network. If the host accepts the offer, the DHCP server leases the IP address for a specific period of time. Using a DHCP server simplifies the administration of a network because the software keeps track of IP addresses. Automatically configuring TCP/IP also reduces the possibility of assigning duplicate or invalid IP addresses. For a computer on the network to take advantage of the DHCP server services, the computer must be able to identify the server on the local network. A computer can be configured to accept an IP address from a DHCP server by selecting the "Obtain an IP address automatically" option in the NIC configuration window. If your computer cannot communicate with the DHCP server to obtain an IP address, the Windows operating system will automatically assign a private IP address. If your computer is assigned an IP address in the range of 169.254.0.0 to 169.254.255.255, you computer will only be able to communicate with other computers in the same range. An example of when these private addresses would be useful is in a classroom lab where you wish to prevent access outside of your network. This operating system feature is called Automatic Private IP Addressing (APIPA). APIPA continually requests an IP address at five-minute intervals from a DHCP server for your computer. To access a DNS server, a computer uses the IP address configured in the DNS settings of the NIC in the computer. For a computer on the network to take advantage of the DHCP server services, the computer must be able to identify the server on the local network. A computer can be configured to accept an IP address from a DHCP server by selecting the "Obtain an IP address automatically" option in the NIC configuration window. The DHCP settings are configured the same when using either a wired or wireless NIC.
• #16: 8.3.4 Describe Internet protocols and applications Timing is crucial to network operation. Protocols require messages to arrive within certain time intervals so that computers will not wait indefinitely for messages that may have been lost. Therefore, systems maintain one or more timers during transmission of data. Protocols also initiate alternative actions if the network does not meet the timing rules. These are the main functions of protocols: Identifying errors Compressing the data Deciding how data is to be sent Addressing data Deciding how to announce sent and received data Here is a summarized list of some of the more common protocols used on networks and the Internet. These protocols are used to browse the web, send and receive e-mail, and transfer data files. TCP/IP - A protocol used to transport data on the Internet. NETBEUI and NETBIOS – A small, fast protocol designed for a workgroup network that requires no connection to the Internet. IPX and SPX – A protocol used to transport data on a Novell Netware network. HTTP and HTTPS – A protocol that defines how files are exchanged on the Web. FTP – A protocol that provides services for file transfer and manipulation. SSH – A protocol that is used to connect computers together securely. Telnet – A protocol that uses a text-based connection to a remote computer. POP – A protocol used to download email messages from an email server. IMAP – A protocol used to download email messages from an email server. SMTP – A protocol used to send mail in a TCP/IP network. Student Activity: The student course content includes a matching activity, 8.3.4 Network Protocols. To complete this matching activity, students will match the definition to the appropriate protocol.
• #17: 8.3.5 Define ICMP Ping is a troubleshooting tool used to determine basic connectivity. These command line switches that can be used with the ping command. Four ICMP echo requests (pings) are sent to the destination computer. If it is reachable, the destination computer responds with four ICMP echo replies. The percentage of successful replies can help you to determine the reliability and accessibility of the destination computer. It is also possible to use ping to find the IP address of a host when the name is known. If you ping the name of a website, for example, www.cisco.com, the IP address of the server displays. Other ICMP messages are used to report: Undeliverable packets Data on an IP network that includes source and destination IP addresses Whether a device is too busy to handle the packet A data packet arrives at a router, which is a networking device that forwards data packets to other networks. If the router does not know where to send the packet, the router deletes it. The router then sends an ICMP message back to the sending computer. A busy router may send an ICMP message to the sending computer advising it to slow down because of network congestion.
• #18: 8.4 Describe the physical components of a network There are many devices that can be used in a network to provide connectivity. The device you use will depend on how many devices you are connecting, the type of connections that they use, and the speed at which the devices operate. These are the most common devices on a network: The physical components of a network are needed to move data between these devices. The characteristics of the media determine where and how the components are used. These are the most common media used on networks.
• #19: 8.4.1 Identify names, purposes, and characteristics of network devices Hubs To make data transmission more extensible and efficient than a simple peer-to-peer network, network designers use specialized network devices, such as hubs, switches, routers, and wireless access points, to send data between network devices. The type of connection that is needed determines the device that is used. This process means that all traffic from a device connected to the hub is sent to all the other devices connected to the hub every time the hub transmits data. This causes a great amount of network traffic. Bridges and Switches Files are broken up into small pieces of data, called packets, before they are transmitted over a network. This allows for error checking and easier retransmission if the packet is lost or corrupted. Address information is added to the beginning and to the end of packets before they are transmitted over the network. The packet, along with the address information, is called a frame. LANs are often divided into sections called segments bounded by bridges. A typical bridge may have just two ports, linking two segments of the same network. A switch is a more sophisticated device than a bridge. A switch maintains a table of the MAC addresses for computers that are connected to each port. When a frame arrives at a port, the switch compares the address information in the frame to its MAC address table. The switch then determines which port to use to forward the frame.
• #20: 8.4.1 Identify names, purposes, and characteristics of network devices Router While a switch connects segments of a network, routers are devices that connect entire networks to each other. Switches use MAC addresses to forward a frame within a single network. Routers use IP addresses to forward frames to other networks. Wireless Access Points Wireless access points provide network access to wireless devices such as laptops and PDAs. The wireless access point uses radio waves to communicate with radios in computers, PDAs, and other wireless access points. An access point has limited range of coverage. Large networks require several access points to provide adequate wireless coverage.
• #21: 8.4.1 Identify names, purposes, and characteristics of network devices Multipurpose Devices There are network devices that perform more than one function. It is more convenient to purchase and configure one device that serves all of your needs than to purchase a separate device for each function. This is especially true for the home user. In your home, you would purchase a multipurpose device instead of a switch, a router, and a wireless access point. The Linksys 300N is an example of a multipurpose device.
• #22: 8.4.2 Identify names, purposes, and characteristics of common network cables Twisted-Pair Cabling Until recently, cables were the only medium used to connect devices on networks. A wide variety of networking cables are available. Coaxial and twisted-pair cables use copper to transmit data. Fiber-optic cables use glass or plastic to transmit data. These cables differ in bandwidth, size, and cost. As a technician, you need to know what type of cable to use in different situations so that you are able to install the correct cables for the job. You will also need to be able to troubleshoot and repair problems that you encounter. Twisted-pair is a type of copper cabling that is used for telephone communications and most Ethernet networks. A pair of wires forms a circuit that can transmit data. The pair is twisted to provide protection against crosstalk, which is the noise generated by adjacent pairs of wires in the cable. Pairs of copper wires are encased in color-coded plastic insulation and twisted together. An outer jacket protects the bundles of twisted pairs called poly-vinyl chloride (PVC). PVC will produce hazardous fumes when burned. Most network cables are installed in the plenum space, or areas in the ceiling, in the walls, and under the floor. If cables with the PVC jackets do burn in the plenum space, hazardous fumes can spread quickly through a building. To avoid this danger, only install plenum-grade fire resistant cabling in the plenum space. When electricity flows through a copper wire, a magnetic field is created around the wire. A circuit has two wires, and in a circuit, the two wires have oppositely charged magnetic fields. When the two wires of the circuit are next to each other, the magnetic fields cancel each other out. This is called the cancellation effect. Without the cancellation effect, your network communications become slow due to the interference caused by the magnetic fields. There are two basic types of twisted-pair cables: Unshielded twisted-pair (UTP) Has two or four pairs of wires Relies on the cancellation effect for reduction of interference caused by electromagnetic interface (EMI) and radio frequency interference (RFI) Most commonly used cabling in networks Has a range of 328 ft (100 meters) Shielded twisted-pair (STP) Each pair is wrapped in metallic foil to better shield the wires from electrical noise. Four pairs of wires are then wrapped in an overall metallic braid or foil. STP reduces electrical noise from within the cable. It also reduces EMI and RFI from outside the cable. Facts about STP Prevents interference better than UTP. Primarily used outside North America. Disadvantages of STP More expensive because of extra shielding. More difficult to install because of the thickness. Metallic shielding must be grounded at both ends. If not, shield acts like an antenna picking up unwanted signals. Category Rating UTP comes in several categories that are based on two factors: The number of wires in the cable The number of twists in those wires Category 3 is the wiring used for telephone connections. It has four pairs of wires and a maximum data transmission rate of up to 16 Mbps. Category 3 telephone cable is usually terminated into an RJ-11 connector. Category 5 and Category 5e have four pairs of wires with a maximum data transmission rate of up to 100 Mbps. Category 5 and 5e are the most common network cables used. Category 5e has more twists per foot than Category 5 wiring. These extra twists further prevent interference from outside sources and the other wires within the cable. Category 6 cable uses a plastic divider to separate and maintain the position of the pairs of wires relative to each other. This prevents interference. The pairs also have more twists than Category 5e cable. Category 5, 5e, and 6 cables terminate into an RJ-45 connector. An RJ-11 telephone connector has six pins and an RJ-45 connector has eight pins.
• #23: 8.4.2 Identify names, purposes, and characteristics of common network cables Coaxial Cable Coaxial cable is a copper-cored cable surrounded by a heavy shielding. Coaxial cable is used to connect computers in a network. There are several types of coaxial cable, including the following: Thicknet or 10Base5 - Coax cable that was used in networks and operated at 10 megabits per second with a maximum length of 500 meters. Thinnet or 10Base2 - Coax cable that was used in networks and operated at 10 megabits per second with a maximum length of 185 meters. RG-59 - Most commonly used for cable television in the US RG-6 - Higher quality cable than RG-59 with more bandwidth and less susceptibility to interference
• #24: 8.4.2 Identify names, purposes, and characteristics of common network cables Fiber-Optic Cable Signal can travel several miles or kilometers before the signal needs to be regenerated. Common connectors for fiber-optic networks are SC, ST, and LC. These three types of fiber-optic connectors are half-duplex, which allows data to flow in only one direction. Therefore, two cables are needed. Two types of glass fiber-optic cable: Multimode - Cable that has a thicker core than single-mode cable. It is easier to make, can use simpler light sources (LEDs), and works well over distances of a few kilometers or less. Single-mode - Cable that has a very thin core. It is harder to make, uses lasers as a light source, and can transmit signals dozens of kilometers with ease. Student Activity: The student course content includes a Packet Tracer activity, 8.4.2 Cabling a Simple Network. Develop an understanding of the basic functions of Packet Tracer. Create a simple network using two hosts. Observe the importance of using the correct cable type to connect PCs.