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Introduction to networks Learning objective After completing this topic, you should be able to identify the features of networks.
1. Network basicsBasic networks consist of two or more computers connected by a data cable.
At their most complex, networks may consist of thousands of computers in different regions.
Note
A computer that doesn’t connect to other computers is known as a standalone system.
The primary function of a network is to enable users to share resources such as files and folders, hardware, and software.
Networks also enable
centralized user administration and support
centralized security and password management
the central storage of resources, so that multiple users can access them at the same time
Types of hardware that networks enable users to share include
CPUs
drives
modems
printers, scanners, and cameras
CPUs
An important advantage of networks is that they enable users to share processing tasks among the CPUs of multiple computers. You can, for example, split a huge calculating task into several smaller tasks and delegate each of these tasks to different CPUs. The CPUs can then perform their delegated tasks at the same time. This increases available processing power, and can dramatically decrease required processing time.
drives
Networks enable the sharing of drives, including hard drives, floppy drives, CD and DVD drives, and universal serial bus (USB) drives.
Sharing drives enables multiple computers to access the same data, whether it’s stored centrally–on a single computer–or distributed among multiple computers.
The sharing of CD and DVD drives enables computers without these drives to access information stored on CD or DVD, via other computers on which the drives are installed.
modems
The sharing of modems on a network enables more than one computer to access the Internet or perform fax functions at the same time. In small companies, Internet and e-mail facilities may be provided by a single modem attached to a central server.
printers, scanners, and cameras
On a network, multiple computers can share devices such as printers, scanners, and digital cameras or video equipment. The sharing of video equipment enables network users to participate in activities such as video conferencing and video chatting. Cameras are widely shared on the Internet as webcams. Examples of hardware that computers can’t share include most internal components–like power supplies, fans, and internal cards.
Question
What are the functions of a network?
Options:
To enable centralized management
To enable resource sharing
To increase CPU speeds
Answer
Functions of a network include enabling the sharing of resources and enabling centralized management.
Option 1 is correct. Networks enable you to centralize the management of users and of security. They also enable you to manage data and resources such as software, by storing them on central servers.
Option 2 is correct. A network’s primary function is to enable users to share data, software, and specific types of hardware–such as printers–among multiple computers.
Option 3 is incorrect. Networking computers doesn’t increase the speed or processing capacity of their CPUs. However, it does enable multiple CPUs to combine their processing power, with each CPU processing parts of a larger task at the same time.
Components of a network include
network protocols
network interface cards (NICs)
cable
hubs or switches
network protocols
A network protocol is a standard–or set of rules–that governs how computers in a network communicate, to ensure that they can interoperate. A single network may use several different network protocols.
Protocols may, for example, specify that all outgoing data transmissions include specific information, such as the address of the source machine, and the type and size of the data for transmission.
network interface cards (NICs)
A NIC is the physical hardware that enables a computer to transmit data to one or more other computers. The specific NIC on a computer often determines the type of network to which the computer can connect, and the speed at which it connects to a network.
On very small networks, computers may connect via cable between their communication ports, rather than by using NICs.
cable
Network cable is the most common method of connecting computers in a local network. The type of NIC installed on a computer determines the type of cable it requires. The most popular cable today is twisted-pair, Category 5 (CAT5) Ethernet cable. Other types of network cable include fibre optic cable, coaxial cable terminated by Bayonet Neill-Concelman (BNC) connectors, and copper cable.
Wireless networks are networks in which computers use media other than cable–such as radio frequencies–to communicate.
hubs or switches
Both hubs and switches are hardware devices that connect two or more computers together and allow them to communicate with each other. They perform traffic control in networks. For large networks, you can connect multiple hubs or switches to support more computers.
A hub connects multiple Ethernet network segments so that they act as a single segment. Only one computer connected to the hub can transmit data at a time. Unlike a hub, a switch uses dedicated lines to connect specific network nodes. It splits network traffic and transmits it to different destinations, rather than to all networked computers.
Question
Match each network component to a description of its function.
Options:
Cable
Switch
Network protocol
NIC
Targets:
Controls the transmission of data to multiple computers
Enables a computer to support a network connection
Enables computers to communicate by setting a standard for data transmission
Provides a physical connection between computers
Answer
A switch controls the transmission of data to multiple, networked computers. A NIC enables a computer to support a network connection, a network protocol enables computers to communicate by setting a standard for data transmission, and cable provides a physical connection between computers.
Except in wireless networks, cable provides the physical connections between the NICs of computers, and between NICs and a hub or switch. Cable isn’t always necessary, as in the case of wireless networks.
A switch controls the transmission of data between computers, to ensure that it reaches the required network destinations.
A network protocol is a set of rules that governs how computers transmit and interpret data. It ensures that computers can interoperate, through the use of standard methods.
On a computer, the NIC is the physical hardware that enables network communication. The type of NIC installed determines which type of cable and which network protocols the computer can support.
Basic types of networks include local area networks (LANs) and wide area networks (WANs).
A LAN is a network that covers a small geographic area–for example, to connect computers in a single company building or across a small group of university buildings.
A WAN is a cluster of LANs linked by routers, which direct data from one LAN to another. WANs cover a wider area than LANs–they may, for example, connect multiple company branches, each of which has its own LAN. The Internet is an example of a WAN.
Most networks transmit data in the form of data packets–units of information into which full transmissions are split.
Each data packet generally consists of a header, which contains information such as sender and destination address, and a payload, which contains the data for transmission.
Using data packets–rather than transmitting data in a single stream–helps limit the effects of transmission errors. If a fault affects only a single packet, for example, just this packet can be resent to transmit a full message successfully.
2. Introduction to TCP/IPTransmission Control Protocol/Internet Protocol (TCP/IP) is the most commonly used suite of protocols for data transmission across a network.
It’s also the standard set of protocols that the Internet uses–any computer requires TCP/IP to connect to the Internet.
On SUSE Linux machines used as servers, you often need to ensure that TCP/IP is installed and correctly configured.
Features of TCP/IP include
a flexible naming system
support for multiple connection types
support for routing
standardization
a flexible naming system
TCP/IP supports both numeric and alphanumeric device names, and so enables the use of both IP addresses and user-friendly host names. It currently supports approximately four billion IP addresses.
support for multiple connection types
TCP/IP supports several types of connections, including those governed by the Transfer Control Protocol (TCP), Internet Control Message Protocol (ICMP), and User Datagram Protocol (UDP). It provides varying levels of error correction for different connection types.
support for routing
On an appropriately configured system, TCP/IP can transmit data packets between different networks. This is known as routing.
standardization
The TCP/IP protocols are documented and maintained by the Internet Engineering Task Force (IETF), ensuring their standardization between different computer systems. Question
What are features of TCP/IP?
Options:
Standardization
Support for multiple connection types
Support for numeric naming only
Support for routing
Answer
TCP/IP is highly standardized, and supports both multiple connection types and routing.
Option 1 is correct. The TCP/IP protocols are documented and maintained by IETF, which ensures their standardization. As a result, many different systems can interoperate using TCP/IP.
Option 2 is correct. TCP/IP supports several types of connections, including those governed by TCP, ICMP, and UDP.
Option 3 is incorrect. TCP/IP supports numeric IP addresses, and user-friendly host names based on alphanumeric characters.
Option 4 is correct. On a routing device, TCP/IP enables the transfer of data packets between two or more networks.
For a computer to operate on a TCP/IP network, each computer must be assigned an IP address and a subnet mask.
An IP address takes the form of four numbers between 0 and 255, separated by dots. An example IP address is 192.168.100.20.
Each IP address includes the following parts:
Network ID
Host ID
Network ID
The first part of an IP address is a network ID, which identifies a network. All computers on the network share this ID.
Computers with different network IDs can’t communicate without using a router.
Host ID
The second part of an IP address is the host ID, which uniquely identifies a single host on a network. Each host ID on a network must be unique, although there may be identical hosts on separate networks. Computers with the same network ID can communicate with each other without using a router. A subnet mask identifies which components of an IP address identify a network, and which identify a host on the network. It consists of four values of either 0 or 255, separated by dots.
The number 255 identifies a network ID, and the number 0 identifies a host ID. For example, the subnet mask of 255.255.0.0 for the IP address 192.168.100.20 indicates that the 192.168 part of the address is the network ID and that 100.20 is the host ID.
In IP addresses, the number 0 identifies all networks, and the number 255 identifies all hosts on corresponding networks.
For example, the address 192.168.100.255 refers to all computers in the network 192.168.100.0 with a subnet mask of 255.255.255.0.
Addresses terminating in 255 are known as broadcast addresses, because you can use them to broadcast messages to all hosts in networks.
IP addresses are converted into domain names–and vice versa–by an international system of servers known as the Domain Name System (DNS).
On the Internet, DNS makes it possible for servers to locate resources such as web pages using URLs–for example, www.interswift.com.
In addition to configuring each host on a network with an IP address and subnet mask, you can choose to assign a default gateway.
A gateway device–or router–connects networks using different communications protocols. It has two or more IP addresses, to enable it to communicate with multiple networks.
In most networks, the default gateway IP address is assigned within the first few addresses–for instance, 192.168.100.1–to make it easier to remember.
Question
Match each address to its description.
Options:
10.7.180.0
10.7.180.3
192.168.38.255
255.255.255.0
Targets:
A broadcast address
A subnet mask
The IP address for a network
The IP address of a specific host
Answer
192.168.38.255 is a broadcast address, 255.255.255.0 is a subnet mask, 10.7.180.0 is the IP address for a network, and 10.7.180.3 is the IP address for a specific host.
The 0 at the end of the address 10.7.180.0 identifies the entire range of addresses for the network 10.7.180, from 10.7.180.1 to 10.7.180.254.
The address 10.7.180.3 is an IP address that would be assigned to a specific network host. The host ID of the address is within the allowable range for it not to refer to anything else on the network.
The 255 in the address 192.168.38.255 indicates that it’s a broadcast address for the network 192.168.38.0. It identifies all computers–or hosts–in the network.
The address 255.255.255.0 is a subnet mask, which always contains four values of either 255 or 0. This subnet mask indicates that the first three numbers in an IP address are the network ID, and that the last number is the host ID.
SummaryA basic network consists of two or more connected computers that enable users to share resources, including files and folders, software, and specific hardware. Networks also enable centralized management. Network components include network protocols, network interface cards (NICs), cable, and hubs or switches.
Transmission Control Protocol/Internet Protocol (TCP/IP) is the most commonly used suite of protocols for data transmission across a network. It’s also the suite of protocols that the Internet uses. TCP/IP supports both numeric IP addresses and alphanumeric names, as well as connections of different types.
Table of Contents | Top of page |
| Learning objective |
| 1. Network basics |
| 2. Introduction to TCP/IP |
| Summary |