Lesson 2—Networking BASICS1 Networking BASICS Network Media Unit 1 Lesson 2

Lesson 2—Networking BASICS2 Objectives Explain how data transmissions are sent and received. List and describe the types of transmission media. Describe the functions of a network interface card.

Lesson 2—Networking BASICS3 Types of Networks There are two types of networks by which information is transmitted: –circuit switched networks – packet switched networks

Lesson 2—Networking BASICS4 Circuit Switched Network There is a dedicated and direct physical connection between sender and receiver. No other transmissions can take place while the connection is active. Once the transmission is ended, other connections can be made with other devices. It is ideal for voice communications because there are no interruptions from other devices or delays.

Lesson 2—Networking BASICS5 Packet Switched Network This network requires data transmission be broken into smaller units called packets. Each packet is sent independently through the network. It is used for data transmission because data is not as time-sensitive as voice communication. It allows multiple devices to share one line or frequency. It facilitates error correction.

Lesson 2—Networking BASICS6 Signaling Techniques There are two ways that a signal is sent across a network medium: – baseband signaling – broadband signaling

Lesson 2—Networking BASICS7 Baseband Signaling Sends one data signal across the network media Entire capacity of the media is used for the one data signal Signals are transmitted in a digital format Many devices can send and receive across the medium, but only one at a time

Lesson 2—Networking BASICS8 Baseband Signaling

Lesson 2—Networking BASICS9 Broadband Signaling Divides the cable into several different channels Signals are transmitted at different frequencies in an analog mode Allows many different signals to be sent simultaneously on a single cable Signal sent in only one direction Used for computer network data transmissions

Lesson 2—Networking BASICS10 Broadband Signaling

Lesson 2—Networking BASICS11 Factors Affecting Transmissions The flow of a signal down the network media can become distorted. Common types of distortions are attenuation and interference.

Lesson 2—Networking BASICS12 Attenuation Loss of signal power Measured by the decrease in decibels (db) over a specific distance

Lesson 2—Networking BASICS13 Interference Interference is caused when a strong external signal interferes with a signal. Radio frequency interference (RFI) - interference caused by broadcast signals from a radio or television transmitter. Electromagnetic interference (EMI) - motor or source of intense electrical activity creates an electromagnetic signal that interferes with a data signal. Near end crosstalk (NEXT) and Far end crosstalk (FEXT) - interference from another data signal being transmitted on adjacent wire.

Lesson 2—Networking BASICS14 Transmission Media Copper cables Fiber optic cables Wireless

Lesson 2—Networking BASICS15 Copper Cables Thin coaxial Shielded twisted pair (STP) Unshielded twisted pair (UTP) UTP rated by Category 1 - 6

Lesson 2—Networking BASICS16 Copper Cables

Lesson 2—Networking BASICS17 Copper Cables

Lesson 2—Networking BASICS18 Fiber Optic This cable uses a thin cylinder of glass to send light impulses. The cable consists of a strand of glass (core) surrounded by a glass tube (cladding). Single mode - one light source flashes a light down the cable. Multimode - supports many simultaneous light transmissions.

Lesson 2—Networking BASICS19 Fiber Optic

Lesson 2—Networking BASICS20 Wireless Transmission is sent and received through invisible waves Less expensive than copper or fiber optic lines. Allows the user to move freely around the office or campus and still remain connected to the network Fastest-growing segment of network media today

Lesson 2—Networking BASICS21 Wireless Transmissions Infrared transmits data using infrared (IR) light. IR shares many of the same properties as visible light. Radio frequency signals can be transmitted over radio waves similar to local radio station transmissions. The signal comes in at a lower power level and does not reach as far.

Lesson 2—Networking BASICS22 Network Interface Card The NIC serves as the connection between the personal computer and the network media. It connects to the computer on its base by plugging into an expansion slot of the computer. Another connection is accessible from the outside of the computer and has connections for the cables to plug into the network.

Lesson 2—Networking BASICS23 Network Interface Card Changes from parallel to serial transmission Creates packets Determines when to send Transmits packet

Lesson 2—Networking BASICS24 Network Interface Card

Lesson 2—Networking BASICS25 Summary Switching involves moving (switching) the signal from one wire or frequency to another. A circuit switched network creates a dedicated and direct physical connection between the sender and receiver. No other transmissions can take place while the connection is active, but once the transmission is ended, other connections can be made with other devices. Circuit switching is ideal for voice communications. Computer networks sending data use packet switched networks. Packet switching requires that the data transmission be broken into smaller units called packets. Each packet is then sent independently through the network to reach the destination.

Lesson 2—Networking BASICS26 Summary (continued) Baseband signaling sends one data signal across the network media. The entire capacity of the media is used for the one data signal that is transmitted in a digital format, which is made up of short impulses of off and on. The other type of signaling tech- nique is known as broadband signaling. Broadband transmis- sion divides the cable into several different channels. It does this because the signals are transmitted at different frequencies in an analog, or continuous, mode. Broadband transmission allows many different signals to be sent simultaneously on a single cable. Computer data networks use baseband signaling instead of broadband signaling.

Lesson 2—Networking BASICS27 Summary (continued) The flow of a signal down the network media can sometimes become distorted. The two common types of distortions are attenuation and interference. As the data travels, it meets resis- tance, which causes the signal to weaken gradually. This loss of signal power is known as attenuation. Interference or noise is caused when a strong external signal interferes with the signal being transmitted. Radio frequency interference (RFI) refers to interference caused by broadcast signals from a radio or television transmitter. Electromagnetic interference (EMI) may be caused by a variety of sources. The source of near end crosstalk (NEXT) interference is from another data signal being transmitted. Far end crosstalk (FEXT) is similar to NEXT except that the interference is measured at the far end of the wire.

Lesson 2—Networking BASICS28 Summary (continued) There are many different types of network media, yet they all can be classified into three major categories: copper, fiber optic, and wireless. Thin coaxial cable is approximately one-quarter of an inch in diameter, has a single copper wire at its center, and is surrounded by a layer of insulation. Around the insulation is a braided copper mesh channel, and everything is covered by a thick outer shield of insulation. Twisted pair cable has become the standard today for copper cabling used in computer net- works, replacing thin coaxial cable. Twisted pair cable is two insulated copper wires that are twisted around each other. Each pair is then bundled together with other pairs in a jacket. There are two types of twisted pair cables. Shielded twisted pair (STP) cables have a foil shielding on the inside of the jacket, which reduces interference. Unshielded twisted pair (UTP) cables do not have any shielding.

Lesson 2—Networking BASICS29 Summary (continued) A fiber optic cable uses a very thin cylinder of glass, instead of copper, at its center. Fiber optic cables send light impulses instead of transmitting electrical signals. Wireless communica- tion uses no visible connection, such as a copper cable or fiber optic line, between the network devices. Instead, the transmis- sion is sent and received through invisible waves. Transmission signals can be sent by infrared light waves or radio frequency waves.

Lesson 2—Networking BASICS30 Summary (continued) When connecting a personal computer to the transmission media on a LAN, hardware known as a network interface card (NIC) is used. A NIC serves as the connection between the personal computer and the network media. The NIC connects to the computer on its base by plugging into one of the expansion slots of the computer. The other connection, found on the side of the NIC, is accessible from the outside of the computer and has connections for the cables to plug into the network (or an antenna for wireless transmissions). These connections depend on the type of network media being used.