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Section 8.1 Explain the role of carriers in WAN transmissions

Section 8.1 Explain the role of carriers in WAN transmissions Compare and contrast DUN and VPN connections Explain the benefits of circuit switching Describe how message switching works Describe packet switching Section 8.2 Describe how networks transmit data using the X.25 protocol

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Section 8.1 Explain the role of carriers in WAN transmissions

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  1. Section 8.1 • Explain the role of carriers in WAN transmissions • Compare and contrast DUN and VPN connections • Explain the benefits of circuit switching • Describe how message switching works • Describe packet switching • Section 8.2 • Describe how networks transmit data using the X.25 protocol • Explain how frame relay transmits data • Describe how ATM works • Identify the uses of B-ISDN

  2. Section 8.3 • Show how FDDI transmits data • Describe how SONET transmits data • Explain the benefits of SMDS

  3. pp. 224-230 How a WAN Works 8.1 Guide to Reading Main Ideas Circuit-switched networks use a direct, physical connection to transmit data back and forth. Message-switched networks send entire transmissions between intermediaries. Packet-switched networks route packets through virtual circuits. Key Terms carrier services remote access dial-up networking (DUN) Virtual Private Network (VPN) circuit-switched network message switching packet switching Packet Switching Exchange (PSE)

  4. pp. 224-230 How a WAN Works 8.1 Carriers After a network grows beyond the confines of the LAN, a carrier service is required. Carriers provide a variety of services which are connected through remote access. carrier services Data transfer services provided by telecommunications companies, such as AT&T, Sprint, or Verizon. (p. 224) remote access A direct connection to a network using regular dial-up lines. After the connection is made, the user can work on the network as if in the office. (p. 224)

  5. pp. 224-230 How a WAN Works 8.1 Carriers Remote access connections are established through either a dial-up network (DUN) or virtual private network (VPN). The advantages of a VPN are that users benefit from faster network connections, privacy, and security. dial-up networking (DUN) A client service using regular telephone lines to connect to a network. (p. 224) Virtual Private Network (VPN) An alternative to using a dial-up network connection. Is a network connection between two computers. With a VPN, a remote user can securely access the internal network from a remote location. (p. 226)

  6. pp. 224-230 How a WAN Works 8.1 Switching Technologies • Data in the WAN is transported through various technologies: • Circuit switching • Message switching circuit-switched network A network that creates a direct physical connection between the sender and receiver.(p. 228) message switching A technology used to route an entire message from one system to another. That message is routed through intermediate (go-between) station and does not involve a direct physical connection between the sender and receiver. (p. 228)

  7. pp. 224-230 How a WAN Works 8.1 Switching Technologies Message switching sends the entire message to intermediary stations that decide which route to use.

  8. pp. 224-230 How a WAN Works 8.1 Switching Technologies Packet switching is commonly found in LANs. Packets are routed through Packet Switching Exchanges until they reach their destination. packet switching A transmission method in which all transmissions are broken into small units and sent over the network. Packets are reassembled at the destination computer. (p. 229) Packet Switching Exchange (PSE) Go-betweens in the packet switching process. The PSE inspects the packet’s destination address, consults a routing table, and forwards the packet at the highest possible speed. (p. 229)

  9. pp. 224-230 How a WAN Works 8.1 Switching Technologies Packet-switching networks send packets along the best route available.

  10. pp. 224-230 How a WAN Works 8.1 You Try It • Activity 8A – Setting Up a DUN Connection (p. 225) • Activity 8B – Setting Up a VPN Connection (p. 226) • Activity 8C – Tracing Packets (p. 229)

  11. pp. 232-236 Sending Data across a WAN 8.2 Guide to Reading Main Ideas X.25 is a packet-switching protocol originally designed for analog telephone lines. Frame relay uses permanent, virtual circuits and reliable, digital lines to transmit data. ATM transmits data, voice, and video over many types of lines. Key Terms X.25 Data Terminal Equipment (DTE) packet assembler/ disassembler (PAD) Data Circuit-terminating Equipment (DCE) frame relay Asynchronous Transfer Mode (ATM) cell relay broadband ISDN (B-ISDN)

  12. pp. 232-236 Sending Data across a WAN 8.2 X.25 Packet-Switching Protocol Computers on an X.25 network can receive and transmit data at the same time. This is also called full-duplex communication. X.25 A connection-oriented, packet-switching protocol designed for use on analog telephone lines. Computers on an X.25 network can receive and transmit data at the same time. (p. 232)

  13. pp. 232-236 Sending Data across a WAN 8.2 X.25 Packet-Switching Protocol • The X.52 protocol concentrates on the interface through which transmission flows. The interface is made up of the following devices: • Data Terminal Equipment (DTE) • Packet assembler/dissembler (PAD) Data Terminal Equipment (DTE) X.25 device terminology. There are no computers, hosts, or nodes. Instead, sending and receiving computers are referred to simply as this. (p. 232) packet assembler/disassembler (PAD) A device in X.25 transmissions that prepares packets for transmission and disassembles the packets that come in. (p. 232)

  14. pp. 232-236 Sending Data across a WAN 8.2 X.25 Packet-Switching Protocol • Data Circuit-terminating Equipment (DCE) • Packet switching exchanges (PSEs) Data Circuit-Terminating Equipment (DCE) Packets are sent here from the DTE or PAD. A DCE might be a modem or packet switch. A DCE is located at each end of the connection. (p. 232)

  15. pp. 232-236 Sending Data across a WAN 8.2 Frame Relay Frame relay is faster than the X.52 protocol. Frame relay networks connecting LANs to a WAN rely on routers and switching equipment. frame relay A newer form of packet switching that relies on digital technologies, such as fiber optic and ISDN. (p. 233)

  16. pp. 232-236 Sending Data across a WAN 8.2 ATM Another type of switching technology is Asynchronous Transfer Mode (ATM). Like a frame relay, ATM is designed to take advantage of digital media. Asynchronous Transfer Mode (ATM) A connection-oriented networking technology. Like frame relay, ATM is designed to take advantage of digital media. (p. 234)

  17. pp. 232-236 Sending Data across a WAN 8.2 ATM ATM is useful for high-speed LAN and WAN networking over a range of media types and relies on cell relay. ATM transmits data in 53-byte cells. cell relay Used with ATM transmissions, a high-speed transmission method based on fixed-size units that are known as cells. (p. 235)

  18. pp. 232-236 Sending Data across a WAN 8.2 ATM ATM takes incoming data and packages the contents in uniform, 53-byte cells. At the receiving end, ATM sends it cells out onto a WAN in a steady stream for delivery.

  19. pp. 232-236 Sending Data across a WAN 8.2 B-ISDN • ATM was created for broadband ISDN (B-ISDN) and B-ISDN services are divided into two categories: • Interactive services • Distributed services broadband ISDN (B-ISDN) The next generation of ISDN that is capable of delivering high quantities of data. (p. 236)

  20. pp. 238-244 Developing Technologies 8.3 Guide to Reading Main Ideas FDDI transmits data over fiber optic cabling using a ring topology. SONET multiplexes incoming signals for transmission over very-high-speed optical cabling. SMDS transmits data in any format between networks. Key Terms Synchronous Optical NETwork (SONET) Synchronous Digital Hierarchy (SDH) optical carrier (OC) Synchronous Transport Signal (STS) Switched Multimegabit Data Services (SMDS)

  21. pp. 238-244 Developing Technologies 8.3 FDDI FDDI was developed based on ring topology and token passing. It uses fiber optic as its medium of transmission. FDDI was developed for two primary reasons. First, it was designed to support and extend the capabilities of older LANs, such as Ethernet and Token Ring. Second, it provides a reliable infrastructure for businesses moving mission-critical applications to networks.

  22. pp. 238-244 Developing Technologies 8.3 FDDI • Although FDDI was developed specifically for use with fiber optic cable, it can operate on a variety of cable types. • Multimode fiber optic cable • Single-mode fiber optic cable • Category 5 Unshielded Twisted Pair copper wiring • IBM Type 1 Shielded Twisted Pair copper wiring

  23. pp. 238-244 Developing Technologies 8.3 FDDI FDDI topology is similar to Token Ring, except that it operates using optical transmissions. Another important distinction is that FDDI is characterized by two counter-rotating rings (known as a dual-ring topology). An FDDI topology by itself usually does not make use of hubs.

  24. pp. 238-244 Developing Technologies 8.3 FDDI FDDI networks are limited to rings no longer than 100 kilometers apiece. They are also limited to no more than 500 nodes per ring. FDDI is a high-speed, high-bandwidth network based on optical transmissions. It is most often used as a network backbone for connecting high-end computers.

  25. pp. 238-244 Developing Technologies 8.3 SONET Synchronous Optical NETwork (SONET) is transmitted over the fiber optic cables that are used by long-distance carriers. The European standard is Synchronous Digital Hierarchy (SDH). Synchronous Optical NETwork (SONET) An American National Standards Institute (ANSI) standard for the transmission of different types of digital information using optical media—data, voice, and video. (p. 240) Synchronous Digital Hierarchy (SDH) A European standard for the transmission of different types of digital information using optical media—data, voice, and video. (p. 240)

  26. pp. 238-244 Developing Technologies 8.3 SONET SONET multiplexes many incoming signals for high-speed transport.

  27. pp. 238-244 Developing Technologies 8.3 SONET • Two signal definitions lie at the heart of the SONET standard regarding multiplexing capability: • Optical carrier (OC) • Synchronous Transport Signals (STSs) optical carrier (OC) A signal definition in the SONET standard used by fiber optic media and translated roughly to speed and carrying capacity. (p. 241) Synchronous Transport Signal (STS) The electrical equivalents of OC levels and are used by nonfiber media. See also optical carrier. (p. 241)

  28. pp. 238-244 Developing Technologies 8.3 SONET SONET converts electrical (STS) signals to optical (OC) levels for transport. It also “unconverts” them (OC to STS) at the point in which the transmissions leave the SONET media. SONET frames are sent continuously – whether they contain data or not.

  29. pp. 238-244 Developing Technologies 8.3 SMDS Switched Multimegabit Data Services (SMDS) is a means for businesses to connect to LANs in separate locations. It is a less expensive alternative to dedicated leased lines. SMDS is a connectionless, packet-switched technology well-suited to the type of “bursty” traffic characteristic of LAN (or LAN-to-LAN) communications. Switched Multimegabit Data Services (SMDS) A broadband public networking service offered by communications carriers. (p. 243)

  30. pp. 238-244 Developing Technologies 8.3 SMDS SMDS is a connectionless service that provides WAN transmissions on an as-needed basis.

  31. Chapter 8 Resources For more resources on this chapter, go to the Introduction to Networks and Networking Web site at http://networking.glencoe.com.

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