Tài liệu giảng dạy CCNA - module 06 chapter 19-Remote Access Technologies

1 Module 06 WAN Technology Chapter 19 Remote Access Technologies 2 Table of Content 1 Perspectives on the PSTN 2 Analog Modems 3 Integrated Services Digital Network 4 Digital Subscriber Line 5 Cable Modems 6 Comparison of Remote Access Technologies 3 1. Perspectives on the PSTN 4 Analog signal  Sound waves travel through the air by vibrating the air. The human ear hears the sound because the ear vibrates as a result of the air inside the ear moving, which, in turn, causes the brain to process the sounds that were heard by the ear.  The PSTN, however, cannot forward sound waves. Instead, a telephone simply converts the sound waves into an analog electrical signal. The PSTN can send the electrical signal between one phone and another. On the receiving side, the phone converts the electrical signal back to sound waves. 5 Digital signal  Electrically, digital signals use a defined set of both positive and negative voltages, which, in turn, represent either a binary 0 or a binary 1. 6 Converting Analog Voice to Digital Voice Digital T1 line Telco voice switch Telco voice switch Local loop (analog) Local loop (analog) PCM codec converts Digital ←→ Analog PCM codec converts Digital ←→ Analog PSTN 7 2. ANALOG MODEMS 8 Basic Operation of Modems over PSTN Digital T1 line Telco voice switch Telco voice switch Local loop (analog) Local loop (analog) PCM codec converts Digital ←→ Analog PCM codec converts Digital ←→ Analog PSTN Modem converts Digital ←→ Analog Modem converts Digital ←→ Analog 9 Modulation and Demodulation • Amplitude Modulated, Frequency Modulated, Phase modulation 10 Point-to-Point Protocol Features with Modems  Most computers today use PPP as the data-link protocol when using modems.  PPP supports both synchronous communication, as typically is done over leased point-to-point lines, as well as asynchronous communication, which typically is done over dialed circuits using modems.  PPP includes some features that are important when using modems to dial into an ISP:  PPP includes the capability of dynamically assigning an IP address to a device on the other end of the PPP link.  PPP supports that Challenge Handshake Authentication Protocol (CHAP), which popularly is used to allow the dial-in user to supply a username and password to gain access to the ISP network. [...]... called a DSL access multiplexer (DSLAM)  DSL allows for a concurrent voice call to be up at the same time as the data connection  Unlike modems and ISDN, DSL’s data component is always on— in other words, you don’t have to signal to set up a data circuit 20 DSL STANDARDS Service Download Upload ADSL 1.54 4-8 .192Mbps 1 6-6 40Kbps SDSL 1.54 4-2 .048Mbps 1.54 4-2 .048Mbps HDSL 1.54 4-2 .048Mbps 1.54 4-2 .048Mbps... Point-to-Point Protocol (PPP) links 14 ISDN channels  ISDN uses out-of-band signaling, the delta (D channel), for call setup and signaling  ISDN uses bearer channels, also called B channels, as clear data paths Each B channel provides 64 kbps of bandwidth  Each ISDN B channel can make a separate serial connection to any other site in the ISDN network 15 D Channel Call Setup Signaling and Resulting B-Channel... 1.54 4-8 .192Mbps 1 6-6 40Kbps SDSL 1.54 4-2 .048Mbps 1.54 4-2 .048Mbps HDSL 1.54 4-2 .048Mbps 1.54 4-2 .048Mbps IDSL 144Kbps 144Kbps RADSL 64Kbps-8.192Mbps 1 6-7 68Mbps CDSL 1Mbps 1 6-1 60Kbps 21 Protocols Used with a DSL Router 22 5 Cable Modems 23 Cable modem  Cable modems provide an always-on Internet access service, while allowing you to surf the Internet over the cable and make all the phone calls you want over your telephone... and K56Flex V.92 56/33 kbps or 48 kbps for each direction Connects and finds correct speed more quickly than V.90; allows “modem-onhold” 12 3 Integrated Services Digital Network 13 Introducing ISDN  The ISDN standards define the hardware and call setup schemes for end-to-end digital connectivity  ISDN allows digital signals to be transmitted over existing telephone wiring  ISDN brings digital connectivity... users  MCNS defines the use of a multiplexing method called timedivision multiple access (TDMA), in which each home user is granted regular time periods during which to send upstream data These time slots happen multiple times per second By using TDMA, most collisions can be avoided 29 Summary  An overview of remote access technologies:  Analog modem  ISDN  DSL  Cable modem 30 ... It’s a little like having an “Internet” channel to go along with CNN, TBS, ESPN, The Cartoon Network, and all your other favorite cable channels 24 Cable Modems Terminology 25 6 Comparison of Remote Access Technologies 26 Layer 1 and Layer 2 between the Home and the Head End  The data going toward the home as downstream data, and data from the home as upstream data  Downstream data uses standards that... of the fact that the signals are broadcast to all subscribers in a section of the cable plant 27 Layer 1 and Layer 2 between the Home and the Head End (cont.)  CATV standards call for the use of a data-link protocol called Multimedia Cable Network Systems (MCNS) MAC  MCNS is similar to Ethernet’s MAC, as defined in the IEEE 802.3 specification, including the use of Ethernet MAC addresses So, although... at the same time You can make two calls to the same ISP, increasing the speed You also can use one B channel for data and make a voice call using the other B channel 17 ISDN Installation and Cabling RS-232 ISDN modem 2 wires Telco  A COM port or a USB port connects to the ISDN modem or the terminal adapter (TA) 18 4 Digital Subscriber Line 19 THE KEY FEATURES OF DSL  DSL allows analog voice signals . 1 Module 06 WAN Technology Chapter 19 Remote Access Technologies 2 Table of Content 1 Perspectives on the PSTN 2 Analog Modems 3. rate than modems  B channels are suitable for negotiated Point-to-Point Protocol (PPP) links 15 ISDN channels  ISDN uses out-of-band signaling, the delta (D channel), for call setup and signaling. than V.90; allows “modem-onhold” 13 3. Integrated Services Digital Network 14 Introducing ISDN  The ISDN standards define the hardware and call setup schemes for end-to-end digital connectivity