voice and data communications jobs

... the data And the receiver of data may wish to be assured that the received data have not been altered in transit and that the data actually come from the purported sender Finally, a data communications ... transmit and process all types of data and information Both the technology and the technical standards or- ganizations are driving toward integrated public systems that make virtually all data and ... Part Three, Four, or Five Trang 6 CHAPTER 1 DaTA COMMUNICATIONS AND NETWORKING OVERVIEW 1.1 A Communications Model 1.2 Data Communications 13 Data Communication Networking Wide Area Networks

Ngày tải lên: 13/09/2012, 10:21

... Look at Video and Data Services.’’ Video and data are the second and third legs of the three-legged IP-enabled stool. Recently, we examined Voice over IP, which is the other leg. And as we modernize ... COMMU- NICATIONS: A LOOK AT VIDEO AND DATA SERVICES WEDNESDAY, APRIL 20, 2005 H OUSE OF R EPRESENTATIVES , C OMMITTEE ON E NERGY AND C OMMERCE , S UBCOMMITTEE ON T ELECOMMUNICATIONS AND THE I NTERNET , Washington, ... OF COMMUNICA- TIONS: A LOOK AT VIDEO AND DATA SERVICES HEARING BEFORE THE SUBCOMMITTEE ON TELECOMMUNICATIONS AND THE INTERNET OF THE COMMITTEE ON ENERGY AND COMMERCE HOUSE OF REPRESENTATIVES ONE

Ngày tải lên: 18/02/2014, 00:20

... Fundamentals of Data and Signals TRUE/FALSE The terms ? ?data? ?? and “signal” mean the same thing ANS: F PTS: REF: 30 By convention, the minimum and maximum values of analog data and signals are ... network It is important to understand that the terms ? ?data? ?? and “signal” not mean the same thing, and that in order for a computer network to transmit data, the data must first be converted into ... forms of data transmitted between a transmitter and a receiver is textual data ANS: T PTS: REF: 51 24 Certain control characters provide data transfer control between a computer source and computer

Ngày tải lên: 19/10/2017, 16:27

... WHY STUDY DATA COMMUNICATIONS DATA COMMUNICATION 1.3 NETWORKS Components Distributed Processing Network Criteria Applications 1.4 PROTOCOLS AND STANDARDS Protocols Standards 1.5 STANDARDS ORGANIZATIONS ... 2000 2:30 PM DATA COMMUNICATIONS AND NETWORKING Second Edition FM Page ii Wednesday, February 23, 2000 2:30 PM FM Page iii Wednesday, February 23, 2000 2:30 PM DATA COMMUNICATIONS AND NETWORKING ... encoding, modulating, and error detection before learning about data transfer across the Internet This eliminates the need for two courses: One for telecommunications and one for data communications

Ngày tải lên: 24/10/2017, 13:15

... with enterprise-wide and departmental-level applications, business processes, and workflows 1.5 Voice communications, data communications, image communications, and video communications are all ... business campus) and long distance, has been growing at a high and steady rate for decades Network traffic is no longer limited to voice and data and increasingly includes image and video Increasing ... are stored Data being captured and stored includes documents, e-mail messages, voice- mail messages, text messages, and social media data Other data sources being captured, transmitted, and stored

Ngày tải lên: 08/11/2019, 14:53

... with enterprise-wide and departmental-level applications, business processes, and workflows 1.5 Voice communications, data communications, image communications, and video communications are all ... business campus) and long distance, has been growing at a high and steady rate for decades Network traffic is no longer limited to voice and data and increasingly includes image and video Increasing ... are stored Data being captured and stored includes documents, e-mail messages, voice- mail messages, text messages, and social media data Other data sources being captured, transmitted, and stored

Ngày tải lên: 31/01/2020, 15:51

... whatever  form  is  agreed  upon  by  the  parties  creating  and? ? using  the  data.   Data? ? communications  are  the  exchange  of  data? ? between  two  devices  via  some  form  of  transmission medium such as a wire cable.  ... Topics discussed in this section: Components Data? ?Representation Data? ?Flow 1.2 Figure 1.1  Five components of? ?data? ?communication 1.3 Figure 1.2 ? ?Data? ?flow (simplex, half­duplex,? ?and? ?full­duplex) 1.4 1-2 NETWORKS ... PROTOCOLS AND STANDARDS In this section, we define two widely used terms:  protocols  and? ? standards.  First,  we  define  protocol,  which  is  synonymous with rule. Then we discuss standards, which 

Ngày tải lên: 23/09/2020, 13:31

... multinational  body  dedicated  to  worldwide agreement on international standards. An ISO  standard  that  covers  all  aspects  of  network  communications? ? is  the  Open  Systems  Interconnection  (OSI) model. It was first introduced in the late 1970s.  ... transport,  and? ? application.  However,  when  TCP/IP  is  compared  to  OSI,  we  can  say  that  the  TCP/IP  protocol  suite  is  made  of  five  layers:  physical,  data? ?link, network, transport,? ?and? ?application ... data? ?link, network, transport,? ?and? ?application Topics discussed in this section: Physical? ?and? ?Data? ?Link Layers Network Layer Transport Layer Application Layer 2.28 Figure 2.16  TCP/IP? ?and? ?OSI model 2.29 2-5 ADDRESSING Four levels of addresses are used in an internet employing 

Ngày tải lên: 23/09/2020, 13:31

... states.  Analog  data? ? take  on  continuous values. Digital? ?data? ?take on discrete values Topics discussed in this section: Analog? ?and? ?Digital? ?Data Analog? ?and? ?Digital Signals Periodic? ?and? ?Nonperiodic Signals ... Periodic? ?and? ?Nonperiodic Signals 3.3 Note Data can be analog or digital Analog data are continuous and take continuous values Digital data have discrete states and take discrete values 3.4 Note Signals ... second, bandwidth in bits per second, refers to the speed of bit transmission in a channel or link Example 3.42 The bandwidth of a subscriber line is 4 kHz for? ?voice? ?or  data.  The bandwidth of this line for? ?data? ?transmission

Ngày tải lên: 23/09/2020, 13:32

... Scrambling 4.2 Figure 4.1  Line coding? ?and? ?decoding 4.3 Figure 4.2  Signal element versus? ?data? ?element 4.4 Example 4.1 A  signal  is  carrying  data? ? in  which  one  data? ? element  is  encoded  as  ... digital  data? ?by using digital signals. The conversion involves  three  techniques:  line  coding,  block  coding,  and? ? scrambling.  Line  coding  is  always  needed;  block  coding? ?and? ?scrambling may or may not be needed ... between 0? ?and? ?1? Solution We assume that the average value of c is 1/2 The baud rate is then 4.5 Note Although the actual bandwidth of a digital signal is infinite, the effective bandwidth is

Ngày tải lên: 23/09/2020, 13:32

... 5.29 Note The total bandwidth required for AM can be determined from the bandwidth of the audio signal: BAM = 2B 5.30 Figure 5.17  AM band allocation 5.31 Note The total bandwidth required for ... signal  elements do we need? Solution In this example, S = 1000, N = 8000, and r and L are unknown We find first the value of r and then the value of L 5.7 Figure 5.3  Binary amplitude shift keying ... 5.3 We  have  an  available  bandwidth  of  100  kHz  which  spans  from  200  to  300  kHz.  What  are  the  carrier  frequency? ?and? ?the bit rate if we modulated our? ?data? ?by  using ASK with d = 1?

Ngày tải lên: 23/09/2020, 13:32

... Figure 6.5  FDM demultiplexing example 6.9 Example 6.1 Assume  that  a  voice? ? channel  occupies  a  bandwidth  of  4  kHz. We need to combine three? ?voice? ?channels into a link  with a bandwidth of 12 kHz, from 20 to 32 kHz. Show the  ... configuration, using the frequency domain. Assume there  are no guard bands Solution We shift (modulate) each of the three voice channels to a different bandwidth, as shown in Figure 6.6 We use the 20- to 24-kHz bandwidth for the first channel, ... the  simultaneous  transmission  of  multiple  signals  across  a  single  data? ? link. As? ?data? ?and? ?telecommunications use increases, so  does traffic Topics discussed in this section: Frequency­Division Multiplexing

Ngày tải lên: 23/09/2020, 13:32

... Topics discussed in this section: Bandwidth Sharing CM? ?and? ?CMTS Data? ?Transmission Schemes: DOCSIS 9.30 Figure 9.16  Division of coaxial cable band by CATV 9.31 Note Downstream data are modulated using ... carry  frequencies  between 300? ?and? ?3300 Hz, giving them a bandwidth of  3000 Hz. All this range is used for transmitting? ?voice,   where  a  great  deal  of  interference  and? ? distortion  can  be accepted without loss of intelligibility ... exchange carriers and competitive local exchange carriers 9.4 Figure 9.2  Switching offices in a LATA 9.5 Figure 9.3  Point of presences (POPs) 9.6 Note The tasks of data transfer and signaling are

Ngày tải lên: 23/09/2020, 13:33

... arithmetic. Figure 10.24 shows the process at the sender  and? ?at the receiver. The sender initializes the checksum  to  0  and? ? adds  all  data? ? items  and? ? the  checksum  (the  checksum is considered as one? ?data? ?item? ?and? ?is shown in  ... numbers  and? ? compares  the  result with the sum. If the two are the same, the receiver  assumes no error, accepts the five numbers,? ?and? ?discards  the sum. Otherwise, there is an error somewhere? ?and? ?the  ... adds all? ?data? ?items (including the checksum); the result  is 45. The sum is wrapped? ?and? ?becomes 15. The wrapped  sum is complemented? ?and? ?becomes 0. Since the value of  the  checksum  is  0,  this  means  that  the  data? ? is  not  corrupted.  The 

Ngày tải lên: 23/09/2020, 13:33

... but it knows that the incoming? ?data? ?must be delivered to  the IP protocol because the NCP protocol used before the  data? ?transfer was IPCP After? ?data? ?transfer, the user then terminates the? ?data? ?link  connection,  ... most  important  responsibilities  of  the  data? ? link  layer  are  flow  control ? ?and? ? error  control.  Collectively,  these functions are known as? ?data? ?link control Topics discussed in this section: ... chosen two options (not shown in the figure): using PAP  for  authentication  and? ? suppressing  the  address  control  fields.  Frames  3  and? ? 4  are  for  authentication.  Frames  5  and? ?6 establish the network layer connection using IPCP

Ngày tải lên: 23/09/2020, 13:34

... Figure 12.1 ? ?Data? ?link layer divided into two functionality­oriented sublayers 12.2 Figure 12.2  Taxonomy of multiple­access protocols discussed in this chapter 12.3 12-1 RANDOM ACCESS In  random access ... that  the  data? ? on  the  channel             D  =  (d1  ⋅   c1  +  d2  ⋅   c2  +  d3  ⋅   c3  +  d4  ⋅   c4).  The receiver which wants to get the? ?data? ?sent by station 1  multiplies these? ?data? ?by c1 ... needs  to|      generate a random number with a value of 0 or 1. This      means that TB  is either 0 ms (0 × 2) or 2 ms (1 × 2),      based on the outcome of the random variable 12.7 Example 12.1 (continued)

Ngày tải lên: 23/09/2020, 13:34

... functions of the physical layer? ?and? ?the? ?data? ?link layer  of major LAN protocols Topics discussed in this section: Data? ?Link Layer Physical Layer 13.2 Figure 13.1  IEEE standard for LANs 13.3 Figure 13.2  HDLC frame compared with LLC? ?and? ?MAC frames ... Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display 13-1 IEEE STANDARDS In  1985,  the  Computer  Society  of  the  IEEE  started  a  project,  called  Project  802,  to  set  standards  to  enable  intercommunication  ... Figure 13.1  IEEE standard for LANs 13.3 Figure 13.2  HDLC frame compared with LLC? ?and? ?MAC frames 13.4 13-2 STANDARD ETHERNET The original Ethernet was created in 1976 at Xerox’s  Palo Alto Research Center (PARC). Since then, it has 

Ngày tải lên: 23/09/2020, 13:34

... request  and? ? reply  packets encapsulated in Ethernet frames Solution Figure  21.5  shows  the  ARP  request  and? ? reply  packets.  Note that the ARP? ?data? ?field in this case is 28 bytes,? ?and? ? that  ... options: ­n,  ­r,  and? ? ­a.  The  ­n  option  gives  the  numeric  versions  of  IP  addresses, the ­r option gives the routing table,? ?and? ?the ­a  option  gives  all  addresses  (unicast  and? ? multicast).  ... The delivery of a packet to a host or a router requires  two levels of addressing: logical? ?and? ?physical. We need  to be able to map a logical address to its corresponding physical  address  and? ? vice  versa.  This  can  be  done  by  using either static or dynamic mapping

Ngày tải lên: 23/09/2020, 13:36

... packet and forwards it to all interested interfaces 22.77 Note PIM-DM is used in a dense multicast environment, such as a LAN 22.78 Note PIM-DM uses RPF and pruning and grafting strategies to handle ... guarantees that each destination receives one and only one copy of the packet 22.72 Figure 22.43  RPF, RPB,? ?and? ?RPM 22.73 Note RPM adds pruning and grafting to RPB to create a multicast shortest ... Delivery, Forwarding, and Routing 22.1 Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display 22-1 DELIVERY The  network  layer  supervises  the  handling  of  the 

Ngày tải lên: 23/09/2020, 13:37

... Control and Quality of Service 24.1 Copyright © The McGraw­Hill Companies, Inc. Permission required for reproduction or display 24-1 DATA TRAFFIC The  main  focus  of  congestion  control  and? ? ... network—the  number of packets a network can handle. Congestion  control  refers  to  the  mechanisms  and? ? techniques  to  control  the  congestion  and? ? keep  the  load  below  the  capacity Topics discussed in this section: ... environment  for  the traffic.  So,  before talking about congestion control? ?and? ?quality of  service, we discuss the? ?data? ?traffic itself Topics discussed in this section: Traffic Descriptor Traffic Profiles

Ngày tải lên: 23/09/2020, 13:37