Network+ Chapter 7

  1. ISDN is considered to be what type of WAN connection?

    C. Circuit-switched connection
  2. What is the data rate of an OC-3 connection?

    C. 155.52 Mbps
  3. Which of the following WAN technologies commonly use unshielded twisted pair (UTP)? (Choose three.)

    a. Cable modem
    b. ISDN
    c. DSL modem
    d. POTS dial-up modem
    • b. ISDN
    • c. DSL modem
    • d. POTS dial-up modem
  4. How many channels on an E1 circuit are available for voice, video, or data?

    C. 30
  5. Which PPP authentication method provides one-way authentication and sends credentials in clear text?

    B. PAP
  6. What DSL variant has a distance limitation of 18,000 ft. between a DSL modem and its DSLAM?

    A. ADSL
  7. What kind of network is used by many cable companies to service their cable modems and contains both fiber-optic and coaxial cabling?

    C. HFC
  8. What locally significant identifier is used by a Frame Relay network to reference a virtual circuit?

    D. DLCI
  9. How big is the payload portion of an ATM cell?

    C. 48 bytes
  10. What is the size of an MPLS header?

    A. 32 bits
  11. What are the three categories of WAN connections?
    • Dedicated leased line
    • Circuit-switched connection
    • Packet-switched connection
  12. What is a dedicated leased line?
    A connection interconnecting two sites.
  13. Which WAN connection category is the most expensive and why?

    C. Dedicated leased line - because the user does not have to share the connection with other users.
  14. What is a packet-switched connection?
    Similar to a dedicated leased line except packet-switched connections allow multiple users to share the bandwidth.
  15. Is an ATM connection a packet-switched connection?
    No, because it is a fixed cell length 53 bytes cells and not a variable length frame.
  16. Which are fast WAN links or LAN links?

    A. WAN links
    B. LAN links
    B. LAN links
  17. Bandwidth is measured in kbps, Mbps, Gbps.  How are optical networks measured.
    Optical Carrier (OC)
  18. What are OC speeds?
    • OC-1 - 51.84 Mbps
    • OC-3 is 155.52 Mbps (3x the speed of OC-1).
  19. What are bandwidths of some common WAN technologies?
    • WAN                              Typical Bandwidth
    • Technology

    • Frame relay                    56Kbps to 1.544Mbps
    • T1                                   1.54Mbps
    • T3                                   44.736Mbps
    • E1                                   2.048 Mbps
    • E3                                   34.4Mbps
    • ATM                                155Mbps to 622Mbps
    • SONET                           51.84Mbps to 159.25Gbps
  20. What speeds can Long-Term Evolution (LTE) support concerning wireless and cell phone technology?
    100Mbps for mobile usage and 1Gbps for stationary devices.
  21. What are the two major radio systems used with cellular technology?
    • Code division multiple access (CDMA) 
    • Global System for Mobiles (GSM)
  22. What is WiMAX?
    Worldwide interoperability for Microwave Access (WiMAX).
  23. What is HSPA+?
    High-Speed Packet Access (HSPA+) - Max data rate is 84Mbps.
  24. How conversations broken up in a T1, E1, T3 and E3 digital circuit?
    Conversations are broken up into 64Kbps channels, where a single 64Kbps channel is called a Digital Signal 0 (DS0).
  25. What is the common protocol used with dedicated leased lines?
    Point-to-Point Protocol (PPP)
  26. What is the name of the device where T1, E1, T3, E3 circuits terminate?
    Channel service unit/data service unit (CSU/DSU).
  27. What type of connector is used to terminate a CSU/DSU
    RJ48C connector - 10 metal connectors instead of 8 contained in RJ45 connector.

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  28. Break down a T1 circuit.
    • Composed of 24 DS0s called DS1.  
    • Bandwidth is 1.544Mbps.
    • T1 frame is 193 bits = 24 channels 64Kbps (DS0) * 8 bits per channel + 1 framing bit = 24*8=192 +1 = 193
    • Nyquist Theoram requires 8000 samples per second for VOX comms (or at least twice the highest frequency of 4000 Hz).
    • Total bandwidth is 193 bit frames * 8000 samples per second = 1.544Mbps.
  29. What are two popular methods for grouping T1 frames, where multiple groups are sent at once?
    • Super Frame - Combines 12 standard 193 bit frames
    • Extended Super Frame - Combines 24 standard 193 bit frames.
  30. What places utilize T1 circuits?
    • North America
    • Japan
  31. Explain and E1 circuit.
    • E1 circuit has 32 channles.
    • Only 30 of the 32 channels are used to transmit data
    • First channel is used for framing and sychronization
    • The sevententh channel is a Layer 4 (Session).  It sets up, maintains, and tears down a call.
    • E1 bandwidth is 2.048Mbps (8000 samples per second * 8 bits per samples = 2,048,000 bits per second).
  32. Explain a T3 circuit.
    Similar to a T1, T3 combines 672 DS0s into a single connection called a DS3 with a bandwidth of 44.7Mbps.
  33. Explain E3 circuit.
    • Bandwidth is 34.4Mbps.
    • Misnomer is E3 is greater than the bandwidth of T3 because E1 is greater than a T1, but E1 44.7Mbps is larger than E3 34.4Mbps.
  34. CSU/DSU is a device on what layer?

    D. Layer 1 (Physical Layer)
  35. What are the three challenge types of Point-to-Point Protocol (PPP)?
    • Password Authentication Protocol (PAP)
    • Challenge-Handshake Authentication Protocol (CHAP)
    • Microsoft Challenge-Handshake Authentication Protocol (MS-CHAP)
  36. What layer of the OSI model does a Synchronous Optical Network (SONET) operate?
    Layer 1 (physical layer) because its media is fiber optic.
  37. What are the two classifications of an Integrated Service Digital Network (ISDN)?
    • Basic Rate Interface (BRI)
    • Primary Rate Interface (PRI)
  38. What is the basic structure of a BRI and PRI circuit?
    • Basic rate interface (BRI)  - Two 64Kbps B-channels and one 16Kbps D channel
    • Primary rate interface (PRI) - ISDN circuit built on a T1 or E1 circuit.
  39. Break down a PRI circuit structure.
    A primary rate interface circuit is built on a T1/E1 circuit.  T1 ckt has 24 channels (23 B-channels and 1 64Kbps D channel).  The D-channel is the Session Layer (Layer 4) channel that sets up, maintains, and tears down the connections.
  40. Describe the fields that make up an Asynchronous Transfer Mode (ATM) header.
    • ATM header is 5 bytes in length 
    • GFC (Generic Flow Control) - uses 4 bits to locally indicate a congestion condition.
    • VCI (Virtual Circuit Identifier) - uses 16 bits to indicate VC.
    • VPI (Virtual Path Identifier) - uses 8 bits to id an ATM virtual path.
    • PTI (Payload Type Indicator) - uses 3 bits to indicate the type of payload being carried in a cell.
    • HEC (Header Error Control) - uses 8 bits to detect and correct errors in an ATM cell header.
  41. What is MPLS?
    Multiprotocol Label Switching is a WAN technology used by service providers.  It is popular because it supports multiple protocols on the same network.
  42. What layer of the OSI model does a MPLS header operate?
    Between Layer 2 (Data Link Layer) and Layer 3 (Network Layer).
  43. What is the size of an MPLS header?
    The Multiprotocol Label Switching header or shim header is 32 bits.
  44. What are the elements of MPLS
    • CPE (Customer Premise Equipment) - resides at customer's site which connects to the MPLS provider.
    • CE (Customer Edge) - customer router that provides connectivity between the customer network and service provider.
    • ELSR (Edge Label Switch Router) - resides at the edge of an MPLS service provider's cloud and interconnects to multiple customers.
    • PE (Provider Edge) - MPLS service provider router that connects to a customer's router.
    • LSR (Label Switch Router) - resides a part of a service provider's MPLS cloud and makes forwarding decisions based on labels applied to frames.
    • P (Provider) - internal service provider router.  Does not interface with customer routers.
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Network+ Chapter 7
Wide Area Networks