TDC 364 Homework 10 final EXAM

02/18/2020 TDC 364 HW-Extra 1 of 8 Homework 10 1. What is the codec schmes used in the TDC364 lab? a. G.711 and G.729A b. G.711 and G.723.1 c. G.711 and G.726 d. G.711 and iLBC 2. The X-lite software used in the TDC364 VoIP lab is _______ a. User Agent Client (UAC) only, no UAS b. User Agent Server (UAS) only, no UAC c. Both UAC and UAS d. SIP Prosxy server 3. What is the SIP proxy server for the TDC364 lab? a. Aserisk b. Xlite c. Google Talk d. SkyPE 4. In the FreePBX setting, what is the directory that contians the SIP configuration files? a. /etc/freepbx b. /etc/asterisk c. /var/log/aserisk d. /etc/voip 5. What is the security tool on FreePBX to protect hacker intrusion? a. IPFIX b. Checkpoing c. Fail2ban d. Guardian 6. Which of the follow SIP message is used for event notification? a. MESSAGE b. NOTIFY c. REGISTER d. INVITE 7. Which of the follow SIP message is to support instant messaging service? a. MESSAGE b. NOTIFY c. REGISTER d. SUBSCRIBE 8. Which of the following SIP messages are used to support Presence Service? a. INVITE and 200 OK b. REGISTER and 200 OK c. SUBSCRIBE and NOTIFY d. MESSAGE and ACK 9. Which of the following SIP message could be acknowledged by PRACK? a. INVITE b. 180 Ringing c. 100 OK d. ACK 10. Which of the following SIP message is to support call on-hold? a. INVITE This study source was downloaded by from CourseH on :19:11 GMT -05:00 b. HOLD c. MESSAGE d. WAIT 11. Which of the following SIP message is used by the Proxy server to alert the voice mail server of incoming calls? a. MESSAGE b. NOTIFY c. SETUP d. INVITE 12. In the SIP-based VoIP network, how does a user subscribe to the Voice Mail service? a. The user sends the SUBSCRIBE message to the Voice Mail serer. b. The user sends the SUBSCRIBE message to the Proxy server. c. The Voice Mail server sends the SUBSCRIBE message (with user info) to the Proxy server. d. The Voice Mail server sends the REGISTER message (with user info) to the Proxy server. 13. Which of the following network element is required for Call Center Service? a. Key System b. IAD c. ACD d. Modem 14. Which of the following service is used by Call Center to automatically (no human agent) interact with incoming caller? a. AA b. ACD c. SDN d. Codec 1. (7 pt) Based on the lab work, what is the bandwidth (data rate) of ILBC? a. Time Interval Start time stamp End time stamp Time interval (sec) ~ 1.0 seconds b. Number of RTP Packets Sequence number of 1st RTP Sequence number of the last RTP Number of RTP packets (two-way) ~66 packets Number of RTP packets (one-way) ~33 packets c. Number of RTP packets in one second: 33 packets/sec d. Voice payload size: 50 bytes e. Bandwidth (data rate in bps): 13.2 kbps 2. (5 pt) The following is a wireshark screenshot of a VoIP call. Use the screenshot to answer the questions below. This study source was downloaded by from CourseH on :19:11 GMT -05:00 a. (2 pt) What is the call setup time? Call setup time is defined from the end of dialing to the 1st ringing. Show the call setup time in miliseconds (ms). Time stamp of 1st INVITE 10. Time stamp of 180 Ringing 11. Call setup time (in ms) 210 b. (2 pt) How long is the ringing of this call? The duration of the ringing is from the 1st ringing to the phone being picked up by the callee. Show your answer in seconds (sec). Time stamp of 180 Ringing 11. Time stamp of 200 OK 49. Duration of Ringing (sec) 38 c. (1 pt) What is the codec scheme used in this call? iLBC (5 pt) What is Voice Virtual Private Network (VPN)? How does SIP support Voice VPN? Definition: A private intra-office dialing over a public/shared network. Voice VPN is to use private dialing (4- or 5-digit dialing) to remote offices over the company WAN or the public Internet. [Private dialing on a private network is not VPN because it is not virtual. Private dialing over a public (shared) network is VPN.] Implementation: The SIP proxy translates the dialed digits into the SIP address which is transmitted over the IP network, either the company WAN or the public Internet. The nature of the IP network makes it a global VPN service. The essence of VPN is about address translation: from a private address (4-digit dialing) to a public address (IP address) which is routed over a public (shared) network. 3. (5 pt) Compared to the legacy call center, list three advantages of IP-based call center. a. Ease of ACD function b. Global VPN This study source was downloaded by from CourseH on :19:11 GMT -05:00 c. Virtual Call center d. Ease for development and deployment of new voice features 2. What is the major difference between 3G and 4G mobile wireless network? a. 4G has higher data rate than 3G. b. 4G is more secure than 3G c. 4G has higher call capacity than 3G. d. 4G uses different frequency spectrums than 3G. 3. For the cellular service (AMPS), if the bandwidth per channel were 20 kHz instead of 30 kHz, how many channels (both bearer and signaling channels) would be available in each block? (Note that there are two blocks, A & B). a. 450 b. 500 c. 625 d. 1,200 4. Which of the following frequency spectrum is newly allocated to support 4G/LTE. a. 850 MHz b. 1.9 GHz c. 1.7/2.1 GHz d. 600/700 MHz 5. In the cellular service (AMPS), when k=8 for the cell group, how many simultaneous conversations are available per cell? (Note: there are 21 channels reserved for signaling.) a. 32 b. 49 c. 64 d. 80 6. In the legacy mobile wireless network, what is the physical connection between Base Station (BS) and Mobile Switching Center (MSC)? a. Wireless Connection (802.11) b. Optical Fiber c. T1 d. Ethernet (100BaseTX) 7. Which of the following is NOT a digital wireless technology? a. LTE b. CDMA c. GSM d. AMPS 8. Which of the following mobile wireless technology has the best efficiency of frequency use? (supporting the highest number of simultaneous calls within a given frequency spectrum.) a. Frequency Division Multiple Access b. Code Division Multiple Access c. Time Division Multiple Access d. Wave Division Multiple Access 9. Which of the following is not a multiple access technology for mobile wireless communication: a. Carrier Sense Multiple Access b. Frequency Division Multiple Access c. Time Division Multiple Access d. Code Division Multiple Access This study source was downloaded by from CourseH on :19:11 GMT -05:00 10. HLR is located on which of the following device? a. Cell Phone b. Base Station c. Mobile Switch Center (MSC) Switch d. PSTN Central Office Switch 11. Which of the following function is not required on a mobile handset? a. Coding/decoding b. Encapsulation of voice payload in IP packets c. Modulation/Demodulation d. Interleaving 12. Frequency reuse does NOT apply to a. AMPS b. CDMA (IS-95) c. TDMA (IS-54/136) d. GSM 13. Which of the following mobile wireless technology does not support Subscriber Identity Module (SIM)? a. CDMA (IS-95) b. GSM c. UMTS d. LTE 14. What is the purpose of interleaving used in GSM and CDMA? a. increasing bandwidth b. improvement of security protection c. ease of error detection d. ease of error correction 15. What is the signaling used for call establishment on IMS? a. SS7 b. SIP c. Q.931 d. H.323 16. In the IMS call flow, what is the message to acknowledge 180 Ringing? a. 100 Trying b. 200 OK c. PRACK d. None, no need to acknowledge 180 Ringing Part II: Questions (20 point) – do not copay-and-paste from lecture notes 1. Mobile Wireless Technology Evolution EDGE 2.5G (generation) AMPS 1G CDMA (IS-95) 2G EVDO 3G GSM 2G LTE 4G 2. Soft vs. Hard hand-off This study source was downloaded by from CourseH on :19:11 GMT -05:00 Description of Hard hand-off: Each BS transmits a beacon message. MS on hearing uses the strongest beacon message. Changes the routing to the new BS. MSC is controlling the handoff. Description of Soft hand-off: When phone us in a call moves from one cell to another, handoff gets to multiple process. First the phone noticed the second cell, and the call is routed to both cells. As the phone continues and uses the stronger cell and drops the weak cell. It is not all-or-nothing transition. MSC controls the routing. Major Difference: Soft handoff has almost zero hand-off time. Hard handoff has at least around 200ms Hand-off time. Example of Mobile Wireless Technology: Hard hand-off: TDMA Soft Hand-off: CDMA TDC364-hw08 17. In the case of SIP-based Toll Fraud attack, what is the SIP message used by the hackers to probe the SIP serer? a. PROBE b. MESSAGE c. SUBSCRIBE d. REGISTER 18. Which of the following SIP-based security attack has immediate financial gains for the hackers? a. Eavesdropping b. Toll Fraud c. Denial of Service d. Registration Hijacking 19. In the case of SIP-based DoS attacks, which of the SIP message is likely to be used by the hackers? a. PROBE b. MESSAGE c. INVITE d. SUBSCRIBE 20. What is the protocol to secure the signaling channel of VoIP? a. SIPS (RFC 3261) b. SRTP (RFC 3711) c. MIKEY (rfc 3830) d. IPSec 21. What is the protocol to secure the bearer channel of VoIP? a. SIPS (RFC 3261) b. SRTP (RFC 3711) c. MIKEY (rfc 3830) d. IPSec 22. In the case of toll fraud of International Premium Rate and Revenue Sharing (IPRS), which NANP country/region is the most likely place to be used by hackers? a. Dominica b. Somalia c. Canada d. Mexico 23. Which of the following SIP message does not support authentication? (i.e., cannot be authenticated) a. REGISTER b. INVITE This study source was downloaded by from CourseH on :19:11 GMT -05:00 c. BYE from caller d. BYE from callee 24. Which of the following phone service is required for facility-based VoIP Service Providers? a. 0 – operator service b. 411 service c. 911 service d. Collect call service 25. In the E911 service, who is responsible for routing to an incoming call to the PSAP? a. The caller b. PBX c. Local Telephone Switch d. Tandem Office Switch 26. In the E911 service, how does PSAP get the street address of caller’s location (wired call)? a. The caller has to give his/her street address to the PSAP over the phone. b. PSAP queries MSAG which has the caller’s address. c. Local telephone switch sends the street address to PSAP. d. The caller uses text message to send his/her address to PSAP. 27. In the IETF I3 standard, what is the URN address for emergency service? a. urn:service:sos b. urn:service:911 c. urn:service:psap d. urn:service: emergency 28. In the IETF I3 standard, how does PSAP gets the user location? a. Same as the legacy PSTN service via ALI and MSAG b. The civil and Geo data is included in the SIP message. c. Caller sends a separate e-mail to PSAP for location information. d. IETF I3 does not support location identification. 29. What is CALEA? a. It is a regulation for wiretapping by Law Enforcement Agent (LEA). b. It is a regulation for VoIP payload encryption. c. It is a regulation about E911 service to PSAP. d. It is a regulation about Internet telephony. 30. What is the difference in network architecture before and after CALEA? a. Before CALEA, wiretapping by LEA is prohibited by law for any reason. b. Before CALEA, LEA cannot do wiretapping without the cooperation of the target user. c. Before CALEA, LEA has a dedicated trunk from LEA to the CO switch. d. Before CALEA, LEA needs to install IAP at the Central Office switch. 31. Which of the following is a technical challenge for VoIP providers to support CALEA? a. VoIP providers do not keep detailed call records of subscribers. b. Both signaling and bearer traffic may not go through the VoIP provider’s network. c. VoIP bearer traffic may not go through a VoIP provider’s network. d. VoIP providers do not have resources and expertise to support CLALEA. Reference the data in Lecture-09 and discuss why it is easier for hackers to launch an INVITE flooding attack than a REGISTER flooding attack. For hackers it is easier to use Invite flooding because with sending 120 INVITE message hackers can cause an effective DoS attack. But for REGISTER hackers need 250 messages. Also, Invite flooding causes attack overflow of the system and REGISTER flooding causes the reduction of the CPU. This study source was downloaded by from CourseH on :19:11 GMT -05:00 3. Show the protocol stacks to secure the SIP trunking service. You need to show the protocol stacks for both signaling traffic and bearer traffic. 4. List three security measures to protect the IP-PBX from toll fraud attacks. (do not use protection measures for general data networks). a. To avoid internet connection to IP-PBX b. Limit toll call per user c. Enable password for all SIP clients. 5. What are the key requirements of the E911 service? a. Routing the correct Public Safety Access Point (PSAP) based on the caller location b. Automatic Number Identification (ANI) which caller number will be routed to the PSAP automatically c. Automatic Location Identification (ALI) which caller location (street address) will be routed to the PSAP automatically using MSAG This study source was downloaded by from CourseH on :19:11 GMT -05:00 Powered by TCPDF ()