Learn About Implementing Cisco IOS Unified Communications
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1 | 2 | These questions are based on 640-460: Implementing Cisco IOS Unified Communications
A Self Test Software Practice Test
Objective: Describe the components of the Cisco Unified Communications Architecture.
Sub-objective: Describe the function of endpoints in a UC environment.
Single answer, multiple-choice
Which protocol is supported by Cisco IP phones and Cisco gateways operating at the endpoints layer of the Cisco Unified Communications system?
A. RTP
B. MGCP
C. SCCP
D. G.711
Answer:
C
Tutorial:
Skinny Call Control Protocol (SCCP) is a Cisco protocol used for communication between IP phones or gateways and Cisco Unified Communications Manager. It follows the server/client model, in which the main control and processing is done by the Unified Communications Manager, which is the central call-control unit. Any device, software or application that connects to the network and directly interacts with the end user will come under the endpoints layer. Other products that function as endpoints are wireless phones, video phones, analog phones, cell phones, PCs and instant messenger clients.
There are four layers to the Cisco Unified Communications system: the infrastructure layer, the endpoints layer, the applications layer and the call processing layer. All of these layers and their functionalities complete a VoIP structure.
Real-Time Transport Protocol (RTP) is a standardized packet format for delivering real-time traffic such as audio and video.
Media Gateway Control Protocol (MGCP) is used for communication with gateways. It is not used for communicating with IP phones.
G.711 is a codec used in Cisco Unified Communications. It is not a protocol.
References:
Cisco > Support > Unified Communications Architecture Basics
CCNA Voice Official Exam Certification Guide (Cisco Press, ISBN 1-58720-207-7), Chapter 7: Gateway and Trunk Concepts - Trunking CME to Other VoIP Systems
Objective: Describe PSTN components and technologies.
Sub-objective: Describe time division and statistical multiplexing.
Single answer, multiple-choice
Which technique is used by the Public Switched Telephone Network (PSTN) for transmitting multiple digitized data, voice and video signals simultaneously over one communications media?
A. Frequency Division Multiplexing (FDM).
B. Time Division Multiplexing (TDM).
C. Code Division Multiple Access (CDMA).
D. Wavelength Division Multiplex (WDM).
Answer:
B
Tutorial:
Time Division Multiplexing (TDM) is the correct option. In TDM, the bandwidth of a link is divided into separate channels with fixed time slots. Multiple bit streams are transmitted through these channels with time slots and are recollected at the destination. TDM can be defined as total available time divided into several users. The best example of TDM is the telephone system.
Frequency Division Multiplexing (FDM) is an incorrect option because in FDM, carrier bandwidth is divided into sub-channels of different frequency widths, each carrying a signal at the same time in parallel. FDM is used in analog transmissions such as twisted pair telephone line, cable access, cellular, radio and TV communications.
Code Division Multiple Access (CDMA) is an incorrect option because this technique is used in wireless technology and digital communication. CDMA uses code division in which the transmitter is given a code to transmit multiple data simultaneously.
Wavelength Division Multiplex (WDM) is an incorrect option. WDM works on the same principles as FDM, but WDM applies to digitized wavelengths of light in optical fiber.
References:
Cisco > Introduction to DWDM Technology > Introducing DWDM > Time-Division Multiplexing
CCNA Voice Official Exam Certification Guide (Cisco Press, ISBN 1-58720-207-7), Chapter 1: Perspectives on Voice Before Convergence - Sending Multiple Calls over a Single Line
Objective: Describe VoIP components and technologies.
Sub-objective: Describe the process of voice packetization.
Single answer, multiple-choice
What are the two components of a Real-Time Transport Protocol (RTP) media stream?
A. TCP and UDP.
B. UDP and Data.
C. RTCP and Data.
D. RTCP and UDP.
Answer:
C
Tutorial:
Real-Time Transport Control Protocol (RTCP) and data are the two components of an RTP media stream. Real-Time Transport Protocol (RTP) is a standardized packet format for delivering real-time traffic, such as audio and video. RTCP provides control information for RTP streams in packaging and delivering multimedia but does not transfer any data itself.
While sending data or completing a call, there are two parts of a RTP stream:
• Data: Delivers real-time data and real-time properties for applications. It also helps in loss detection and identification of stream contents.
• RTCP: Provides media control and quality of service (QoS) feedback. It also helps in identifying the participants in the RTP session.
Since phone conversations of any type are bidirectional, two streams are required to complete a call.
TCP and UDP are incorrect. Transmission Control Protocol (TCP) is one of the two transport protocols of the IP suite. TCP ensures sequential, reliable delivery of data from one program running on a computer to another program on another computer. User Datagram Protocol (UDP) is the other transport protocol of the IP suite. UDP is used to send short messages or datagrams from one computer to another in a networked environment on a connectionless (non-guaranteed) basis. It is the underlying transport protocol that encapsulates RTP, but RTP runs on top of UDP. Neither is part of the RTP stream itself.
References:
Cisco > Articles > Network Technology > General Networking > VoIP: An In-Depth Analysis
CCNA Voice Official Exam Certification Guide (Cisco Press, ISBN 1-58720-207-7), Chapter 7: Gateway and Trunk Concepts - Understanding RTP and RTCP
Objective: Describe and configure gateways, voice ports and dial peers to connect to the PSTN and service provider networks.
Sub-objective: Describe and configure voice dial peers.
Single answer, multiple-choice
Which is NOT an option of the dtmf-relay command?
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