Explain the role of a VoIP gateway. Under what circumstances is a gateway recommended for an organization's VoIP network?
Why should the IT department of a company, that plans to switch to VoIP, baseline its data network before the actual implementation?
o Define the PSTN hierarchy and key components of the network.
o Explain telephony terms such as E.164 numbering plan, Telecommunications Act of 1996, Dual Tone Multi Frequency (DTMF), special information tones, Pulse Code Modulation (PCM), Time Division Multiplexing (TDM), local loop/last mile, and demarcation point.
o Evaluate PSTN user experience from technical perspective, such as sound quality and call setup delay.
o Describe enterprise telephony systems and services, such as PBX, Automatic Call Distribution (ACD), and Centrex, and compare their operations, core features, and functionality.
o Describe hardware and software components of a legacy circuit-switched PBX.
o Analyze the pros and cons of circuit-switched PBX systems.
o Discuss advantages of packet switching as compared to circuit switching, and recognize the driving force behind network convergence.
o Discuss disadvantages of packet switching as compared to circuit switching, and identify challenges of VoIP technologies.
o Explain the basic functionality of an audio codec.
o Determine parameters that are typically used for comparing audio codecs.
o Analyze trade-offs, for example, bandwidth consumption versus accumulated delay versus voice quality, when choosing audio codecs for a deployment scenario.
o Explain the encapsulation and transmission process of voice traffic in VoIP.
o Discuss the potential impact of voice packet payload size on capacity design and VoIP performance.
o Explain the reason that voice traffic is carried over UDP, not TCP.
o Evaluate ways to reduce VoIP bandwidth consumption, such as header compression and Voice Activity Detection (VAD).
o Describe the role of RTCP in VoIP, and interpret sender's report and receiver's report.
o Discuss the history and functionality of VoIP control signaling such as SIP, H.323, and MEGACO.
o Describe the role of VoIP server or gatekeeper.
o Illustrate a typical call processing procedure using SIP.
o Describe telephone and PBX features, such as telepresence and unified messaging, that are made available by VoIP.
o Assess limitations of VoIP E911 as compared to traditional landline E911 service.
o Describe the role of signaling gateway in VoIP.
o Describe the role of media gateway in VoIP.
o Compare PBX trunk options such as analog, digital, and SIP trunks.
o Choose traffic or queuing models, such as Erlang B and Erlang C, to formulate the relationship among Grade of Service (GoS), traffic load, and trunk capacity of a local telephony system.
o Estimate trunk capacity of a local telephony system.
o Estimate capacity of WAN connections for voice traffic among multiple branch locations.
o Define and quantify typical QoS criteria of voice traffic.
o Explain traffic prioritization on network devices such as switches and routers.
o Analyze limitations of prioritization on providing QoS to voice traffic.
o Define network performance attributes that correlate with voice quality.
o Discuss the role of baselining and trending on network performance monitoring.
o Estimate one-way end-to-end delay in VoIP.
o Discuss security vulnerabilities of a typical VoIP system.
o Propose and evaluate best practices for voice traffic security.
o Conduct cost analysis of deploying a VoIP system such as capital cost, monthly recurring changes, and Return on Investment (ROI).
o Conduct data network analysis to assess upgrading required by VoIP services.
o Plan an enterprise VoIP system by applying knowledge on traffic engineering, VoIP control signaling, VoIP hardware/software, etc.