Voice over IP: Hands-On

Introduction to VoIP

Traditional voice and data networks

• The Public Switched Telephone Network
• Packet-switched data networks
• OSI and IETF reference models

Realising the benefits of VoIP

• Using data networks to transmit voice and video traffic
• Taking advantage of new communications features available with SIP and H.323

Applying VoIP Fundamentals

Defining multimedia conferences

• Voice, video, data and mixed conversions
• Key VoIP hardware and software components
• Gateways and gatekeepers
• Signalling and data protocols

Deploying H.323 or SIP within your organisation

• SIP vs. H.323
• Configuring and testing SIP IP PBX and IP phones
• Setting up voice and video conferencing
• Creating ring groups for a call center
• Tuning network quality-of-service for user satisfaction

Analysing H.323 and SIP calls

• Capturing SIP and H.323 signalling exchanges
• Implementing and analysing silence suppression
• In-depth analysis of SIP signalling messages
• Registering with a gatekeeper or proxy
• RTCP messages

Leverage SIP for Seamless Communication

Building the IP infrastructure

• Packetising voice for carriage through the IP network with RTP
• Employing reliable signalling with TCP
• Maintaining real-time voice performance with RTP

Analysing VoIP signalling

• Distinguishing between SIP, H.323, H.225 and H.245
• Applying SDP to SIP packets
• Call setup and teardown

Addressing within VoIP networks

• Mapping phone numbers to IP addresses
• Gatekeepers, proxies, locations and call servers

Measuring voice quality

• Mean opinion scores (MOS)
• Detecting flaws in transmitted voice
• Grade of service and capacity planning

Voice Quality Engineering

Classifying factors that affect voice quality

• Encoding voice effectively
• Comparing codecs
• Assessing the effects of delay and loss on quality

Selecting the best codec

• G.711, G.722, G.723, G.726, G.729
• Testing for differences in performance
• Adaptive techniques
• Voice companding: μ-law, A-law

Open and multivendor systems

• Anatomy of IP phones
• Open source Asterisk IP PBX
• Gateways to the PSTN legacy phone network

Capacity planning for voice over packet

• Determining bandwidth needs
• Comparing LAN and WAN performance
• Assessing the impact on data networks

Designing Networks to Carry VoIP

Calculating bandwidth service requirements

• Traffic engineering
• Measuring sporadicity of signals
• Sizing service loading for multisite operation
• Designing VoIP service: case study

Minimising delay and delay variation

• Calculating queuing delays
• Sizing link capacity needs and required trunk speeds
• Calculating expected routing delays
• Controlling admission in commercial services
• Employing Random Early Discard (RED)
• Designing for high availability

Delivering Quality on Real Networks

Exploiting the Internet with VoIP services

• Making calls with IP phones over the Internet
• Providing international voice services
• Linking a call centre to the Internet
• Adding VoIP to an e-commerce Web site

Employing quality services on intranets

• Resource Reservation Protocol (RSVP)
• Configuring IP precedence
• Multiprotocol Label Switching (MPLS)
• Observing the effects of data traffic and fair queuing on voice services
• Mixing voice and data traffic effectively