Abdellatif O. Abdellatif Sudatel Telecom Group

Abdellatif O. Abdellatif Sudatel Telecom Group

Voice Over IP

1 Why An Organization Would Use IPT 2 Definition 3 IP Telephony QoS 4 How Your Voice Becomes A Packet 5 MOS 6 SIP & H.323 7 Contrast between PSTN and NGN / Smooth Migration

Why an organization would use IPT Trackable Cost Saving : o Moves, Adds, and Changes (MACS) o Bandwidth and equipment efficiency o Lower cost of transmission o New applications and devices

1 Why An Organization Would Use IPT 2 Definition 3 IP Telephony QoS 4 How Your Voice Becomes A Packet 5 MOS 6 SIP & H.323 7 Contrast between PSTN and NGN / Smooth Migration

Definition IP Telephony – Transmission of voice, fax, and related services over packet-switched IP- based networks. Internet Telephony – Specific sub-set of IP Telephony in which the principal transmission network is the public Internet. – Voice-over-the-Net (VoN); Internet Phone; Net Telephony.

Definition Voice-over-IP (VoIP) – Specific sub-set of IP Telephony in which the principal transmission network(s) is (are) private, managed IP-based network(s). – Voice-over-DSL (VoDSL)

IP Telephony Instead of using traditional circuit switch systems for voice communications, IP Telephony uses a packet protocol originally designed for data communications Circuit Switched - PSTN Packet Switched – Data Network

Configuration Options PC-to-PC ISP Internet ISP PSTN USER A PSTN USER B USER BModem Modem Server

PC-to-Phone IP Telephony Provider ISP Internet IPTP Gateway PSaTN PSTN USER A Modem USER B

Phone-to-Phone Management IP Network Gateway Gateway Network of IP Telephony Service Provider PSTN USER A USER B USER B USER B USER A PSTN

Public Switched Telephone Network Initially, PC to PC voice calls over the Internet Gateways allow PCs to also reach phones PSTN Gate way Multimedia PC IP Network Gate way PSTN Multimedia PC or phones to reach phones

1 Why An Organization Would Use IPT 2 Definition 3 IP Telephony QoS 4 How Your Voice Becomes A Packet 5 MOS 6 SIP & H.323 7 Contrast between PSTN and NGN / Smooth Migration

IP Telephony QoS 10 Packet loss (%) 9 8 Unacceptable for Voice or Fax 7 ITU G.114 Utility Recommendation 6 5 4 3 2 Possibly Tolerable for Voice Operational Target for Voice and Fax 1 0 10 0 20 0 30 0 40 0 50 0 Delay (ms)

The Three Current Models OF QOS o Best Effort o Integrated Services (INTSERV ) o Differentiated Services (DIFF SERV)

QoS: Delays-1 Network Delay Sender Delay: Coding delay Packeting delay Transmission delay 2 3 4 5 6 IP Network 1 T Receiver Delay: Decoding delay DePacketing delay Receiver delay 1 3 5 Loss Packet T"#T’#T Sender Network Receiver 4 6

Delay-2 Fixed Delay Components Propagation Serialization Processing: (coding, compression, decompression, decoding)

Delay-3 Variable Delay Components Queuing delay Dejitter buffers Variable packet sizes

1 Why An Organization Would Use IPT 2 Definition 3 IP Telephony QoS 4 How Your Voice Becomes A Packet 5 MOS 6 SIP & H.323 7 Contrast between PSTN and NGN / Smooth Migration

How Your Voice Becomes A Packet Voice Encoding : Analog to Digital The Nyquist Theorem Quantization and Quantization Techniques Compressing Voice - compression Techniques - CODECs

How to Turn Voice Into Bits The 4 Step Recipe : 1. Take Many Sample Of The Analog Signal 2. Calculate A number Representing Each Sample (quantization ) 3. Convert The Number To Binary 4. (Optional) compression

The Nyquist Theorem A tribute to Dr Nyquist o The Nyquist Theorem : “ if you sample a signal in regular intervals at least twice the highest Channel frequency the samples will contain enough information to accurately reconstruct the signal”

The Nyquist Theorem o Some Important Frequencies : The Human Ear : 20-20,000 Hz Human speech : 200- 9,000 Hz Telephone Channels : 300- 3, 400 Hz Nyquist Theorem : 300- 4,000 Hz

Quantization Techniques o Waveform Algorithms ( Encode everything ) - PCM - AD PCM o Source Algorithms ( Encode changes ) - CS- ACELP - LDCELP

CODECs Waveform CODECs - G.711 Uses PCM coding and chomps up 64 kbps - G.726 Used AD PCM Coding and eats 32 kbps or 24 kbps or 16 kbps

1 Why An Organization Would Use IPT 2 Definition 3 IP Telephony QoS 4 How Your Voice Becomes A Packet 5 MOS 6 SIP & H.323 7 Contrast between PSTN and NGN / Smooth Migration

Mean opinion score MOS How Good Do They Sounds ? Based On Mean Opinion Score Scale Of 1-5 Toll Quality Is 4,0 MOS Compression Method Bit Rate(kbps ) MOS score Compression delay (ms) G.711 PCM 64 4.1 0.75 G.726 ADPCM 32.0 3.2 1 G.728 LD-CELP 16.0 3.61 3-5 G.729 CS-ACELP 8 3.92 10 G.729a CS-ACELP 8 3.7 10 G.723 1 MP-MLQ 06.3 3.9 30 G.723 1 ACELP 05.3 3.65 30 iLBC 15.2 4.1

DSP o Digital signal processors are the engines behind a voice network o Perform the following: - Analog to digital conversion - conferencing - Echo cancellation - Voice activity Detect - Comfort noise - Transcoding

1 Why An Organization Would Use IPT 2 Definition 3 IP Telephony QoS 4 How Your Voice Becomes A Packet 5 MOS 6 SIP & H.323 7 Contrast between PSTN and NGN / Smooth Migration

IP Telephony Signaling Protocols: H.323 Describes terminals and other entities that provide multimedia communications services over Packet Based Networks (PBN) which may not provide a guaranteed Quality of Service. H.323 entities may provide real-time audio, video and/or data communications.

H.323 Components Gatekeeper Multipoint Control Unit Circuit Switched Networks Packet Based Network Terminal Gateway

SIP: Session Initiation Protocol Session Initiation Protocol - An application layer signaling protocol that defines initiation, modification and termination of interactive, multimedia communication sessions between users. IETF RFC 2543 Session Initiation Protocol

SIP Distributed Architecture SIP Components Location Server Redirect Server Registrar Server PSTN User Agent Gateway Proxy Server Proxy Server

Contents 1 Why An Organization Would Use IPT 2 Definition 3 IP Telephony QoS 4 How Your Voice Becomes A Packet 5 MOS 6 SIP & H.323 7 Contrast between PSTN and NGN / Smooth Migration

Smooth Migration Soft switch Tandem /toll exchange Packet core network LE IN App Server NMS Soft switch ISUP STP LE Policy Service Soft switch Packet core network SG TMG WMG switch PSTN AMG IAD PC Phone SIP H.323 Phone Phone PLMN

Contrast between PSTN and NGN Intelligent Service Server SoftSwitch Service Server CPU Switching Array Signaling Module IP Core Trunk Module SS7 Signaling Gateway User Access Module Trunk Gateway Trunk Gateway Trunk Gateway User Access Gateway

Final Thoughts One approach, which is hotly debated in the VoIP market, is to rip out your old PBX, phones and wiring and replace everything with IP phones. That might work in some cases, particularly where the old PBX is long past its expiration date, but it isn't always the best approach.

Consider deploying IP Telephony based on a Phased Approach Understand the benefits that the technology offers, not just the costs Have a Plan

References o http://www.protocols.com/papers/voip.htm o http:// communication howstuffworks.com/iptelephony o http://www.networkmagazine.com/encyclopedia/ search?term IPtelephony o CCNA voice cbt nuggets o CCNP-ngts-VoIP

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