Abdellatif O. Abdellatif Sudatel Telecom Group

Voice Over IP

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

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

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

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 PSTN Internet ISP Modem USER B Server PSTN ISP USER B Modem USER A

PC-to-Phone PSaTNPSTN Internet ISPIPTP Modem USER A USER B Gateway IP Telephony Provider

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

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

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

IP Telephony QoS Operational Target for Voice and Fax Possibly Tolerable for Voice Unacceptable for Voice or Fax ITU G.114 Utility Recommendation Delay (ms) Packet loss (%)

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

QoS: Delays T Loss Packet T"#T’#T IP Network Network Delay Sender Network Receiver Sender Delay: Coding delay Packeting delay Transmission delay …  Receiver Delay: Decoding delay DePacketing delay Receiver delay … 

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

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

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

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 : ,000 Hz Telephone Channels : , 400 Hz Nyquist Theorem : ,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

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

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 MethodBit Rate(kbps )MOS scoreCompression delay (ms) G.711 PCM G.726 ADPCM G.728 LD-CELP G.729 CS-ACELP G.729a CS-ACELP G MP-MLQ G ACELP iLBC

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

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

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 Gateway Multipoint Control Unit Gatekeeper Circuit Switched Networks Packet Based Network Terminal

SIP: Session Initiation Protocol 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 Redirect Server Location Server Registrar Server User Agent Proxy Server Gateway SIP Components Proxy Server PSTN

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

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

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

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 o communication howstuffworks.com/ip- telephony o search?term=IPtelephony search?term=IPtelephony o CCNA_voice_cbt_nuggets o CCNP-ngts-VoIP

Thanks!!!