Introduction to VOIP

Introduction To VOIP Session 1 & 2 © 2003, cdaga tech. All rights reserved. 1 Overview Change in The Way We communicate PBX Bell’s Early Phone PABX’s EPABX’s Digital Telephony IP Phones Mobile Telephony © 2003, cdaga tech, Inc. All rights reserved. Course acronym #-2 Voice (VoIP) Infrastructure & Applications Traditional Circuitswitched, TDM-based Voice Network © 2003, cdaga tech, Inc. All rights reserved. Course acronym #-3 Why IP Telephony? •Integrate Voice with data •Use of Multiservice applications •Less Transmission Bandwidth © 2003, cdaga tech, Inc. All rights reserved. Course acronym #-4 Problems QoS on Public Networks © 2003, cdaga tech, Inc. All rights reserved. Course acronym #-5 The Model Party Voice Gateways Network Can Be IP/Frame Relay or ATM Based © 2003, cdaga tech, Inc. All rights reserved. Course acronym #-6 Issues •Voice Coding •Identification •Transmission © 2003, cdaga tech, Inc. All rights reserved. Course acronym #-7 Voice and The Human Ear © 2003, cdaga tech, Inc. All rights reserved. Course acronym #-8 Analog to Digital PCM Pulse Code Modulation 8K Sample 8 bits code 64Kbps Throughput ADPCM Adaptive Differential PCM 8K Sample 4 bits Code 32K Throughput © 2003, cdaga tech, Inc. All rights reserved. Course acronym #-9 Aggregating Voice Channels: INPUTS Analog or Digital Interface Cards Ch. 1 Ch. 2 Ch. 3 Ch. 4 Ch. 5 Ch. 6 Framing Bit (8000 per Second) Time Division Multiplexing (TDM) in a T1/E1 Channel Bank OUTPUT 8,000 Frames per Second (1 Frame per 125 µs) Eight Bits from Each Channel Input In Sequential Order Next Frame Framing Bit T1 Multiplexer Ch 1 Ch 2 Ch 3 Ch 4 Ch 5 Ch 6 Chs 7-23 Ch 24 Ch 1, etc Chs. 7-23 Ch. 24 Each Input Represents 64 kbps © 2003, cdaga tech, Inc. All rights reserved. 64 kbps x 24 = 1.536 Mbps Add Framing Bits = 8 Kbps Total Bit Rate: 1.544 Mbps = “T1” 64 kbps x 32 = 2.048 Mbps = “E1” with 30 voice, 1 framing & 1 signaling channel Course acronym #-10 Today’s Public Switched Telephone Network (PSTN) SCP SS7 Signaling Network STP STP Signaling Link Bearer facility Combined facility CAS End Office SSP SS7 Transport SSP SS7 SSP Network ISDN PRI PBX Cisco TAC 800-553-2447 408-555-2447 Phone A 732-555-4237 Public (SS7) network for Intelligent Network Services PBX (Private Branch Exchange) © 2003, cdaga tech, Inc. All rights reserved. Course acronym #-11 PSTN Local Call Flow © 2003, cdaga tech, Inc. All rights reserved. Course acronym Reference: http://www.iec.org/online/tutorials/ss7/ #-12 The Tyranny of the DS0 (Signaling Link) • Switching and transport based on circuits • Rigid structure yields higher cost for packet services Customer Premise Local CO Class-5 DS0 Switch DS1 DS0 DS1 DS3 SONET ADM OC-3/12 OC-48 OC-48 3/1 DACS DS3 Class-4 Switch Interexchange DS0 Local CO Class-4 Switch DS0 Class-5 Switch Customer Premise DS0 Switching DS1 DS1 DS1 DS0 Transport DS3 DS3 DS3 3/1 DACS DS3 SONET ADM DS1 OC-48 OC-3/12 © 2003, cdaga tech, Inc. All rights reserved. Course acronym #-13 Traditional Digital Telephony vs Packet Based Traditional synchronous digital channel continuous bits being generated Packet Speech transported as data packet generated only when speech is there © 2003, cdaga tech, Inc. All rights reserved. Course acronym #-14 Voice vs. Data Switching Class 5 Voice Switch TDM Network Trunk Line Multilayer Data Switch Data Network Uplink Router Switch Port Handset aggregator All telephones get a single analog/digital line (DS0) All devices have a phone number defined on the switch All devices have access but trunks are oversubscribed (Lines > Trunks) Path selection based on static least cost routing or ARS © 2003, cdaga tech, Inc. All rights reserved. Computer aggregator All devices get dedicated bandwidth (BW) 10/100/1000 Mbps All devices have an IP address defined on the host All devices have access but uplinks are oversubscribed (Station BW > Uplink BW) Path selection based on dynamic least cost route Course acronym #-15 Traditional Vs IP SCP Signaling Network In-/Out-of-band STP STP Sig Link Bearer facility PBX Phone A X1001 CO Trunks Transport SSP Network SSP PBX Phone B X2001 CO Trunks SS7, QSIG, Proprietary Wide Area Switch Computer A 200.1.1.1 Router Network Router Switch Computer B 200.1.2.1 Course acronym #-16 Ethernet BGP, OSPF, EIGRP, RIP In-band Routing/Signaling Ethernet © 2003, cdaga tech, Inc. All rights reserved. Traditional Vs IP Numbering Plan Direct Inward Dial Area Code Exchange Line Internet Protocol Addressing Network Sub Node Extension Host Host 609 642 7000 7001 172.16. 2. 1 172.16. 1. 1 Exchange Sub-Network Sub-Network 609 642 XXXX Area Code 172.16. LEC 609-XXX-XXXX Advertised to PSTN 2. X 172.16. 1. X Network 609 XXX XXXX IXC © 2003, cdaga tech, Inc. All rights reserved. 172.16. X. X ISP 172.16.0.0 255.255.0.0 Advertised to Internet Course acronym #-17 Connection vs. Connectionless X1001 Connection signaled based on destination number Connection remains up for duration of call Class 4 X2001 PBX T1 Class 5 Class 4 Class 5 T1 PBX X1001 10.1.1.1 Each packet contains destination address UDP packets are routed by hop, flow, or destination 10.1.2.1 Voice X2001 10.1.2.1 R2 R1 R3 R4 10.1.2.1 Voice Switch Switch © 2003, cdaga tech, Inc. All rights reserved. Course acronym #-18 Voice Coding Standards Quantize 256 Steps Using 8 Bits 4000 Hz Analog Signal Sample Compand Quantize Encode Frame = 0101 Sample 8,000/sec DS0 = Nyquist Frequency 64 Kbps Analog Audio Source ITU specified Everything Is Bits G.711 Pulse Code Modulation (PCM) is the DS0 © 2003, cdaga tech, Inc. All rights reserved. Course acronym #-19 G.711 Family 8k Sample 8bits – 256 levels of amplitude 4bits – 64 levels of amplitude 2bits – 8 levels of amplitude Voice suffers for bandwidth © 2003, cdaga tech, Inc. All rights reserved. Course acronym #-20 LPC Linear Predictive Code Models human speech uses 64k PCM as Input © 2003, cdaga tech, Inc. All rights reserved. Course acronym #-21 Why use PCM/LPC •This form of voice is the standard output of digital PBXs and telephone switches. •PCM coding chips are inexpensive because of their broad usage in telephone networks. •Both LPC and PCM/ADPCM coding of voice information are standardized by the ITU in its G-series recommendations. The most popular voice coding standards for telephony and packet voice include the following: •G.711, which describes the 64 kbps PCM voice coding technique •G.726, which describes ADPCM coding at 40, 32, 24, and 16 kbps. •G.728, which describes code-excited linear-predictive (CELP) voice compression, requiring only 16 kbps of bandwidth. •G.729, which describes adaptive CELP (ACELP) compression •G.723.1, which describes a coded representation that can be used for compressing speech © 2003, cdaga tech, Inc. All rights reserved. Course acronym #-22 Compression Quality 1. Compression is just a Aproximation 2. May be good for G.729 3. Suffers from distortion © 2003, cdaga tech, Inc. All rights reserved. Course acronym #-23 How Are CODECs Compared? (Mean Opinion Score) Source Channel Simulation Impairment Codec “X” “Nowadays—a Chicken Leg Is a Rare Dish” Rating 5 4 3 2 1 Speech Quality Excellent Good Fair Poor Unsatisfactory Level of Distortion Imperceptible Just Perceptible—Not Annoying Perceptible—Slightly Annoying Annoying but Not Objectionable Very Annoying—Objectionable MOS of 4.2 = Toll Quality © 2003, cdaga tech, Inc. All rights reserved. Course acronym #-24 1 2 3 4 5 1 2 3 4 5 Codec Cheet Sheet Mean Native Voice Encoding Opinion Bit Rate Quality Compression Score Kbps G.711 PCM G.726 ADPCM G.728 LD-CELP G.729 CS-ACELP G.729a CS-ACELP G.723.1 ACELP 4.1 3.85 3.61 3.92 3.7 3.65 64 32 16 8 8 5.3 A B C A B C BW D C B A A A Dual DTMF CPU Comp A B B B C C A B C B C D A B C C B C Music on Hold A B C C D D © 2003, cdaga tech, Inc. All rights reserved. Course acronym #-25 Evils of Packet Telephony Loss Delay Delay Variation (Jitter) © 2003, cdaga tech, Inc. All rights reserved. Course acronym #-26 Router Voice Interfaces Switch Switch FXO FXS E&M E&M Switch FXO FXS T1 T1 FXO—Foreign Exchange Office FXS—Foreign Exchange Station E&M—Ear and Mouth T1 – CAS & CCS (PRI & QSIG) © 2003, cdaga tech, Inc. All rights reserved. Course acronym #-27 Loss Sources of Packet Loss—Congestion IP IP IP Multilayer Campus Router WAN Multilayer Router Campus IP IP IP Edge/Egress 1. Congestion on WAN Link 2. Proper QoS Mechanisms not Deployed 3. Campus Congestion less concerning WAN 1. Global WAN Congestion 2. Central to Remote Circuit Speed Mismatch 3. Remote Site to Central Site over subscription 4. Improper PVC Design/Provisioning © 2003, cdaga tech, Inc. All rights reserved. Course acronym #-28 Delay Compression Method PCM (G.711) 32K ADPCM (G.726) 16K LD-CELP (G.728) 8K CS-ACELP (G729) 8K CS-ACELP (G.729a) 6.3 MPMLQ (G.723.1) 5.3K ACELP (G.723.1) © 2003, cdaga tech, Inc. All rights reserved. MOS Score 4.4 4.2 4.2 4.2 4.2 3.98 3.5 Delay (msec) 0.75 1 3-5 10 10 30 30 Course acronym #-29 Delay Goal Cumulative Transmission Path Delay Avoid the “Human Ethernet” CB Zone Satellite Quality High Quality 0 100 200 300 400 Time (msec) Delay Target 500 Fax Relay, Broadcast 600 700 800 ITU’s G.114 “Recommendation” = 0–150 msec 1-Way Delay © 2003, cdaga tech, Inc. All rights reserved. Course acronym #-30 Delay—Fixed Sources of Fixed Delay IP IP IP Multilayer Campus Router WAN Multilayer Router Campus IP IP IP WAN Edge/Egress Codec Processing—Packetization (TX) Serialization De-Jitter Buffer Propagation Delay—6us per Km Serialization Delay © 2003, cdaga tech, Inc. All rights reserved. Course acronym #-31 Delay—Variable Sources of Variable Delay IP IP IP Multilayer Campus Router WAN Multilayer Router Campus IP IP IP Edge/Egress Queuing Delay (Congestion) De-Jitter Buffer No or Improper Traffic Shaping Config Large Packet Serialization on Slow links Variable Size packets Less Common in Campus © 2003, cdaga tech, Inc. All rights reserved. WAN Global WAN Congestion Central to Remote Site Speed Mismatch (Fast to Slow) PVC Over Subscription (Remote to Central Site) Bursting above committed rates Course acronym #-32 Handling Delay Traditional Voice Networks 125 microseconds for T1/J1 (1.5 to 2Mbps) Data networks Delay may exceed 200ms People start “u talk – I talk” on Public nets private nets use QoS © 2003, cdaga tech, Inc. All rights reserved. Course acronym #-33 Transport Options Leased Lines ATM Frame Relay IP © 2003, cdaga tech, Inc. All rights reserved. Course acronym #-34 ATM Protocol Model Data Class Service Class A TDM Channel (DS-1—DS-3) Constant End-to-End AAL-1 1 Byte 47 Bytes AAL-2 1 -3 Bytes 45-47 Bytes 5 Bytes ATM Physical Interface © 2003, cdaga tech, Inc. All rights reserved. Course acronym #-35 Class B Variable Rate (Compressed Video) Class C Blocked Data (Frame Relay) Variable Variable AAL-5 0 Bytes 48 Bytes Class D Data Service (SMDS) Bit Rate Timing Adaption Layer Convergence Sublayer User Payload ATM Layer AAL-3/4 4 Bytes 44 Bytes Voice Over ATM PBX PRI ATM CES Interworking Function ATM WAN PBX PRI ATM CES Interworking Function ATM Access Interface AAL1 / AAL2 / AAL5 © 2003, cdaga tech, Inc. All rights reserved. Course acronym #-36 VoFR Multiplexing Model VoFR Service User VoFR Service Data User Data User SubChannel 1 (Voice) SubChannel 2 (Voice) SubChannel 3 (Data) SubChannel N FRF.3.1 Multiprotocol Encapsulation FRF.3.1 Multiprotocol Encapsulation Voice/Data Sub-Channel Multiplexing Frame Relay Frame Relay Data Link Connection Data Link Connection 16 16 Frame Relay Frame Relay Data Link Connection Data Link Connection 17 17 Frame Relay Frame Relay Data Link Connection Data Link Connection N N Frame Relay Physical Interface Source: Frame Relay Forum © 2003, cdaga tech, Inc. All rights reserved. Course acronym #-37 VOFR Services VoFR Service User Voice Data FAX Faults Dialed FAX Digits Bits (CAS Signaling) Silence Information Primary Payloads Signaled Payloads VoFR Service Service Data Units Frame Relay Service Source: Frame Relay Forum © 2003, cdaga tech, Inc. All rights reserved. Course acronym #-38 IP Transport H.323 Endpoint A IP Token Ring Voice UDP RTP Voice UDP RTP Voice UDP RTP Voice UDP RTP Voice UDP RTP Voice UDP RTP Voice UDP RTP Voice Voice Course acronym #-39 Packet Frame Token Ring IP R1 ATM or Frame Relay FR or ATM IP IP R2 Ethernet 802.3 IP IP IP e H.323 Endpoint B © 2003, cdaga tech, Inc. All rights reserved. Vo* Transport Summary Consideration Bandwidth Efficiency Router Egress QoS WAN QoS Serialization Delay (<768 Kbps) Open Architecture Cost © 2003, cdaga tech, Inc. All rights reserved. VoIP Medium w/o cRTP Low w/cRTP (Depends on L2) CBWFQ w/LLQ IP RTP Priority L3 to L2 QoS Mapping LL—MLPPP FR—FRF.12 ATM—Dual VC IP Endpoints (H.323, SIP, MCCP) APIs Low (no VC mesh) VoFR Low VoATM AAL2—Low AAL5—Medium AAL1—High Voice Priority Queue WAN Switch Robust QoS (CBR, ABR, UBR) Dual VCs Voice Priority Queue WAN Switch Proprietary QoS (High Priority VC) FRF.12 Transport only Transport only Low w/o PVC mesh Medium w/SVCs High w/PVC mesh Course acronym #-40 Low w/o mesh High w/mesh IP Signaling Protocols ITU-T H.323 Session Initiation Protocol (SIP) Media Gateway Control Protocol (MGCP) © 2003, cdaga tech, Inc. All rights reserved. Course acronym #-41 Multimedia Application Models Terminal Traditional Host Peer H.323, SIP Peer Client SCCP, MGCP MGC Server Terminals are managed by the switch & cannot talk directly to other terminals Peer endpoints can place calls without a call agent but use call agents for name resolution/redirection Client endpoints cannot place calls without their call agent but create media streams peer to peer © 2003, cdaga tech, Inc. All rights reserved. Course acronym #-42 Summary Analog to Digital Voice Codec VoATM VoFR VoIP © 2003, cdaga tech, Inc. All rights reserved. Course acronym #-43 Key Points about Packet Voice Technology H.323 and SIPare suitable protocols to deploy large service provider VoIP networks Protocols such as MGCP, SS7, ISDN, CAS/R2 can be combined or interworked with VoIP protocols. When the appropriate architecture and features are deployed, high availability & quality can be delivered for a large variety of voice services © 2003, cdaga tech, Inc. All rights reserved. Course acronym #-44 Voice Infrastructure & Applications © 2003, cdaga tech, Inc. All rights reserved. Course acronym #-45 Sometimes Technologies are slow to change… © 2003, cdaga tech, Inc. All rights reserved. Course acronym #-46 “Before 200x: Your personal voice device is your telephone.” Your Name Here. Questions ??? This was just an introduction.. So I expect a lot of questions …. But They will be answered in future sessions ☺ © 2003, cdaga tech, Inc. All rights reserved. Course acronym #-48