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Customer Snapshot                                                                                                         ...
Categorizing and Defining the Symptoms                                          Noise

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Elements That Affect End-to-End Delay                                                                                     ...
Voice QoS Requirements                                                                                                    ...
QoS is Needed to Minimize Packet Loss,
      Delay and Delay Variation                                                    ...
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  1. 1. Agenda Service Provider VoIP Architectures Recognizing Voice Quality Issues Service Provider VoIP Classifying Voice Quality Attributes to Root Quality Issues Cause Address Voice Quality by Implementing Quality of Service (QoS) Faisal Chaudhry, CCIE Echo Talal Siddiqui, CCIE Miscellaneous VAD, Clocking, Fax, Modem, DTMF © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 1 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 2 Long Distance Voice High Level Overall Voice Architecture Architecture PSTN Gateway Data Network Softswitch PSTN SSP SLT SSP Softswitch (MGC) SLT SGW Softswitch SGW (MGC) Transit/Tandem M Voice M Gateways VoIP GW Gateway Remote sites over WAN Gateway IP Local VoCable VoIP GW Services /VoETTx Network Call Agent PSTN VoIP Bearer traffic Gateway Residential SIP Proxy PBX MG H.323 (IMS) Access Gatekeeper IP Phone GK SSP SLT Signalling : MGCP, H.323, SIP, SLT SSP SGW SGW SS7 (SIGTRAN) Voice CPE Business & Call Gateway Gateway Manager Residential © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential Access 3 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 4 Voice over Broadband (Cable, ETTx …) Cable Telephony Solution – Cable MSO Announcement • TWC went in Customer PoP Super PoP VM Server Softswitch service in March PremisesModem Subscriber A Cable Modem Cable uBR7246 Cisco BTS 2003 Softswitch Other Networks • Supplementary Cable Cable Modem Modem SS7 SS7 A Link Services (CFx, Router CW etc) for Multi- Internet uBR10012 Layer IP Network Analog Switch MGX Subscriber B (MGX) VSM Triple play services subscribers HFC DS-3, OC-3, Si V IMT Plant OC-12 Core PSTN MxU V Res. Villas • Service is $39.95 Subscriber C Cable Cable Modem Router Class 4/5 Modem Switch SS7 GW SBC per month and Session Border Controller includes AS5x00 PSTN unlimited calls in Cisco 3660 MF, FGD Interconnect US Cable Cable Modem Modem uBR7200VXR 911 AT Voice Mail/ Annc CALEA MF, FGD IP-IP CableLabs UM Server Server Server Interconnect OPS qualified Feature Servers Subscriber D http://www.linerunnermaine.com/index.cgi © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 5 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 6 1
  2. 2. Customer Snapshot Telecom Italia: China Unicom FINANCIAL TIMES Wednesday Telecom Italia takes Europe's biggest step in Voice over IP with Cisco Systems and Italtel (…….) 100% of Telecom Italia's national Rome-Milan voice calls and 50% of its international European voice calls now run over a converged “VoIP/MPLS" 1E HRB 1E SY network WRMQ CC 12 E LZ HHHT 2E 1E 1E 1E “We chose VoIP because we could save two thirds of BJ 1E 2E DL YC 2E TJ SJZ 1E XN 1E TY 2E JN 2E 2E our transit operating expenses and give our XA Services Tibet 1E 1E WH 2E ZZ 1E 2E 10 E customers and shareholders a better service. By the Calling Card CD 1E CQ 1E 1E AH 2E NJ SH 2E end of 2003, we estimate that 80% of Telecom Italia's Post-paid 1E GY 1E 1E CX 2E 2E FZ HZ 2E transit voice traffic will travel over the Cisco Systems Pre-paid re-chargeable KM LZ GZ 2E XM 2E and Italtel Multiservice solution. We chose Cisco 8E Pre-paid non re-chargeable 12E 1E SZ Systems and Italtel because they had the most Single stage dialing: HN reliable solution. Cisco Systems has more National & International Transit experience in IP technology and VoIP than any Scalability 350 Cities other infrastructure company and the Directory gatekeeper technology partnership with Italtel provides additional expertise 1000s of E1 Capacity in the switching carrier environment" Extensibility Foundation for move into residential 700M Minutes per Month broadband telephony said Stefano Pileri, head of Telecom Italia's domestic network © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 7 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 8 Business Service: Managed Hosted IP Telephony Managed & Hosted IP Telephony configuration SP Hosted SP Hosted Access Managed Voice service for Enterprises by SP: Infrastructure Service (DSL, ETTx…) CPE Sites Central Central On-premises or Centralized Hosted Call Control LDAP Voicemail H.323 Interface to the PSTN/PLMN (Centralized or on- Softswitch Gatekeepers (or SIP) premises) SS7 Signaling GK Interface to Legacy equipment (such as PBX, GK Voicemail) Call Control MGCP Dial plan Management TDM Voice Billing Firewall Customer Premises Equipment e.g. Analog or IP Phones Voice Gateways LAN Switch Media Resources Need to cater for QoS, Resiliency, Security … (Conf. Bridge, Xcode …) © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 9 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 10 Managed IP Telephony with Call Control on customer premises Agenda SP Hosted Infrastructure Access CPE Sites Service Provider VoIP Architectures H.323 Voicemail Recognizing Voice Quality Issues Softswitch Gatekeepers SS7 (or SIP Proxy) (optional) Call Control Classifying Voice Quality Attributes to Root Signaling GK PSTN Cause GK MGCP Address Voice Quality by Implementing Firewall Access TDM Voice Router Quality of Service (QoS) Echo Call Control Voice Gateway LAN Switch Miscellaneous (optional) Voicemail VAD, Clocking, Fax, Modem, DTMF PSTN © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 11 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 12 2
  3. 3. Categorizing and Defining the Symptoms Noise Noise Absolute Silence Conversation is still Intelligible; presence of Cause: Aggressive Voice Activity Detection (VAD) static, hum, crosstalk intermittent popping Voice distortion Clicking Cause: Clock Slips or Other Digital Errors Problem that affects the voice itself Echoed voice Crackling Garbled voice Cause: Poor Electrical Connection, Electrical Interference Volume distortion Crosstalk Cause: Signal Leakage Due to Wires Located in Close Proximity © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 13 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 14 Noise (Cont.) Echoed Voice Hissing Listener Echo Cause: VAD Cause: Long Echo Tail; Echo Canceller Is (ECAN) Not Activating Static Talker Echo Cause: Codec Mismatch; Enhanced by VAD Cause: Long Echo Tail; ECAN Is Not Activating Tunnel Voice Cause: Tight Echo with Some Loss © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 15 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 16 Garbled Voice Volume Distortion Fuzzy Voice Choppy Voice Cause: Too Much Gain on the Signal Cause: Consecutive Packets Lost or Excessively Delayed Disabling DSP Predictive Insertion Where Silence Is Muffled Voice Inserted Instead Cause: Overdriven Signal or Some Other Cause That Eliminates or Reduces Signal Level at Frequencies Inside the Key Range Synthetic Voice for Voice (Between 440 and 3500) Cause: Single Packet Loss or Delay Beyond the Bounds of the De-Jitter Buffer Playout Period Soft Voice Cause: Attenuated Signal Underwater Voice Tinny Voice Cause: A Common Cause of This Problem Is G729 IETF and Cause: Overdriven Signal that Eliminates or Reduces Signal Pre-IETF Codec Mismatch Level at Frequencies Outside the Key Range for Voice (Between 440Hz and 3500Hz) © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 17 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 18 3
  4. 4. Agenda Problem and Root Cause Association Service Provider VoIP Architectures Synthetic Voice Packet Loss Recognizing Voice Quality Issues Fuzzy Voice Classifying Voice Quality Attributes to Root Absolute Silence Delay Cause Static and Hissing Echo Return Loss Address Voice Quality by Implementing Quality of Service (QoS) Muffled Voice Gain Adjustment Echo Soft Voice Jitter Miscellaneous VAD, Clocking, Fax, Modem, DTMF Choppy Voice VAD Listener Echo © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 19 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 20 Classifying Voice Quality Attributes to Root Cause Basic Guidelines for of Voice over IP Transmit voice traffic the fastest way possible Quality of Network VAD, Codecs Delay is bad (worsens echo, awkward conversations, etc.) Service Transmission • Absolute silence Minimize as many sources of delay as possible Loss Plan • Clipping Goal: keep delay to less than 150ms • Static and hissing • Loss • Gain adjustment • Underwater voice Transmit VOIP packets as a steady, smooth stream • Jitter • ERL Any delay should be consistent • Delay Inconsistent delay is called “Jitter” • Synthetic voice • Talker echo Synchronization, Compensating for Jitter creates additional delay • Robotic voice • Listener echo Cabling • Choppy voice • Tunnel voice • Crackling Drop any packets received out of order • Periods of silence • Fuzzy voice • Clicking • Muffled voice Voice does not tolerate delays…it’s better to drop the packet • Crosstalk • Tinny voice CODEC logic can compensate for some dropped packets Above all…it’s gotta sound good (subjective) © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 21 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 22 Voice QoS Requirements Agenda End-to-End Latency Hello? Hello? Service Provider VoIP Architectures Avoid the Recognizing Voice Quality Issues “Human Ethernet” Classifying Voice Quality Attributes to Root Cause CB Zone Address Voice Quality by Implementing Satellite Quality Quality of Service (QoS) High Quality Fax Relay, Broadcast Echo 0 100 200 300 400 500 600 700 800 Time (msec) Miscellaneous Delay Target VAD, Clocking, Fax, Modem, DTMF ITU’s G.114 Recommendation: ≤ 150msec One-Way Delay ITU’ One- © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 23 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 24 4
  5. 5. Elements That Affect End-to-End Delay Calculate Delay Budget Coder Queuing Serialization De-Jitter Buffer Propagation Delay Delay 25 ms Delay 6 ms Delay 3 ms 50 ms 32 ms PSTN (Private Line Network) IP WAN Los Angeles Munich Fixed Delay Variable Delay Campus Branch Office Coder Delay G.729 (5 msec look ahead) 5 msec Propagation CODEC Queuing Serialization Jitter Buffer Coder Delay G.729 (10 msec per frame) 20 msec and Network Packetization Delay—Included in Coder Delay Fixed Fixed Variable Variable + (6.3 µs/Km) Queuing Delay 64 kbps Trunk ~6 msec (Can Be Reduced (Can Be Reduced 20–50 ms (Sampling rate) Using LLQ) Using LFI) Network Delay Serialization Delay 64 kbps Trunk 3 msec (Variable) Propagation Delay (Private Lines) 32 msec Network Delay (e.g. Public Frame Relay Svc) N/A—Private Line N/A—Private Line Goal: End-to-End Delay (Should Be < 150 ms) 150mx As per ITU G.114 Recommendations De-Jitter Buffer ~50 msec Delay Total ~116 msec © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 25 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 26 Voice QoS Requirements Voice QoS Requirements Factors which Degrade Voice Quality Factors which Degrade Voice Quality Packet Loss Packet Loss Voice Voice Voice Voice Voice Voice Voice Voice 4 3 2 1 4 3 2 1 Voice Voice Voice Voice Voice Voice Voice Voice Voice 4 3 2 1 4 3 2 1 3 Voice Voice 3 Reconstructed Voice Sample 3 Voice Current Cisco gateway DSP CODEC algorithms can correct Reconstructed Voice Sample for 30 msec of lost voice by using predictor algorithm 3 Generally 1 G.729A voice packet contains 20 msec of voice Lost packets induce “clipping” and temporarily expand the jitter buffer, which increases end-to-end latency One lost Voice over IP packet causes a MODEM retrain; Two drops can cause a call disconnect Causes of packet loss: Network quality, network congestion and delay variation © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 27 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 28 Voice QoS Requirements Voice QoS Requirements Factors which Degrade Voice Quality De-Jitter Buffer Operation Variable Delay – Jitter Normal Operating Sender Receiver Queue Depth Voice Frames Voice Frames From Network V V V VV VV VV VV VV V V V V to DSP decode PBX Network PBX Variable Fixed Playout Arrival Rate Over Flow: Under Flow: Rate = Codec Frame Queue Fills If Quiescent Point: Queue Empties If = Codec Frame Rate +/- ∆ Voice Frame Specified in mSec Voice Frame Rate Arrive Too Fast Arrive too Slow Sender Transmits t When voice call starts, the de-jitter buffer fills up to the quiescent point As voice frames arrive too fast, the queue fills Sink Receives As voice frames arrive too slowly, the queue empties D1 D2 = D1 D 3 = D2 t Depth of queue varies with network operation Over-/-under flow will cause gaps in speech and underwater voice © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 29 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 30 5
  6. 6. Voice QoS Requirements Voice QoS Requirements De-Jitter Buffer Operation Summary for Voice Variable Delay—Jitter Buffer Under/Over Runs Latency ≤ 150 ms Cisco GW DSPs Uses an Adaptive Jitter Buffer Voice which has10 msec of “Extra” Buffer Jitter ≤ 30 ms One-Way Requirements Packet Dropped If Instantaneous Jitter Is > 10 msec Loss ≤ 1% 50ms of possible Jitter Buffer 17–106 kbps guaranteed priority bandwidth per call Bandwidth for Voice-Control traffic per call Smooth Network CODEC SCCP: 150 bps + Layer 2 overhead Benign CAC must be enabled (Integrated Drop sensitive Services) Delay sensitive <=10ms UDP priority Calculated Jitter Buffer Based on Variable Network Delay in msec (packet RTP Timestamp) © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 31 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 32 Enabling QoS QoS Operation Differentiated & Integrated Services Standards Differentiated Services QoS Approach Classification: DSCP settings & attribute within a packet to differentiate (L3) RFC 3246: If mark packet with EF then PHB is to move this packet to front of queue during congestion. Mark at the edge! Trust Boundary: Define and Enforce a Trust Boundary at the Network Edge QUEUEING AND Scheduling: Assign Packets to One of Multiple Queues (based on CLASSIFICATION AND MARKING (SELECTIVE) DROPPING Post-Queuing Operations Classification) for Expedited Treatment Through the Network Provisioning: Accurately Calculate required Bandwidth for All Applications Plus Element Overhead Out of band signaling for BW: RSVP Central Site PSTN SRST Router IP WAN Campus Branch Office © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 33 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 34 QoS Operation Enabling QoS Differentiated Services QoS Approach DiffServ QoS Approach in SP Summary Queuing Classification Classification Classification Classification Policing Marking Shaping Policing Scheduling Marking Shaping Marking Scheduling Scheduling Core Router Edge Edge Router Router 1st Operation in Diff Discard Misbehaving Mark closest Congestion Post Queuing Serv is to classify: Traffic: to to the source: Management & Operations: - All traffic looks Maintain Network Mark Traffic Avoidance: Fragmentation Classification same until Integrity According to Congestion due to & Interleaving. Classification Core classification & behavior and speed mismatch Shaping: Policing marking Business (store & may Control Bursts Marking Router Marking - Identify and Split Policies reorder). and Conform Shaping Prioritize, Protect Traffic Scheduling Traffic into Scheduling Different Classes and Isolate Traffic Classification based on Markings Scheduling © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 35 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 36 6
  7. 7. QoS is Needed to Minimize Packet Loss, Delay and Delay Variation Queuing on the IP Phone (Edge device) Where QoS Is Needed Mini-switch inside the IP Phone re-tags the packets from Central Site Remote Branch access port In your network, what edge device is used? L2 or L3? Type of L2? Si WAN IP Phone Switch ASIC Si Untrusted: Phone ASIC Will Re- Write CoS = 0 COS = 5 QoS—Campus Access QoS—Campus Distribution QoS—WAN QoS—Branch • Define trust boundary • Layer 3 Policing • Low-latency Queuing • Classification and Trust COS = 5 • Classification on IP • Multiple Queues on All • Link Fragmentation and Boundaries on IP Phone , Phone and Access Ports; Priority Queuing Interleave Access Layer Switch and Switch for VoIP Router • Bandwidth Provisioning • Multiple Queues on IP • WRED Within Data • Multiple Queues on IP • Admission Control Phone and All Access Phone and Access Ports Queue for Congestion Ports COS = 0 COS = 7 Management © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 37 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 38 Queuing on the IP Phone (Edge device) Queue 0 (PQ) Queue ? TX Voice RTP Packets RX Queue 1 Queue 2 QoS in Campus Queue 3 • Priority Queue (PQ) is for VoIP RTP traffic (CoS = 5) • Round-Robin Scheduling with a PQ Timer © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 39 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 40 Is QoS Needed in the Campus? Campus QoS Considerations Typical Campus Oversubscription Ratios Core Si Si “Just throw more bandwidth at Typical 4:1 it. That will solve the Distribution Oversubscription problem!” Si Si Typical 20:1 Oversubscription Access Maybe, Maybe Not; Campus Congestion Is a Buffer Management Issue © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 41 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Confidential 42 7

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