Paketový přenos hlasu Jaroslav Martan Cisco Systems jmartan cisco

Скачать презентацию Paketový přenos hlasu Jaroslav Martan Cisco Systems jmartan cisco

95506c9db101d4ec31ca85c62c2b5d76.ppt

Количество слайдов: 142

Data Is Overtaking Voice Evolution from TDM-based transport to packets/cells or a combination Relative Load Data Is 23 x Voice Traffic 30 25 20 Data 15 10 Data Is 5 x Voice Traffic 5 0 1990 Voice 1995 2000 2005 Year Source: Electronicast 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 3

TDM Transport Efficiency Types of Traffic Utilization Voice PBX Wasted Bandwidth Legacy 50– 60% LAN Video Single WAN Link Time Slot Assignments • Wasted bandwidth • No congestion 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 4

Packet Transport Efficiency Types of Traffic Voice Utilization Legacy 90– 95% LAN Video PBX Q U E Cells/Frames/Packets Individual Packets • High bandwidth efficiency • Congestion management 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 5

Voice Network Transport • Voice Network Transport is typically TDM circuit-based: T 1/E 1 DS 3/E 3 SONET (OC-3, OC-12, etc. ) • But can also be packet-based: ATM Frame Relay IP 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 6

Planning and Implementation • Today Tie-line replacement Toll-bypass Off Premise Extension (OPX) Router key system replacement Small office IP phone system (< 100 users) • Tomorrow Virtual call centers Campus IP phone system (> 1000 users) Enhanced integrated data/voice applications Unified messaging 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 7

Voice Transport Mechanisms Layer 3—Vo. IP Layer 2—Vo. FR, Vo. ATM • Operates in heterogeneous network (ubiquitous) • Requires rigid homogenous network or L 2 gateways • Connectionless (requires sequence numbers) • Connection oriented (frames arrive in order) • “Soft” Qo. S • “Hard” Qo. S • Layer 2 and 3 overhead • Layer 2 overhead • Standards-based H. 323 (MGCP coming) • Standards based (FRF. 11/12, ATM AAL 1/2/5) 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 8

Voice Compression • Objective: reduce bandwidth consumption Compression algorithms are optimized for voice Unlike data compression: these are “loose” • Drawbacks/tradeoffs Quantization distortion Tandem switching degradation Delay (echo) 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 10

Voice Compression Technologies Unacceptable 64 Business Quality Toll Quality * PCM (G. 711) (Cellular) Bandwidth (Kbps) * 32 ADPCM 32 (G. 726) * 24 16 ADPCM 24 (G. 726) * * ADPCM 16 (G. 726) LDCELP 16 (G. 728) 8 0 * LPC 4. 8 * CS-ACELP 8 (G. 729) Quality 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 11

Speech-Coding Schemes • Waveform coders Non-linear approximation of the actual waveform Examples: PCM, ADPCM • Vocoders Synthesized voice Example: LPC • Hybrid coders Linear waveform approximation with synthesized voice 401 0985_05 f 9_c 1 Example: CELP © 1999, Cisco Systems, Inc. 12

Digitizing Voice: PCM Waveform Encoding Review • Nyquist Theorem: sample at twice the highest frequency Voice frequency range: 200 -3400 Hz Sampling frequency = 8000/sec (every 125µs) Bit rate: (2 x 4 k. Hz) x 8 bits per sample = 64, 000 bits per second (DS-0) • By far the most commonly used method CODEC PCM = DS-0 64 Kbps 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 13

Voice Compression—CELP • Code excited linear predictive • Very high voice quality at low-bit rates, processor intensive, use of DSPs • G. 728: LD-CELP— 16 Kbps • G. 729: CSA-CELP— 8 Kbps G. 729 a variant— “stripped down” 8 kbps (with a noticeable quality difference) to reduce processing load, allows two voice channels encoded per DSP 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 14

Voice CODECs: Hybrid Coders PCM Encoder Filtering 111001001001011 Sampling Sample Quantizing Frames PCM Decoder Encoding Vocal. Cords Throat Nose Mouth Human Speech Model 401 0985_05 f 9_c 1 Model Parameters Analysis © 1999, Cisco Systems, Inc. 10110010 Parameters Model Parameters Synthesis 15

Digital Speech Interpolation (DSI) • Voice Activity Detection (VAD) • Removal of voice silence • Examines voice for power, change of power, frequency and change of frequency • All factors must indicate voice “fits into the window” before cells are constructed • Automatically disabled for fax/modem 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 16

Voice Activity Detection - 31 dbm B/W Saved Voice Activity (Power Level) Hang Timer No Voice Traffic Sent SID Buffer - 54 dbm Pink Noise Voice “Spurt” 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. Silence Time Voice “Spurt” 17

Bandwidth Requirements Voice Band Traffic Encoding/ Compression Result Bit Rate G. 711 PCM A-Law/µ-Law 64 kbps (DS 0) G. 726 ADPCM 16, 24, 32, 40 kbps G. 729 CS-ACELP 8 kbps G. 728 LD-CELP 16 kbps G. 723. 1 CELP 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 6. 3/5. 3 kbps Variable 18

Voice CODEC Cheat Sheet Mean Native Encoding Voice Opinion Bit Rate Compression Quality Score Kbps BW Dual DTMF CPU Comp Music on Hold G. 711 PCM 4. 1 64 A D A A G. 726 ADPCM 3. 85 32 B C B B G. 728 LD-CELP 3. 61 16 C B B C C C G. 729 CS-ACELP 3. 92 8 A A B B C C G. 729 a CS-ACELP 3. 7 8 B A C C B D G. 723. 1 ACELP 3. 65 5. 3 C A C D 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 19

Packet Efficiency OH Frame/Packet Payload OH 4 Bytes 1488 Bytes 4 Bytes Payload = 1488 OH Cell 5 Bytes Overhead = 8 Efficiency = 99. 5% Payload 48 Bytes Payload = 48 Overhead = 5 Efficiency = 89. 6% • Small vs large packet sizes • Fixed vs variable sized packets 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 21

Vo. FR Multiplexing Model Vo. FR Service User Data User FRF. 3. 1 Multiprotocol Encapsulation Frame Relay Data Link Connection 17 Frame Relay Data Link Connection N Vo. FR Service Sub. Channel 1 (Voice) Sub. Channel 2 (Voice) Sub. Channel 3 (Data) Sub. Channel N Voice/Data Sub-Channel Multiplexing Frame Relay Data Link Connection 16 Frame Relay Physical Interface Source: Frame Relay Forum 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 22

FRF. 11 Concept • Extension of frame relay application support for compressed voice • Multiplexing of up to 255 sub-channels • Support of multiple payloads • Support of data sub-channel 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 23

Multiple Sub-Channel Payloads in an FRF. 11 Frame Voice Payload 1 Voice Payload 2 Sub-Frame 1 DLCI Voice Payload Sub-Frame 2 Information Field Frame 3 Data Payload Voice Payload Sub-Frame 3 CRC 4 Data Payload Sub-Frame 1 DLCI Information Field CRC Frame Source: Frame Relay Forum 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 26

Vo. FR Services Vo. FR Service User Voice Data FAX Faults Dialed FAX Digits Primary Payloads Bits (CAS Signaling) Silence Information Signaled Payloads Vo. FR Service Data Units Frame Relay Service Source: Frame Relay Forum 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. www. cisco. com 27

Voice Payload Options 10 ms of voice Small Payload Low Delay High Overhead High PPS High CPU Load Original Voice Information 10 ms of voice crc 10 ms of voice 3 Small Frames crc hdr 10 ms of voice hdr crc 10 ms of voice hdr Large Payload High Delay Low Overhead Low PPS Low CPU Load 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. crc 10 ms of voice hdr 1 Large Frame 28

Network Design Options Full Mesh of PVCs Voice PVCs Go to One Central Site D Site C Site A Site B • Separate voice and data PVCs—Maximizes quality of service • Combine voice and data on one PVC—Minimizes recurring costs • Or use some combination 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 29

Data/Voice Over Frame Relay Vo. FR Service User Data User FRF. 3. 1 Multiprotocol Encapsulation Frame Relay Data Link Connection 17 Frame Relay Data Link Connection N Vo. FR Service 3600 2600 V 7200 Frame Relay Carrier Network V 3600 V Sub. Channel 1 (Voice) 7200 PVC Carrying Voice 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 2500 Branch Sites Sub. Channel N Frame Relay Data Link Connection 16 7200 Central Site 3600 V Frame Relay Physical Interface High-Speed Access Port at Central Sites (T 1/E 1) Frame Relay PVC (<64 K CIR) 2500 Sub. Channel 3 (Data) Voice/Data Sub-Channel Multiplexing FRF. 11/12 Frame Relay PVC 2600 V Sub. Channel 2 (Voice) 2500 Low-Speed Access Port at Branch Sites (64 Kbps CIR) 30

Calculating Vo. FR Bandwidth • Assumptions • G. 729 Codec at 8 Kbps • 50 PPS (using 2– 10 ms samples) • 2 bytes of DLCI header • 2 bytes of FRF. 11 header • 1 byte of sequence number • 2 byte CRC 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 31

Calculating Vo. FR Bandwidth • Voice payload calculation 20 Msec voice sample * 8 Kbps (for G. 729)/ 8 bits/byte = 20 bytes Note: to derive the payload for G. 711, substitute 64 kbps = 160 bytes • Packet size calculations 20 byte payload + 7 byte Header = 27 bytes (Header = DLCI/FRF. 11/seqn/CRC) • Bandwidth calculations 27 b/voice packet * 8 bits/byte * 50 pps = 10. 8 Kbps per call 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 32

CIR Critical Factors • PVC design Full mesh vs star Shared vs separate PVCs for voice and data • Potential concurrent calls Bandwidth per call Switched through calls • Pre-existing data environment Utilization prior to adding voice 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 33

Vo. FR Summary • FRF. 11 standards-based voice and function syntax • FRF. 12 standards-based fragmentation for data, mitigates delay and delay variation • Proper PVC design for network requirements • Balance voice quality, delay, bandwidth, CIR 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 34

References • [1] FRF. 3. 1, R. Cherukuri (ed), Multiprotocol Encapsulation Implementation Agreement, June 22– 1995 • [2] FRF. 9, D. Cantwell (ed), Data Compression Over Frame Relay Implementation Agreement, January 22– 1996 • [3] FRF. 11. 1 K. Rehbehn, R. Kocen, T. Hatala (eds), Voice Over Frame Relay Implementation Agreement, December 1998 • [4] FRF. 12, A. Malis (ed), Frame Relay Fragmentation Implementation Agreement, 1997 • [5] ITU Recommendation Q. 922, ISDN Data Link Layer Specification for Frame Mode Bearer Services, 1992 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 35

Characteristics of ATM Voice Data Video Cells • Uses small—fixed-sized cells • Connection-oriented • Supports multiple service types • Applicable to LAN and WAN 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 38

AAL Cell Tax AAL-1 Cell Tax AAL-2 Cell Tax 5 Byte Header 1 Byte 47 Byte Payload 1– 47 Byte Payload AAL-3/4 Cell Tax AAL-5 Cell Tax 5 Byte Header 44 Byte Payload 401 0985_05 f 9_c 1 1– 48 Bytes © 1999, Cisco Systems, Inc. 4 Bytes No Tax 48 Byte Payload 40

CES Reference Model CBR Service Interface ATM Network PBX CBR Equipment ATM Access Interface ATM CES Interworking Function 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. ATM CES Interworking Function 41

Structured vs Unstructured CES Structured Unstructured Nx 64 DS 1 ATM Network DS 1 Nx 64 • Intended to emulate pointto-point fractional DS 1 or E 1 circuit • Allows Nx 64 Kbps independent emulated circuits to share one DS 1 • Can be configured to minimize ATM bandwidth 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. DS 1 ATM Network DS 1 • Intended to emulate point-to-point DS 1 or E 1 circuit • Allows one 1. 54 or 2. 04 Mbps emulated circuit per DS 1 • Can be used with equipment with non-standard framing • Allows simple configuration of service 42

ATM AAL 5 Voice and Data Cells Data Voice Data PKT V PBX Voice • • 401 0985_05 f 9_c 1 Data Voice Data PKT V PBX Voice AAL 5 does not require convergence sub-layer 48 Byte payload available for voice/data Voice payload = voice sample + padding = 48 bytes 5 byte ATM header © 1999, Cisco Systems, Inc. 44

ATM AAL 5 Voice Cells 53 Bytes 28 Byte Padding 20 Byte Voice Payload ATM Layer 5 Byte Header 48 Bytes • G. 729 compression with 20 ms voice sample • No AAL 5 CS “cell tax” • 28 Bytes “overhead” due to padding 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 45

Vo. ATM Bandwidth • Voice payload calculation 20 msec voice sample * 8 Kbps (for G. 729)/8 bits/byte = 20 bytes Note: to derive the payload for G. 711, substitute 64 Kbps = 160 bytes • Packet size calculations 20 byte payload + 28 byte pad +5 byte header = 53 bytes • Bandwidth calculations 53 b/voice packet * 8 bits/byte * 50 pps = 21. 2 Kbps per call 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 46

Frame Relay/ATM Interworking Regional Office Headquarters 256 k Cisco Frame Relay MC 3810 T 1/E 1 ATM Service Provider T 1/E 1 Digital PBX PSTN Cisco MC 3810 ISP • Network interworking FRF. 5 Frame Relay encapsulation • Service interworking compatible FRF. 8 Carrier compatible 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 47

Vo. ATM—Summary • ATM reference model • Fixed size cells—Delay • Service category—CBR, VBR, ABR • Service criteria for Qo. S, SCR, CDVT • Chose service for requirements— Circuit emulation (AAL 1) voice over AAL 5 • Combined networks 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 48

IP Ubiquity H. 323 Endpoint A Voice IP ATM or Frame Relay FR or ATM R 2 Ethernet 802. 3 e H. 323 Endpoint B 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. IP UDP RTP Voice Frame UDP RTP Voice IP R 1 Packet IP Token Ring UDP RTP Voice IP UDP RTP Voice 51

H. 323—Multimedia Standard for IP Networks • The H. 323 standard provides a foundation for audio, video, and data communications across IP-based networks, including the Internet • Original standard approved in 1996 and H. 323 V 2 was approved January 1998 • H. 323 is an umbrella recommendation from the International Telecommunications Union (ITU) that sets standards for multimedia communications over Local Area Networks (LANs) that do not provide a guaranteed Quality of Service (Qo. S) • H. 323 is H. 320 Recast for IP LAN 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 52

Vo. IP Uses ITU H. 323 System Control and User Interface Video I/O Equipment Audio I/O Equipment Video Codec H. 261, H 263 Audio Codec G. 711, G. 722, G. 723, G. 723. 1, G. 728, G. 729 System Control H. 245 Control Call Control H. 225. 0 RAS Control H. 225. 0 User Data Applications T. 120 Session Layer and Above Receive Path Delay H. 225. 0 Layer LAN Stack 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 53

H. 323 Vo. IP Layers IP Layered Model H. 323 Vo. IP Model User Caller Application Presentation Session TCP Email ID E. 164 Phone No. Audio Codec (G. 711, G. 729, G. 723. 1, . . ) H. 225, H. 245, RTP, RTCP UDP Port Number IP Data Link Frame Relay DLCI, 802. 3 MAC, ATM VPI/VCI Physical 401 0985_05 f 9_c 1 IP Address V. 35, T 1, T 3 © 1999, Cisco Systems, Inc. 54

H. 323—System Components • H. 323 defines four major components for a network-based communications system Terminals Gateways Gatekeepers Multipoint Control Units 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 55

H. 323—System Components H. 323 MCU H. 323 Terminal Scope of H. 323 WAN RSVP H. 323 Gatekeeper H. 323 Terminal H. 323 Gateway PSTN V. 70 Terminal 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. H. 324 Terminal ISDN Speech Terminal H. 320 Terminal Speech Terminal 56

H. 323 Generic Call Flow TCP Connection H. 323 SETUP CONNECT (H 245 Address) Q. 931 TCP Connection H. 245 Messages Open Logical Channels (RTCP Address) H. 245 (RTCP and RTP Addresses) (RTCP Address) (RTCP and RTP Addresses) RTP Stream RTCP Stream 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. Media 57

RTP/RTCP—RFCs 1889/1890 • End-to-end network transport function Payload type identification—voice, video, compression type Sequence numbering Time stamping Delivery monitoring • RTCP (Real-Time Control Protocol) 4 Bytes V E R CC M Payload Type Sequence Number 4 Bytes RTP Timestamp 4 Bytes Synchronization Source (SSRC) ID 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 58

H. 323 Gateway G. 711 PCM G. 726 ADPCM G. 728 LD-CELP G. 729 CS-ACELP G. 729 A CS-ACELP G. 723. 1 ACELP Qo. S IP Network G. 711 PCM Analog L 2 IP UDPRTP Voice Gateway Frame Relay ATM Ethernet FDDI Token Ring 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. PSTN FXO FXS E&M T 1 PRI 59

Gatekeeper Functions • Mandatory services: Address translation Admissions control Bandwidth control Zone management 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. • Optional services: Call control signaling Call authorization Bandwidth management and reservation Call management Gatekeeper management information data structure Directory services 60

H. 323—H. 323 Direct Call Model Services Plane IN Service Logic AAA, Address Resolution Call Control Plane Signaling and Call Control Service Access Function Switch-Based Service Logic End to End Voice Services Service Logic Call Logic Connection Plane Connection Negotiation Transcoding Bearer Switching Media Control: H. 323 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. Switching Logic OSS Billing Net. Mgt. Fault Mgt Service Provisioning Cust. Provisioning H. 323 61

H. 323—Gatekeeper Routed Call Model Services Plane Service Logic IN Service Logic AAA, Directory Service Address Resolution IN/AIN—CTI APIs Call Control Plane Signaling and Call Control Service Access Function Switch-Based Service Logic End to End Voice Services Call Logic OSS GK to GK Gatekeeper Protocol Billing Net. Mgt. Fault Mgt. Service Provisioning Cust. Provisioning Gatekeeper H. 225 H. 245 RAS Connection Plane Connection Negotiation Transcoding Bearer Switching Media Control: H. 225, H. 245 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. Switching Logic 62

Gatekeeper Mandatory Services • Address Translation Translates H. 323 aliases or E. 164 addresses into IP transport addresses (e. g. 10. 1. 1. 1 port 1720) • Admissions Control Authorizes access to the H. 323 network • Bandwidth Control Manages endpoint bandwidth requirements • Zone Management Provides the above functions to all terminals, gateways, and MCUs that register to it 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 63

RAS Messages • GRQ/GCF/GRJ (Discovery) Unicast—Multicast, find a gatekeeper • RRQ/RCF/RRJ (Registration) Endpoint alias/IP address binding, endpoint authentication • ARQ/ACF/ARJ (Admission) Destination Address Resolution, Call Routing • LRQ/LCF/LRJ (Location) Inter-gatekeeper communication • DRQ/DCF/DRJ (Disconnect) Get rid of call state 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 64

H. 323 Message Exchange Gatekeeper A LRQ Gatekeeper B LCF ACF IP Network ARQ V Gateway A Phone A 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. H. 225 (Q. 931) Setup H. 225 (Q. 931) Connect H. 245 RTP ARQ V Gateway B Phone B 65

LRQ Forwarding in Action Directory-Gatekeeper GK LRQ IP Network LCF GK ACF ARQ V Gateway A ARQ ACF H. 225 (Q. 931) Setup H. 225 (Q. 931) Connect H. 245 RTP V Gateway B Phone A 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 66

H. 323 Resources • H. 323 Standards ftp: //itu-t: sg 15!avc@ftp. gctech. co. jp/ • Vo. IP Forum ftp: //ftp. imtc-files. org/imtc-site/Vo. IPAG/Incoming • General Information http: //www. pulver. com 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 67

Intelligent Endpoints—SIP Goals • To supports some or all of five facets of establishing and terminating multimedia communications: User location User capabilities User availability Call setup Call handling 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 68

SIP Call Flow—Proxy cs. columbia. edu ? 4 Location Server INVITEhgs@play From: cz@cs. tu-berlin. de To: herring@cs. columbia. edu Call-ID: 980827@lion. cs cz@cs. tuberlin. de 8 200 OK 2 Hgs@play cs. tu-berlin. de From: cz@cs. tu-berlin. de To: herring@cs. columbia. edu Call-ID: 19970827@lion. cs herring 1 INVITEherring@cs. columbia. edu 3 6 200 OK From: cz@cs. tu-berlin. de To: herring@cs. columbia. edu Call-ID: 980827@lion. cs CONNNECTEDhgs@play From: cz@cs. columbia. edu To: herring@cs. columbia. edu Call-ID: 980827@lion. cs From: cz@cs. tu-berlin. de To: herring@cs. columbia. edu Call-ID: 19970827@lion. cs Lion 9 CONNECTEDherring@cs columbia. edu Call-ID: 19970827@lion. cs 12 200 OK 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 7 Tune Play hgs 10 11 200 OK 70

SIP Call Flow—Redirect cs. columbia. edu ? cz@cs. tuberlin. de 4 302 Moved Temporarily Location: hgs@play. cs. columbia. edu From: cz@cs. tu-berlin. de To: herring@cs. columbia. edu Call-ID: 970827@lion. cs 2 Location Server Hgs@play cs. tu-berlin. de From: cz@cs. tu-berlin. de To: herring@cs. columbia. edu Call-ID: 19970827@lion. cs herring 1 INVITEherring@cs. columbia. edu 3 5 INVITEhgs@play Lion From: cz@cs. tu-berlin. de To: herring@cs. columbia. edu Call-ID: 980827@lion. cs Tune 7 200 OK 6 From: cz@cs. tu-berlin. de To: herring@cs. columbia. edu Call-ID: 19970827@lion. cs 8 CONNECTEDhgs@play. cs. columbia. edu Call-ID: 970827@lion. cs Play hgs 9 200 OK 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 71

SIP Resources • SIP standard ftp: //ftp. ietf. org/internet-drafts/draft-ietfmmusic-sip-04. txt • General SIP information http: //www. cs. columbia. edu/~hgs/sip/ 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 72

SIP vs. H. 323 Comparison • Scope SIP—Full-featured multimedia protocol H. 323—Full-featured video conferencing • Status SIP—Basic SIP ready for proposed standard H. 323—V 3 in ITU approval cycle • Interoperability SIP—Initial bake-off, some interoperability achieved H. 323—Demonstrated, but problematic 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 73

SIP vs. H. 323 Comparison • Call setup overhead SIP—as little as one round trip H. 323— 7 or 8 round-trips (2 in V 2) • Call control functions SIP—Relies on existing protocols H. 323—Based on GK functions • Control transport SIP—UDP (multicast, firewalls) 401 0985_05 f 9_c 1 H. 323—TCP © 1999, Cisco Systems, Inc. 74

Repeat: Voice Is Not A Network • Voice is an Application • Complete understanding of Voice Application fundamentals helps us to design and build better Networks 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 75

Packet Telephony Architecture Choices • Intelligent Network/Simple Endpoints SS 7, Gateway Control Protocol (SGCP/MGCP) • Simple Network/Intelligent Endpoints Session Initiation Protocol (SIP) • Hybrid—Intelligent Network and Endpoints H. 323 • Layer 2 Access Networks Voice Carriage Vo. FR (FRF 11), Vo. ATM 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 76

Data and Voice Opposite Needs/Behavior Data Voice • Bursty • Smooth • Greedy • Benign • Drop sensitive • Drop insensitive • Delay sensitive • TCP retransmits • UDP best effort 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 78

TDM vs Frame vs Cell TDM Frame/Packet Cell • TDM—Constant delay, wasted bandwidth • Frame/packet—Variable delay, highly efficient • Cell—Improved delay, less efficient 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 79

Qos Terminology Queuing / Scheduling Policing • • Limiting the packet rate No buffering Input and output mechanism Drop policies for traffic that exceeds rate tail drop, RED, WRED • CAR, Queue tail-drop Traffic Shaping • • Limiting the packet rate Buffering to smooth traffic flow Output mechanism GTS, FRTS, ATM shaping Call Admission Control • Disallow new traffic if insufficient resources available 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. • • Queuing: Organize packets waiting to go out on an interface Scheduling: When interface is free - decide which of the waiting packets to send next Nodal significance CQ, PQ, WFQ, CBWFQ. . . Tagging / Marking / Colouring • • • Set bits in packet header Indication to guide priority and queuing machanisms Network significance Can be changed/adjusted by any network node IP Precedence, DSCP 80

Voice over IP Protocols Vo. IP Is Not Bound to H. 323 (H. 323 Is a Signaling Protocol) Many Other Signaling Protocols—MGCP, SIP, Etc. Commonality—Voice Packets Ride on UDP/RTP Voice Payload G. 711, G. 729, G. 723(. 1) Transport RTP/UDP Network IP Link MLPPP/FR/ATM AAL 1 Physical – – – 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 81

“Payload” Bandwidth Requirements for Various Codecs Encoding/Compression Resulting Bit Rate G. 711 PCM A-Law/u-Law 64 kbps (DS 0) G. 726 ADPCM 16, 24, 32, 40 kbps G. 727 E-ADPCM 16, 24, 32, 40 kbps G. 729 CS-ACELP 8 kbps G. 728 LD-CELP 16 kbps G. 723. 1 CELP 6. 3/5. 3 kbps 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 82

Vo. IP Packet Format Vo. IP Packet Link UDP IP Header X Bytes 20 Bytes 8 Bytes RTP Header 12 Bytes Voice Payload X Bytes • Payload size, PPS and BPS vendor implementation specific • For example: Not Including Link Layer Header or CRTP Cisco Router at G. 711 Cisco Router at G. 729 Cisco IP Phone at G. 711 Cisco IP Phone at G. 723. 1 = 160 Byte Voice Payload at 50 pps (80 kbps) = 20 Byte Payload at 50 pps (24 kbps) = 240 Byte Payload at 33 pps (74. 6 kbps) = 24 Byte Payload at 33 pps (17 k bps) Note—Link Layer Sizes Vary per Media 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 83

Various Link Layer Header Sizes “Varying Bit Rates per Media” Example—G. 729 with 60 Byte Packet (Voice and IP Header) at 50 pps (No RTP Header Compression) Media Bit Rate Ethernet 14 Bytes 29. 6 kbps PPP 6 Bytes 26. 4 kbps Frame Relay 4 Bytes 25. 6 kbps ATM 401 0985_05 f 9_c 1 Link Layer Header Size 5 Bytes Per Cell 42. 4 kbps Note—For ATM a Single 60 Byte Packet Requires Two 53 Byte ATM Cells © 1999, Cisco Systems, Inc. 85

Domains of Qo. S Consideration Requirement - “End to End” Quality of Service (Qo. S) IP Multilayer Campus Router IP WAN IP IP Campus 401 0985_05 f 9_c 1 Multilayer Campus Router WAN Edge/Egress WAN Backbone Avoiding Loss, Delay and Delay Variation (Jitter) Strict Prioritization of Voice © 1999, Cisco Systems, Inc. 86

Loss Sources of Packet Loss—Congestion IP Multilayer Campus Router IP IP IP Edge/Egress 1. Congestion on WAN Link 2. Proper Qo. S Mechanisms Not Deployed 3. Campus Congestion Less Concerning 401 0985_05 f 9_c 1 WAN Multilayer Campus Router © 1999, Cisco Systems, Inc. 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 87

Anatomy of a Carrier Customer Premises Equipment Access Lines Inter-Node Trunks “The Cloud/Carrier” Frame Relay, ATM WAN Switch Fabric Inter-Node Trunk Over Subscription Often 3: 1 or Higher 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 88

Where WAN Congestion and Delay Can Occur Router WAN Switch Access IGX/8400 T 1 Ingress T 1 Queue T 1 Trunk Queue Router Egress 56 Queue kbps Ingress Queue Packets Arrive at Greater than PIR or CIR PIR = Peak Information Rate 401 0985_05 f 9_c 1 Inter-Nodal Trunk WAN Switch IGX/8400 Access 56 kbps © 1999, Cisco Systems, Inc. Global Trunk Congestion Egress Port Congestion VC Over Subscription 89

Bursting—What Is Your Guarantee? Options Router WAN Switch Access IGX/8400 T 1 Ingress T 1 Queue Trunk Queue Shape to CIR— No Bursting Mark Data DE (Discard Eligible) The Safest Only Drop Data Upon Congestion Not Popular Data Gets Dropped 1 st Compared to Other Subscribers 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. Inter-Nodal Trunk WAN Switch IGX/8400 Access 56 kbps Trunk Queue Router Egress 56 Queue kbps Two PVC’s—Data + Voice Active Traffic Management Voice—Keep Below CIR Data—Allow for Bursting ABR, FECN/BECN, Fore. Sight Need DLCI Prioritization at WAN Egress Only Invoked when congestion/Delays has Already Occurred 90

Congestion Detection and Feedback Effectiveness Depends on Round Trip Delay Router WAN Switch Access IGX/8400 T 1 Ingress T 1 Queue Inter-Nodal Trunk Queue ABR/ Foresight WAN Switch IGX/8400 Access 56 kbps Router Egress 56 Queue Trunk Queue kbps ABR/ Foresight FECN/ BECN ABR—Available Bit Rate FECN/BECN Notification Foresight/CLLM Can Send a Rate Down from Point of Congestion Requires Far End to Reflect a FECN and Send and BECN Back to Source Indicating a Rate Down Can Send a Rate Down from Point of Congestion 401 0985_05 f 9_c 1 Speeds up Rate Down Time over FECN/BECN Congestion Must Occur to Invoke, Congestion Relief Can be as Long as One Round Trip Time © 1999, Cisco Systems, Inc. 91

WAN Queuing and Buffering Router WAN Switch Access IGX/8400 T 1 Ingress T 1 Queue Packets Arrive at Line Rate Placed in Ingress Queue Trunk Queue Inter-Nodal Trunk WAN Switch IGX/8400 Access 56 kbps Trunk Queue Router Egress 56 Queue kbps Packets De-Queue at Line Rate Packets Leak into Trunk at PIR—(Peak Information Rate) Typically Lowest Access Rate— 56 kbps 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 92

Delay Sender Receiver PBX Network PBX First Bit Transmitted Last Bit Received A Processing Delay A Network Transit Delay t Processing Delay End-to-End Delay 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 93

Delay—Fixed Sources of Fixed Delay IP Multilayer Campus Router IP WAN Multilayer Campus Router IP IP IP Edge/Egress Codec Processing—Packetization (TX) Serialization De-Jitter Buffer 401 0985_05 f 9_c 1 IP © 1999, Cisco Systems, Inc. WAN Propagation Delay— 6 us per Km Serialization Delay 94

Delay—Variable Sources of Variable Delay IP Multilayer Campus Router IP WAN Multilayer Campus Router 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 401 0985_05 f 9_c 1 IP © 1999, Cisco Systems, Inc. WAN Global WAN Congestion Central to Remote Site Speed Mismatch (Fast to Slow) PVC Over Subscription (Remote to Central Site) Bursting Above Committed Rates 96

Voice Delay Guidelines One Way Delay (msec) Description 0– 150 Acceptable for Most User Applications 150– 400 Acceptable Provided That Administrations Are Aware of the Transmission Time Impact on the Transmission Quality of User Applications 400+ Unacceptable for General Network Planning Purposes; However, It Is Recognized That in Some Exceptional Cases This Limit Will Be Exceeded ITU’s G. 114 Recommendation 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 97

Delay Budget Goal < 150 ms Cumulative Transmission Path Delay Avoid the “Human Ethernet” CB Zone Satellite Quality Fax Relay, Broadcast High Quality 0 100 200 300 400 500 600 700 800 Time (msec) Delay Target ITU’s G. 114 “Recommendation” = 0– 150 msec 1 -Way Delay 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 98

An Example • Assumptions: We have eight trunks We are going to use CS-ACELP that uses 8 Kbps per voice channel Our uplink is 64 Kbps Voice is using a high priority queue and no other traffic is being used 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 99

Delay Calculation Los Coder Delay Queuing Delay Angeles 25 ms 6 ms Dejitter Buffer 50 ms Propagation Delay— 32 ms Munich (Private Line Network) Serialization Delay 3 ms Fixed Delay Coder Delay G. 729 (5 msec Look Ahead) Coder Delay G. 729 (10 msec per Frame) Variable Delay 5 msec 20 msec Packetization Delay—Included in Coder Delay 21 msec Max Queuing Delay 64 kbps Trunk Serialization Delay 64 kbps Trunk 3 msec Propagation Delay (Private Lines) 32 msec Network Delay (e. g. , Public Frame Relay Svc) Dejitter Buffer 401 0985_05 f 9_c 1 Total © 1999, Cisco Systems, Inc. Variable Delay Component 50 msec 110 msec 100 82

Variable Delay Calculation • We have eight trunks, so in the worst case we will have to wait for seven voice calls prior to ours • To put one voice frame out on a 64 Kbps link takes 3 msec • 1 byte over a 64 Kbps link takes 125 microseconds. We have a 20 byte frame relay frame with 4 bytes of overhead. 125 * 24 = 3000 usecs or 3 msec • Does not factor in waiting for a possible data packet or the impact of variable sized frames • Assumes voice prioritization of frames 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 101

Large Packets on Slow Links 56 kbps Line Real-Time MTU Elastic Traffic MTU 214 ms Serialization Delay for 1500 Byte Frame at 56 kbps Large Packets “Freeze Out” Voice—Results in Jitter 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 102

Slow-Link Efficiency Tools Fragmentation and Interleave Not Needed on Links Greater than 768 kbps Before Real-Time MTU Elastic Traffic MTU 214 -ms Serialization Delay for 1500 -byte Frame at 56 kbps After Elastic MTU Real-Time MTU Elastic MTU Solutions 401 0985_05 f 9_c 1 Point to Point Links—MLPPP with Fragmentation and Interleave Frame Relay—FRF. 12 (Voice and Data Can Use Single PVC) ATM—(Voice and Data Need Separate VCs on Slow Links) © 1999, Cisco Systems, Inc. 103

Fragment Size Matrix Assuming 10 ms Blocking Delay per Fragment Link Speed Fragment Size 56 kbps 70 Bytes 64 kbps 80 Bytes 128 kbps 160 Bytes 256 kbps 512 kbps 320 Bytes 640 Bytes 768 kbps 1000 Bytes 1536 kbs 2000 Bytes 401 0985_05 f 9_c 1 X © 1999, Cisco Systems, Inc. Fragment Size = 10 ms Time for 1 Byte at BW Example: 4 G. 729 Calls on 128 kbps Circuit Fragment Blocking Delay = 10 ms (160 bytes) Q = (Pv*N/C) + LFI Q = (480 bits*4/128000) + 10 ms = 25 ms Worst Case Queuing Delay = 25 ms Q = Worst Case Queuing Delay of Voice Packet in ms Pv = Size of a Voice Packet in Bits (at Layer 1) N = Number of Calls C = Is the Link Capacity in bps LFI = Fragment Size Queue Delay in ms 104

Fragmentation Frame Size Matrix Real Time Packet Interval 10 ms 30 ms 40 ms 56 kbps 70 Bytes 140 Bytes 210 Bytes 280 Bytes 350 Bytes 700 Bytes 1400 Bytes 64 kbps 80 Bytes 160 Bytes 240 Bytes 320 Bytes 400 Bytes 800 Bytes 1600 Bytes 128 kbps 160 Bytes 320 Bytes 480 Bytes 640 Bytes 800 Bytes 1600 Bytes X 3200 Bytes 256 kbps 320 Bytes 640 Bytes 960 Bytes 1280 Bytes 1600 Bytes 1280 Bytes 1920 Bytes 2560 Bytes X X 6400 Bytes 640 Bytes X 3200 Bytes 512 kbps X 12800 Bytes X 768 kbps 1000 Bytes 2000 Bytes 3000 Bytes 4000 Bytes 5000 Bytes 10000 Bytes 20000 Bytes 1536 kbs Link Speed 20 ms 2000 Bytes X X 4000 X Bytes X X 6000 X Bytes X 8000 X Bytes 50 ms 100 ms 200 ms X 10000 X Bytes X 20000 X Bytes X X X 40000 X Bytes X —Fragmentation not an issue due to BW + Interval Combination 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 105

When Is Fragmentation Needed? Frame Size 1024 64 512 256 128 1 Bytes Bytes Byte 1024 64 1500 512 256 36 ms 128 143 us 9 ms 18 ms 72 ms 144 ms Bytes Bytes 56 kbps 1500 Bytes 214 ms 125 us 8 ms 16 ms 32 ms 64 ms 128 ms 187 ms Link 128 kbps Speed 256 kbps 62. 5 us 4 ms 8 ms 16 ms 32 ms 64 ms 93 ms 31 us 2 ms 4 ms 8 ms 16 ms 32 ms 46 ms 512 kbps 15. 5 us 64 kbps 9 ms 8 ms 4 ms 2 ms 768 kbps 10 us 1536 kbs 5 us 768 kbps 1 ms 10 us 18 ms 16 ms 8 ms 1 ms 4 ms 36 ms 32 ms 16 ms 2 ms 320 us 32 ms 144 ms 214 ms 128 ms 187 ms 64 ms 8 ms 93 ms 16 ms 32 ms 46 ms 8 ms 16 ms 23 ms 2. 56 ms 5. 12 ms 10. 24 ms 15 ms 4 ms 640 us 64 ms 4 ms 8 ms 640 us 1. 28 ms 72 ms 1. 28 ms 2. 56 ms 5. 12 ms 7. 5 ms 640 us 1. 28 ms 2. 56 ms 5. 12 ms 10. 24 ms 15 mss • Depends on the queuing delay caused by large 1536 kbs 5 us 320 us 640 us 1. 28 ms 2. 56 ms 5. 12 ms 7. 5 ms frames at a given speed—fragmentation generally not needed above 768 kbps 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 106

Qo. S Needs • Campus Bandwidth minimizes Qo. S issues • WAN edge Qo. S “starts” in the WAN—a must • WAN considerations Often forgotten or misunderstood— a must 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 107

Three Classes of Qo. S Tools Vo. IP 1 1 V V V 3 SNA Data Router 2 3 2 1 2 3 3 • Prioritization Classification + Queuing • Slow Link Efficiency Link Fragmentation and Interleave (LFI ) Compression, Voice Activity Detection (VAD) • Traffic Shaping Speed Mismatches 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 108

Vo. IP Bandwidth Solution Version IHL Type of Service Identification Time to Live Total Length Flags Protocol Fragment Offset Header Checksum Source Address Destination Address Options Padding Source Port Length V=2 P Destination Port Checksum X CC M PT Sequence Number Timestamp Synchronization Source (SSRC) Identifier 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. RTP Header Compression • 20 ms @ 8 kbps yields 20 -byte payload • IP header 20; UDP header 8; RTP header 12 2 X payload! • Header compression 40 bytes to 2 or 4 bytes • Hop-by-Hop on slow links <512 kbps • CRTP—Compressed Real-time Protocol 109

Send Fewer Packets Link Efficiency • VAD “B” versions of G. 729 contain a built-in IETF VAD algorithm, no need to configure VAD Rule-of-thumb: 30 -35% reduction in BW - a more valid assumption for larger pipes (T 1 and above) Depends on application (e. g. Music-on-Hold makes VAD 0%) • Variable Payload Size Specify #samples per packet Changes the BW, delay and pps characteristics of the call Usability depends on the delay budget of the network values > default: decreases BW, and increases delay values < default: increases BW, and decreases delay 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 110

Traffic Differentiation Mechanisms IP Precedence and 802. 1 p Layer 2 802. 1 Q/p Data PREAM. SFD Packet DA SA Three Bits Used for Co. S (User Priority) TAG 4 Bytes PT DATA FCS Layer 3 IPV 4 Version To. S Length 1 Byte ID offset TTL Proto FCS IP-SA IP-DA Data Standard IPV 4: Three MSB Called IP Precedence (Diff. Serv Will Use Six D. S. Bits Plus Two for Flow Control) • Layer 2 mechanisms are not assured end-to-end • Layer 3 mechanisms provide end-to-end classification 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 111

IP Precedence “Controlling WFQ’s De-queuing Behavior” IP Packet Data Weight = 4096 (1 + IP Precedence) IP Precedence Weight To. S Field 3 Bit Precedence Field 0 4096 1 2048 2 1365 3 1024 4 819 5 682 6 585 7 512 • IP Precedence Not a Qo. S Mechanism turned on in the router “In Band” Qo. S Signaling—Set in the End Point 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 112

Precedence to VC Mapping VC Bundle VC 1 VC 2 VC 3 VC 4 ATM Network Assign to VC Based on: IP Precedence RSVP Policy Routing 401 0985_05 f 9_c 1 Note: WAN Qo. S is Only as Good as Specified ATM VC Parameters • VC bundle—multiple VCs for each IP adjacency • Separate VC for each IP Co. S • WRED, WFQ, or CBWFQ runs on each VC queue © 1999, Cisco Systems, Inc. 113

Queuing Overview Prioritization - Queuing • Queuing and scheduling significant when: there is contention for BW, i. e. congestion traffic shaping smoothing share voice & data on same infrastructure • Several sets of queues: VC queues (FR, ATM) Interface queues Transmit ring queues (driver) • Queuing method for voice much more significant on slow access links (<2 M) • WFQ is inadequate to provide good voice quality under all circumstances 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 114

Priority and Custom Queuing (PQ, CQ) Prioritization - Queuing PQ and CQ are not recommended for voice CQ PQ • 4 Queues: High, Medium, Normal, Low • Packets classified by protocol or interface • FIFO within priority • Absolute priority scheduling • Lower priority queues may starve 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. • 16 Queues • Packets classified by protocol or interface • FIFO within priority • Weighted round robin scheduling • WRED and RSVP not supported • Guarantees BW per queue, not delay 115

Weighted Fair Queuing (WFQ) Prioritization - Queuing 24 kbps flow gets 28 kbps (only needs 24 kbps) Router Queue Structure 24 kbps Voice flow Processor Dynamic Queue Per Flow 1 2 2 2 2 1 1 2 Classify 500 kbps flow 2 2 2 Dequeue 500 kbps flow gets 28 kbps 2 1 2 1 56 kbps Line Speed Transmit Scheduling Default on links 2 meg or less When congestion exists, traffic in queues shares bandwidth based on the weights “Not as effective when MANY flows” 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 116

Weighted Fair Queuing (WFQ) Prioritization - Queuing Before 12. 0(5)T Weight = 4096 (1 + IP Prec) IP Prec <12. 0(5)T Weight 0 4096 1 2048 2 1365 3 1024 4 819 5 682 6 585 7 512 RSVP 4 RTP Reserve 128 RTP Priority N/A 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 12. 0(5)T and later Weight = 32768 (1 + IP Prec) >=12. 0(5)T Weight 32768 16384 10923 8192 6554 5461 4681 4096 4 N/A 0 117

Weighted Fair Queuing (WFQ) Prioritization - Queuing 2 2 2 3 IP Precedence 7 4 4 . . . 5 5 . . . 6 • • Reserved queues (RSVP and RTP Reserve) . . . Weight: • IP Precedence • RSVP/RTP Reserve 1 1 . . . Q Classification: • Source address • Dest address • Source port • Dest. Port • IP Precedence 6 6 Dequeue IP Precedence 0 (Best Effort/Hash queues) Packets within the same weight are scheduled based on arrival time Routing protocols and LMI bypass WFQ algorithm ALL RSVP traffic queued at weight 4, not just voice RSVP traffic at weight 128 until reservation succeeds, then 4 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 118

IP Precedence Flow Bandwidth Calculation Example Flow A BW = ( ) Circuit Flow A “Parts” X Bandwidth Sum of all Flow “Parts” Example A Example B 56 kbps Link 2—Vo. IP Flows A+B at 24 kbps (IP Prec 0) 2—FTP Flows at 56 kbps (IP Prec 0) 2—Vo. IP Flows A+B at 24 kbps (IP Prec 5) 2—FTP Flows at 56 kbps (IP Prec 0) ( 1 ) 14 kbps = X 56 kbps 4 6 ( 14) 24 kbps = X 56 kbps 14 kbps Not Suitable for a 24 kbps Flow Not Example of Many Flows with WFQ and Equal Precedence Flows 24 kbps Suitable for a 24 kbps Flow Suitable Weighted “Fair” Queuing WFQ Preferring IP Precedence 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 119

IP Precedence No Admission Control Moral of the Story: Know Your Environment, Voice Traffic Patterns etc. Recommendations for Certain Bandwidth’s to Follow Example C 56 kbps Link 2—Vo. IP Flow’s at 24 kbps (IP Prec 5) 4—FTP Flows at 56 kbps (IP Prec 0) 6 ( 16) 21 kbps = X 56 kbps 21 kbps Not Suitable for a 24 kbps Flow Not RTP Header Compression Would Help Since it Would reduce Vo. IP Flow to 11. 2 kbps Also RSVP or CBWFQ 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 120

IP Precedence and WFQ Prioritization - Queuing Calculating given Flow BW based on IP Precedence under congestion ( Flow A “Parts” (1 + IP Prec) Sum of all Flow “Parts” ) X Circuit BW = Flow A BW BW Example A Example B Example C 56 kbps link 2 Vo. IP Flows, 24 K (IP Prec 0) 2 FTP Flows, 56 K (IP Prec 0) 2 Vo. IP Flows, 24 K (IP Prec 5) 2 FTP Flows, 56 K (IP Prec 0) 2 Vo. IP Flows, 24 K (IP Prec 5) 6 FTP Flows, 56 K (IP Prec 0) 1 6 6 ( 4 ) X 56 kbps = 14 K ( 14) X 56 kbps = 24 K 14 kbps NOT suitable for a NOT 24 K Vo. IP flow 24 K SUITABLE for a 24 K SUITABLE Vo. IP flow 18. 6 K NOT suitable for a NOT 24 K Vo. IP flow No IP Precedence With IP Precedence More flows with IP Precedence 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. ( 18) X 56 kbps = 18. 6 K 121

Class-Based WFQ (CBWFQ) Prioritization - Queuing Class queues 1 1 . . . 2 Max: 63 (64 including the default class-queue) 2 2 3 De-queue Default class-queue OR 5 . . . Classify 6 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 5 WFQ System 6 6 (unclassified traffic) 122

Prioritization Tools “Protecting Voice from Data” Vo. IP (High) 1 1 Data (Low) 2 2 Data (Low) 3 3 Data (Low) 4 4 4 Router PQ V 5 3 2 V V 1 1 1 WAN Circuit 4 WFQ Qo. S Queuing Tools IP RTP Priority (Point-to-Point Links + Frame Relay) IP to ATM Qo. S (Multiple VCs or CBWFQ within VC) Identifying and Giving Priority to Voice 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 123

Weighted RED • WRED: In the event packets need to be dropped, what class of packets should be dropped Packets Classified as Blue Start Dropping at a 50% Queue Depth. Drop Rate Is Increased as Queue Depth Is Increased Packets Classified as Gold Are Dropped at 90% Queue Depth WRED Benefit for Vo. IP: Maintain Room in Queue, and if Packets Must be Dropped “Avoid” Dropping Voice 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 124

WRED Congestion Avoidance Maximize Data Goodput Adjustable Drop Probabilities (from “show interface”) Queuing strategy: random early detection (RED) mean queue depth: 56 drops: class random tail min-th max-th mark-prob 0 4356 0 20 40 1/10 Data 1 0 22 40 1/10 Flow 2 0 24 40 1/10 Prec = 0 3 0 26 40 1/10 4 0 28 40 1/10 5 0 30 40 1/10 6 0 33 40 1/10 Voice 7 0 35 40 1/10 Flow rsvp 0 37 40 1/10 Prec = 5 Uncontrolled Congestion Managed Congestion • Accommodate burstiness • “Less” drop probability for higher priority flows (Vo. IP) • Does not protect against flows that do not react to drop For example, extremely heavy UDP flow can overflow WRED queue 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 125

RSVP Bandwidth Reservation • IETF signaling protocol Reservation of bandwidth and delay • Flow can be signaled by end station or by router (static reservation) • For H. 323 Vo. IP: Effective as a BW reservations mechanism Not effective as Call Admisions Control: RSVP signaling takes place after call setup as port numbers need to be known End Points Send Unicast Signaling Messages (RSVP PATH + RESV) RSVP PATH Message FXS RSVP RESV Message RSVP enabled router sees the PATH and RESERVE messages and allocate the appropriate queue space for the given flow 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. Non RSVP enabled routers pass the Vo. IP flow as best effort 126

WAN Provisioning/ Design Considerations 128 kbps 256 kbps Remote Sites 512 kbps T 1 Frame Relay, ATM 768 kbps T 1 Central Site Central to Remote Speed Mismatch Traffic Shaping—Prevents Delay or Loss in WAN—A Must Remote to Central Over Subscription—Do Not Add additional T 1’s at Central Site, or Traffic Shaping—from Remotes at Reduced Rate (< Line Rate) 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 127

Bursting Considerations “Guidelines” • Single PVC—limit bursting to committed rate (CIR) The safest—you are guaranteed what you pay for • Single PVC—mark data discard eligible Your data gets dropped first upon network congestion • Single PVC—utilize BECN’s, foresight or ABR Only invoked when congestion has already occurred Round trip delays—Congestion indication must get back to source • Dual PVCs—one for voice and one for data One for data (may burst), one for voice (keep below CIR) Must Perform PVC prioritization in frame cloud (Cisco WAN gear does) Fragmentation rules still apply for data PVC Moral of the Story—“Know Your Carrier” 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 128

Traffic Shaping Overview Traffic Shaping • Vo. IP-over-serial: needs no traffic shaping BW is guaranteed at line speed • Vo. IPov. FR and Vo. FR: Use FRTS - applicable per VC GTS is applicable only per interface - does not have the desired effect when voice and data PVCs exist on the interface Set min-CIR equal to “voice bandwidth” + a little overhead to ensure good voice quality under WAN congestion situations On PVC carrying voice, shape strictly to CIR - don’t burst • Vo. ATM: Use ATM traffic shaping 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 129

Traffic Shaping—When and Why? Result: 128 kbps Buffering which Will Cause Delay and Eventually Dropped Packets 256 kbps Remote Sites 512 kbps T 1 Frame Relay, ATM 768 kbps T 1 Central Site 1. Central to Remote-Site Speed Mismatch 2. To Avoid Remote to Central Site Over-Subscription 3. To Prohibit Bursting above Committed Rate What Are You Guaranteed Above Your Committed Rate? 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 130

Understanding Shaping Parameters Frame Relay Traffic Shaping “Average” Traffic Rate Out of an Interface Challenge—Traffic Still Clocked Out at Line Rate CIR (Committed Information Rate) Average Rate over Time, Typically in Bits per Second Bc (Committed Burst) Amount Allowed to Transmit in an Interval, in Bits Be (Excess Burst) Amount Allowed to Transmit Above Bc per Second Interval Equal Integer of Tme Within 1 sec, Typically in ms. Number of Intervals per Second Depends on Interval Length Bc and the Interval Are Derivatives of Each Other Interval = 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. Bc CIR Example 125 ms = 8000 bits 64 kbps 131

Frame Relay Traffic Shaping Port speed Rate CIR Bc Time • Frame relay traffic shaping shapes total PVC traffic to conform to CIR, Bc and Be. • It is possible to use access lists to mark some data streams as DE Ensures that if the total PVC traffic exceeds the traffic contract (CIR/Bc) and the carrier network tags or drops traffic to compensate, the data is dropped and the voice is not affected However, there is no mechanism which allows non-voice traffic to be marked DE only when in excess of the traffic contract. 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 132

Example—Traffic Shaping in Action High Volume Data Flow Towards a 128 kbps Line Rate Shaping to 64 kbps Bc CIR Interval = 125 ms Interval = 8000 bits 64000 bps Cisco Default Bc=1/8 CIR = 125 ms Interval 0 Bits per Interval of bits Time at 128 kbps Rate 16000 bits 32000 bits 48000 bits 64000 bits 80000 bits 96000 bits 112000 bits 128, 000 bits Line Rate 128 kbps Net Result: 8000 X 8 = 64 bkps 62. 5 ms 0 ms 125 ms 250 ms 375 ms 500 ms 625 ms When 8000 bits (Bc) Transmitted Credits Are Exhausted and No More Packet Flow in that Interval. This Happens at the 62. 5 ms Point of the Interval. 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 75 0 ms 875 ms 1000 ms Time— 1 Second When a New Interval Begins Bc (8000 bit). Credits Are Restored and Transmission May Resume. Pause in Transmission Is 62. 5 ms in the Case. 133

Bc setting Considerations for Vo. IP Set Bc Lower if Line Rate to CIR Ratio Is High Example: T 1 Line Rate Shaping to 64 kbps Bc = 8000 Bc 125 ms Interval = 64 kbps CIR Bc = 1000 Bc 15 ms Interval = 64 kbps CIR T 1 can transmit 193, 000 bits in 125 ms T 1 can transmit 23, 000 bits in 15 ms 0 bits 193000 bits Bits per increment of time at 128 kbps 0 bits 23000 bits 125 ms Interval Traffic Flow Time 120 ms 5 ms 0 ms 125 ms At T 1 Rate 8000 Bits (Bc) Are Exhausted in 5 ms. Halting Traffic Flow for that PVC for the Rest of that Interval. Even for Voice! 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 120 ms of Potential Delay for Voice Until New Interval Begins and Bc Credits Are Restored 15 ms Interval 10 ms Traffic Flow Time . 6 ms 0 ms 15 ms At T 1 Rate 1000 Bits (Bc) Still Are Exhausted in 5 ms. Halting Traffic Flow for that PVC for the Rest of that Interval. Even for Voice! 10 ms of Potential Delay for Voice Until New Interval Begins and Bc Credits Are Restored 134

High Speed WAN Backbone Frame Relay/ATM Example Frame Relay ATM • Prioritization IP-ATM Co. S - with IP Prec • Link Efficiency WFQ - With IP Prec • Link Efficiency FRF. 12 if remote is low speed N/A • Traffic Shaping Shape to VC Parameters Frame Relay Traffic Shaping Burst with care Point to Point • Prioritization DWFQ/CBWFQ - with IP Prec • Link Efficiency N/A • Traffic Shaping Shape to CIR or Burst with care N/A > 2 meg 7200 7500 High Speed WAN Headquarters 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. Regional Office 135

Low Speed WAN Edge: Pt-to-Pt Low Speed Edge: <2 M Pt to Pt Considerations • Prioritization Central / Regional Office PQ-WFQ/IP RTP Priority (if available) 7200 / 7500 WFQ/CBWFQ with IP Precedence • Link Efficiency MLPPP with Fragmentation and Interleave VAD (If Desired) CRTP (If Desired) 64 kbps • Traffic Shaping N/A 3600 Branch Office 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 136

Low Speed WAN Edge: Frame Relay Low Speed Edge: <2 M Remote Branch Considerations • Prioritization Central / Regional Office PQ-WFQ/IP RTP Priority (if available) WFQ with IP Precedence 7200 / 7500 • Central Site Considerations • • Link Efficiency FRF. 12 PVCs to low speed remotes MUST use FRF. 12 VAD (If Desired) CRTP (If Desired) • FRF. 12 VAD (If Desired) CRTP (If Desired) T 1 Prioritization PQ-WFQ/IP RTP Priority (if available) WFQ with IP Precedence Traffic Shaping Link Efficiency Frame Relay • Traffic Shaping FRTS Shape to CIR or Burst with care 128 kbps 3600 Branch Office FRTS Shape to CIR or at minimum remote’s line rate - Burst with care 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 137

Low Speed WAN Edge: ATM typically greater than T 1 Central / Regional Office Central Site + Remote Branch Considerations • Prioritization IP-ATM Co. S with IP Precedence 7200 / 7500 • Link Efficiency T 1 and above “typically” not needed • Traffic Shaping Shape to VC Parameters Burst with care ATM 3600 Branch Office 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 138

Summary • Voice traffic engineering principles still apply • Packet-based voice trunks can provide efficiency with high quality if properly engineered • The biggest impact on voice quality over a data network will be as a result of the delay and delay variation 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. 139

Qo. S Tools Categories • Prioritization Purpose: Give priority treatment to real-time sensitive traffic Queuing /Scheduling: WFQ, CBWFQ, IP RTP Priority (PQ-WFQ), WRED Classification (Tagging, Marking, Colouring): IP Precedence, CAR, DSCP, IP RTP Reserve, IP RTP Priority • Link/Bandwidth Efficiency Purpose: Limit delay on slow links Fragmentation & Interleaving (LFI): FRF. 12, MLPPP, MTU Size Compression: Header compression (CRTP), payload compression (codec) Send Fewer Packets: Variable Size Payload, VAD • Traffic Shaping Purpose: Smooth out speed mismatches GTS, FRTS, ATM TS • Bandwidth Management Purpose: Check/reserve/restrict bandwidth for certain flows BW Reservation/Guarantee: RSVP, CBWFQ, IP RTP Priority 401 0985_05 f 9_c 1 Call Admissions Control: RSVP, GK zone bandwidth, # ingress ports © 1999, Cisco Systems, Inc. 140

Vo. IP Low Speed Link (<768 Kbps) Challenges and Solutions Challenge Solutions Congestion Intelligent Queuing Delay and Delay Jitter WFQ, IP Precedence, RSVP, Priority Queuing Packet Residency Interleaving Slow Link Freeze-out by Large Packets FRF. 12, MLPPP, IP MTU Size Reduction, Faster Link Bandwidth Consumption Compression Header Size on Low Bandwidth Links Codecs, RTP Header Compression, Voice Activity Detection WAN Oversubscription, Bursting 401 0985_05 f 9_c 1 © 1999, Cisco Systems, Inc. Traffic Management Router Traffic Shaping to CIR, High Priority PVC, Data Discard Eligibility 141