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QOS

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  1. QOS Module 12

  2. Points clés du module • Les trois raisons d’échec de la voix • Les précautions nécessaires pour réussir avec la VoIP • Implémenter la VoIP sur des LANs

  3. Sommaire • Contrôle du délai • Sources du délai • Contrôle de la jigue • Fonction LFI • Contrôle de la sérialisation du délai • Process de compression de l’en-tête RTP • Contrôle du délai de Queuing

  4. Contrôle du délai Walkie talkie Interactive One hop satellite VOIP Put the old PBX back in now. 0 100 200 300 400 500 600 700 800 Time (ms) PBX Delay target ITU’s G.114 recommendation: 0 to 150 (ms) one-way delay

  5. 1,500 byte data packet 7.8 ms 20 ms Queuing 20 ms packet .33 ms 66 byte voice packet 5 ms G.729 look ahead Serialization 10 ms Processing 61 ms Network Queuing 165.3 ms total 40 ms Jitter buffer 1,500 byte data packet 7.8 ms 3 ms G.729 Serialization 66 byte voice packet 10 ms Processing .33 ms Les sources du délai

  6. ADPCM, G.726 32 Kbps 10 ms 2.5 ms 10 ms CS - ACELP, 8.0 Kbps 10 ms 2.5 ms 10 ms G.729A MP - MLQ, 6.3 Kbps 30 ms 5 ms 20 ms G.723.1 MP - ACELP, 5.3 Kbps 30 ms 5 ms 20 ms G.723.1 Délai de traitement du codec Codec Rate Sample Size Best Case Worst Case

  7. Délai de l’algorithme Codec Algorithmic Delay

  8. Délai de paquetisation Coder Payload Size (Bytes) Packetization Delay (ms) Payload Size (Bytes) Packetization Delay (ms)

  9. Le délai de serialisation Taille de la trame (octets) Vitesse de la ligne (Kbps)

  10. Délai de queuing 56 Kbps Line In Out Real-time MTU Elastic MTU 214 ms serialization delay for 1500-byte frame at 64 Kbps

  11. The voice packets were sent with 20 millisecond spacing. 10 9 8 7 6 5 4 3 2 1 Voice frames sent to the Network V V V V V V V V V V Delay in ms 60 62 68 85 60 55 70 50 55 60 10 9 8 7 6 5 4 3 2 1 V V V V V V V V V V Jitter 0 -2 -5 -25 0 +5 -10 +10 +5 0 10 9 8 7 6 5 4 3 2 1 Dejittered voice frames to DSP V V V V V V V V V V Variation ranges from +10 to –25 = 35 ms jitter. Gestion de la jigue

  12. 214 ms 1,500 byte data packet 20 ms Queuing 20 ms packet 66 byte voice packet 10 ms 5 ms G.729 look ahead Serialization 10 ms Processing 61 ms Network Queuing 597 ms total 40 ms Jitter buffer 1,500 byte data packet 214 ms 3 ms G.729 Serialization 66 byte voice packet 10 ms 10 ms Processing Exemple de latence LFI

  13. 56 Kbps link In Out Real-time MTU Elastic MTU 214 ms serialization delay for 1,500 byte frame at 64 Kbps 56 Kbps link In Out Addendum to PPP specification Elastic MTU Elastic MTU Real-time MTU Elastic MTU Multilink PPP avec LFI

  14. Low latency queuing Classification by port and socket LLQ Traffic destined for interface Classify Fragmented frames interleaved with time-sensitive traffic Voice packets 1,500 byte Ethernet frame LLQ LFI Fragment size based on serialization delay Fonctionnement du LFI

  15. Gigabit Ethernet link In Out Voice frame A 1,500 byte frame takes 12 sec to serialize. Gestion du lien Gigabit

  16. 10 ms 1,500 byte data packet 20 ms LFI 20 ms packet Queuing 66 byte voice packet 10 ms 5 ms G.729 look ahead Serialization 10 ms Processing 61 ms Network Queuing 189 ms total 40 ms Jitter buffer 1,500 byte data packet 10 ms 3 ms G.729 Serialization 66 byte voice packet 10 ms 10 ms Processing Latence avec LFI sur un lien à 56 k

  17. Real-Time Packet Interval (10 ms) 20 ms 30 ms 10 ms Example: 70 bytes 210 bytes 140 bytes 56 Kbps .010 seconds x 56 Kbps = 70 bytes 80 bytes 240 bytes 160 bytes 64 Kbps 8 bits per byte 160 bytes 480 bytes 320 bytes 128 Kbps 320 bytes 960 bytes 640 bytes 256 Kbps 640 bytes 1,920 bytes 1,280 bytes X 512 Kbps 960 bytes 2,880 bytes X X 1,920 bytes 768 Kbps 1,920 bytes 5,760 bytes X 3,840 bytes X X 1,536 Kbps X : Fragmentation not an issue due to bandwidth and interval combination Matrice LFI

  18. IP 1stBANK 1stBANK 1stBANK Branch office UDP RTP = 2 bytes Branch office 256 Kbps link 768 Kbps link 1st RTP header compression: Approximately 11.2 Kbps per call Uncompress 56 Kbps Link Compress Compress Uncompress Branch office Corporationmain site Must be a link: HDLC, PPP, Frame Relay, ATM AAL-5, MPLS Gestion du délai de sérialisation

  19. Queues Classify Priority Guaranteed bandwidth 1 Dequeuing rules ______ ______ ______ ______ Voice video data LLQ Guaranteed bandwidth 2 Best effort Low latency queuing: • The only option • Creates a priority queue for voice packets • Will not starve other queues if priority queue is constantly full • Cisco’s choice for voice packet queuing * Approximately nineteen 78 byte packets equal one 1,500 byte packet. Délai de Queuing

  20. Connexion Admission Control • Téléphone : Interdire des services, c’est mieux que de dégrader des services • Data : Dégrader des services, c’est mieux que d’interdire des services CAC No busy tone? Busy tone? Should the call be allowed to go through?

  21. CR = Core routerER = Edge router You need a 32 Kbps connection to talk with me. ER PATH message ER CR CR CAC CAC CR CAC CAC CAC CR CR ER ER CAC ER RSVP

  22. Established reservation: Half the job is done. ER ER CR CR CR CR CR ER ER ER RSVP Half Duplex

  23. ER ER CR CR CAC You need a 32 Kbps connection to talk with me. CR OK CAC CAC CAC (Reserve penguin) CAC CR CR ER ER ER CAC Chemin inverse

  24. Full duplex reservation ER ER CR CR CR CR CR ER ER ER RSVP – établissement de la réservation

  25. SETUP Call setup initiated CALL PROCEEDING OGW  TGW Reservation initiated PATH OGW  TGW Reservation limited PATH RESV RESV OGW Originating Gateway TGW Terminating Gateway RESV CONFIRMATION ALERTING H.323 Call setup signaling RSVP reservation initiated by TGW RSVP reservation initiated by OGW CONNECT Call connected Normal call disconnect initiated RELEASE COMPLETE PATH TEAR OGW  TGW Reservation teardown initiated OGW  TGW Reservation teardown initiated PATH TEAR PATH TEAR PATH TEAR RSVP – Synchronisation QoS avant qu’un téléphone ne sonne

  26. CR • Check DSCP • Forward packets • ER • Classify • Mark • Police ER ER CR CR CR VPN CR CR ER CoS 7: Pilot CoS 7 - Pilot CoS 7 - Pilot CoS 7 - Pilot CoS 7 - Pilot CoS 7 - Pilot CoS 7 - Pilot CoS 6 - First CoS 6 - First CoS 6: First CoS 6 - First CoS 6 - First CoS 6 - First CoS 6 - First ER CoS 5 - Business CoS 5 - Business CoS 5 - Business CoS 5 - Business CoS 5 - Business CoS 5: Business CoS 5 - Business CoS 4 - Coach CoS 4 - Coach CoS 4 - Coach CoS 4 - Coach CoS 4 - Coach CoS 4: Coach CoS 4 - Coach ER CoS 3: Standby CoS 3 - Standby CoS 3 - Standby CoS 3 - Standby CoS 3 - Standby CoS 3 - Standby CoS 3 - Standby I want a first class connection. CoS 2: Baggage CoS 2 - Baggage CoS 2 - Baggage CoS 2 - Baggage CoS 2 - Baggage CoS 2 - Baggage CoS 2 - Baggage Diffserv

  27. Destination Address Ethernet Version .2 header (14 octets) Destination Address (cont.) Source Address Source Address (cont.) Type Ver IHL Total Length Type of Service Identifier Flags Fragment Offset Entête IP (minimum length 20 octets) Time to Live Protocol Header Checksum Source Address Destination Address Options and Padding IP Datagram Entête UDP (8 octets) Source Port Destination Port Length Checksum V P X CC M PT Sequence Number Entête RTP (12–16 octets) Time Stamp Synchronization Source Contributing Source (optional) 20 msVoice G.729 (20 octets) Data link trailer (4 octets) Type IP du champ service

  28. TOS field TOS field DSCP (DIFF-SERV code point) 000000 = DE (Default) 101100 = EF (Expedited Forwarding) DSCP CU 6 bits 2 bits Champ IP TOS