11 © 2005 Global Knowledge Network, Inc. All rights reserved. Contains proprietary and confidential information. Do not distribute. QOS Module 12

11© 2005 Global Knowledge Network, Inc. All rights reserved. Contains proprietary and confidential information. Do not distribute.

QOS

Module 12


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


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


Contrôle du délai

ITU’s G.114 recommendation: 0 to 150 (ms) one-way delay

Time (ms)

0 100 200 300 400

Walkie talkieWalkie talkie

One hop satelliteOne hop satellite

Put the old PBX back in now.Put the old PBX back in now.

InteractiveInteractive

Delay target

500 600 700 800

PBXPBX

VOIPVOIP


Les sources du délai

G.729 look ahead

20 ms packet20 ms

5 ms

Processing 10 ms

61 ms

1,500 byte data packet

7.8 ms

66 byte voice packet

.33 ms

66 byte voice packet .33 ms

G.729 3 ms

Processing 10 ms

165.3 ms total

Jitter buffer 40 ms

Serialization

Queuing

Network

Serialization

Queuing

1,500 byte data packet 7.8 ms


Délai de traitement du codec

ADPCM, G.726 32 Kbps 10 ms 2.5 ms 10 ms

CS-ACELP, G.729A 8.0 Kbps 10 ms 2.5 ms 10 ms

MP-MLQ, G.723.1 6.3 Kbps 30 ms 5 ms 20 ms

MP-ACELP, G.723.1 5.3 Kbps 30 ms 5 ms 20 ms

CodecCodec RateRate SampleSize

SampleSize

BestCaseBestCase

WorstCase

WorstCase


Délai de l’algorithme

ADPCM, G.726 0 ms

CS-ACELP, G.729A

5 ms

MP-MLQ, G.723.1

7.5 ms

MP-ACELP, G.723.1

7.5 ms

ADPCM, G.726 0 ms

CS-ACELP, G.729A

5 ms

MP-MLQ, G.723.1

7.5 ms

MP-ACELP, G.723.1

7.5 ms

CodecCodec Algorithmic DelayAlgorithmic Delay


Délai de paquetisation

PCM,

G.711

64

Kbps 160 20 240 30

ADPCM,

G.726

32

Kbps 80 20 120 30

CS-ACELP,

G.729

8.0

Kbps 20 20 30 30

MP-MLQ,

G.723.1

6.3

Kbps 24 30 48 60

MP-ACELP,

G.723.1

5.3

Kbps 20 30 40 60

CoderCoder PayloadSize (Bytes)

PayloadSize (Bytes)

PacketizationDelay (ms)


PayloadSize (Bytes)

PayloadSize (Bytes)




Le délai de serialisation

19.2 56 64 128 256 384 512 768 1024 1544 2048

38 15.83 5.43 4.75 2.38 1.19 0.79 0.59 0.40 0.30 0.20 0.15

48 20.00 6.86 6.00 3.00 1.50 1.00 0.75 0.50 0.38 0.25 0.19

64 26.67 9.14 8.00 4.00 2.00 1.33 1.00 0.67 0.50 0.33 0.25

128 53.33 18.29 16.00 8.00 4.00 2.67 2.00 1.33 1.00 0.66 0.50

256 106.67 36.57 32.00 16.00 8.00 5.33 4.00 2.67 2.00 1.33 1.00

512 213.33 73.14 64.00 32.00 16.00 10.67 8.00 5.33 4.00 2.65 2.00

1024 426.67 146.29 128.00 64.00 32.00 21.33 16.00 10.67 8.00 5.31 4.00

1500 625.00 214.29 187.50 93.75 46.88 31.25 23.44 15.63 11.72 7.77 5.86

2048 853.33 292.57 256.00 128.00 64.00 42.67 32.00 21.33 16.00 10.61 8.00

Taille de la trame (octets)

Vitesse de la ligne (Kbps)


Délai de queuing

56 Kbps Line

214 ms serialization delayfor 1500-byte frame at 64 Kbps

Real-time MTU Elastic MTU

In Out


Gestion de la jigue

V V VV V V V

Voice frames sent to the Network

Dejittered voice frames to DSP

V VV

V V VV V V VV VV

The voice packets were sent with 20 millisecond spacing.

V V VV V V VV VV

0+5+10-10+50-25-5-20

60555070556085686260Delay in ms

Jitter

Variation ranges from +10 to –25 = 35 ms jitter.

10 9 8 7 6 5 4 3 2 1

10 9 8 7 6 5 4 3 2 1

10 9 8 7 6 5 4 3 2 1



Exemple de latence LFI


214 ms

66 byte voice packet 10 ms

1,500 byte data packet 214 ms


597 ms total

61 ms

G.729 look ahead

20 ms packet

Processing

G.729

Processing

Jitter buffer

Serialization

Queuing

Network

Serialization

Queuing

20 ms

5 ms

10 ms

3 ms

10 ms

40 ms


Multilink PPP avec LFI

56 Kbps link

Elastic MTU Real-time MTU

Addendum to PPP specification

214 ms serialization delayfor 1,500 byte frame at 64 Kbps

56 Kbps link

Elastic MTU Elastic MTU

Real-time MTU Elastic MTU

In Out

In Out


Fonctionnement du LFI

LLQ

Classify

Low latency queuing

LLQLFI

Traffic destinedfor interface

1,500 byte Ethernet

frame

Voice packets

Classification by port and socket

Fragment size based on serialization delay

Fragmented framesinterleaved with time-sensitive traffic



Gestion du lien Gigabit

Gigabit Ethernet link

In Out

A 1,500 byte frametakes 12 sec to serialize.

Voice frame


Latence avec LFI sur un lien à 56 k

189 ms total


10 ms


1,500 byte data packet 10 ms


G.729 look ahead

20 ms packet

Processing

G.729

Processing

Jitter buffer

Serialization

Network

Serialization

Queuing

20 ms

5 ms

10 ms

3 ms

10 ms

40 ms

QueuingLFI

61 ms


Matrice LFI

XX: Fragmentation not an issue due to bandwidth and interval combination

Real-Time Packet Interval

56 Kbps70

bytes140

bytes210

bytes

10 ms 20 ms 30 ms

64 Kbps80

bytes160

bytes240

bytes

128 Kbps160

bytes320

bytes480

bytes

256 Kbps

512 Kbps

768 Kbps

1,536 Kbps

320bytes

640bytes

960bytes

640bytes

1,280bytes

1,920bytes

960bytes

1,920bytes

2,880bytes

1,920bytes

3,840bytes

5,760bytesX X

XXX

X

(10 ms)

Example:

.010 seconds x 56 Kbps

8 bits per byte= 70 bytes


Gestion du délai de sérialisation

Branch office

Branch office

1st

1stBANK1stBANK

1stBANK1stBANK 1stBANK1stBANK

Branch office

56 Kbps

Link

256 Kbps link 768 Kbps link

Compress

Uncompress

Uncompress

Compress

RTP

UDP

IP

Corporationmain site

= 2 bytes

RTP header compression:Approximately 11.2 Kbps per call

Must be a link:HDLC, PPP, Frame Relay, ATM AAL-5, MPLS


Délai de Queuing

* Approximately nineteen 78 byte packets equal one 1,500 byte packet.

Low latency queuing:The only optionCreates a priority queue for voice

packetsWill not starve other queues if priority

queue is constantly fullCisco’s choice for voice packet queuing

Classify

Voicevideodata

Priority

Guaranteed bandwidth 1

Dequeuing rules________________________

LLQ

Queues

Guaranteed bandwidth 2

Best effort


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

Busy tone?No busy tone?

Should the call be

allowed to go through?

CAC


RSVP

ER

CR

CR CR

CR

ER

ER

CR

ER

ER

CAC

CAC

CACCAC

You need a 32 Kbps connection to talk with me.

CAC

CAC

CR = Core routerER = Edge routerCR = Core routerER = Edge router

PATH message


RSVP Half Duplex

ER

CR

CR CR

CR

ER

ER

CR

ER

ER

Established reservation: Half the job is done.


Chemin inverse

ER

CR

CR CR

CR

ER

ER

CR

ER

ER

CAC

CAC

CACCAC

You need a 32 Kbps connection to talk with me.

OK

CAC(Reserve penguin)

CAC


RSVP – établissement de la réservation

ER

CR

CR CR

CR

ER

ER

CR

ER

ER

Full duplex reservation


RSVP – Synchronisation QoS avant qu’un téléphone ne sonne

SETUP

CALL PROCEEDING

PATH

PATH

RESV

RESV

ALERTING

CONNECT

RELEASE COMPLETE

PATH TEAR

PATH TEAR

PATH TEAR

PATH TEAR

RESV CONFIRMATION

Call setup initiated

OGW TGW Reservation limited

Call connected

Normal call disconnect initiated

OGW TGW Reservation teardown

initiated

OGW TGW Reservation initiated

OGW Originating Gateway TGW Terminating Gateway

OGW TGW Reservation teardown initiated

H.323 Call setup signaling RSVP reservation initiated by TGW RSVP reservation initiated by OGW


Diffserv

ER

CR

CR CR

CR

ER

ER

CR

ER

ER

VPN

CoS 7: Pilot

CoS 6: First

CoS 5: Business

CoS 4: Coach

CoS 3: Standby

CoS 2: Baggage

CoS 7 - Pilot

CoS 6 - First

CoS 5 - Business

CoS 4 - Coach

CoS 3 - Standby

CoS 2 - Baggage

CoS 7 - Pilot

CoS 6 - First

CoS 5 - Business

CoS 4 - Coach

CoS 3 - Standby

CoS 2 - Baggage

CoS 7 - Pilot

CoS 6 - First

CoS 5 - Business

CoS 4 - Coach

CoS 3 - Standby

CoS 2 - Baggage

CoS 7 - Pilot

CoS 6 - First

CoS 5 - Business

CoS 4 - Coach

CoS 3 - Standby

CoS 2 - Baggage

CoS 7 - Pilot

CoS 6 - First

CoS 5 - Business

CoS 4 - Coach

CoS 3 - Standby

CoS 2 - Baggage

CoS 7 - Pilot

CoS 6 - First

CoS 5 - Business

CoS 4 - Coach

CoS 3 - Standby

CoS 2 - Baggage

I want a first class connection.

CRCheck DSCPForward packets ER

ClassifyMarkPolice


Type IP du champ serviceIP

Dat

agra

m

Ethernet Version .2 header

(14 octets)

Entête IP (minimum length 20 octets)

Entête UDP (8 octets)

G.729 (20 octets)

Data link trailer (4 octets)

Entête RTP (12–16 octets)

20 msVoice

Contributing Source (optional)

Synchronization Source

Time Stamp

V P X CC M PT Sequence Number

Length Checksum

Source Port Destination Port

Options and Padding

Destination Address

Source Address

Time to Live Protocol Header Checksum

Identifier Flags Fragment Offset

Ver IHL Type of Service Total Length

Source Address (cont.) Type

Source Address

Destination Address (cont.)

Destination Address


Champ IP TOS

TOS field

2 bits6 bits

DSCPDSCP CUCU

DSCP (DIFF-SERV code point)000000 = DE (Default)101100 = EF (Expedited Forwarding)

DSCP (DIFF-SERV code point)000000 = DE (Default)101100 = EF (Expedited Forwarding)

TOS field

Documents

11 © 2005 Global Knowledge Network, Inc. All rights reserved. Contains proprietary and confidential information. Do not distribute. QOS Module 12