CVOICE 6.0 S01 L04

© 2008 Cisco Systems, Inc. All rights reserved. CVOICE v6.0—1-1

Introducing Voice over IP

Understanding Codecs, Codec Complexity, andDSP Functionality


Codecs perform encoding and decoding on a digital data stream or signal.

Codecs translate VoIP media streams into another format: A to D, D to D, or D to A.

Various codec standards define the compression rate of the voice payload.

Supported Cisco codecs include:

– G.711

– G.722

– G.726

– G.728

– G.729

– G.723.1

– GSM FR

– iLBC

Codecs


Codec Bandwidth Sample Size Packets

G.711 64 kb/s 240 33

G.711 64 kb/s 160 50

G.726r32 32 kb/s 120 33

G.726r32 32 kb/s 80 50

G.726r24 24 kb/s 80 25

G.726r24 24 kb/s 60 33

G.726r16 16 kb/s 80 25

G.726r16 16 kb/s 40 50

G.728 16 kb/s 80 13

G.728 16 kb/s 40 25

G.729 8 kb/s 40 25

G.729 8 kb/s 20 50

G.723r63 6.3 kb/s 48 16

G.723r63 6.3 kb/s 24 33

G.723r53 5.3 kb/s 40 17

G.723r53 5.3 kb/s 20 33

Impact of Voice Samples and Sample Size on Bandwidth


Data-Link Overhead

Ethernet II: 18 bytes of overhead

PPP: 6 bytes of overhead

FRF.12 Layer 2 header: 6 bytes of overhead

MP: 6 bytes of overhead


Security and Tunneling Overhead

IPsec: 50 to 57 bytes

L2TP or GRE: 24 bytes

MLP: 6 bytes

MPLS: 4 bytes


CodecCodec Speed

Sample SizeFrame Relay

Frame Relay with cRTP

Ethernet

Bits per Second

BytesBits per Second

Bits per SecondBits per Second

G.711 64,000 240 76,267 66,133 79,467

G.711 64,000 160 82,400 67,200 87,200

G.726r32 32,000 120 44,267 34,133 47,467

G.726r32 32,000 80 50,400 35,200 55,200

G726r24 24,000 80 37,800 26,400 41,400

G.726r24 24,000 60 42,400 27,200 47,200

G.726r16 16,000 80 25,200 17,600 27,600

G.726r16 16,000 40 34,400 19,200 39,200

G.728 16,000 80 25,200 17,600 27,600

G.728 16,000 40 34,400 19,200 39,200

G.729 8000 40 17,200 9600 19,600

G.729 8000 20 26,400 11,200 31,200

G.723r63 6300 48 12,338 7350 13,913

G.723r63 6300 24 18,375 8400 21,525

G.723r53 5300 40 11,395 6360 12,985

G.723r53 5300 20 17,490 7420 20,670

Calculating the Total Bandwidth for a VoIP Call


Codec Codec Speed Sample Size Frame RelayFrame Relay with

VAD

G.711 64,000 240 76,267 49,573

G.711 64,000 160 82,400 53,560

G.726r32 32,000 120 44,267 28,773

G.726r32 32,000 80 50,400 32,760

G726r24 24,000 80 37,800 24,570

G.726r24 24,000 60 42,400 27,560

G.726r16 16,000 80 25,200 16,380

G.726r16 16,000 40 34,400 22,360

G.728 16,000 80 25,200 16,380

G.728 16,000 40 34,400 22,360

G.729 8000 40 17,200 11,180

G.729 8000 20 26,400 17,160

G.723r63 6300 48 12,338 8019

G.723r63 6300 24 18,375 11,944

G.723r53 5300 40 11,395 7407

G.723r53 5300 20 17,490 11,369

Effects of VAD


Media resource: A software-based or hardware-based entity that performs media-processing functions on the data streams to which it is connected. Transcoding: The conversion from one codec to another.

Voice termination: The digitization and packetization of an analog signal on a TDM interface.

MTP: Two supported types on Cisco IOS routers:

– Software MTPs

– Hardware MTPs

Conferencing: Network-based conference bridge is required to facilitate multiparty conferences in VoIP network.

Digital Signal Processors


IP WAN

PSTNPhone1-1

2001Phone1-2

2002Phone2-1

3001Phone2-2

3002

Transcoding or conferencing

San Jose Chicago

Router1 Router2

Conferencing

G.711

G.729IVR

Media Resource Deployment Example


Codec Complexity

Medium Complexity (Four calls per DSP)

High Complexity (Two calls Per DSP)

G.711 (a-law and mu-law) G.728

G.726 (all versions) G.723 (all versions)

G.729A, G.729AB G.729, G.729B

Fax Relay Fax Relay


router(config)# voice-card 1router(config-voicecard)# codec complexity ?

high Set codec complexity high. High complexity, lower call density.

medium Set codec complexity medium. Mid range complexity and call density.

<cr>

Cisco-router(config-voicecard)# codec complexity high

C549

C5510router(config)# voice-card 1router(config-voicecard)# codec complexity ? flex Set codec complexity Flex. Flex complexity, higher call density.

high Set codec complexity high. High complexity, lower call density.

medium Set codec complexity medium. Mid range complexity and call density.

secure Set codec complexity secure.

Cisco-router(config-voicecard)# codec complexity flex

Configuring Codec Complexity


Verifying Codec ComplexityHQ-1# show voice dsp DSP DSP DSPWARE CURR BOOT PAK TX/RXTYPE NUM CH CODEC VERSION STATE STATE RST AI VOICEPORT TS ABORT PACK COUNT==== === == ======== ======= ===== ======= === == ========= == ===== ============ ----------------------------FLEX VOICE CARD 0 ------------------------------ *DSP VOICE CHANNELS*

CURR STATE : (busy)inuse (b-out)busy out (bpend)busyout pending LEGEND : (bad)bad (shut)shutdown (dpend)download pending

DSP DSP DSPWARE CURR BOOT PAK TX/RXTYPE NUM CH CODEC VERSION STATE STATE RST AI VOICEPORT TS ABRT PACK COUNT===== === == ========= ======= ===== ======= === == ========= == ==== ============ *DSP SIGNALING CHANNELS*DSP DSP DSPWARE CURR BOOT PAK TX/RXTYPE NUM CH CODEC VERSION STATE STATE RST AI VOICEPORT TS ABRT PACK COUNT===== === == ========= ======= ===== ======= === == ========= == ==== ============C5510 002 01 {flex} 8.2.0 alloc idle 0 0 0/2/0 02 0 0/0C5510 002 02 {flex} 8.2.0 alloc idle 0 0 0/2/1 02 0 0/0------------------------END OF FLEX VOICE CARD 0 ----------------------------


DSP Requirements for Media Resources

Number of DSPs depends on DSP type, required media resources, and codecs:

– C5510 (used on PVDM2) has higher performance than C549 (used on PVDM)

Single DSP can only be used as a single media resource:

– Either voice termination, conferencing, transcoding or MTP

DSP calculator helps calculation of required DSPs:

– http://www.cisco.com/cgi-bin/Support/DSP/dsp-calc.pl

– Support voice termination, conferencing, transcoding,and MTP


DSPs per PVDM2

PVDM2 Number of C5510 DSPs

PVDM2-8 1/2

PVDM2-16 1

PVDM2-32 2

PVDM2-48 3

PVDM2-64 4


Conferencing DSP Resources

C549 (PVDM; for example, NM-HDV)

C5510 (PVDM2; for example, ISR, NM-HDV2)

Maximum Participants per Conference

6 8

G.711 Conferences per DSP

1 8

Mixed-Mode Conferences per DSP

1 2


Transcoding DSP Resources

From Low Complexity To:C549 (PVDM; for

example, NM-HDV)C5510 (PVDM2; for

example, ISR, NM-HDV2)

G.711 (a-law, mu-law) Sessions per DSP

4 16

G.729A, G.729AB, GSM FR Sessions per DSP

4 8

G.729, G.729B, GSM EFR Sessions per DSP

4 6


DSP Calculator

DSP Calculator URL:http://www.cisco.com/cgi-bin/Support/DSP/dsp-calc.pl

Select the router model.

Select the Cisco IOS release.

1

2


DSP Calculator (Cont.)

Select router VICs.

Specify the number of calls.

3

4


DSP Calculator (Cont.)

Specify the number of transcoding sessions.

Specify the number of conferences.

5

6


DSP Calculator Results

Calculate required DSPs or PVDMs.

7Sample Cisco IOS

configuration.


1. Determine DSP resource requirements

2. Enable SCCP on the Cisco Unified Communications Manager interface or Cisco Unified Communications Manager Express

3. Configure enhanced conferencing and transcoding

Configuring Conferencing and Transcoding on Voice Gateway Routers


DSP Farm Configuration Example

IP WAN

San Jose Chicago

sccp ccm 10.1.1.201sccp local FastEthernet 0/0sccpvoice-card 0 dsp services dspfarm

PSTN

sccp ccm 10.1.1.201sccp local FastEthernet 0/0sccpvoice-card 0 dsp services dspfarm

Router1 Router2

Phone1-11001

Phone1-21002

Phone2-12001

Phone2-22002

Cisco Unified Communications

Manager 10.1.1.201


IP WAN

San Jose Chicago

PSTN

Router1 Router2

Phone1-11001

Phone1-21002

Phone2-12001

Phone2-22002

dspfarm profile 1 transcode codec g711ulaw codec g711alaw codec g729ar8 codec g729abr8 codec g729r8 maximum sessions 6 associate application SCCP no shutdown

dspfarm profile 1 conference codec g711ulaw codec g711alaw codec g729ar8 codec g729abr8 codec g729r8 codec g729br8 maximum sessions 2 associate application SCCP no shutdown

DSP Profile Configuration Example

Cisco Unified Communications

Manager 10.1.1.201


sccp ccm {ip-address | dns} identifier identifier-number [port port-number] [version version-number]

router(config)#

Adds a Cisco Unified Communications Manager server to the list of available servers to which the Cisco voice gateway can register.

sccp local <interface>

router(config)#

Selects the local interface that SCCP applications use to register with Cisco Unified Communications Manager.

sccp

router(config)#

Enables SCCP and brings it up administratively.

DSP Farm Configuration Commands for Enhanced Media Resource


voice-card slot

router(config)#

Enters the voice card configuration mode.

dsp services dspfarm

router(config-voicecard)#

Enables DSP farm services.

dspfarm profile profile-identifier {conference | mtp | transcode}

router(config)#

Creates a DSP farm profile for conferencing, MTP, or transcoding.

DSP Farm Configuration Commands for Enhanced Media Resource (Cont.)


codec codec-type

router(config-dspfarm-profile)#

Specifies the allowed codecs.

maximum sessions number


Defines the maximum number of sessions.

associate application SCCP


Enables SCCP for the profile.

DSP Farm Configuration Commands for Enhanced Media Resource (Cont.)


Router# show dspfarm profile 1Dspfarm Profile Configuration

Profile ID = 1, Service = CONFERENCING, Resource ID = 1 Profile Description : Profile Admin State : UP Profile Operation State : ACTIVE Application : SCCP Status : ASSOCIATED Resource Provider : FLEX_DSPRM Status : UP Number of Resource Configured : 2 Number of Resource Available : 2 Codec Configuration Codec : g711ulaw, Maximum Packetization Period : 30 , Transcoder: Not Required Codec : g711alaw, Maximum Packetization Period : 30 , Transcoder: Not Required Codec : g729ar8, Maximum Packetization Period : 60 , Transcoder: Not Required Codec : g729abr8, Maximum Packetization Period : 60 , Transcoder: Not Required Codec : g729r8, Maximum Packetization Period : 60 , Transcoder: Not Required Codec : g729br8, Maximum Packetization Period : 60 , Transcoder: Not Required

DSP farm profile active and associated with

SCCP

Verifying Media Resources


Router# show dspfarm dsp allSLOT DSP VERSION STATUS CHNL USE TYPE RSC_ID BRIDGE_ID PKTS_TXED PKTS_RXED

0 5 1.0.6 UP N/A FREE conf 1 - - -0 5 1.0.6 UP N/A FREE conf 1 - - -

Total number of DSPFARM DSP channel(s) 2Two conference

bridges configured

Verifying Media Resources (Cont.)


Summary

Codecs are used to compress and decompress various types of data that would otherwise use up large amounts of bandwidth.

Voice sample size is a variable that can affect the total bandwidth used.

Several factors must be included in calculating the overhead of a VoIP call.

Codec choice, data-link overhead, sample size, and RTP have positive and negative impacts on total bandwidth.

Codec complexity affects the call density.


Summary (Cont.)

DSPs enable Cisco platforms to efficiently process digital voice traffic.

The number of DSPs required is a key factor when deploying media resources using DSPs.

The configuration of transcoding and conferencing on a voice gateway involves several components.

DSP farm services are enabled on the voice card, and DSP profiles create the actual media resource.

You may verify DSP media resources using show dspfarm commands.

CVOICE 6.0 S01 L04

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