Transcript Bandwidth per Voice Calls with Standard IP Header

Communications Alliance

Overview and update
AusNOG1, Sydney, Australia, 15 November 2007
James Duck
Communications Alliance
Communications Alliance

• Created from a merger of ACIF and SPAN:
–“Communications Alliance was formed in 2006 to
provide a unified voice for the Australian
communications industry and to lead it into the
next generation of converging networks,
technologies and services.”
• A company resourced by its members
• Not a government body, nor a lobby group
• http://commsalliance.com.au
Sample of CA Activities

• Develop industry positions on
policy
• Seminars, Forums, Roundtables
• Compliance
• Project based
Working Groups/Committees
• Advisory Groups
Sample of CA Topics

• End user / Consumer
–premium services, accessibility, priority
assistance, universal service, life threatening calls,
etc.
• Customer Equipment
–Standards for phones, modems, filters, PBXs, etc.
• Networks, Operations
–ADSL(2+), VDSL, ordering, provisioning,
numbering, emergency calls, law enforcement,
infrastructure deployment, portability, etc.
General trends

• Next Generation / Emerging Services
–Transition from legacy to IP-based networks
and services
–Services and applications may be
decoupled from or integrated with networks
• Types of services
–High interactivity – voice/video
calls/conferencing
–Lower interactivity – streaming video, file
transfers
• So … what to focus on?
What to focus on?

• High impact
–Voice and video
–Networks and Services
• High sensitivity
–Sensitive to delay
–Sensitive to variability
• Two related topics emerged…
IP Network Quality of Service

• Define a default set of traffic classes
• Include delay, jitter and loss performance
• Packet marking and handling
• Align with international activity
• Produce related test documents
• Between User-Network Interfaces
• More information on Friday morning
VoIP Quality of Service

• Provide a measure of VoIP quality in a usable
format e.g. ITU-T/ETSI E-model
• Consider Network IP QoS service classes
• Align with international activity
• Consider interworking with existing voice
networks e.g. PSTN/ISDN.
• Assess requirements related to transcoding.
• Produce related test documents.
• Mouth to ear
What is “Quality of Service”?

• ITU-T “SANCHO” database ...
http://www.itu.int/sancho/
–Returns 20 answers
–Includes “dynamic” QoS and “extended” QoS
• What about “Quality of Experience” (QoE)?
–ITU held a two and half day
“Workshop on "End-to-End QoE/QoS"”
http://www.itu.int/ITU-T/worksem/qos/200606/programme.html
• MIT Communications Futures Program
http://cfp.mit.edu/resources/index.html
–White paper on Inter-provider QoS
SANCHO = “ITU-T Sector Abbreviations and defiNitions for a teleCommunications tHesaurus Oriented database”
VoIP QoS

• Based on:
–E model (ITU-T Rec. G.107) and
–R value (ITU-T Rec. G.108)
• Other options:
–Mean Opinion Score (MOS) (ITU-T Rec. P.800)
arguably subjective, expensive, time
consuming, inconvenient.
–Perceptual Evaluation of Speech Quality
(PESQ) (ITU-T Rec. P.862) does not address
conversational speech factors such as delay,
signal level, echo, impairment.
Factors affecting VoIP QoS

• Major Factors affecting VoIP QoS:
–Delay
–Distortion e.g. codec choice
–Echo
–Loss / level plan
• Other factors include:
–Noise level e.g. room noise
–Advantage e.g. mobility, remote access
–Sidetone
R Value from ITU-T G.108

• R = Ro – Is – Id – Ie-eff + A, where:
–Ro = Signal to noise
–Is = combination of all impairments
–Id = impairments caused by delay
–Ie-eff = impairments caused by low
bit rate codecs
–A = Advantage
Transmission Rating (R) limits
for voice services (1)

Category
R limit
% of
Calls
Comment
Examples
Unmanaged voice service
N/A
N/A
Best Efforts voice service; no
guarantee on voice
quality
A
≥ 50
95%
Nearly all users dissatisfied
B
≥ 60
95%
Many users dissatisfied
‘Best
Efforts’
C
D
≥ 70
≥ 80
95%
95%
Some users dissatisfied
G.729a codec on a wired
network, achieving voice
quality similar to that
experienced on a cellular
mobile service
Satisfied
G.711 codec on a wired
network, achieving voice
quality similar to that
experienced on a POTS
voice service
Transmission Rating (R) limits
for voice services (2)

Category
R limit
% of
Calls
Comment
Examples
E
≥ 90
95%
Very Satisfied
G.711 codec in an ideal network
environment
F
≥ 100
95%
G
≥ 110
95%
H
≥ 120
95%
Not generally available
G.722.2 (wideband) codecs,
QoS enabled network(s)
Impact of delay on QoS

100
Users
very satisfied
90
E-model rating R
Users
satisfied
80
Some users
dissatisfied
70
Many users
dissatisfied
60
Nearly all
users
dissatisfied
50
0
100
200
300
400
Mouth-to-ear-delay/ms
500
G.114_F01
Impact of distortion /
compression on R

User Satisfaction
100
Very
satisfactory
90
Increasing Ie
Satisfactory
80
G.711
Some users
dissatisfied
R
G.729A
G.723.1
70
Many users
dissatisfied
60
Exceptional
limiting case
50
0
100
200
300
One-way Delay (ms)
400
500
Impact of echo on R

This means that
TELR needs to be
about 65dB to
completely remove
echo
100
User Satisfaction
E-Model reference
Very
satisfactory
90
Satisfactory
80
TELR = 65 dB
Some users
dissatisfied
R
TELR = 55 dB
Increasing
Echo
70
TELR = 60 dB
Many users
dissatisfied
TELR = 50 dB
TELR = 45 dB
60
Exceptional
limiting case
50
0
100
200
300
One-way Delay (ms)
400
500
Impact of packet loss on R

G.729A Packet Loss Performance
User Satisfaction
100
Very
satisfactory
90
G.729A
G.711 Reference
G.711 @ PL = 0%
Satisfactory
G.729A @ PL = 0%
80
Some users
dissatisfied
R
G.729A @ PL = 1%
70
G.729A @ PL = 2%
Many users
dissatisfied
G.729A @ PL = 3%
60
G.729A @ PL = 4%
Exceptional
limiting case
50
0
100
200
300
400
500
One-way Delay (ms)
PL = Packet Loss
Codec choice and codec
negotiation

• Each codec has advantages and disadvantages:
–encoding via a frame codec (e.g. G.729) can introduce
delay
–waveform codecs (e.g. G.711) require more bandwidth
• Include G.711 (A-law) as an available codec to
ensure interoperability.
• Use packet loss concealment in conjunction with
waveform codecs (e.g. G.711).
• Use RFC 3264 for codec negotiation between end
points
Codec choice - example

• Waveform/Frame codecs require
more/less bandwidth – example for
20ms sample:
–G.711 at 64kbps, IPv4:
•200 bytes including 40 byte header
•92 kbps over Ethernet
–G.729a at 8kbps, IPv4:
•60 bytes including 40 byte header
•37 kbps over Ethernet
–8:1 ratio excluding header
–2.5:1 ratio including header
Bandwidth per voice calls
with standard IP header
(5% additional bandwidth allowed for RTCP packets)
Bandwidth per Voice Calls with Standard IP Header
Codec
Codec Bit Rate

G.711
G.729a
64 kbps
8 kbps
Voice Sample (ms)
10
20
30
10
20
30
IP Payload size (bytes)
80
160
240
10
20
30
IPv4 Packet size (40 byte header)
IPv6 Packet size (60 byte
header)
120
140
200
220
280
300
50
70
60
80
70
90
Ethernet
Ethernet bytes
(per packet)
Ethernet bandwidth IPv4
per voice flow (kbps)
IPv4
IPv6
150
170
230
250
310
330
80
100
90
110
100
120
IPv6
120
136
92
100
82.7
88
64
80
37
44
26.7
32
ATM Transport (ADSL/ADSL2+) (Includes 6 bytes for PPP)
ATM bytes
(PPPoAAL5oATM)
IPv4
IPv6
ATM bandwidth per IPv4
voice flow (kbps)
IPv6
159
212
265
265
371
371
106
106
106
106
106
159
127.2
169.6
106
106
98.93
98.93
84.8
84.8
42.4
42.4
28.27
42.4
Transcoding

• Transcoding/Tandeming - successive encoding
by different/same codecs
• Reduce and preferably eliminate it
• Support the G.711 (A-law) codec to avoid:
–transcoding (distortion) or
–Inability of endpoints to negotiate a mutually
agreeable codec (i.e. call failure).
• Preferably no enforced transcoding on call
gateway(s) at a point of interconnection
• should avoid transcoding between CELP
codecs (e.g. G.729) or between CELP and
ADPCM (G.726/G.722) codecs.
Transport scenarios

• Single Carrier
–IP Access and Core networks
–TDM access and core, IP access network
• Two Carriers
–TDM access and core, IP core and access.
–TDM Access & IP Core, IP Access
• Three Carriers
–IP Access, TDM Core, IP Access
Other variables

• Transport combinations
–Pure IP
–TDM to IP, IP to TDM,
–IP-TDM-IP
–IP-TDM-Mobile
• Access speeds
• Test types
–Design, Operational, Fault
• Equipment
–Analogue phone + ATA/IAD
–IP handset, DECT phone behind ATA, WiFi LAN segment
VoIP QoS Status

• Quality of Service parameters for Voice
over Internet Protocol (VoIP) services
Industry Guideline (CA G634:2007)
published end October 2007
http://commsalliance.com.au/documents/guidelines
• VoIP QoS Testing Arrangements
Guideline (CA G635:2007) at ballot
• Complements IP Network QoS activity
• Next steps
Other Activities –
VoIP Working Group

• technical, regulatory and consumer protection
components of a voice service
• Fact sheets & guides for providers, end users
• Liaison with government e.g. ACMA and DCITA
• Interconnection subgroup
• Fault handling/restoration and customer
support
Possible Technical Activities

• Interconnecting SIP services
–e.g. number formats (E.164, NSN, 0+NSN, ENUM)
–minimum codec set.
• Consistent approach to services e.g. how to
handle DTMF tones on an IVR
• An interconnection model for IP based
networks
• Define/adopt common technical interfaces,
processes for interception
• IP Location Information
• Participation invited/welcome
Contacts

• W: http://commsalliance.com.au
• E: [email protected]
• T: +61 2 9959 9111
• F: +61 2 9954 6136
• Level 9, 32 Walker St, North Sydney
• P.O. Box 444, Milsons Point, NSW 1565