TIA-921 (PN-3-0062) and ITU-T G.NIMM
Network Model for Evaluating Multimedia Transmission Performance Over Internet Protocol
Jack Douglass, SpirentChair TIA TR30.3
August 2005
TIA TR41.4-05-08-008
TIA-921 (PN-3-0062) and ITU-T G.NIMM
Jitter, Latency, Burst Loss, Gap Loss
Packet Loss, Out-of-Order Packets
Route Flapping, Link Failure
Scenario Based Time Varying
IP Network Impairments
IP Network Impairment EmulatorBased on TIA-921 and ITU-T G.NIMM
Types of DUTsIP PhonesPOTS over IPMedia Gateways MGCUser AgentsCall Agents Media ServersVideo Gatekeepers Application Servers Edge Routers GatewaysModemsFax
Source DeviceUnder Test
DestinationDevice Under
Test
IP NetworkImpairment Emulator
Ethernet Ethernet
TIA-921 (PN-3-0062) and ITU-T G.NIMM Network Model for Evaluating Multimedia Transmission Performance
TIA-921 / ITU-T G.NIMM
Network Impairments and Parameters that Affect Voice and Video Quality
• Network Architecture
• Types of Access Links
• QoS controlled Edge Routing
• MTU Size
• Packet Loss (Frame Loss)
• Out of order packets
• One Way Delay (Latency)
• Variable Delays (Jitter)
• Background Traffic (Occupancy)
• Timing Drift
• Route Flapping
• Signaling protocol mismatches
• Network faults
• Link Failures
• Voice Only Impairments– Echo
– Voice coding algorithms
– A/D and D/A Conversion
– Noise – Circuit and External
• Video Only Impairments– Video coding algorithms
– Variable and Fixed Frame Rates
– Video Complexity
TIA-921and ITU-T G.NIMM IP Network Model
Core IP NetworkLAN A
Local AccessB
1000BaseX* 100BaseT Switch100BaseT Hub10BaseT* WLAN (~4 Mbit/s)----------------------Occupancy levelPacket loss
64 kbit/s*128 kbit/s256 kbit/s*384 kbit/s512 kbit/s*768 kbit/s
*T1 (1.536 kbit/s)E1 (1.920 kbit/s)E3 (34 Mbit/s)*T3 (44 Mbit/s)
ADSL (~256 kbit/s)*Cable (~256 kbit/s)Fiber (1-10 Gbit/s)
--------------------Occupancy levelQoS edge router
LAN B
Route flappingOne-way delay
JitterPacket loss
DestinationDevice B
Local AccessA
64 kbit/s*128 kbit/s256 kbit/s*384 kbit/s512 kbit/s*768 kbit/s
*T1 (1.536 kbit/s)E1 (1.920 kbit/s)E3 (34 Mbit/s)*T3 (44 Mbit/s)
ADSL (~2 Mbit/s)*Cable (~3 Mbit/s)Fiber (1-10 Gbit/s)
--------------------Occupancy levelQoS edge router
SourceDevice A
* Case used in impairment tables
1000BaseX* 100BaseT Switch100BaseT Hub10BaseT* WLAN (~4 Mbit/s)----------------------Occupancy levelPacket loss
TIA-921and ITU-T G.NIMM IP Network Model
• Typically test are run in one direction
• Tests may be run in both directions
• Impairments occur in both directions
Core IP Netw orkLAN A
LocalAccess B
LAN data rateLAN occupancy
Access data ratesAccess occupancyMTU size
LAN B
Route f lappingLink f ailureOne-way delayJitterPacket loss
DestinationDev ice B
LocalAccess ASource
Dev ice A
Access data ratesAccess occupancyMTU size
LAN data rateLAN occupancy
Direction of Test
TIA-921 and ITU-T G.NIMMTest Profiles Based on QoS Classes
• Statistically based models for different QoS Classes
Service Test Profiles
QoS Class(Y.1541)
Applications (Examples) Node Mechanisms
Network Techniques
Well‑Managed IP Network(Profile A)
0 High quality video and VoIP, VTC (Real-time applications, loss sensitive, jitter sensitive, high interaction)
Strict QoS, guaranteed no over subscription on links
Constrained routing and distance
Best-EffortIP Network(Profile B)
1 VoIP, VTC (Real-time applications, jitter sensitive, interactive)
Separate queue with preferential servicing, traffic grooming
Less constrained routing and distances
UnmanagedIP Network,Internet(Profile C)
2 Lower quality video and VoIP, signaling, transaction data (highly interactive) Separate queue,
drop priority
Constrained routing and distance
3 Transaction data, interactive Less constrained routing and distances
4 Short transactions, bulk data (low loss)
Long queue, drop priority
Any route/path
5 Traditional Internet applications (default IP networks)
Separate queue (lowest priority) Any route/path
TIA-921 and ITU-T G.NIMMTest Profiles Based on QoS (Y.1541) Classes
Profile C Un-Managed NetworkImpairment Ranges
Table 4
Profile BBest Effort Managed Network
Impairment Ranges Table 3
Profile AWell Managed Network
Impairment Ranges Table 2
Different test profiles for different Service Level Agreements (SLAs)
Impairment Type Units Range
Jitter ms 0 to +/- 250
One Way Average Latency
ms 50 to 800
Sequential Packet Loss
# of sequential packets
2 to 500
Rate of Sequential Loss
sec-1 < 10-1
Random Packet Loss
% 0 to 20
Out of Sequence Packets
% 0 to 20
Impairment Type Units Range
Jitter ms 0 to +/- 75
One Way Average Latency
ms 50 to 200
Sequential Packet Loss
# of sequential packets
2 to 5
Rate of Sequential Loss
sec-1 < 10-3
Random Packet Loss
% 0 to 2
Out of Sequence Packets
% 0 to 0.1
Impairment Type Units Range
Jitter ms 0 to +/- 50
One Way Average Latency
ms 20 to 60
Sequential Packet Loss
# of sequential packets Random
loss
onlyRate of Sequential Loss
sec-1
Random Packet Loss
% 0 to 0.05
Out of Sequence Packets
% 0 to 0.001
TIA-921 and ITU-T G.NIMM 8 Impairment Severity Combinations
Table 10: Impairment Severity Combinations
Severity=> A B C D E F G H
Impairment Units
Profile A LOO % 50 30 15 5 0 0 0 0
Profile B LOO % 5 25 30 25 10 5 0 0
Profile C LOO % 5 5 10 15 20 25 15 5
Source Location (A) Parameters
LAN A Occupancy % 1 2 3 5 8 12 16 20
Access A Occupancy % 0 1 2 4 8 15 30 50
MTU A bytes 512 512 1508 1508 1508 1508 1508 1508
Core Network Impairments
Route flap interval seconds 0 3600 1800 900 480 240 120 60
Route flap D delay ms 0 2 4 8 16 32 64 128
Delay ms 4 8 16 32 64 128 256 512
Jitter ms 5 10 15 20 30 50 75 100
Link fail interval seconds 0 3600 1800 900 480 240 120 60
Link fail duration ms 0 64 128 256 400 800 1600 3000
Packet loss % 0 0.01 0.02 0.04 0.1 0.2 0.5 1
Destination Location (B) Parameters
Access B Occupancy % 0 1 2 4 8 15 30 50
MTU B bytes 512 512 1508 1508 1508 1508 1508 1508
LAN B Occupancy % 1 2 3 5 8 12 16 20
TIA-921 and ITU-T G.NIMM LAN and Access Rates
Table 7: Access Rates for Home Locations
Table 8: Access Rates for Business LocationsTable 6: LAN Rates for Business Locations
Table 5: LAN Rates for Home Locations
133 LAN/Access Rate Combinations
Home Rates
Business Rates
LAN Rate LOO Represents
Mbit/s %
4 75 802.11b, 10BaseT hub
20 25 802.11g, 100BaseT hub
LAN Rate LOO Represents
Mbit/s %
4 20 802.11b, 10BaseT
20 20 802.11g, 100BaseT hub
100 60 100 BaseT switched, Gbit Ethernet
Access Rate LOO Represents
Toward core From core %
kbit/s kbit/s
128 768 40 Cable, ADSL
384 1536 50 Cable, ADSL
384 3000 10 Cable, ADSL
Access Rate LOO Represents
Toward core From core %
kbit/s kbit/s
384 1536 40 ADSL entry
384 3000 15 ADSL premium
1536 1536 40 T1
43000 43000 5 T3
LAN and Access Rates (New Revision of Standard/Recomendation) will change as network conditions change
Testing with Fixed Levels of IP Impairments
• IP Impairment network emulators exist today that provide fixed or semi-fixed levels of IP impairments.
• Real IP Network Impairments Vary Over Time significantly over time and are bursty in nature
Fixed Jitter & Packet Loss
Fixed Packet Jitter
TIA-921 and ITU-T G.NIMMStatistically Based IP Network Impairment Conditions (ICs) based on SLAs
IC– 96AProbability (LOO = 0.00256% )
Call Quality Metric
Impairment Condition
TIA-921 and ITU-T G.NIMMStatistically Based IP Network Impairment Conditions (ICs) based on SLAs
Call Quality Metric
Impairment Condition
IC– 96EProbability (LOO = 0.01025% )
TIA-921 and ITU-T G.NIMMStatistically Based IP Network Impairment Conditions (ICs) based on SLAs
Link Failure
Route Flap
Call Quality Metric
Impairment Condition
IC– 96HProbability (LOO = 0.00256%)
TIA-921 and ITU-T G.NIMMStatistically Based IP Network Impairment Conditions (ICs) based on SLAs
• Each Impairment Condition has a Likely-hood of Occurrence (LOO)
– Based on real IP Network Statistics
– Based on Network Architecture
– Based on Classes of Service
• Definitive set of test conditions
– 1064 Impairment Combinations
– Tests may be automatically
– Typically 2 min per Impairment Condition
• Approximately 1.5 days to run complete set of tests
– Impairment Condition may be correlated with appropriate quality measurement
• Voice Quality Metric (MOS, PESQ, PSQM, R-Factor)
• Video Quality Metric
Mean Opinion Score - Listening Quality vs. TIA-921 Network Model Coverage(G.711 PLC, 40 ms jitter buffer)
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
% Network Model Coverage
MO
S-L
Q Test Profile A
Test Profile B
Test Profile C
TIA-921 and ITU-T G.NIMM Example of Network Model Coverage (NMC) Curve
Test Results from 1064 Statistically based IP Network Impairment Combinations
TIA-921 and ITU-T G.NIMM Example of Network Model Coverage (NMC) Curve
Test Results from 1064 Statistically based IP Network Impairment Combinations
R-Factor - Listening Quality vs. TIA-921 Network Model Coverage(G.711 PLC, 40 ms. jitter buffer)
0
10
20
30
40
50
60
70
80
90
100
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
% Network Model
R-L
Q
Test Profile A
Test Profile B
Test Profile C
History of TR30.3 Network Model Standards• TIA/EIA 496A-1989: Interface Between Data Circuit Terminating
Equipment (DCE) and the Public Switched Telephone Network
– Included Network Model for Evaluating Modem Performance
• TIA/EIA TSB 37A-1994: Telephone Network Transmission Model for Evaluating Analog Modem Performance, which became ITU-T Recommendation V.56bis-1995
• EIA/TIA TSB 38-1994: Test Procedures for Evaluation of 2-Wire 4 Kilohertz Voice Band Duplex Modems, which became ITU-T Recommendation V.56ter-1996
• ANSI/TIA/EIA 3700-1999: Telephone Network Transmission Model for Evaluating Analog Modem Performance
• ANSI/TIA/EIA 793 -2000: North American Telephone Network Transmission Model for Evaluating Analog Client and Digitally Connected Server Modems
• ANSI/TIA 876 – 2002: North American Network Access Transmission Model for Evaluating xDSL Modem Performance
TR30.3 Liaison Activities
• Liaisons activities between TR30.3 and appropriate committees to develop TIA-921 (PN-3-0062), Network Model for Evaluating Multimedia Transmission Performance Over Internet Protocol– TR41.4
– TR45.5
– ITU-T SG12
– ITU-T SG9
– ITU-T SG15
• Working with Operating Companies and Service providers to provide statistically accurate IP network impairment model
TIA-921 Target Audience for Network Model
• Network Equipment Manufacturers
• Operating Companies
• Service Providers
• Design Engineers
• Test houses
• Magazines and product reviewers
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