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Transcript of 1 Mona Habib & Nirmala Bulusu Improving QoS of VoIP over Wireless Networks (IQ-VW) CS522 –...
1
Mona Habib & Nirmala BulusuMona Habib & Nirmala Bulusu
Improving QoS of VoIP over Wireless Networks
(IQ-VW)
Improving QoS of VoIP over Wireless Networks
(IQ-VW)
CS522 – 12/09/2002
2
AgendaAgenda
Voice over IP (VoIP): Why?
VoIP Protocols: H.323 and SIP
Quality of Service (QoS)
Wireless Networks
Testbed Configuration
Testing Scenarios
QoS Test Results
Comments
Voice over IP (VoIP): Why?
VoIP Protocols: H.323 and SIP
Quality of Service (QoS)
Wireless Networks
Testbed Configuration
Testing Scenarios
QoS Test Results
Comments
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Reduce toll costs for long-distance telephone calls
Helps consolidate separate voice and data networks for cost-effectiveness and bandwidth utilization.
Provides features not available in traditional voice telephony, such as video conferencing and simultaneous data transmission (e.g. whiteboard) for true multimedia communications.
Provides integration between data and telephony applications for business -- “click to talk” on a web site for ordering or customer support.
Reduce toll costs for long-distance telephone calls
Helps consolidate separate voice and data networks for cost-effectiveness and bandwidth utilization.
Provides features not available in traditional voice telephony, such as video conferencing and simultaneous data transmission (e.g. whiteboard) for true multimedia communications.
Provides integration between data and telephony applications for business -- “click to talk” on a web site for ordering or customer support.
Why Voice over IP?Why Voice over IP?
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IP NetworkIP NetworkGatekeeperGatekeeper
ISDNISDN
WirelessWireless
PSTNPSTN
GatewayGateway
TerminalTerminal
TerminalTerminal
FaxFax
PBXPBX
Enterprise ClassEnterprise ClassCarrier ClassCarrier Class
Enterprise NetworkEnterprise Network
GatewayGateway
MCUMCU
SS7 NetworkSS7 Network
Voice over IP Network ComponentsVoice over IP Network Components
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Voice over IP - The Standards BattleVoice over IP - The Standards Battle
H.323- Primary standard for enterprise networks- Supported in many carrier networks
SIP - Session Initiation Protocol - Common for IP phones and PCs - Gaining popularity as signaling protocol due to its
versatility
H.323- Primary standard for enterprise networks- Supported in many carrier networks
SIP - Session Initiation Protocol - Common for IP phones and PCs - Gaining popularity as signaling protocol due to its
versatility
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Link & Physical Layer
IP
UDP TCP
RTP
Voice CodecG.711, 723,
729, etc. RTCPH.225RAS
H.225 Call
SignalingH.245
Audio Application
Terminal Control & Management
H.323 Protocol StackH.323 Protocol Stack
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Link & Physical Layer
IP
UDP TCP
RTP
Voice CodecG.711, 723,
729, etc. RTCP SIP SDP
Audio Application
Terminal Control & Management
SIP Protocol StackSIP Protocol Stack
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Codec: Speech to DataCodec: Speech to Data
Transforms between Speech (analog) to data (digital) Bandwidth
101011110
Algorithm G.723.1 G.729 G.728 G.726
Rate (Kbs) 5.3 - 6.3 8 16 32
Complexity Highest High Lower Low
Compare with 64Kbs end to endCompare with 64Kbs end to end
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Quality of ServiceQuality of Service
• Offered Service• Reachability• Availability• Reliability• Price
• Offered Service• Reachability• Availability• Reliability• Price
Service QualityService Quality Voice QualityVoice Quality
Traditional PSTN• Level• Delay• Echo• Clarity:
• Intelligibility• Noise• Fading• Cross talk
Traditional PSTN• Level• Delay• Echo• Clarity:
• Intelligibility• Noise• Fading• Cross talk
In addition in IP Networks• Delay• Delay-Jitter• Clarity:
• Packet Loss• Bandwidth• Compression
In addition in IP Networks• Delay• Delay-Jitter• Clarity:
• Packet Loss• Bandwidth• Compression
GatewayGateway IP NetworkIP NetworkPSTN NetworkPSTN Network H.323/SIP TerminalH.323/SIP TerminalPhonePhone
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Wireless NetworksWireless Networks
802.11a
Operates in the 5 GHz frequency band
Supports bandwidths up to 54 MB, range of 150+ feet
Has 12 data channels
Uses Orthogonal Frequency Division Multiplexing (OFDM)
Performs at short distances
Incompatible with 802.11b
802.11a
Operates in the 5 GHz frequency band
Supports bandwidths up to 54 MB, range of 150+ feet
Has 12 data channels
Uses Orthogonal Frequency Division Multiplexing (OFDM)
Performs at short distances
Incompatible with 802.11b
802.11b Operates in the 2.4 GHz frequency
band
Supports bandwidths up to 11 MB , range of 150+ feet
Has 3 data channels
Uses Direct Sequence Spread Spectrum modulation (DSSS)
Handles long distances better than 802.11a
802.11b Operates in the 2.4 GHz frequency
band
Supports bandwidths up to 11 MB , range of 150+ feet
Has 3 data channels
Uses Direct Sequence Spread Spectrum modulation (DSSS)
Handles long distances better than 802.11a
802.11 is an IEEE standard for wireless LANs
802.11a and 802.11b are two variants of the standard
Most recent variant: 802.11g (compatible with 802.11b)
802.11 is an IEEE standard for wireless LANs
802.11a and 802.11b are two variants of the standard
Most recent variant: 802.11g (compatible with 802.11b)
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Wireless Network SecurityWireless Network Security
Vulnerabilities:
Unauthorized user access
Eavesdropping (network can be tapped using a sniffer)
Authentication: EAP (Extensible Authentication Protocol)
EAP interacts with a Remote Authentication Dial-In User Service (RADIUS) server to provide authentication for wireless client devices.
Encryption: WEP (Wired Equivalent Privacy)
Scrambles the communication between the access point and client devices to keep the communication private.
Both the access point and client devices use the same WEP key to encrypt and decrypt radio signals.
Vulnerabilities:
Unauthorized user access
Eavesdropping (network can be tapped using a sniffer)
Authentication: EAP (Extensible Authentication Protocol)
EAP interacts with a Remote Authentication Dial-In User Service (RADIUS) server to provide authentication for wireless client devices.
Encryption: WEP (Wired Equivalent Privacy)
Scrambles the communication between the access point and client devices to keep the communication private.
Both the access point and client devices use the same WEP key to encrypt and decrypt radio signals.
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Wireless Network ConfigurationWireless Network Configuration
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QoS Testbed – HW ConfigurationQoS Testbed – HW Configuration
Gatekeepercalvin.uccs.edu
Gatekeepercalvin.uccs.edu
Ethernet Clientwait.uccs.edu
Ethernet Clientwait.uccs.edu
Ethernet Clientwind.uccs.eduEthernet Clientwind.uccs.edu
Wireless Client(DHCP)
Wireless Client(DHCP)
Wireless Client(DHCP)
Wireless Client(DHCP)
Lab #3Lab #3
Lab #2Lab #2 Lab #1Lab #1
Cisco AironetAccess PointCisco AironetAccess Point
RADIUS Servervinci.uccs.eduRADIUS Servervinci.uccs.edu
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QoS Testbed – SW ConfigurationQoS Testbed – SW Configuration
Public Domain Software
Gatekeeper: Vovida Open Communication Application Library (VOCAL)
VOCAL SIP to H.323 Converter: SIPH323CSGW
Clients: MSN Messenger 4.6 (allows use of communication services other than .Net Passport)
Network Analyzer: Ethereal
Other Software:
QoS analysis tools provided by Daniel Hertrich
Voice over Misconfigured Internet Telephones (VOMIT)
Wavfix.c: Program to create WAVE file header. Used to replay captured voice data
Public Domain Software
Gatekeeper: Vovida Open Communication Application Library (VOCAL)
VOCAL SIP to H.323 Converter: SIPH323CSGW
Clients: MSN Messenger 4.6 (allows use of communication services other than .Net Passport)
Network Analyzer: Ethereal
Other Software:
QoS analysis tools provided by Daniel Hertrich
Voice over Misconfigured Internet Telephones (VOMIT)
Wavfix.c: Program to create WAVE file header. Used to replay captured voice data
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QoS Testing ScenariosQoS Testing Scenarios
Ethernet to Ethernet
Ethernet to Wireless
Ethernet to 802.11a
Ethernet to 802.11b
Ethernet to 802.11b + Wireless security
Wireless to Wireless
802.11a to 802.11a
802.11b to 802.11b
802.11b to 802.11b + Wireless security
Ten test runs per scenario. Sound files include speech (male and female) and music.
Ethernet to Ethernet
Ethernet to Wireless
Ethernet to 802.11a
Ethernet to 802.11b
Ethernet to 802.11b + Wireless security
Wireless to Wireless
802.11a to 802.11a
802.11b to 802.11b
802.11b to 802.11b + Wireless security
Ten test runs per scenario. Sound files include speech (male and female) and music.
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QoS Test ResultsSample Inter-packet Delay Graph
QoS Test ResultsSample Inter-packet Delay Graph
802.11b - 802.11b
0
4
8
12
16
20
24
28
32
36
40
0 10 20 30 40 50 60
Tme (sec)
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QoS Test ResultsSample Jitter Time Graph
QoS Test ResultsSample Jitter Time Graph
802.11b - 802.11b
-0.4
-0.36
-0.32
-0.28
-0.24
-0.2
-0.16
-0.12
-0.08
-0.04
0
0.04
0.08
0.12
0.16
0.2
0.24
0.28
0.32
0.36
0.4
0 10 20 30 40 50 60
Time (sec)
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QoS Test Results: Average Jitter per CallEthernet to Wireless (802.11a vs. 802.11b)QoS Test Results: Average Jitter per CallEthernet to Wireless (802.11a vs. 802.11b)
Ethernet to Wireless802.11a vs. 802.11b
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
1.4
1.5
1.6
1 2 3 4 5 6 7 8 9 10
Call Numbers
Ethernet 802.11a 802.11b
Distance from AP ~15-20 ft. Excellent signal strength with both 802.11a and 802.11b. 802.11a performed better than 802.11b.
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QoS Test Results: Average Jitter per CallEthernet to Wireless (with and without WEP)
QoS Test Results: Average Jitter per CallEthernet to Wireless (with and without WEP)
Ethernet to Wireless802.11b vs. 802.11b + security
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
1.4
1.5
1.6
1 2 3 4 5 6 7 8 9 10
Call Numbers
Ethernet 802.11b 802.11b+Sec
More research/testing needed to validate these results. Tests performed on different days (maybe different network load).
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QoS Test Results: Average Jitter per CallWireless to Wireless (802.11a vs. 802.11b)QoS Test Results: Average Jitter per CallWireless to Wireless (802.11a vs. 802.11b)
Wireless to Wireless802.11a vs. 802.11b
0
100
200
300
400
500
600
1 2 3 4 5 6 7 8 9 10
Call Numbers
Ethernet 802.11a 802.11b
Each client’s distance from AP ~15-20 ft. Peer-to-peer ~30-40 ft. Poor signal strength for 802.11a, excellent for 802.11b.
21
QoS Test Results: Average Jitter per CallWireless to Wireless (with and without WEP)
QoS Test Results: Average Jitter per CallWireless to Wireless (with and without WEP)
Wireless to Wireless802.11b vs. 802.11b +security
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
1.4
1.5
1.6
1 2 3 4 5 6 7 8 9 10
Call Numbers
Ethernet 802.11b 802.11b+Sec
No significant difference in results. Need to investigate further to check at which point packets are captured by Winpcap.
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QoS Test Results: Loss of DataQoS Test Results: Loss of Data
No loss of data observed during all test runs (except the 802.11a to 802.11a test).
Good subjective assessment of QoS (user listening to the received sound). Clear sound with no interruptions, with the exception of an initial delay.
Poor signal strength during 802.11a to 802.11a test (20-40% on both ends).
High data loss rate observed (for e.g., transmitted 196 out of 1434 packets). Loss rate of ~86-93%.
Extremely poor sound quality (unintelligible, broken, …)
Packets lost at the sender’s end, as seen by Ethereal captured data. This needs to be investigated further as it affects interpretation of the results.
No loss of data observed during all test runs (except the 802.11a to 802.11a test).
Good subjective assessment of QoS (user listening to the received sound). Clear sound with no interruptions, with the exception of an initial delay.
Poor signal strength during 802.11a to 802.11a test (20-40% on both ends).
High data loss rate observed (for e.g., transmitted 196 out of 1434 packets). Loss rate of ~86-93%.
Extremely poor sound quality (unintelligible, broken, …)
Packets lost at the sender’s end, as seen by Ethereal captured data. This needs to be investigated further as it affects interpretation of the results.
23
QoS Test Results: ObservationsQoS Test Results: Observations
Smooth sound quality for all test but 802.11a to 802.11a test, despite existing inter-packet delays and jitters.
Replaying captured packets (after reassembling Wave file) reflected inconsistent delays, yet sound was clear at the receiving client.
Sound quality improved by client’s handling of timings (e.g., using RTP to synchronize relative timings).
Quality variations were most perceived in test #7, which had highest overlap of speech and music.
Loss of data has the highest effect on QoS.
Smooth sound quality for all test but 802.11a to 802.11a test, despite existing inter-packet delays and jitters.
Replaying captured packets (after reassembling Wave file) reflected inconsistent delays, yet sound was clear at the receiving client.
Sound quality improved by client’s handling of timings (e.g., using RTP to synchronize relative timings).
Quality variations were most perceived in test #7, which had highest overlap of speech and music.
Loss of data has the highest effect on QoS.
Let’s listen to a sample reassembled sound file … …
24
How to Improve QoS?How to Improve QoS?
Problem Delay and jitter
Packet loss due to congestion
Problem Delay and jitter
Packet loss due to congestion
Solution Separate queues for time
sensitive traffic RTP
More bandwidth Resource Reservation Protocol
(RSVP) Differentiated Service (DiffServ) Multi-Protocol Label Switching
(MPLS) RFC 2597 and RFC 2598
Solution Separate queues for time
sensitive traffic RTP
More bandwidth Resource Reservation Protocol
(RSVP) Differentiated Service (DiffServ) Multi-Protocol Label Switching
(MPLS) RFC 2597 and RFC 2598
25
Future Research/TestsFuture Research/Tests Inject background traffic Synchronize time on all testbed components and
calculate initial connection delay Evaluate the effect of using different codecs PC-to-Phone quality testing Evaluate wireless network performance at different
distances from the access point Evaluate wireless network performance using multiple
access points with overlapping coverage Assess compatibility of 802.11 variants Evaluate existing QoS solutions (e.g., RSVP) Evaluate QoS of VoIP using H.323 clients Detect transmission sampling rate for replay based on
timestamps of the captured packets Evaluate QoS of VoIP using a PDA client (might require
porting a SIP client to a PDA)
Inject background traffic Synchronize time on all testbed components and
calculate initial connection delay Evaluate the effect of using different codecs PC-to-Phone quality testing Evaluate wireless network performance at different
distances from the access point Evaluate wireless network performance using multiple
access points with overlapping coverage Assess compatibility of 802.11 variants Evaluate existing QoS solutions (e.g., RSVP) Evaluate QoS of VoIP using H.323 clients Detect transmission sampling rate for replay based on
timestamps of the captured packets Evaluate QoS of VoIP using a PDA client (might require
porting a SIP client to a PDA)
26
ReferencesReferences
Collins, Daniel (2001). Carrier Grade Voice over IP, McGraw-Hill.
Ferguson, Paul and Geoff Huston (1998). Quality of Service, Wiley Computer Publishing.
Douskalis, Bill (2000). IP Telephony: The Integration of Robust VoIP Services, Prentice Hall PTR.
Keey, David G., Cullen Jennings, and Luan Dang (2002). Practical VoIP using VOCAL, O’Reilly Network.
Gast, Matthew (2002). 802.11 Wireless Networks: The Definitive Guide, O’Reilly Network.
Hertrich, Daniel et al. (2001). “Evaluating QoS for Voice over IP in Wireless LANs”, Technical Report, Telecommunication Networks Group.
Useful links: VoIP-WLAN-QoS Useful Links
Collins, Daniel (2001). Carrier Grade Voice over IP, McGraw-Hill.
Ferguson, Paul and Geoff Huston (1998). Quality of Service, Wiley Computer Publishing.
Douskalis, Bill (2000). IP Telephony: The Integration of Robust VoIP Services, Prentice Hall PTR.
Keey, David G., Cullen Jennings, and Luan Dang (2002). Practical VoIP using VOCAL, O’Reilly Network.
Gast, Matthew (2002). 802.11 Wireless Networks: The Definitive Guide, O’Reilly Network.
Hertrich, Daniel et al. (2001). “Evaluating QoS for Voice over IP in Wireless LANs”, Technical Report, Telecommunication Networks Group.
Useful links: VoIP-WLAN-QoS Useful Links