This document describes an experiment to evaluate the impact of different Tunneling Compressed RTP (TCRTP) multiplexing schemes on voice quality over IP (VoIP) under varying network conditions. The experiment multiplexed VoIP packets using TCRTP tunnels with different numbers of flows and measured the resulting voice quality using the R-factor metric. With a high-capacity router buffer, all TCRTP schemes showed step-like quality degradation as background traffic increased. With a time-limited buffer, smaller tunnels led to smoother quality decline. More flows per tunnel reduced overhead and allowed higher background traffic levels before quality dropped.

1. Presentación
Jose Saldana
Jenifer Murillo
Julián Fernández Navajas
G RUPO DE
T ECNOLOGÍAS DE LAS
COMUNICACIONES
CPS - University of Zaragoza, Spain
José Ruiz Mas
Eduardo Viruete Navarro
José I. Aznar

2. Index
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS

3. 3
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS
Introduction
The use of Internet for multimedia
transmission is growing as bandwidth
increases.
Services with hard real-time
requirements:
- VoIP: Voice over IP
- Videoconferencing
- Online Gaming
CCNC January 9-11, 2011. Las Vegas
Influence of the Distribution of TCRTP Multiplexed flows on VoIP

4. 4
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS
RTP packet overhead
IP header
UDP header
RTP header
Sample
Sample
20 bytes
8 bytes
12 bytes
10 bytes
10 bytes
VoIP packet with 2 G.729a samples
Efficiency: 33% for IPv4
CCNC January 9-11, 2011. Las Vegas
Influence of the Distribution of TCRTP Multiplexed flows on VoIP

5. 5
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS
Two possible improvements
Improvement 1: RTP compression schemes:
- CRTP: RFC 2508, February 1999
- ECRTP: RFC 3545, July 2003: Enhanced CRTP
for scenarios with packet loss, packet
reordering and long delays.
- ROHCv2: RFC 5225, April 2008
They use the repeatability of IP/UDP/RTP
headers to compress them.
Problem: Only hop-by-hop. Solution: tunneling.
CCNC January 9-11, 2011. Las Vegas
Influence of the Distribution of TCRTP Multiplexed flows on VoIP

6. 6
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS
Increasing the number of samples
Improvement 2: More samples in a single
packet. If different flows share the same path
(voice trunking)
CCNC January 9-11, 2011. Las Vegas
Influence of the Distribution of TCRTP Multiplexed flows on VoIP

7. 7
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS
Increasing the number of samples
CCNC January 9-11, 2011. Las Vegas
Influence of the Distribution of TCRTP Multiplexed flows on VoIP

8. 8
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS
TCRTP: Tunneling Multiplexed Compressed RTP
(RFC 4170)
IP header
UDP header
RTP header
IP header
Sample
Sample
IP header
L2TP
RH
PPP
PPPMux
Sample
UDP header
Sample
RH
PPPMux
RTP header
Sample
Sample
Sample
Sample
RH
PPPMux
IP header
Sample
UDP header
RTP header
Sample
Sample
Sample
Real scale
- Header compression: ECRTP (40 to 5 bytes)
- Multiplexing: PPPMux
- Tunneling: L2TPv3
Reducing overhead, bandwidth saving
CCNC January 9-11, 2011. Las Vegas
Influence of the Distribution of TCRTP Multiplexed flows on VoIP

9. 9
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS
TCRTP: Tunneling Multiplexed Compressed RTP
(RFC 4170)
IP header
UDP header
RTP header
IP header
Sample
Sample
IP header
L2TP
RH
PPP
PPPMux
Sample
UDP header
Sample
RH
PPPMux
RTP header
Sample
Sample
Sample
Sample
RH
PPPMux
IP header
Sample
UDP header
RTP header
Sample
Sample
Sample
Real scale
- Header compression: ECRTP (40 to 5 bytes)
- Multiplexing: PPPMux
- Tunneling: L2TPv3
Reducing overhead, bandwidth saving
CCNC January 9-11, 2011. Las Vegas
Influence of the Distribution of TCRTP Multiplexed flows on VoIP

10. 10
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS
TCRTP: Tunneling Multiplexed Compressed RTP
(RFC 4170)
IP header
UDP header
RTP header
IP header
Sample
Sample
IP header
L2TP
RH
PPP
PPPMux
Sample
UDP header
Sample
RH
PPPMux
RTP header
Sample
Sample
Sample
Sample
RH
PPPMux
IP header
Sample
UDP header
RTP header
Sample
Sample
Sample
Real scale
- Header compression: ECRTP (40 to 5 bytes)
- Multiplexing: PPPMux
- Tunneling: L2TPv3
Reducing overhead, bandwidth saving
CCNC January 9-11, 2011. Las Vegas
Influence of the Distribution of TCRTP Multiplexed flows on VoIP

11. 11
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS
TCRTP: Tunneling Multiplexed Compressed RTP
(RFC 4170)
IP header
UDP header
RTP header
IP header
Sample
Sample
IP header
L2TP
RH
PPP
PPPMux
Sample
UDP header
Sample
RH
PPPMux
RTP header
Sample
Sample
Sample
Sample
RH
PPPMux
IP header
Sample
UDP header
RTP header
Sample
Sample
Sample
Real scale
- Header compression: ECRTP (40 to 5 bytes)
- Multiplexing: PPPMux
- Tunneling: L2TPv3
Reducing overhead, bandwidth saving
CCNC January 9-11, 2011. Las Vegas
Influence of the Distribution of TCRTP Multiplexed flows on VoIP

12. 12
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS
TCRTP: Tunneling Multiplexed Compressed RTP
IP header
UDP header
RTP header
IP header
Sample
Sample
IP header
L2TP
RH
PPP
PPPMux
Sample
UDP header
Sample
RH
PPPMux
RTP header
Sample
Sample
Sample
Sample
RH
IP header
Sample
UDP header
RTP header
Sample
Sample
Sample
PPPMux
Real scale
Disadvantages:
- New added delays (small)
- Processing charge
Increasing packet size: Good or bad?
CCNC January 9-11, 2011. Las Vegas
Influence of the Distribution of TCRTP Multiplexed flows on VoIP

13. 13
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS
Influence of the router
- Packet loss can be modified with the
change of packet size, depending on the
policy of the router’s buffer.
- The amount and size distribution of
background traffic will affect the real-time
traffic.
- We will use R-factor for comparatives.
Takes into account delay and packet loss.
CCNC January 9-11, 2011. Las Vegas
Influence of the Distribution of TCRTP Multiplexed flows on VoIP

14. 14
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS
Buffer size and buffer policies
- We will compare
- High-capacity buffer
- Time-limited buffer (80 ms)
IP network
.
.
.
MUX
RTP
CCNC January 9-11, 2011. Las Vegas
DEMUX
RTP multiplexing
.
.
.
RTP
Influence of the Distribution of TCRTP Multiplexed flows on VoIP

15. 15
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS
High capacity buffer
- 1Mbps shared. 15 flows
R factor
15 RTP
85
15 TCRTP
80
R
75
70
65
60
400
450
500
550
600
650
700
750
800
850
900
950
1000
background traffic (kbps)
CCNC January 9-11, 2011. Las Vegas
Influence of the Distribution of TCRTP Multiplexed flows on VoIP

16. 16
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS
High capacity buffer
- 1Mbps shared. 15 flows
R factor
15 RTP
85
15 TCRTP
80
75
R
Step-like graphs. When the
bandwidth is not enough, the
quality falls
70
65
60
400
450
500
550
600
650
700
750
800
850
900
950
1000
background traffic (kbps)
CCNC January 9-11, 2011. Las Vegas
Influence of the Distribution of TCRTP Multiplexed flows on VoIP

17. 17
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS
High capacity buffer
- 1Mbps shared. 15 flows
R factor
15 RTP
85
15 TCRTP
80
75
R
Bandwidth saving allows a bigger
amount of background traffic
70
Native RTP
Packet size: 60 bytes
432 kbps
65
TCRTP
Packet size: 550 bytes
172 kbps
60
400
450
500
550
600
650
700
750
800
850
900
950
1000
background traffic (kbps)
CCNC January 9-11, 2011. Las Vegas
Influence of the Distribution of TCRTP Multiplexed flows on VoIP

18. 18
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS
Time-limited buffer
- 1Mbps shared. 20 flows
20 RTP
R-factor
82
20 TCRTP
80
78
Effect of Bandwidth
saving
76
R-factor
74
72
70
68
66
64
62
60
400
450
500
550
600
650
700
750
800
850
900
950
1000
background traffic (kbps)
CCNC January 9-11, 2011. Las Vegas
Influence of the Distribution of TCRTP Multiplexed flows on VoIP

19. 19
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS
Time-limited buffer
- 1Mbps shared. 20 flows
20 RTP
R-factor
82
20 TCRTP
80
78
76
R-factor
74
Non step-like graphs. The bigger the
packet size, the bigger the slope
72
70
68
66
64
62
60
400
450
500
550
600
650
700
750
800
850
900
950
1000
background traffic (kbps)
CCNC January 9-11, 2011. Las Vegas
Influence of the Distribution of TCRTP Multiplexed flows on VoIP

20. 20
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS
Time-limited buffer
- 1Mbps shared. 20 flows
20 RTP
R-factor
82
20 TCRTP
80
78
TCRTP
Packet size: 550 bytes
225 kbps
76
R-factor
74
72
70
68
Native RTP
Packet size: 60 bytes
576 kbps
66
64
62
60
400
450
500
550
600
650
700
750
800
850
900
950
1000
background traffic (kbps)
CCNC January 9-11, 2011. Las Vegas
Influence of the Distribution of TCRTP Multiplexed flows on VoIP

21. 21
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS
Time-limited buffer
- Is it better to use only one tunnel or to
group calls into a number of tunnels?
R factor
20 RTP
85
20 TCRTP
2x10 TCRTP
80
75
R
70
65
60
55
50
400
450
500
550
600
650
700
750
800
850
900
950
1000
background traffic (kbps)
CCNC January 9-11, 2011. Las Vegas
Influence of the Distribution of TCRTP Multiplexed flows on VoIP

22. 22
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS
Motivation of this work
- Study the influence of different TCRTP
multiplexing schemes on the perceived
quality, depending on buffer policies.
- We will use 40 RTP flows sharing the same
path, but divided on:
- l tunnels of k flows (l x k = 40)
-
1 tunnel of 40 flows
2 tunnels of 20 flows
4 tunnels of 10 flows
CCNC January 9-11, 2011. Las Vegas
5 tunnels of 8 flows
8 tunnels of 5 flows
40 RTP flows
Influence of the Distribution of TCRTP Multiplexed flows on VoIP

23. Index
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS

24. 24
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS
General Scheme
- Use of a testbed
Real Traffic in a testbed
Offline post-processing
Buffer
policies
VoIP
Network
delays
+
Dejitter
buffer
Background
Router
Traffic
Generation
CCNC January 9-11, 2011. Las Vegas
Traffic
Capture
Traffic
Trace
Final
Results
Influence of the Distribution of TCRTP Multiplexed flows on VoIP

25. 25
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS
Traffic generation
- Background traffic
- 50% 40 bytes
- 10% 576 bytes
- 40% 1500 bytes
- Only UDP, in order to avoid flow control:
always the same background traffic.
- Different rates to saturate the access
router: 2Mbps.
CCNC January 9-11, 2011. Las Vegas
Influence of the Distribution of TCRTP Multiplexed flows on VoIP

26. Index
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS

27. 27
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS
High capacity buffer
1x40 TCRTP
R-factor
2x20 TCRTP
82
4x10 TCRTP
80
5x8 TCRTP
78
8x5 TCRTP
R-factor
76
74
72
70
68
66
64
62
1200
1300
1400
1500
1600
1700
1800
1900
2000
background traffic (kbps)
CCNC January 9-11, 2011. Las Vegas
Influence of the Distribution of TCRTP Multiplexed flows on VoIP

28. 28
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS
High capacity buffer
1x40 TCRTP
R-factor
2x20 TCRTP
82
4x10 TCRTP
80
5x8 TCRTP
78
8x5 TCRTP
R-factor
76
74
72
Step-like graphs
70
68
66
64
62
1200
1300
1400
1500
1600
1700
1800
1900
2000
background traffic (kbps)
CCNC January 9-11, 2011. Las Vegas
Influence of the Distribution of TCRTP Multiplexed flows on VoIP

29. 29
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS
High capacity buffer
1x40 TCRTP
R-factor
2x20 TCRTP
82
4x10 TCRTP
80
5x8 TCRTP
78
8x5 TCRTP
R-factor
76
74
72
The bigger the bandwidth saving,
the better the behaviour
70
68
66
64
62
1200
1300
1400
1500
1600
1700
1800
1900
2000
background traffic (kbps)
CCNC January 9-11, 2011. Las Vegas
Influence of the Distribution of TCRTP Multiplexed flows on VoIP

30. 30
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS
Time-limited buffer
R-factor
1x40 TCRTP
82
2x20 TCRTP
78
4x10 TCRTP
5x8 TCRTP
74
8x5 TCRTP
No mux
R-factor
70
66
62
58
54
50
46
1200
1300
1400
1500
1600
1700
1800
1900
2000
background traffic (kbps)
CCNC January 9-11, 2011. Las Vegas
Influence of the Distribution of TCRTP Multiplexed flows on VoIP

31. 31
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS
Time-limited buffer
R-factor
1x40 TCRTP
82
2x20 TCRTP
78
4x10 TCRTP
5x8 TCRTP
74
8x5 TCRTP
No mux
R-factor
70
66
The graphs
present a slope
62
58
54
50
46
1200
1300
1400
1500
1600
1700
1800
1900
2000
background traffic (kbps)
CCNC January 9-11, 2011. Las Vegas
Influence of the Distribution of TCRTP Multiplexed flows on VoIP

32. 32
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS
Time-limited buffer
R-factor
4th
82
1x40 TCRTP
2x20 TCRTP
78
4x10 TCRTP
5x8 TCRTP
74
8x5 TCRTP
No mux
R-factor
70
66
Not ordered by the
bandwidth saving
62
58
54
50
46
1200
1300
1400
1500
1600
1700
1800
1900
2000
background traffic (kbps)
CCNC January 9-11, 2011. Las Vegas
Influence of the Distribution of TCRTP Multiplexed flows on VoIP

33. 33
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS
Time-limited buffer
R-factor
1x40 TCRTP
82
1st
78
4x10 TCRTP
5x8 TCRTP
74
8x5 TCRTP
No mux
R-factor
70
66
2x20 TCRTP
Not ordered by the
bandwidth saving
62
58
54
50
46
1200
1300
1400
1500
1600
1700
1800
1900
2000
background traffic (kbps)
CCNC January 9-11, 2011. Las Vegas
Influence of the Distribution of TCRTP Multiplexed flows on VoIP

34. 34
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS
Time-limited buffer
1x40 TCRTP
14
Percentage of Background Traffic Packet Loss
2x20 TCRTP
4x10 TCRTP
Packet Loss (%)
12
5x8 TCRTP
8x5 TCRTP
10
8
Ordered by bandwidth saving
6
4
2
0
1200
1300
1400
1500
1600
1700
1800
1900
2000
background traffic (kbps)
CCNC January 9-11, 2011. Las Vegas
Influence of the Distribution of TCRTP Multiplexed flows on VoIP

35. Index
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS

36. 36
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS
Asymptotic bandwidth relationship
Bandwidth Saving X for p = 0.95
BW compressed/BW native
S=10 bytes
Xrh S=10
S=20 bytes
0,9
Xrh=20
S=30 bytes
0,8
Xrh S=30
X
0,7
0,6
0,5
0,4
0,3
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
k
CCNC January 9-11, 2011. Las Vegas
Influence of the Distribution of TCRTP Multiplexed flows on VoIP

37. 37
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS
Asymptotic bandwidth relationship
Bandwidth Saving X for p = 0.95
BW compressed/BW native
S=10 bytes
Xrh S=10
S=20 bytes
0,9
Xrh=20
S=30 bytes
0,8
Xrh S=30
X
0,7
Bandwidth
saving increase
0,6
0,5
0,4
0,3
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
k
CCNC January 9-11, 2011. Las Vegas
Influence of the Distribution of TCRTP Multiplexed flows on VoIP

38. 38
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS
Linear packet size increase
Packet size
RTP S=10 bytes
800
RTP S=20 bytes
RTP S=30 bytes
TCRTP S=10 bytes
700
TCRTP S=20 bytes
TCRTP S=30bytes
600
bytes
500
400
300
200
100
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19 20
k
CCNC January 9-11, 2011. Las Vegas
Influence of the Distribution of TCRTP Multiplexed flows on VoIP

39. 39
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS
Linear packet size increase
Packet size
RTP S=10 bytes
800
RTP S=20 bytes
RTP S=30 bytes
TCRTP S=10 bytes
700
Packet size
increase
TCRTP S=20 bytes
TCRTP S=30bytes
600
bytes
500
400
300
200
100
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19 20
k
CCNC January 9-11, 2011. Las Vegas
Influence of the Distribution of TCRTP Multiplexed flows on VoIP

40. 40
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS
Linear packet size increase
Packet size vs Bandwidth
1x40
1200
2x20
1 tunnel of 40
flows
4x10
1000
5x8
8x5
40 RTP
Packet size (bytes)
800
2 tunnels of
20 flows
600
4 tunnels of
10 flows
400
5 tunnels of 8
flows
200
40 native RTP
flows
8 tunnels of 5
flows
0
0
200
400
600
800
1000
1200
Bandwidth (kbps)
CCNC January 9-11, 2011. Las Vegas
Influence of the Distribution of TCRTP Multiplexed flows on VoIP

41. 41
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS
Linear packet size increase
Packet size vs Bandwidth
1x40
Bandwidth
decrease
2x20
1200
1000
5x8
8x5
Packet size
increase
800
Packet size (bytes)
4x10
40 RTP
600
400
200
0
0
200
400
600
800
1000
1200
Bandwidth (kbps)
CCNC January 9-11, 2011. Las Vegas
Influence of the Distribution of TCRTP Multiplexed flows on VoIP

42. 42
INTRODUCTION
MEASUREMENTS
RESULTS
DISCUSSION
CONCLUSIONS
Conclusions
- The decision of the number of tunnels has
an influence on R-factor.
- The buffer policy has to be taken into
account in order to take the correct
decision. Previous measurements.
- The increase of packet size may increase
packet loss, so it could be better to have a
number of tunnels.
- Asymptotic behaviour.
CCNC January 9-11, 2011. Las Vegas
Influence of the Distribution of TCRTP Multiplexed flows on VoIP

43. Presentación
Jose Saldana
Jenifer Murillo
Julián Fernández Navajas
G RUPO DE
T ECNOLOGÍAS DE LAS
COMUNICACIONES
CPS - University of Zaragoza, Spain
José Ruiz Mas
Eduardo Viruete Navarro
José I. Aznar