Jose Saldana, "The Effect of Multiplexing Delay on MMORPG TCP Traffic Flows," Consumer Communications and Networking Conference, CCNC 2014. Las Vegas, January 10, 2014, pp 447-452. ISBN 978-1-4799-2356-4.

2. CCNC 2014, The 11Th Annual IEEE Consumer Communications & Networking Conference
January 10-13 Las Vegas, Nevada USA
The Effect of Multiplexing Delay
on MMORPG TCP Traffic Flows
Jose Saldana

3. Index
1.
2.
3.
4.
5.
Introduction
Traffic optimization method
Simulations setup
Tests and results
Conclusions
The Effect of Multiplexing Delay on MMORPG TCP Traffic Flows. CCNC 2014

4. Index
1.
2.
3.
4.
5.
Introduction
Traffic optimization method
Simulations setup
Tests and results
Conclusions
The Effect of Multiplexing Delay on MMORPG TCP Traffic Flows. CCNC 2014

5. Introduction
 Small-packet services
 Real-time: High interactivity requirements
 VoIP
 Online games (some of them use TCP)
 Non real-time: M2M, signaling, etc.
The Effect of Multiplexing Delay on MMORPG TCP Traffic Flows. CCNC 2014

6. Introduction
 High header-to-payload ratio. Low efficiency
 VoIP
 FPS game
 MMORPG game
 M2M
The Effect of Multiplexing Delay on MMORPG TCP Traffic Flows. CCNC 2014

7. Introduction
 TCM-TF (Tunneling Compressed Multiplexed
Traffic Flows) is a proposal for improving the
efficiency of these flows by:
 Header compression
 Multiplexing
 Tunneling
payload
payload
payload
RTP
TCP
UDP
UDP
IP
IP
IP
Real-time traffic
No compr. / ROHC / IPHC / ECRTP
PPPMux / Other
Multiplexing layer
GRE / L2TP / Other
Tunneling layer
IP
 30% to 55% saving
 Status: IETF draft
Compression layer
Network Protocol
The Effect of Multiplexing Delay on MMORPG TCP Traffic Flows. CCNC 2014

8. Introduction
 Tradeoff. Advantages:
 Bandwidth savings
 pps reduction (energy savings)
 At the cost of
 Added processing requirements
 Additional multiplexing delay
The Effect of Multiplexing Delay on MMORPG TCP Traffic Flows. CCNC 2014

9. Introduction
 VoIP: Multiplexing delay < IPT
Native VoIP
traffic
...
Inter-pkt time
Inter-pkt time
Inter-pkt time
...
...
...
...
...
Optimized
traffic
...
...
 Online games: We define a multiplexing period
Native game
traffic
...
Period
Period
Period
...
...
...
...
...
Optimized
traffic
...
The Effect of Multiplexing Delay on MMORPG TCP Traffic Flows. CCNC 2014
...

10. Introduction
 VoIP: Multiplexing delay < IPT
Native VoIP
traffic
...
Inter-pkt time
Inter-pkt time
Inter-pkt time
...
...
...
...
...
Optimized
traffic
...
...
 Online games: We define a multiplexing period
Native game
traffic
...
Period
Period
Period
...
...
...
...
...
Optimized
traffic
...
The Effect of Multiplexing Delay on MMORPG TCP Traffic Flows. CCNC 2014
...

11. Introduction
 Sawtooth-shaped delay
PE
Added
delay
PE
time
 For UDP traffic, it is just an additional jitter
 What is the effect of this on MMORPG TCP flows?
 We are modifying the RTT. Does this harm the
playability?
The Effect of Multiplexing Delay on MMORPG TCP Traffic Flows. CCNC 2014

12. Introduction
 We will study the effect of “sawtooth” delay
on the traffic of an MMORPG, i.e. a TCPbased game
 Application-limited TCP (different from
network-limited TCP)
 Some TCP mechanisms are not useful
The Effect of Multiplexing Delay on MMORPG TCP Traffic Flows. CCNC 2014

13. Introduction
 We will use the most popular MMORPG:
World of Warcraft
The Effect of Multiplexing Delay on MMORPG TCP Traffic Flows. CCNC 2014

14. Index
1.
2.
3.
4.
5.
Introduction
Traffic optimization method
Simulations setup
Tests and results
Conclusions
The Effect of Multiplexing Delay on MMORPG TCP Traffic Flows. CCNC 2014

15. Traffic optimization method
 Scenarios where a number of flows share a path:




The aggregation network of an operator
Tunnels between different offices of a company
Internet Café
Wireless or satellite connections
Native
Native
TCM
TCM
ingress
TCM
egress
Common network
segment
The Effect of Multiplexing Delay on MMORPG TCP Traffic Flows. CCNC 2014

16. Traffic optimization method
 TCM-TF optimization example
One IPv4/TCP packet 1500 bytes
η=1460/1500=97%
Five IPv4/UDP/RTP VoIP packets with two samples of 10 bytes
η=100/300=33%
One IPv4/UDP/RTP packet ofmultiplexing five two sample packets
One IPv4 TCMTF Packet VoIP with two samples of 10 bytes
η=100/161=62%
η=20/60=33%
saving
One IPv4/UDP server-to-client packet of Counter Strike with 9 players
η=160/188=85%
Four IPv4/UDP client-to-server packets of Counter Strike
η=61/89=68%
One IPv4/TCM packet multiplexing four client-to-server Counter Strike packets
saving
η=244/293=83%
TCP ACKs without payload
Seven IPv4/TCP client-to-server packets of World of Warcraft. E[P]=20bytes
η=80/360=22%
One IPv4/TCMTF packet multiplexing seven client-to-server WoW packets
η=80/175=45%
The Effect of Multiplexing Delay on MMORPG TCP Traffic Flows. CCNC 2014
saving

17. Traffic optimization method
 The effect of delay and jitter on subjective quality
MOS
5
4.5
Good quality
4
Medium
quality
MOS
3.5
3
delay=20ms
2.5
delay=40ms
2
Bad quality
delay=60ms
delay=80ms
1.5
delay=100ms
1
0
10
20
30
40
50
60
period (ms)
70
80
90
The Effect of Multiplexing Delay on MMORPG TCP Traffic Flows. CCNC 2014
100

18. Index
1.
2.
3.
4.
5.
Introduction
Traffic optimization method
Simulations setup
Tests and results
Conclusions
The Effect of Multiplexing Delay on MMORPG TCP Traffic Flows. CCNC 2014

19. Simulations setup
 Other simulation details
 ns2 FullTCP is used for WoW flows
 Push bit is set to 1, in order to send
packets as soon as generated
 By default, we use Questing traffic
 We can compare:
 Sawtooth-shaped delay with PE
 Fixed delay PE/2
The Effect of Multiplexing Delay on MMORPG TCP Traffic Flows. CCNC 2014

20. Tests and results
 Generation of WoW traffic in ns2
 A traffic model including five different activities:
Trading, Questing, Dungeons, Raiding, Player vs Player
 The model generates APDUs and IPTs
 Only client-to-server traffic is multiplexed
Game
clients
BG
A
B
P
Mux →
O
N
A’
M
C
The Effect of Multiplexing Delay on MMORPG TCP Traffic Flows. CCNC 2014
B’
C’
Game
servers
BG

21. Index
1.
2.
3.
4.
5.
Introduction
Traffic optimization method
Simulations setup
Tests and results
Conclusions
The Effect of Multiplexing Delay on MMORPG TCP Traffic Flows. CCNC 2014

22. Tests and results
 How does multiplexing delay impair the game traffic?
 Is fairness between multiplexed and non-multiplexed
flows granted?
 Figures of merit:
 Throughput is not interesting here
 RTT parameters estimated by TCP: smoothed RTT
and RTT variation
 Retransmission Overhead (RO):
bytes sent by TCP retransmissions
bytes generated by the application
The Effect of Multiplexing Delay on MMORPG TCP Traffic Flows. CCNC 2014

23. Tests and results
A. MMORPG vs FTP Traffic
 50 game flows multiplexed with PE
 50 game flows with an additional delay PE/2
 One FTP in the uplink (TCP SACK)
50 flows
A
50 flows
B
P
One FTP
uplink
A’
O
C
N
M
The Effect of Multiplexing Delay on MMORPG TCP Traffic Flows. CCNC 2014
B’
C’

24. Tests and results
Smoothed RTT
120
100
RTT variation
12
mux PE
fixed delay PE/2
10
8
RTT var [ms]
80
SRTT [ms]
mux PE
fixed delay PE/2
60
40
20
6
4
2
0
0
20
30
40
Multiplexing Period PE [ms]
10
50
 No effect on Smoothed RTT
 Low effect on RTT variation
 Significant effect on
Retransmission Overhead
 If PE grows, the effect gets
noticiable
20
30
40
Multiplexing Period PE [ms]
50
Retransmission Overhead
16%
14%
mux PE
fixed delay PE/2
12%
10%
Overhead
10
8%
6%
4%
2%
0%
10
20
30
40
Multiplexing Period PE [ms]
The Effect of Multiplexing Delay on MMORPG TCP Traffic Flows. CCNC 2014
50

25. Tests and results
B. MMORPG vs UDP Traffic
 50 game flows multiplexed with PE = 30ms
 50 game flows with an additional delay PE/2
 UDP traffic in the uplink
 MMORPG ~300kpbs. Congestion from 700kbps of UDP
50 flows
A
50 flows
B
P
UDP
uplink
A’
O
C
N
M
The Effect of Multiplexing Delay on MMORPG TCP Traffic Flows. CCNC 2014
B’
C’

26. Tests and results
Smoothed RTT
RTT variation
140
8
mux PE=30ms
120
7
fixed delay PE/2=15ms
6
100
5
80
RTT var [ms]
SRTT [ms]
mux PE=30ms
fixed delay PE/2=15ms
60
40
20
4
3
2
1
0
0
650
700
750
Background UDP traffic [kbps]
600
800
 No effect on Smoothed RTT
 The difference is significant in
RTT variation and
Retransmission Overhead
 Unfairness between players
when severe congestion appears
650
700
750
Background UDP traffic [kbps]
800
Retransmission Overhead
40%
35%
mux PE=30ms
fixed delay=15ms
30%
25%
Overhead
600
20%
15%
10%
5%
0%
600
650
700
750
Background UDP traffic [kbps]
The Effect of Multiplexing Delay on MMORPG TCP Traffic Flows. CCNC 2014
800

27. Tests and results
C. Effect of Mux depending on MMORPG activities
 MMORPG with different activities:
 50 game flows multiplexed with PE = 30ms
 50 game flows with an additional delay PE/2
 FTP in the uplink
50 flows
A
50 flows
B
P
One FTP
uplink
A’
O
C
N
M
The Effect of Multiplexing Delay on MMORPG TCP Traffic Flows. CCNC 2014
B’
C’

28. Tests and results
 The effect of multiplexing is more noticieable for the activities
with a higher interactivity, i.e. player vs player and raiding
 These activities generate a higher amount of pps, because a
number of players are involved in the fight
 More “peaceful” activities are better candidates to be muxed
Retransmission Overhead
30%
mux PE=30ms
25%
fixed delay PE/2=15ms
Overhead
20%
15%
10%
5%
0%
trading
questing
dungeons
Activity
raiding
player vs pl
The Effect of Multiplexing Delay on MMORPG TCP Traffic Flows. CCNC 2014

29. Index
1.
2.
3.
4.
5.
Introduction
Traffic optimization method
Simulations setup
Tests and results
Conclusions
The Effect of Multiplexing Delay on MMORPG TCP Traffic Flows. CCNC 2014

30. Conclusions
 Traffic optimization requires a multiplexing delay,
characterized as a delay and a jitter.
 Maximum values of the multiplexing period, so as
not to impair subjective quality.
 Recommended limits for the multiplexing period
have been found
 Multiplexing stresses the unfairness between flows if
network congestion is severe
 The effect of TCP background flows is less significant
 Multiplexing delay is more noticeable for the most
interactive activities
The Effect of Multiplexing Delay on MMORPG TCP Traffic Flows. CCNC 2014

31. Thank you very much!
Jose Saldana