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.
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The Effect of Multiplexing Delay on MMORPG TCP Traffic Flows
1.
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
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
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
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
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
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