Can We Multiplex ACKs without Harming the Performance of TCP?
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The document presents research on the impact of multiplexing ACK packets on TCP performance during high-volume video traffic. Through simulations, it shows that while multiplexing can lead to significant bandwidth savings, there may be a corresponding reduction in throughput when optimized flows share a common bottleneck. The authors suggest further study to balance the trade-off between bandwidth efficiency and throughput loss.
![Tests and Results
Bandwidth [Mbps]
Throughput (RTT = 80 ms)
10
8
6
4
2
0
30
35
40
45
50
55
60
55
60
simulated time [s]
Bandwidth [Mbps]
Throughput (RTT = 80 ms, mux period 50 ms)
10
8
6
4
2
0
30
35
40
45
50
simulated time [s]
Can We Multiplex ACKs without Harming the Performance of TCP? - CCNC 2014](https://image.slidesharecdn.com/berlinccnc2014presentationv3-140115101432-phpapp02/85/Can-We-Multiplex-ACKs-without-Harming-the-Performance-of-TCP-12-320.jpg)
![Tests and Results
Bandwidth [Mbps]
Throughput (RTT = 80 ms)
10
8
6
avg 9.24 Mbps
window reset
every ~7 sec
4
2
0
30
35
40
45
50
55
60
simulated time [s]
Bandwidth [Mbps]
ACKs arrive
Throughput (RTT = 80 ms, mux period 50 ms) in bursts
10
8
6
window reset
every ~9,5 sec
4
2
avg 8.04 Mbps
(12% reduction)
0
30
35
40
45
50
simulated time [s]
Can We Multiplex ACKs without Harming the Performance of TCP? - CCNC 2014
55
60](https://image.slidesharecdn.com/berlinccnc2014presentationv3-140115101432-phpapp02/85/Can-We-Multiplex-ACKs-without-Harming-the-Performance-of-TCP-13-320.jpg)
![Tests and Results
Window size
250
no PE
PE=50ms
Window size
200
150
100
50
0
0
10
20
30
40
50
60
simulation time [s]
Can We Multiplex ACKs without Harming the Performance of TCP? - CCNC 2014
70
80](https://image.slidesharecdn.com/berlinccnc2014presentationv3-140115101432-phpapp02/85/Can-We-Multiplex-ACKs-without-Harming-the-Performance-of-TCP-14-320.jpg)
![Tests and Results
Results: Throughput difference between
multiplexed and non-multiplexed flows
Multiplexing Period PE [ms]
TCP
5
10
15
20
25
Tahoe
4.91 %
10.05 %
31.67 %
7.88 %
49.74 %
Reno
5.95 %
17.78 %
48.62 %
24.29 %
61.92 %
New
Reno
4.82 %
12.95 %
30.52 %
16.70 %
52.87 %
SACK
2.27 %
12.70 %
20.62 %
14.75 %
50.90 %
Can We Multiplex ACKs without Harming the Performance of TCP? - CCNC 2014](https://image.slidesharecdn.com/berlinccnc2014presentationv3-140115101432-phpapp02/85/Can-We-Multiplex-ACKs-without-Harming-the-Performance-of-TCP-17-320.jpg)
![Tests and Results
Results: PE=5 ms
With Throughput difference between
the difference
multiplexed and non-multiplexed flows
is small
Multiplexing Period PE [ms]
TCP
5
10
15
20
25
Tahoe
4.91 %
10.05 %
31.67 %
7.88 %
49.74 %
Reno
5.95 %
17.78 %
48.62 %
24.29 %
61.92 %
New
Reno
4.82 %
12.95 %
30.52 %
16.70 %
52.87 %
SACK
2.27 %
12.70 %
20.62 %
14.75 %
50.90 %
Can We Multiplex ACKs without Harming the Performance of TCP? - CCNC 2014](https://image.slidesharecdn.com/berlinccnc2014presentationv3-140115101432-phpapp02/85/Can-We-Multiplex-ACKs-without-Harming-the-Performance-of-TCP-18-320.jpg)
![Tests and Results
Results: Throughputms
With PE=10 difference between
the difference
multiplexed and non-multiplexed flows
becomes higher
Multiplexing Period PE [ms]
TCP
5
10
15
20
25
Tahoe
4.91 %
10.05 %
31.67 %
7.88 %
49.74 %
Reno
5.95 %
17.78 %
48.62 %
24.29 %
61.92 %
New
Reno
4.82 %
12.95 %
30.52 %
16.70 %
52.87 %
SACK
2.27 %
12.70 %
20.62 %
14.75 %
50.90 %
Can We Multiplex ACKs without Harming the Performance of TCP? - CCNC 2014](https://image.slidesharecdn.com/berlinccnc2014presentationv3-140115101432-phpapp02/85/Can-We-Multiplex-ACKs-without-Harming-the-Performance-of-TCP-19-320.jpg)
![Tests and Results
Results: Throughput difference between
Below 10 ms the
difference may
multiplexed and non-multiplexed flows
become
unacceptable
Multiplexing Period PE [ms]
TCP
5
10
15
20
25
Tahoe
4.91 %
10.05 %
31.67 %
7.88 %
49.74 %
Reno
5.95 %
17.78 %
48.62 %
24.29 %
61.92 %
New
Reno
4.82 %
12.95 %
30.52 %
16.70 %
52.87 %
SACK
2.27 %
12.70 %
20.62 %
14.75 %
50.90 %
Can We Multiplex ACKs without Harming the Performance of TCP? - CCNC 2014](https://image.slidesharecdn.com/berlinccnc2014presentationv3-140115101432-phpapp02/85/Can-We-Multiplex-ACKs-without-Harming-the-Performance-of-TCP-20-320.jpg)
![Tests and Results
Throughput (SACK)
no PE
PE=5 ms
10
Throughput [Mbps]
8
6
4
2
0
900
910
920
930
940
950
960
970
980
Simulation time
Can We Multiplex ACKs without Harming the Performance of TCP? - CCNC 2014
990
1000](https://image.slidesharecdn.com/berlinccnc2014presentationv3-140115101432-phpapp02/85/Can-We-Multiplex-ACKs-without-Harming-the-Performance-of-TCP-21-320.jpg)
![Tests and Results
Throughput (Reno)
no PE
PE=25 ms
10
Throughput [Mbps]
8
6
4
2
0
900
910
920
930
940
950
960
970
980
Simulation time
Can We Multiplex ACKs without Harming the Performance of TCP? - CCNC 2014
990
1000](https://image.slidesharecdn.com/berlinccnc2014presentationv3-140115101432-phpapp02/85/Can-We-Multiplex-ACKs-without-Harming-the-Performance-of-TCP-22-320.jpg)
Can We Multiplex ACKs without Harming the Performance of TCP?
- 1. CCNC 2014, The 11Th Annual IEEE Consumer Communications & Networking Conference January 10-13 Las Vegas, Nevada USA Can We Multiplex ACKs without Harming the Performance of TCP? Jose Saldana, Julián Fernández-Navajas, José Ruiz-Mas
- 2. Index 1. Introduction 2. Tests and results 3. Conclusions Can We Multiplex ACKs without Harming the Performance of TCP? - CCNC 2014
- 3. Index 1. Introduction 2. Tests and results 3. Conclusions Can We Multiplex ACKs without Harming the Performance of TCP? - CCNC 2014
- 4. Introduction Increase of emerging real-time services They use small packets This is modifying the traffic mix present on the Internet Inefficiency of the packets IPv6 makes the problem even worse VoIP packets Can We Multiplex ACKs without Harming the Performance of TCP? - CCNC 2014
- 5. Introduction TCRTP (RFC4170) improves the efficiency of VoIP. It uses three layers: Header compression Multiplexing Tunneling IP network . . . MUX RTP DEMUX RTP multiplexing Can We Multiplex ACKs without Harming the Performance of TCP? - CCNC 2014 RTP . . .
- 6. Introduction Advantage: Bandwidth and pps savings At the cost of an additional multiplexing delay Native VoIP traffic ... Inter-pkt time Inter- pkt time Inter-pkt time ... ... ... ... ... Optimized traffic ... Can We Multiplex ACKs without Harming the Performance of TCP? - CCNC 2014 ...
- 7. Introduction TCM-TF*: Proposal for multiplexing other traffic flows, including UDP (non-RTP) and TCP payload payload RTP payload payload RTP UDP TCP UDP UDP IP IP IP IP ECRTP Compression layer No compr. / ROHC / IPHC / ECRTP PPPMux Multiplexing layer PPPMux / Other L2TP Tunneling layer GRE / L2TP MPLS IP a) TCRTP Network Protocol IP b) TCMTF *draft-saldana-tsvwg-tcmtf-05 Can We Multiplex ACKs without Harming the Performance of TCP? - CCNC 2014
- 8. Introduction TCP video traffic: 69% of all consumer Internet traffic in 2017. When downloading a video, a computer may generate some hundreds of ACKs per second, during some tens of seconds. In some scenarios (e.g. the aggregation network of an operator) high numbers of long-term flows of ACKs share a common path. Header compression ratio of ACKs: from 40 to 7 or 8 bytes (savings of 80%). Can We Multiplex ACKs without Harming the Performance of TCP? - CCNC 2014
- 9. Introduction Is it a good idea to compress and multiplex these flows? Would the multiplexing delay degrade the performance of TCP? Sawtooth-shaped delay PE Added delay PE time Can We Multiplex ACKs without Harming the Performance of TCP? - CCNC 2014
- 10. Index 1. Introduction 2. Tests and results 3. Conclusions Can We Multiplex ACKs without Harming the Performance of TCP? - CCNC 2014
- 11. Tests and Results Dumbbell scenario in ns2 A sawtooth-shaped delay is added to the ACKs B-B’ A O ACK FTP N B P ACK mux (PE) A’ M FTP B’ What is the effect? We use TCP Tahoe (the most basic one) in order to more clearly see the effect First tests: separate A-A’ and B-B’ Can We Multiplex ACKs without Harming the Performance of TCP? - CCNC 2014
- 12. Tests and Results Bandwidth [Mbps] Throughput (RTT = 80 ms) 10 8 6 4 2 0 30 35 40 45 50 55 60 55 60 simulated time [s] Bandwidth [Mbps] Throughput (RTT = 80 ms, mux period 50 ms) 10 8 6 4 2 0 30 35 40 45 50 simulated time [s] Can We Multiplex ACKs without Harming the Performance of TCP? - CCNC 2014
- 13. Tests and Results Bandwidth [Mbps] Throughput (RTT = 80 ms) 10 8 6 avg 9.24 Mbps window reset every ~7 sec 4 2 0 30 35 40 45 50 55 60 simulated time [s] Bandwidth [Mbps] ACKs arrive Throughput (RTT = 80 ms, mux period 50 ms) in bursts 10 8 6 window reset every ~9,5 sec 4 2 avg 8.04 Mbps (12% reduction) 0 30 35 40 45 50 simulated time [s] Can We Multiplex ACKs without Harming the Performance of TCP? - CCNC 2014 55 60
- 14. Tests and Results Window size 250 no PE PE=50ms Window size 200 150 100 50 0 0 10 20 30 40 50 60 simulation time [s] Can We Multiplex ACKs without Harming the Performance of TCP? - CCNC 2014 70 80
- 15. Tests and Results Window evolution. One period 140 no PE PE=50ms 120 Window size 100 Slow start ends later 80 60 Window size increases more slowly 40 20 0 Can We Multiplex ACKs without Harming the Performance of TCP? - CCNC 2014 The period between window resets increases
- 16. Tests and Results Second tests: A-A’ and B-B’ share the bottleneck Are multiplexed flows in clear disadvantage? We will use four different TCP variants: Tahoe FTP A O ACK A’ Reno N M New Reno B FTP P ACK mux (PE) B’ SACK Results: Throughput difference between multiplexed and non-multiplexed flows Can We Multiplex ACKs without Harming the Performance of TCP? - CCNC 2014
- 17. Tests and Results Results: Throughput difference between multiplexed and non-multiplexed flows Multiplexing Period PE [ms] TCP 5 10 15 20 25 Tahoe 4.91 % 10.05 % 31.67 % 7.88 % 49.74 % Reno 5.95 % 17.78 % 48.62 % 24.29 % 61.92 % New Reno 4.82 % 12.95 % 30.52 % 16.70 % 52.87 % SACK 2.27 % 12.70 % 20.62 % 14.75 % 50.90 % Can We Multiplex ACKs without Harming the Performance of TCP? - CCNC 2014
- 18. Tests and Results Results: PE=5 ms With Throughput difference between the difference multiplexed and non-multiplexed flows is small Multiplexing Period PE [ms] TCP 5 10 15 20 25 Tahoe 4.91 % 10.05 % 31.67 % 7.88 % 49.74 % Reno 5.95 % 17.78 % 48.62 % 24.29 % 61.92 % New Reno 4.82 % 12.95 % 30.52 % 16.70 % 52.87 % SACK 2.27 % 12.70 % 20.62 % 14.75 % 50.90 % Can We Multiplex ACKs without Harming the Performance of TCP? - CCNC 2014
- 19. Tests and Results Results: Throughputms With PE=10 difference between the difference multiplexed and non-multiplexed flows becomes higher Multiplexing Period PE [ms] TCP 5 10 15 20 25 Tahoe 4.91 % 10.05 % 31.67 % 7.88 % 49.74 % Reno 5.95 % 17.78 % 48.62 % 24.29 % 61.92 % New Reno 4.82 % 12.95 % 30.52 % 16.70 % 52.87 % SACK 2.27 % 12.70 % 20.62 % 14.75 % 50.90 % Can We Multiplex ACKs without Harming the Performance of TCP? - CCNC 2014
- 20. Tests and Results Results: Throughput difference between Below 10 ms the difference may multiplexed and non-multiplexed flows become unacceptable Multiplexing Period PE [ms] TCP 5 10 15 20 25 Tahoe 4.91 % 10.05 % 31.67 % 7.88 % 49.74 % Reno 5.95 % 17.78 % 48.62 % 24.29 % 61.92 % New Reno 4.82 % 12.95 % 30.52 % 16.70 % 52.87 % SACK 2.27 % 12.70 % 20.62 % 14.75 % 50.90 % Can We Multiplex ACKs without Harming the Performance of TCP? - CCNC 2014
- 21. Tests and Results Throughput (SACK) no PE PE=5 ms 10 Throughput [Mbps] 8 6 4 2 0 900 910 920 930 940 950 960 970 980 Simulation time Can We Multiplex ACKs without Harming the Performance of TCP? - CCNC 2014 990 1000
- 22. Tests and Results Throughput (Reno) no PE PE=25 ms 10 Throughput [Mbps] 8 6 4 2 0 900 910 920 930 940 950 960 970 980 Simulation time Can We Multiplex ACKs without Harming the Performance of TCP? - CCNC 2014 990 1000
- 23. Index 1. Introduction 2. Tests and results 3. Conclusions Can We Multiplex ACKs without Harming the Performance of TCP? - CCNC 2014
- 24. Conclusions Suitability of traffic optimization, based on header compression and multiplexing, to the flows of ACKs The expected bandwidth savings are huge because of the absence of payload Counterpart: throughput reduction when an optimized flow shares a bottleneck with a nonoptimized one The impairments can be maintained in tolerable limits, by setting an upper bound on the period Further study this trade-off between bandwidth saving and throughput reduction Can We Multiplex ACKs without Harming the Performance of TCP? - CCNC 2014
- 25. Thank you very much! Jose Saldana, Julián Fernández-Navajas, José Ruiz-Mas