Effect of Competing TCP Traffic on Interactive Real-Time - PowerPoint PPT Presentation

Effect of Competing TCP Traffic on Interactive Real-Time Communication arvinen ∗ , Binoy Chemmagate ∗ , Aaron Yi Ding ∗ , Laila Ilpo J¨ Daniel ∗ , Markus Isom¨ aki † , Jouni Korhonen ‡ , and Markku Kojo ∗ † Nokia ∗ Department of Computer Science ‡ Nokia Siemens Networks University of Helsinki (moved to Renesas Mobile) March 18, 2013 @ PAM 2013

Outline 1 Introduction 2 Test Arrangements 3 Results 4 Conclusions March 18, 2013 @ PAM 2013 2

Introduction Mobile mixed use devices, so called smartphones, have become very common Using Voice over IP (VoIP) in contrast to traditional dedicated voice calls attracts How well interactive VoIP works in presence of competing TCP traffic? Especially interesting is Web traffic like workload with transients and parallel TCP connections Test the effect of proposed TCP initial window change March 18, 2013 @ PAM 2013 3

Test Arrangements Workloads Emulated interactive audio (CBR, 16kbps payload) alone Emulated interactive audio + bulk TCP connection Emulated interactive audio + emulated Web traffic Parallel flows used, worst-case assumption Real HSPA (3.5G) network, fixed server connected over the Internet A few test iterations with wireless issues causing duplicates, reordering, many consecutive losses, and very long delay spikes were rerun With interactive audio content, limited jitter buffer March 18, 2013 @ PAM 2013 4

TCP Initial Window (IW) IW specifies the largest burst of segments that can be sent at once when a TCP connection becomes established Current standard IW is 3 MSS segments (from 2002) IETF proposal to increase TCP IW from 3 to 10 (draft-ietf-tcpm-initcwnd, published soon as Experimental RFC) IW is sent as back-to-back packets, not ACK clocked Limited congestion control for IW (if SYN loss occurs) More challenging for active queue management (AQM) to respond compared with later TCP phases Traces suggest larger than IW3 is already being used (e.g., Google, Microsoft) March 18, 2013 @ PAM 2013 5

Baseline Results with Audio Only 1 Observations One-way delay 0.8 is good enough for interactive audio 0.6 conversation CDF Median 18.0 0.4 msec Maximum 70.4 msec 0.2 Very few samples > 40 0 msec 0 0.02 0.04 0.06 0.08 0.1 One-way delay (s) March 18, 2013 @ PAM 2013 6

Results with Audio + Bulk Data TCP Transfer 1 Observations Deep buffering 0.8 causes delay increase Interactivity is 0.6 ruined by the CDF excessive delay 0.4 A few samples in the high end might be due 0.2 to wireless link problems (but hard to know 0 0 1 2 3 4 5 which) One-way delay (s) March 18, 2013 @ PAM 2013 7

Results with Audio + Emulated Web Traffic 1 Notes Only samples 0.8 overlapping with TCP included 0.6 1 or 2 TCP CDF flows with IW3 0.4 quite ok, 6 flows not so Clearly larger Audio+1 TCP flows, IW=3 0.2 Audio+1 TCP flows, IW=10 delay with Audio+2 TCP flows, IW=3 Audio+2 TCP flows, IW=10 IW10 than IW3 Audio+6 TCP flows, IW=3 Audio+6 TCP flows, IW=10 0 0 0.2 0.4 0.6 0.8 1 Audio flow one-way delay (s) March 18, 2013 @ PAM 2013 8

Jitter Filter and Loss Period Level Jitter filter “drops” late arriving audio packet Mimics time-bound playback of media Base delay based on previous 2s prior to TCP flows arrival Not lost physically, only delayed too much to be useful Loss period level Loss period level is based on loss periods [RFC3357] the codec encounters due to consecutive packets being “dropped” Value Loss Period Level Description 0 no loss 1 20 ms gap in the stream, no adjacent packet lost 2 40-60 ms of the stream was lost 3 80-100 ms of the stream was lost 4 120-180 ms of the stream was lost 5 200+ ms of the stream was lost March 18, 2013 @ PAM 2013 9

Loss Rate after Applying Jitter Filter 0.9 IW3 IW10 0.8 0.7 Loss rate (median, 25th-75th percentile) 0.6 0.5 0.4 0.3 0.2 0.1 0 4 6 8 1 1 2 4 6 8 1 1 2 4 6 8 1 1 2 4 6 8 1 1 2 4 6 8 1 1 2 4 6 8 1 1 2 0 0 0 0 5 0 0 0 0 0 5 0 0 0 0 0 5 0 0 0 0 0 5 0 0 0 0 0 5 0 0 0 0 0 5 0 m m m 0 0 0 m m m 0 0 0 m m m 0 0 0 m m m 0 0 0 m m m 0 0 0 m m m 0 0 0 m m m m m m m m m m m m m m m m m m s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s Audio+1 short TCP flow Audio+2 short TCP flows Audio+6 short TCP flows March 18, 2013 @ PAM 2013 10

Loss Period Level, Audio + Web Traffic, 40 ms Jitter Buf IW3 IW10 Loss Period Level for Audio with 1 short TCP flow, Jitter Buffer of 40 ms Loss Period Level for Audio with 1 short TCP flow, Jitter Buffer of 40 ms Best - 0 Best - 0 1.2 1.2 1 1 2 2 1.1 1.1 3 3 1 4 1 4 Worst - 5 Worst - 5 Number of packets (normalized) Number of packets (normalized) 0.9 0.9 0.8 0.8 0.7 0.7 0.6 0.6 0.5 0.5 0.4 0.4 0.3 0.3 0.2 0.2 0.1 0.1 0 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 Time (s) Time (s) IP Packet Delay Variation confirmed that worst delays spikes occurred during initial window March 18, 2013 @ PAM 2013 11

Conclusions Packets of the media flow are heavily delayed when competing TCP is present Using parallel TCP flows with IW3 causes significant delay for the media flow Worst effects occur during TCP initial window transmissions IW10 is much worse than IW3 for the competing media flow March 18, 2013 @ PAM 2013 12

Backup Slides March 18, 2013 @ PAM 2013 13

Backup Slides - Paper Figures Audio+2 TCP flows, IW3 Audio+6 TCP flows, IW3 Loss Period Level for Audio with 2 short TCP flows, Jitter Buffer of 40 ms Loss Period Level for Audio with 6 short TCP flows, Jitter Buffer of 40 ms 1.2 Best - 0 1.2 Best - 0 1 1 2 2 1.1 1.1 3 3 4 4 1 1 Worst - 5 Worst - 5 Number of packets (normalized) Number of packets (normalized) 0.9 0.9 0.8 0.8 0.7 0.7 0.6 0.6 0.5 0.5 0.4 0.4 0.3 0.3 0.2 0.2 0.1 0.1 0 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 Time (s) Time (s) March 18, 2013 @ PAM 2013 14

Backup Slides - Paper Figures IW3 IW10 1.2 200ms 1.2 200ms 150ms 150ms 100ms 100ms 1.1 1.1 80ms 80ms 60ms 60ms 1 1 40ms 40ms Number of packets (normalized) Number of packets (normalized) 0.9 0.9 0.8 0.8 0.7 0.7 0.6 0.6 0.5 0.5 0.4 0.4 0.3 0.3 0.2 0.2 0.1 0.1 0 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 Time (s) Time (s) March 18, 2013 @ PAM 2013 15

Loss Period Level, Audio + Web Traffic, 100 ms Jitter Buf IW3 IW10 Loss Period Level for Audio with 1 short TCP flow, Jitter Buffer of 100 ms Loss Period Level for Audio with 1 short TCP flow, Jitter Buffer of 100 ms 1.2 Best - 0 1.2 Best - 0 1 1 1.1 2 1.1 2 3 3 4 4 1 1 Worst - 5 Worst - 5 Number of packets (normalized) Number of packets (normalized) 0.9 0.9 0.8 0.8 0.7 0.7 0.6 0.6 0.5 0.5 0.4 0.4 0.3 0.3 0.2 0.2 0.1 0.1 0 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 Time (s) Time (s) March 18, 2013 @ PAM 2013 16

Loss Period Level, Audio + Web Traffic, 100 ms Jitter Buf Audio+2 TCP flows, IW3 Audio+6 TCP flows, IW3 Loss Period Level for Audio with 2 short TCP flows, Jitter Buffer of 100 ms Loss Period Level for Audio with 6 short TCP flows, Jitter Buffer of 100 ms 1.2 Best - 0 1.2 Best - 0 1 1 2 2 1.1 1.1 3 3 4 4 1 1 Worst - 5 Worst - 5 Number of packets (normalized) Number of packets (normalized) 0.9 0.9 0.8 0.8 0.7 0.7 0.6 0.6 0.5 0.5 0.4 0.4 0.3 0.3 0.2 0.2 0.1 0.1 0 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 Time (s) Time (s) March 18, 2013 @ PAM 2013 17