Flowgrind A TCP Traffic Generator for Developers Arnd Hannemann <arnd.hannemann@credativ.de> 05.10.2016 Arnd Hannemann credativ GmbH 1 / 29
Overview Introduction Flowgrind Architecture Example measurements Summary Arnd Hannemann credativ GmbH 2 / 29
Overview Introduction Motivation Flowgrind Architecture Example measurements Summary Arnd Hannemann credativ GmbH 3 / 29
Measuring network performance Tool requirements Wired Internet Backbone ◮ Background: Wireless Mesh Networks Backbone ◮ Creating load anywhere in the network Mesh Gateways ◮ Measuring TCP performance between Backbone Mesh Routers any two nodes ◮ Testing TCP variants Routing Non-routing Mesh Clients Mesh Clients ◮ Extensive list of TCP metrics Wired Wirless Mesh Wireless Access-Point Connection Connection Connection ◮ Separation of control and test traffic Arnd Hannemann credativ GmbH 4 / 29
Related works Feature Iperf Iperf3 Netperf Thrulay TTCP NUTTCP TCP � � � � � � UDP � � � � � � SCTP – � � – – – Other protocols – – � – – – Kernel statistics – – – – � � Interval reports � � � � – � Concurrent tests against same hosts – � � � � � Concurrent tests against different hosts – � – – – – Distributed tests – – – – – � Bidirectional test connections – – – – – � Test scheduling – – – – – – Traffic generation – – – – – � Control/test data separation – – – – – � Arnd Hannemann credativ GmbH 5 / 29
Motivation for a new tool Shortcomings of existing tools ◮ Client-server architecture ⇒ hard to generate cross-traffic ◮ Separation of data/control traffic Arnd Hannemann credativ GmbH 6 / 29
Overview Introduction Flowgrind Architecture Architecture Client-server architecture RPC Example measurements Summary Arnd Hannemann credativ GmbH 7 / 29
Flowgrind Flowgrind ◮ Is a distributed network performance measurement tool ◮ Focuses on TCP testing/debugging ◮ Knobs to test TCP variants against each other ◮ Dump packet headers with libpcap ◮ Gathers TCP statistics from kernel (Linux/FreeBSD) Arnd Hannemann credativ GmbH 8 / 29
Terminology in Flowgrind Flows Wired Internet ◮ One data connection for each flow Backbone ◮ Flows have a source and a Backbone destination endpoint Mesh Gateways ◮ Test data can be sent in either Backbone Mesh Routers direction ◮ Scheduling, flows can run Routing Non-routing Mesh Clients Mesh Clients sequentially, in parallel or can Wired Wirless Mesh Wireless Access-Point Connection Connection Connection overlap RPC Connection Test Connection Flowgrind Controller Flowgrind Daemon ◮ Individual parameters for each flow Arnd Hannemann credativ GmbH 9 / 29
Problems with client-server architecture Wireless multi-hop network Arnd Hannemann credativ GmbH 10 / 29
Problems with client-server architecture Wireless multi-hop network Client Server Arnd Hannemann credativ GmbH 10 / 29
Problems with client-server architecture Wireless multi-hop network Client Server Arnd Hannemann credativ GmbH 10 / 29
Client-server architecture Overview ◮ Tools like iperf: split into client and server ◮ Flows can only be established between a client and a server, not between servers ◮ Architecture implemented in older versions of Flowgrind Problems with client-server architecture ◮ For multiple clients: external synchronization of test start is needed ◮ Potential different data handling in client and server (e.g. Thrulay) Arnd Hannemann credativ GmbH 11 / 29
Distributed architecture Controller (flowgrind) Wired Internet Backbone ◮ Parses the test parameters ◮ Configures all involved daemons Backbone Mesh Gateways ◮ Presents the results Backbone Mesh Routers Daemon (flowgrindd) ◮ Started on every test node Routing Non-routing Mesh Clients Mesh Clients Wired Wirless Mesh Wireless Access-Point ◮ Performs actual tests Connection Connection Connection RPC Connection Test Connection ◮ Measures performance metrics Flowgrind Controller Flowgrind Daemon Arnd Hannemann credativ GmbH 12 / 29
Remote Procedure Calls (RPC) RPC in Flowgrind ◮ Uses XML-RPC ◮ All calls initiated by controller, no RPC between daemons ◮ Can employ different IP address / interface to separate control and test traffic During a test ◮ Controller periodically queries all daemons for interval results ◮ Formats and prints results upon receiving them Arnd Hannemann credativ GmbH 13 / 29
Overview Introduction Flowgrind Architecture Example measurements Wireless Multi-Hop Network with Cross Traffic AWS example: congestion control algorithms Summary Arnd Hannemann credativ GmbH 14 / 29
Cross-Traffic in a Wireless Multihop Network Test scenario ◮ Measurement performed on testbed ◮ Two flows between two unique pairs of nodes ◮ Routes overlap, one bottleneck link ◮ Second flow started after a delay, stopping earlier Arnd Hannemann credativ GmbH 15 / 29
Topology A E C D Bottleneck link B F ◮ Flow 1 between nodes A and E ◮ Flow 2 between nodes B and F Arnd Hannemann credativ GmbH 16 / 29
Topology Arnd Hannemann credativ GmbH 17 / 29
WMN example: Flowgrind arguments flowgrind -n 2 -i 5 -O b=TCP_CONG_MODULE=reno -F 0 -H s=wlan0.mrouter16/mrouter16,d=wlan0.mrouter8/mrouter8 -T b=900 -F 1 -H s=wlan0.mrouter17/mrouter17,d=wlan0.mrouter9/mrouter9 -T b=300 -Y b=300 Arnd Hannemann credativ GmbH 18 / 29
WMN example: Output # ID begin end through RTT RTT RTT IAT IAT IAT # ID [s] [s] [Mbit] min avg max min avg max S 0 375.011 380.004 0.288782 12916.913 14135.647 15035.946 30.069 183.367 969.321 R 0 375.008 380.001 0.446299 5378.736 7304.811 8322.028 12.080 138.115 1206.780 S 1 375.008 380.009 0.157245 1284.537 2348.903 3978.513 70.058 418.893 2341.099 R 1 375.009 380.010 0.026211 11766.836 11766.836 11766.836 2919.213 2919.213 2919.213 S 0 380.004 385.000 0.288551 13335.203 14015.217 15029.046 63.087 269.419 1427.218 R 0 380.001 385.003 0.406170 7380.097 8201.946 9628.294 16.043 191.917 987.361 cwnd ssth uack sack lost retr fack reor rtt rttvar rto castate mss mtu status # # # # # # 83.000 59 83 0 0 0 0 3 3276.500 50.000 4940.000 open 1448 1500 (n/n) 128.000 107 128 0 0 0 0 3 2879.000 6.000 4252.000 open 1448 1500 (n/n) 44.000 7 44 0 0 0 0 3 2880.500 256.000 4208.000 open 1448 1500 (n/n) 8.000 5 8 0 0 0 0 3 2832.500 149.000 3848.000 open 1448 1500 (n/n) 86.000 59 86 0 0 0 0 3 3654.500 190.000 5072.000 open 1448 1500 (n/n) 142.000 107 142 0 0 0 0 3 3388.500 65.000 4520.000 open 1448 1500 (n/n) Arnd Hannemann credativ GmbH 19 / 29
WMN example: Goodput 1 . 6 Flow 0 from node 16 to 8 Flow 1 from node 17 to 9 1 . 4 1 . 2 1 Goodput [ Mb / s ] 0 . 8 0 . 6 0 . 4 0 . 2 0 0 100 200 300 400 500 600 700 800 900 Time [s] Arnd Hannemann credativ GmbH 20 / 29
WMN example: Congestion Window 400 Congestion Window Slowstart threshold 350 300 Window size [segments] 250 200 150 100 50 0 0 100 200 300 400 500 600 700 800 900 Time [s] Arnd Hannemann credativ GmbH 21 / 29
Test of congestion control algorithms in AWS Test scenario ◮ Measurement performed in VPC ◮ Four flows between a pair of nodes ◮ Four different congestion control algorithms Arnd Hannemann credativ GmbH 22 / 29
AWS: Flowgrind arguments flowgrind -n 4 -H s=172.30.0.122,d=172.30.0.123 -T s=900 -F 0 -O s=TCP_CONGESTION=yeah -F 1 -O s=TCP_CONGESTION=cubic -F 2 -O s=TCP_CONGESTION=highspeed -F 3 -O s=TCP_CONGESTION=htcp Arnd Hannemann credativ GmbH 23 / 29
AWS example: Output # ID 0 S: 172.30.0.138 (Linux 4.6.0-1-amd64), random seed: 1611955119, sbuf = 12582912/0 [B] (real/req), rbuf = 12582912/0 [B] (real/req), SMSS = 8949 [B], PMTU = 9001 [B], Interface MTU = 9001 (unknown) [B], CC = yeah, duration = 900.003/900.000 [s] (real/req), through = 5.758049/0.000000 [Mbit/s] (out/in), request blocks = 79075/0 [#] (out/in) # ID 0 D: 172.30.0.139 (Linux 4.6.0-1-amd64), random seed: 1611955119, sbuf = 12582912/0 [B] (real/req), rbuf = 12582912/0 [B] (real/req), SMSS = 1448 [B], PMTU = 9001 [B], Interface MTU = 9001 (unknown) [B], through = 0.000000/5.684553 [Mbit/s] (out/in), request blocks = 0/78065 [#] (out/in), IAT = 0.004/11.529/281.197 [ms] (min/avg/max), delay = 18.708/11481.539/27539.894 [ms] (min/avg/max) ... Arnd Hannemann credativ GmbH 24 / 29
AWS example: Goodput 500 500 YeAH-TCP CUBIC TCP Highspeed TCP H-TCP 400 400 Goodput in Mb s − 1 300 300 200 200 100 100 0 0 0 100 200 300 400 500 600 700 800 900 Time in s Arnd Hannemann credativ GmbH 25 / 29
Overview Introduction Flowgrind Architecture Example measurements Summary Arnd Hannemann credativ GmbH 26 / 29
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