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Mininet: Moving Forward
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Mininet: Moving Forward
- Mininet: Moving Forward Nikhil Handigol Brandon Heller Vimal Jeyakumar Bob Lantz [Team Mininet] ONRC Annual Day 2013
- Intro to Mininet 3
- TesKng an SDN Idea • Physical switches/hosts? • Testbed? • Simulator? • Emulator? Mininet
- Mininet Your SDN Command-‐Line Interface ScripKng API VM, naKve laptop, or naKve server To start up Mininet: > sudo mn
- Open-‐Source System w/AcKve User Community 6 • 1000+ users • AcKve mailing list • 700+ users, 200+ domains • 20 Google Summer of Code apps • GitHub pull requests mininet.github.com
- Talk Outline • Mininet 1.0: funcKonal fidelity • Mininet 2.0 (HiFi) – Performance Fidelity – “Network Invariants” – Reproducible Research • Prototypes: greater scale
- Mininet 2.0 (HiFi) 8
- Verifying Network ProperKes • “Does my SDN work?” – E.g., func&onal correctness – Same control program + OF funcKonal fidelity • Does not try to solve a harder problem: – “How does my SDN/network perform?” – That is, performance proper&es. – No guarantee or expectaKon of perf. fidelity.
- Example: ConnecKvity in a Fat Tree servers switches 10 20x 4-‐port switches 16x servers sudo mn –-custom ft.py -–topo ft,4 –test pingall
- Verifying Network ProperKes • “Does my SDN work?” – E.g., func&onal correctness – Same control program + OF funcKonal fidelity • “How does my SDN perform?” – E.g., performance proper&es – No guarantee or even expectaKon here
- hosts switches 12 A B Y Z full throughput Two 1 Gb/s flows. Disjoint paths. Example: Performance in a Fat Tree
- hosts switches 13 A B Y Z X collision half throughput Two 1 Gb/s flows. Overlapping paths. Example: Performance in a Fat Tree Throughput might reduce. But by how much? How do you trust the results?
- 14 overlapping events real Kme … … … A B Link Events A: send request B: init xmit 1 xmit 2 B: send reponse A B B HiFiA x1 x2B A B Packet xmit 2 // A: Client while(1) { send_request(socket); wait_for_reply(socket); } // B: Server init(); while(1) { wait_for_request(socket); send_response(socket); } 1 Real Setup B: wait idle B B: send reponse // B: Server init(); while(1) { wait_for_request(socket); send_response(socket); } Real S Sources of Emulator Infidelity Event Overlap
- 15 real Kme … … … A B Link Events A: send request B: init xmit 1 xmit 2 B: send reponse A B B HiFiA x1 x2B A B Packet xmit 2 // A: Client while(1) { send_request(socket); wait_for_reply(socket); } // B: Server init(); while(1) { wait_for_request(socket); send_response(socket); } 1 Real Setup B: wait idle B B: send reponse // B: Server init(); while(1) { wait_for_request(socket); send_response(socket); } Real S Sources of Emulator Infidelity So8ware Forwarding variable delays
- How can we trust emulator results? real Kme … … … A B Link Events A: send request B: init xmit 1 xmit 2 B: send reponse A B B HiFiA x1 x2B A B Packet xmit 2 // A: Client while(1) { send_request(socket); wait_for_reply(socket); } // B: Server init(); while(1) { wait_for_request(socket); send_response(socket); } 1 Real Setup B: wait idle B B: send reponse // B: Server init(); while(1) { wait_for_request(socket); send_response(socket); } Real S CPU <= 50%, so not overloaded, right? Wrong.
- 17 The Mininet-‐HiFi Approach Resource IsolaKon HIGH! Fidelity! METER! MEDIUM! LOW! Fidelity Monitor + 500 Mhz 20 pkt bufs/ port 10 Mb/s, 1ms
- Network Invariants 18
- A Workflow for High Fidelity EmulaKon 19 Create experiment Run the experiment on a PC, with logging Analyze experiment fidelity using “network invariants” Invariants hold: High Fidelity EmulaKon! Instance(s) of behavior that differ from hardware Run again: increase resources or reduce experiment scale 1: what to log? 2: which invariants? 3: how close?
- 20 Packet Gap Invariants queue link switch queue packet spacing (when queue occupied) Rmeasured ≤ Rconfigured ? link capacity
- Example Workflow for One Invariant 21 Create experiment Run the experiment on a PC, with logging Analyze experiment fidelity using “network invariants” Invariants hold: High Fidelity EmulaKon! Instance(s) of behavior that differ from hardware Run again: increase resources or reduce experiment scale 2: Measure packet spacing 3: Is any packet delayed by more than one packet Kme? 1: Log Dequeue Events If this workflow is valid, “pass” same result as hardware. DCTCP
- Data Center TCP (DCTCP) Kme packets in queue TCP DCTCP 22 marking threshold Queue occupied 100% throughput Queue occupied 100% throughput Packet spacing we should see:
- 0 30 60 90 120 Seconds 0 5 10 15 20 25 30 35 40 Packets q-dctcp-plot.txt Hardware Results, 100 Mb/s 23 packets in queue 100% throughput 6 packets variaKon queue occupied
- Emulator Results 24 Does checking an invariant (packet spacing) idenKfy wrong results? same result wrong; limits exceeded 80 Mb/s 100% tput 6 pkts var same result 160 Mb/s 100% tput 6 pkts var 320 Mb/s
- Packet Spacing Invariant w/DCTCP 25 1 pkt med. low high CCDF Percent (log) 25 pkts Error: (log) 10% of the Kme, error exceeds one packet x
- Percentage deviation from expected 0 1 10 100 Percent 26 1 pkt error 10 20 40 numbers are in Mb/s 80 CCDF Percent Packet Spacing Invariant w/DCTCP
- Percentage deviation from expected 0 1 10 100 Percent 27 10 20 40 numbers are in Mb/s 80 1 pkt error CCDF Percent Packet Spacing Invariant w/DCTCP
- Percentage deviation from expected 0 1 10 100 Percent 28 10 20 40 numbers are in Mb/s 80 CCDF Percent Packet Spacing Invariant w/DCTCP 160 Mb/s: failed emulaKon? Beauty of networks invariants is that it catches and quanKfies the error in this run. 1 pkt error
- DemonstraKng Fidelity • Microbenchmarks • ValidaKon Tests • Reproducing Published Research – Do complex results match published ones that used custom hardware topologies? • DCTCP [Alizadeh, SIGCOMM 2010] • Router Buffer Sizing [Appenzeller, SIGCOMM 2004] • Hedera ECMP [Al-‐Fares, NSDI 2010]
- Reproducing Research 30
- 31 Stanford CS244 Spring ’12:
- → Pick a paper. → Reproduce a key result, or challenge it (with data). → You have: $100 EC2 credit, 3 weeks, and must use Mininet-‐HiFi. 32
- CoDel HULL MPTCP Outcast Jellyfish DCTCP Incast Flow CompleKon Time Hedera DCell TCP IniKal CongesKon Window Misbehaving TCP Receivers RED Project Topics: Transport, Data Center, Queuing 33
- CoDel HULL MPTCP Outcast Jellyfish DCTCP Incast Flow CompleKon Time Hedera DCell TCP IniKal CongesKon Window Misbehaving TCP Receivers RED 34 37 students 18 projects 16 replicated
- CoDel HULL MPTCP Outcast Jellyfish DCTCP Incast Flow CompleKon Time Hedera DCell TCP IniKal CongesKon Window Misbehaving TCP Receivers RED 37 students 18 projects 16 replicated 4 beyond 35
- CoDel HULL MPTCP Outcast Jellyfish DCTCP Incast Flow CompleKon Time Hedera DCell TCP IniKal CongesKon Window Misbehaving TCP Receivers RED 37 students 18 projects 16 replicated 4 beyond 2 not replicated 36
- Reproduced Research Examples reproducingnetworkresearch.wordpress.com (or Google “reproducing network research”) 37
- Why might results be different? • Student error / out of Kme: Incast • Original result fragile: RED • Insufficient emulator capacity to match hardware of original experiment – OpKon 1: Scale up – OpKon 2: Slow down: Time DilaKon – OpKon 3: Scale out: Cluster EdiKon
- QuesKons? • Check out Bob’s Cluster EdiKon demo Nikhil Handigol Brandon Heller Vimal Jeyakumar Bob Lantz [Team Mininet]
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