Inferring Queue Sizes in Access Networks by Active Measurement Mark Claypool, Robert Kinicki, Mingzhe Li, James Nichols, and Huahui Wu {claypool, rek, lmz, jnick, flashine}@cs.wpi.edu CS Department at Worcester Polytechnic Institute Worcester, MA 01609 USA Presenter: Mingzhe Li Passive & Active Measurement Workshop (PAM04) December 3, 2018, Antibes Juan-les-Pins, France

Motivation Maximum router queue size: Impact round-trip times Impact throughput Not widely known No related methodology for end-users Estimation of the maximum queue size: Easy-to-use methodology No extra customized software No excessive instrumentation effects Simple and accessible Lots of heterogeneous data PAM04 - Antibes Juan-les-Pins, France

Introduction QFind Validation Measurement A black-box measurement technique to estimate the access queue at last mile router Easy-to-use and accessible Validation Simulation in NS-2 Emulation in NistNet Measurement Volunteers Cable and DSL access links PAM04 - Antibes Juan-les-Pins, France

Outline Introduction QFind Experiments and Results Summary Assumptions 12/3/2018 Outline Introduction QFind Assumptions Methodology Validation Experiments and Results Summary PAM04 - Antibes Juan-les-Pins, France

Assumptions Each access link has a relatively small queue size. (e.g. 10-100 packets) Maximum queue size is independent of link capacity or other link characteristics. Maximum queue size is constant and independent of incoming traffic load. Last mile router is the bottleneck. PAM04 - Antibes Juan-les-Pins, France

Methodology (2). Start ping (3). Download a large file (4). Stop ping Max ping time Min ping time (2). Start ping (3). Download a large file (4). Stop ping (1). Locate a ping destination (5). Compute queue size PAM04 - Antibes Juan-les-Pins, France

Methodology (cont.) Maximum queue size computation: (Eq.4) qp: Queue size in packets T: Throughput (Bps) Dt: Total delay (sec.) (Max ping) s: packet size (bytes) Dl:: Latency (sec.) (Min ping) PAM04 - Antibes Juan-les-Pins, France

Possible Sources of Error TCP receiver window size TCP throughput is limited by max receiver window size. Typical receiver window size: Windows 98: 8 KBytes Windows 2000: 16 KBytes Windows XP: 16 KBytes* Linux: 64 KBytes Different receiver window size limits the reported max queue size. * Undocumented ability to scale receiver windows size dynamically PAM04 - Antibes Juan-les-Pins, France

Validation - Simulation Simulation in NS-2 Max receiver window size: 150 packets Packet size: 1500 Bytes Access link capacity: 768Kbps/192Kbps Queue size: 10, 50, 100 packets Qfind methodology works well in simulation Out 100 simulations Queue = 10 [9, 9] Queue = 50 [48, 49] Queue = 100 [97, 99] PAM04 - Antibes Juan-les-Pins, France

Validation - Emulation NistNet Internet emulation Same topology as simulation Home-node: Windows 2000 & Linux Queue size: 10, 30, 50, 100 packets Validations Using capacity and throughput to compute queue Home node receiver window sizes and OS: Windows 2000 Default: 16 KBytes Windows 2000 customized: 64 KBytes Linux Default: 64 KBytes PAM04 - Antibes Juan-les-Pins, France

Emulation Result PAM04 - Antibes Juan-les-Pins, France

Emulation Results QFind works when receiver window larger than maximum queue size Capacity and throughput Using capacity to compute maximum queue size is more accurate PAM04 - Antibes Juan-les-Pins, France

Outline Introduction QFind Experiments and Results Summary 12/3/2018 Outline Introduction QFind Experiments and Results Measurement overview Measurement results Summary PAM04 - Antibes Juan-les-Pins, France

Measurement Overview Data available online at: http://www.cs.wpi.edu/~claypool/papers/qfind/ During Jan 2004, total 47 volunteers Aggregate results: Access Links: Cable (55%) and DSL (45%) 16 distinct ISP’s Charter are most popular cable ISP (16) Verizon are most popular DSL ISP (11) 5 distinct OS types Windows XP (18) Windows 2000 (11) Windows 98 (1) Linux (6) Mac (3) Unknown (12) PAM04 - Antibes Juan-les-Pins, France

Inferred Queue Size PAM04 - Antibes Juan-les-Pins, France

Summary QFind methodology – Promising Measurement Results Simple and easy-to-use. Only need standard ping and web browser to work. Single TCP flow, won’t cause excessive congestion Try out yourself! http://perform.wpi.edu/downloads/#qfind Validated in simulation and emulation. Maximum receiver window size limits reported maximum queue size. Measurement Results Cable connections have a relatively smaller maximum queue sizes than DSL. PAM04 - Antibes Juan-les-Pins, France

Inferring Queue Sizes in Access Networks by Active Measurement Mark Claypool, Robert Kinicki, Mingzhe Li, James Nichols, and Huahui Wu {claypool, rek, lmz, jnick, flashine}@cs.wpi.edu CS Department at Worcester Polytechnic Institute Worcester, MA 01609 USA Presenter: Mingzhe Li Passive & Active Measurement Workshop (PAM04) December 3, 2018, Antibes Juan-les-Pins, France