1 / 23

Characterizing Residential Broadband Networks

Characterizing Residential Broadband Networks. To Be Presented By Muhammad Atif Qureshi, 20093639. Marcel Dischinger † , Andreas Haeberlen †‡ , Krishna P. Gummadi † , Stefan Saroiu* † MPI-SWS, ‡ Rice University, * University of Toronto. Outline. Background and Problem Statement

sharonclark
Download Presentation

Characterizing Residential Broadband Networks

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Characterizing Residential Broadband Networks To Be Presented By Muhammad Atif Qureshi, 20093639 Marcel Dischinger†, Andreas Haeberlen†‡, Krishna P. Gummadi†, Stefan Saroiu* †MPI-SWS, ‡Rice University, * University of Toronto

  2. Outline • Background and Problem Statement • Motivation – Why Study Residential Broadband Networks? • Why Do We Know So Little? • Finding Broadband Hosts to Measure • The Experiment • Experimental Setup • Experiment Setup and its Validation • Experimental Measurements

  3. Background and Problem Statement – The Last Mile Problem (1/2) • LAN, MAN, WAN – how to connect private users at home to such networks? • Problem of the Last Mile – somehow connect private homes to the public Internet without laying many new cables. • How? • By using existing lines – reuse them for data traffic.

  4. Background and Problem Statement (2/2) • Convergence of telephony (voice), Internet (data), cable (video) – gives birth to broadband networks. • Broadband networks give best of both worlds. • Commonly known as “home networking broadband connection technologies.”

  5. Motivation - Why study residential broadband networks? • Used by millions of users to connect to the Internet • Rapidly growing user base • Used for many different workloads: • Music / movie downloads, VoIP, online games • Yet, researchers know little about the characteristics of deployed cable and DSL networks • Such as provisioned bandwidths, queueing delays, or loss rates • Will have great research implications for designers of future protocols and systems.

  6. Why do we know so little? • Commercial ISPs have no incentives to reveal information about their network deployments • Researchers lack access to broadband networks • Testbeds composed of academic nodes • PlanetLab only has two DSL nodes • Prior studies were limited in scale • Largest study so far had 47 broadband nodes [PAM’04] • Prior studies depended on access to the broadband hosts Challenge: Can we measure hosts without access to them?

  7. The Experiment - Finding broadband hosts to measure (1/2) • Identified IP addresses of broadband hosts using reverse-DNS lookups • E.g., BellSouth’s DNS names follow the schemeadsl-*.bellsouth.net • Sent TCP ACK and ICMP PING probes to the broadband IPs • 1000s of hosts from 100s of DSL/cable ISPs responded

  8. The Experiment - We focused on 11 major ISPs from North America and Europe (2/2) • DSL • Cable

  9. Experimental Setup - How do we measure the broadband hosts? Broadband link Measurement hosts • We measured from well-connected hosts in University networks • TCP ACK / ICMP PING probes sent at 10Mbps for a short duration • Probes saturate the bottleneck, which is often the broadband link • TCP ACK probes saturate just downstream direction • ICMP PING probes saturate both directions • We analyzed probe responses to infer various characteristics Internet Broadband host Last-hop router

  10. Broadband host Last-hop router Experiment Assumption and its Validation - Are broadband links the bottleneck? • Broadband links are the bandwidth bottlenecks along the measured path • More validation results in the paper

  11. Rest of the talk • Allocated link bandwidths • Packet latencies • Packet loss

  12. Outline • Allocated link bandwidths • Do broadband providers allocate advertised link bandwidths? • How do the downstream and upstream bandwidths compare? • Are broadband bandwidths stable over the short-term? • Are broadband bandwidths stable over diurnal time-scales? • Is there evidence for traffic shaping? • Packet latencies • Packet loss

  13. Do ISPs allocate advertised link bandwidths? • DSL ISPs allocate advertised bandwidths • Its dedicated link • Some Cable ISPs do not offer discrete bandwidths • Its shared link • Used asymmetric large-TCP flood PacBell BellSouth Rogers Road Runner

  14. What is the ratio of downstream to upstream bandwidths? • Upstream bandwidths are significantly lower than downstream • Broadband networks are provisioned for client-server workloads • Used symmetric large ICMP flood for upstreams Ameritech PacBell Road Runner Comcast

  15. Are link bandwidths stable over the short-term? • DSL bandwidths are relatively stable, while cable are not • Hard for protocols like TCP to adapt to highly variable cable BWs Unstable (Rogers cable host) Stable (PacBell DSL host)

  16. Outline • Allocated link bandwidths • Packet latencies • How large are broadband queueing delays? • Queues should be proportional to the end-to-end RTT • Recent research recommends even shorter queues [SIGCOMM’04] • How do cable’s time-slotted policies affect transmission delays? • Do broadband links have large propagation delays? • Packet loss

  17. How large are downstream queueing delays? PacBell • Downstream queues are significantly larger than avg. path RTT • Used asymmetric large TCP flood • (RTT max - RTT min) BellSouth Comcast Road Runner

  18. How large are upstream queueing delays? PacBell BellSouth • Upstream queues are extremely large • Packets can experience latencies in the order of seconds • Used symmetric large ICMP flood – estimated downstream value • Greater Upstream Queue length than downstream’s BellSouth Comcast Road Runner

  19. Why are large queues worrisome? • Large queues avoid losses at the cost of latency • Good for web workloads • But, bad for popular emerging workloads • Interactive traffic like VoIP and online games • Multimedia downloads like music and movies • Low latency vs. maximum bandwidth • TCP does not fully drain large queues after a loss event

  20. Outline • Allocated link bandwidths • Packet latencies • Packet loss • Do ISPs deploy active queue management (AQM)? • Tail-drop queue • Active queue management techniques, such as Random Early Detect (RED) • Do broadband links see high packet loss?

  21. Do ISPs deploy active queue management? • 25% of DSL hosts have AQM deployed in the upstream • Used small TCP flood Active queue management (probably RED) (SWBell) Threshold Tail-drop (PacBell)

  22. Conclusion • We presented the first large-scale study of broadband networks • Measured their bandwidth, latency, and loss characteristics • Broadband networks are very different from academic networks • Cable networks have unstable bandwidths • Large queues can cause latencies in the order of seconds • Broadband links have low loss rates, show deployment of AQM • Our findings have important implications for network operators and systems designers

  23. Thank you! Questions?

More Related