Reducing Latency Through Page-aware Management of Web Objects by Content Delivery Networks

As popular web sites turn to content delivery networks (CDNs) for full-site delivery, there is an opportunity to improve the end-user experience by optimizing the delivery of entire web pages, rather than just individual objects. In particular, this paper explores page-structure-aware strategies for placing objects in CDN cache hierarchies. The key idea is that the objects in a web page that have the largest impact on page latency should be served out of the closest or fastest caches in the hierarchy. We present schemes for identifying these objects and develop mechanisms to ensure that they are served with higher priority by the CDN, while balancing traditional CDN concerns such as optimizing the delivery of popular objects and minimizing bandwidth costs. To establish a baseline for evaluating improvements in page latencies, we collect and analyze publicly visible HTTP headers that reveal the distribution of objects among the various levels of a major CDN's cache hierarchy. Through extensive experiments on 83 real-world web pages, we show that latency reductions of over 100 ms can be obtained for 30% of the popular pages, with even larger reductions for the less popular pages. Using anonymized server logs provided by the CDN, we show the feasibility of reducing capacity and staleness misses of critical objects by 60% with minimal increase in overall miss rates, and bandwidth overheads of under 0.02%.

[1]  Albert G. Greenberg,et al.  WebProphet: Automating Performance Prediction for Web Services , 2010, NSDI.

[2]  H. B. Mann,et al.  On a Test of Whether one of Two Random Variables is Stochastically Larger than the Other , 1947 .

[3]  Arun Venkataramani,et al.  NPS: A Non-Interfering Deployable Web Prefetching System , 2003, USENIX Symposium on Internet Technologies and Systems.

[4]  Michael Dahlin,et al.  Coordinated Placement and Replacement for Large-Scale Distributed Caches , 2002, IEEE Trans. Knowl. Data Eng..

[5]  David Wetherall,et al.  Demystifying Page Load Performance with WProf , 2013, NSDI.

[6]  Arun Venkataramani,et al.  Bandwidth constrained placement in a WAN , 2001, PODC '01.

[7]  Jia Wang,et al.  A survey of web caching schemes for the Internet , 1999, CCRV.

[8]  Peter B. Danzig,et al.  A Hierarchical Internet Object Cache , 1996, USENIX ATC.

[9]  Zhe Wu,et al.  Enabling the transition to the mobile web with WebSieve , 2013, HotMobile '13.

[10]  Vyas Sekar,et al.  Understanding website complexity: measurements, metrics, and implications , 2011, IMC '11.

[11]  Hao Che,et al.  Hierarchical Web caching systems: modeling, design and experimental results , 2002, IEEE J. Sel. Areas Commun..

[12]  Edward A. Fox,et al.  Caching Proxies: Limitations and Potentials , 1995, WWW.

[13]  Jeffrey C. Mogul,et al.  Using predictive prefetching to improve World Wide Web latency , 1996, CCRV.

[14]  Arun Venkataramani,et al.  A Non-interfering Deployable Web Prefetching System , 2002 .

[15]  Marc Abrams,et al.  Proxy Caching That Estimates Page Load Delays , 1997, Comput. Networks.

[16]  Michael Dahlin,et al.  Design considerations for distributed caching on the Internet , 1999, Proceedings. 19th IEEE International Conference on Distributed Computing Systems (Cat. No.99CB37003).

[17]  Minyou Wu,et al.  Web Prefetching : Costs , Benefits and Performance , 2002 .

[18]  Vivek S. Pai,et al.  Towards understanding modern web traffic , 2011, SIGMETRICS '11.

[19]  Jean-Chrysostome Bolot,et al.  Performance Engineering of the World Wide Web: Application to Dimensioning and Cache Design , 1996, Comput. Networks.

[20]  Arun Venkataramani,et al.  The potential costs and benefits of long-term prefetching for content distribution , 2002, Comput. Commun..

[21]  Azer Bestavros,et al.  Popularity-aware greedy dual-size Web proxy caching algorithms , 2000, Proceedings 20th IEEE International Conference on Distributed Computing Systems.

[22]  C. Moallemi,et al.  The Cost of Latency ∗ , 2009 .

[23]  Zhe Wu,et al.  Klotski: Reprioritizing Web Content to Improve User Experience on Mobile Devices , 2015, NSDI.

[24]  Luiz André Barroso,et al.  The tail at scale , 2013, CACM.

[25]  David Wetherall,et al.  How Speedy is SPDY? , 2014, NSDI.

[26]  Sandy Irani,et al.  Cost-Aware WWW Proxy Caching Algorithms , 1997, USENIX Symposium on Internet Technologies and Systems.

[27]  Ajay D. Kshemkalyani,et al.  Objective-optimal algorithms for long-term Web prefetching , 2006, IEEE Transactions on Computers.

[28]  Martin F. Arlitt,et al.  Performance evaluation of Web proxy cache replacement policies , 1998, Perform. Evaluation.