Anycast Latency: How Many Sites Are Enough?

Schmidt, Ricardo de O. and Heidemann, John and Kuipers, Jan Harm

citation

Ricardo de O. Schmidt, John Heidemann and Jan Harm Kuipers 2017. Anycast Latency: How Many Sites Are Enough? Proceedings of the Passive and Active Measurement Workshop (Sydney, Australia, Mar. 2017), to appear. [PDF]

abstract

Anycast is widely used today to provide important services such as DNS and Content Delivery Networks (CDNs). An anycast service uses multiple sites to provide high availability, capacity and redundancy. BGP routing associates users to sites, defining the catchment that each site serves. Although prior work has studied how users associate with anycast services informally, in this paper we examine the key question how many anycast sites are needed to provide good latency, and the worst case latencies that specific deployments see. To answer this question, we first define the optimal performance that is possible, then explore how routing, specific anycast policies, and site location affect performance. We develop a new method capable of determining optimal performance and use it to study four real-world anycast services operated by different organizations: C-, F-, K-, and L-Root, each part of the Root DNS service. We measure their performance from more than 7,900 vantage points (VPs) worldwide using RIPE Atlas. (Given the VPs uneven geographic distribution, we evaluate and control for potential bias.) Our key results show that a few sites can provide performance nearly as good as many, and that geographic location and good connectivity have a far stronger effect on latency than having many sites. We show how often users see the closest anycast site, and how strongly routing policy affects site selection.

reference

@inproceedings{Schmidt17a,
  author = {Schmidt, Ricardo de O. and Heidemann, John and Kuipers, Jan Harm},
  title = {Anycast Latency: How Many Sites Are Enough?},
  booktitle = {Proceedings of the  Passive and Active Measurement Workshop},
  year = {2017},
  pages = {to appear},
  month = mar,
  note = {Awarded Best Paper},
  address = {Sydney, Australia},
  publisher = {Springer},
  jlocation = {johnh: pafile},
  project = {ant, lacrend, lander, retrofuture, researchroot, pinest, nipet},
  jsubject = {network_security},
  sortdate = {2017-03-30},
  keywords = {anycast, dns, design, latency},
  url = {https://ant.isi.edu/%7ejohnh/PAPERS/Schmidt17a.html},
  pdfurl = {https://ant.isi.edu/%7ejohnh/PAPERS/Schmidt17a.pdf},
  blog = {https://ant.isi.edu/blog/?p=930},
  copyrightholder = {Springer},
  copyrightterms = {
  An author may self-archive an author-created version of his/her
  article on his/her own website and or in his/her institutional
  repository. He/she may also deposit this version on his/her funder's
  or funder's designated repository at the funder's request or as a
  result of a legal obligation, provided it is not made publicly
  available until 12 months after official publication. He/she may not
  use the publisher's PDF version, which is posted on
  \url{www.springerlink.com}, for the purpose of self-archiving or
  deposit. Furthermore, the author may only post his/her version
  provided acknowledgement is given to the original source of
  publication and a link is inserted to the published article on
  Springer's website. The link must be accompanied by the following
  text: ``The final publication is available at www.springerlink.com''.
  },
  xxxdoi = {xxx}
}

copyright

An author may self-archive an author-created version of his/her article on his/her own website and or in his/her institutional repository. He/she may also deposit this version on his/her funder’s or funder’s designated repository at the funder’s request or as a result of a legal obligation, provided it is not made publicly available until 12 months after official publication. He/she may not use the publisher’s PDF version, which is posted on \urlwww.springerlink.com, for the purpose of self-archiving or deposit. Furthermore, the author may only post his/her version provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer’s website. The link must be accompanied by the following text: “The final publication is available at www.springerlink.com”.