Rupa Krishnan
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Moving Beyond End-to-End Path Information to Optimize CDN Performance
Harsha V. Madhyastha
Sushant Jain
Arvind Krishnamurthy
Thomas Anderson
Jie Gao
Internet Measurement Conference (IMC), ACM, Chicago, IL (2009), pp. 190-201
Preview abstract
Replicating content across a geographically distributed set of servers and redirecting clients to the closest server in terms of latency has emerged as a common paradigm for improving client performance. In this paper, we analyze latencies measured from servers in Google’s content distribution network (CDN) to clients all across the Internet to study the effectiveness of latency-based server selection. Our main result is that redirecting every client to the server with least latency does not suffice to optimize client latencies. First, even though most clients are served by a geographically nearby CDN node, a sizeable fraction of clients experience latencies several tens of milliseconds higher than other clients in the same region. Second, we find that queueing delays often override the benefits of a client interacting with a nearby server.
To help the administrators of Google’s CDN cope with these
problems, we have built a system called WhyHigh. First, WhyHigh measures client latencies across all nodes in the CDN and correlates measurements to identify the prefixes affected by inflated latencies. Second, since clients in several thousand prefixes have poor latencies, WhyHigh prioritizes problems based on the impact that solving them would have, e.g., by identifying either an AS path common
to several inflated prefixes or a CDN node where path inflation is widespread. Finally, WhyHigh diagnoses the causes for inflated latencies using active measurements such as traceroutes and pings, in combination with datasets such as BGP paths and flow records. Typical causes discovered include lack of peering, routing misconfigurations, and side-effects of traffic engineering. We have used WhyHigh to diagnose several instances of inflated latencies, and our efforts over the course of a year have significantly helped improve the performance offered to clients by Google’s CDN.
An anonymized data set is available for download.
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Globally Fair Resource Allocation for Wireless Mesh Networks
Ashish Raniwala
Pradipta De
Srikant Sharma
Tzi-cker Chiueh
17th Intl Symposium on Modelling, Analysis and Simulation of Computer and Telecommunication Systems (MASCOTS) (2009)
Design of a Channel Characteristics-Aware Routing Protocol
Ashish Raniwala
Tzi-cker Chiueh
IEEE Infocom Mini-Symposium on QoS and Performance Evaluation (2008)
An Empirical Comparison of Throughput-Maximizing Wireless Mesh Routing Protocols
Ashish Raniwala
Tzi-cker Chiueh
Fourth Intl Wireless Internet Conference (WICON) (2008)
End-to-End Flow Fairness over IEEE 802.11-based Wireless Mesh Networks
Ashish Raniwala
Pradipta De
Srikant Sharma
Tzi-cker Chiueh
IEEE Infocom Mini-Symposium on 802.11 Wireless LANs (2007)
Evaluation of a Stateful Transport Protocol for Multi-channel Wireless Mesh Networks
Ashish Raniwala
Srikant Sharma
Pradipta De
Tzi-cker Chiueh
International Workshop on Quality of Service (IWQoS), (2007)
MiNT-m: an autonomous mobile wireless experimentation platform
Pradipta De
Ashish Raniwala
Krishna Tatavarthi
Jatan Modi
Nadeem Ahmed Syed
Srikant Sharma
Tzi-cker Chiueh
USENIX MobiSys (2006), pp. 124-137