Web Caching on Smartphones: Ideal vs. Reality . Feng Qian 1 , Kee Shen Quah 1 , Junxian Huang 1 , Jeffrey Erman 2 Alexandre Gerber 2 , Z . Morley Mao 1 , Subhabrata Sen 2 , Oliver Spatscheck 2 1 University of Michigan 2 AT&T Labs - Research. June 27 2012.
Feng Qian1, KeeShen Quah1, Junxian Huang1, Jeffrey Erman2
AlexandreGerber2, Z. Morley Mao1, Subhabrata Sen2, Oliver Spatscheck2
1University of Michigan 2AT&T Labs - Research
June 27 2012
Source: Cisco Visual Networking Index (VNI) Global Mobile Data Traffic Forecast, 2011-2016
Well known protocol for 20 years
What is the state-of-the-art in the context of cellular devices?
Last-Modified: Feb 1 2012 15:00:00
Expires: Feb 10 2012 15:00:00
Feb 1 2012 15:00:00
304 Not Modified
Last-Modified: Feb 12 2012 15:00:00
Expires: Feb 15 2012 15:00:00
Last-Modified: Feb 1 15:00:00
Expires: Feb 10 15:00:00
Last-Modified: Feb 12 15:00:00
Expires: Feb 15 15:00:00
They account for 20% of the total HTTP traffic volume!
User interface for the data
due to HTTPS and app-semantic-related redundancy
It is unlikely that the handset is rebooted during such a short interval.
The benefits are significant even for a small cache.
Dist. of intervals between consecutive cache hits on the same entry (ISP trace)
Compute the impact:ΔE = (E0 – ER) / E0
ΔE: Radio energy impact of redundant transfers (a positive value)
ER: Radio energy consumption in modified traces with redundant transfers removed
E0: Radio energy consumption
in original traces
A huge gap between protocol specification and implementation, leading to significant redundancy of network traffic.
Duplicated transfer: the file has not changed after the cache entry expires, but the handset does not perform cache revalidation.
The file contains "Cache-Control: no-store“. It cannot be cached.
Duplicated transfer: A request is issued before the file expires.
Duplicated transfer: the file has not changed after the cache entry expires, but the server does not recognize the cache revalidation.
The file has changed after the cache entry expires.
The file has not changed after the cache entry expires, and a cache revalidation is properly performed.
UMTS RRC State Machine for a large US 3G carrier
Waiting inactivity timers to expire