Mobile/Gonzales

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Gonzales is a project to find and evaluate ways to enable more efficient mobile browsing.

Goals

The goal of Gonzales is to verify whether we can enhance the mobile browsing experience by achieving the following improvements in a practical way:

  • Reduce radio time
  • Reduce page load times
  • Reduce bandwidth requirements
  • Increase user privacy
  • Increase responsiveness for slow sites

Background

HTTP

TODO

Transport Layer Security (TLS)

TLS handshake

Time [ms]             Client       Server
30                       SYN  -->                           
60                            <--  SYN ACK
90                       ACK  -->
120                           <--  Certificate
150         ChangeChiperSpec  --> 
180                           <--  ChangeCipherSpec
210                     Data  -->   
240                           <--  Data

SPDY

TODO

WiFi

TODO

3G/4G

LTE Mobile Network

Latency [ms]   Type            Device      RAN      Core Network             Internet
                                                    SGW     MME     PGW           
<100           control plane          <--> 
<5             user plane             <-->
30-100         backbone                        <--> 
variable       routing                                                  <-->

Control Plane Latency

               GPRS    EDGE    HSPA   HSPA+   LTE    LTE-Advanced
Latency [ms]   <1000   <1000   <500   <200    <100   <50

Radio Access Network (RAN)

TODO

Radio Resource Controller (RRC)

TODO

Packet Gateway (PGW)

TODO

Serving Gateway (SGW)

TODO

Mobility Management Entity (MME)

TODO

Image Compression

Image Formats

Format Lossy Transparency support Supported by Firefox
JPEG Yes No Yes
PNG No Yes Yes
JNG Yes Yes No
WebP Yes Yes No
BMP No Yes Yes


PNG Compression

Tests are done using a set of PNG images from "real" most visited websites. The sample size is 3432kB.

Compression Method New sample size (kB) Average compression (%) Total time (s)
optipng -o 1 3069 11 22
optipng -o 7 2911 16 343
pngquant 1874 46 18
pngcrush 3062 11 30
pngcrush + optipng -o 5 2850 17 219

Common Misconceptions

Losing radio link means losing TCP connection

The PGW terminates the TCP/UDP connections, application level connectivity is not tied to the physical radio link.

A device session is tied to an IP

The PGW provides NAT services, a device can be mapped to multiple IP/port combinations or multiple devices can share the same IP.

Bandwidth is the decisive factor for page load speed

Bandwidth gives the upper bound on transmission speed under optimal conditions. In realistic environments, considering the speed of light and the shortcomings of the transmission protocol, latency is the limiting factor for the maximum throughput.

Tracking Bugs

The secure SPDY compression proxy requires client-side support, which is tracked in

  • bug 378637 - Add support for connecting to HTTP proxy over HTTPS

The Node.js based proxy prototype is maintained on GitHub: node-gonzales. Please use it to report issues and make pull requests.

System Overview

Gonzales is a secure proxy server that accepts requests via the SPDY protocol and serves compressed content directly from its cache, if available. 

Browser <-SPDY-> Gonzales                                <-HTTP/HTTPS/SPDY-> Web
               |                                         |
               Proxy <-> Cache <-?-> Compressor <-> Loader

Routing requests through a SPDY proxy does require less open TCP connections (multiplexing), decreases packet sizes (header compression) and reduces the number of packets (header caching) compared to HTTP/1. Low bandwidth and high latency connections should benefit from this.

The current trend on the Web shows an increase in average page size, especially due to high-resolution images. Additional image compression and downsizing should decrease the bandwidth requirements and enable faster page loads. To counteract the introduced processing overhead and boost load times for slow pages, we add intermediate caching for the compressed results.

Experimental Setups

To evaluate the system, we test each component in isolation first. We identify third-party systems suitable for integration into the prototype and evaluate them. All qualified systems will be considered for integration or as the base of our final implementation.

SPDY Proxy

Currently, only Google Chrome supports secure SPDY proxies, but it requires valid certificates, which makes it unsuitable for testing. We bypass the missing support by using shrpx in client mode as a forward proxy, and that way simulate SPDY support on any client.

Dependencies:

Here are some experimental setups.

P1

In this setup, we connect a desktop browser via HTTP with a local forwarding proxy, which establishes a SPDY connection with the remote secure SPDY proxy. The secure SDPY proxy connects to a local web proxy to fetch the documents. 

Desktop Client               <-SPDY-> SPDY Proxy <-HTTP-> Web Proxy <-HTTP-> Web
                             |      |            |      |           |
Firefox <-HTTP-> [shrpx -k -p]      --[shrpx -s]--      ----Squid----

P2

This setup is similar to P1, but running on a mobile client. This requires either direct secure SPDY proxy support on the mobile browser, or the usage of a local forwarding proxy running on the mobile device. 

Mobile Client               <-SPDY-> SPDY Proxy <-HTTP-> Web Proxy <-HTTP-> Web
                            |      |            |      |           |
Fennec <-HTTP-> [shrpx -k -p]      --[shrpx -s]--      ----Squid----

Compression

TODO

Caching

TODO

Performance Analysis

Let's collect some ideas here how to profile our prototypes.

Could be useful:

References

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