Hiromi Hirai ( Ochanomizu University )

Total throughput is improved.

It has no negative effect on the others by switching.

We developed a new transmission-control mechanism.

Switching TCP is effective in mobile communication.

Investigate which situation suits for each TCP.

A Study on Transmission-Control Middleware

on Android Terminal in a Wireless LAN Environment

The AP handle a few packets.

The mobile phone can enjoy high speed

networking.

The AP handle a lot of packets.

Each mobile phone is faced with low speed

networking.

Such a situation ・Network traffic is filled with too many packets.

・Additional packets will be lost.

What’s congestion ?

Wired network

is so reliable

Each device avoid

congestion by

independent prediction

We considered a new control

to avoid congestion by

sharing each other’s

communicating condition.

Most of packet

losses take place

In wireless network.

Previous study

Other’s CWND

Own CWND

TCP Log

TcpView A visualization tool for TCP behavior of Android kernel

It parses Kernel Monitor logs and visualizes them.

Extension Exchange each parameters

Visualize other devices’ TCP behavior

Kernel Monitor An existing tool which leaves the log of working TCP.

This is special tool as it is difficult to observe TCP.

It records CWND, the length of socket buffer queue,

error event and which part of source code is executed.

CWND CWND

Experimental behavior

artificial packet loss rate : 2%

TCP-cubic Simple way to predict congestion by packet

losses. When it lost a single packet , it

decreases CWND drastically. It works

conservatively in sending packets.

TCP-original

It is based on TCP-cubic. It works

aggressively. It is effective in high delay

environment(more than 32ms RTT).

CWND is a data sender’s parameter which denotes how many segments it sends for an ACK.

DICOMO2011 Kaori Miki

A Study about Performance Improvement and Analysis of Communication on Android in a Wireless LAN with Kernel Monitor

TIME

TCP-cubic Especially in high packet loss rate

environment, it limits itself too much.

In wireless LAN environment, noise

often slip into the communication.

In wired LAN

High packet loss rate ≒ congestion

In wireless LAN

High packet loss rate ≠ congestion

TCP-original It is improved the demerit of TCP-

cubic. It is optimized for the mobile.

It has negative effect on the others.

Switching TCP middleware

The function of middleware • It observes the machine’s CWND.

• When it finds TCP working, it broadcasts the communicating condition.

• When it accepts other’s information, it selects suitable TCP for the environment.

• The TCP has a proc interface to switch.

• The middleware has a system call to rewrite the proc interface.

The Switching Algorithm • it switches TCP from original to cubic when the middleware notices the other

communication.

• it switches TCP from cubic to original when the middleware notices no other

communication.

Middleware

Experiment

The result of Experiment

Conclusion

• Android device 1 transmits 16 M byte of packets.

• Android device 2, 3 began to transmit 4 M byte of packets to interrupt.

• The middleware of each device share the information of communication.

• It switches TCP while the other device is communicating.

The normal behavior of TCP The behavior of switching TCP

Future works

My graduate thesis

Background