MobileSocket:Library-based Continuous Operation Supportfor Java Applications

Tadashi OKOSHIGraduate School of Media and GovernanceKeio University

slash@ht.sfc.keio.ac.jp

SPA (Systems for Programming and Applications) 1999 @Atagawa, JAPANhttp://www.softlab.is.tsukuba.ac.jp/~kato/spa99/ 1999.3.17-19

Mobile Computing Environment

“Work Continuity” for users

Mobile HostMobile Host

Internet

AA

AA

BB

??

MobileSocket is...

TCP/UDP

IP

Socket interface

TCP/UDP

IP

Socket interface

Application Application

Application Application

MobileSocket libMobileSocket lib MobileSocket libMobileSocket lib

(Mobile-IP)

(TCP-R)(MSOCKS)

MobileSocket Applications (1)

Java Network Applications

Mobile HostMobile Host

Internet

AA

AA

BB

MobileSocket Applications (2)

Java Mobile Applications

AppBAppB

Host-B

Host-A

AppAAppA

AppA’ObjectSerialization

MSockA (SocketX)

MSockA (SocketY)

Host-C

MobileSocket Applications (3)

Even Exchanging Socket...

Host-A Host-B

Host-C

AppAAppA

AppCAppC

AppBAppBMSockA MSockB

MSockA’Send “MobileSocket” Objectvia ObjectSerialization

Today’s Outline

1. Research Background - Continuous Operation -

2. MobileSocket Design3. MobileSocket Mechanism4. MobileSocket Programming5. Evaluation6. Conclusion & Future Work

1. Background

Goal: Continuous Operation for users’ “Work Continuity”

Continuous Operation Framework for Applications Mobility… Transparent Host Identifier Connection Continuity… Stream Consistency

Issues for Continuos Operation

(1) Avoidance of modification in existing applications

(2) Simplified and minimized implementation(3) Byte Stream Consistency support

for virtual circuit connection(4) Adaptation in applications

2. MobileSocket Design

Design Features (1) Mobility and connection continuity support

in application layer (2) User-level library implementation in Java (3) Both implicit & explicit redirection operations (4) Adaptation in applications (JavaEvent model)

Dynamic Socket Switching (DSS)

IPCH

CH

CH

CH

IPMH1

MH1

MH1

MH1

Application(MobileHost)Application

(CorrespondentHost)

Internal SocketConnection (1)

Before

IP Laye

rTCP Layer

Socket

Layer

Mobile

Socket

Layer

Dynamic Socket Switching (DSS)

IP Laye

rTCP Layer

Socket

Layer

Mobile

Socket

Layer

IPCH

CH

CH

CH

IPMH1

MH1

MH1

MH1

IPMH2

MH2

MH2

Application(MobileHost)

After

Application(Correspondent

Host)

Relocation

Internal SocketConnection (2)

Application Layer Window (ALW)

MobileSocketin Sender

MobileSocketin Receiver

DataSocket

ControlSocket

DataData DataData

ACKACK

DataData

Application Application

ALW

DataData

ACKACK ACKACK

DataData

ALW_COUNTERALW_COUNTER

write() read()

recvflush

writestore

count

read

send

User-level sliding window inside libraryprovides Byte Stream Consistency

3. MobileSocket Mechanism

State Transition DiagramTime Sequence

Establishment Implicit Redirection Explicit Redirection

EstablishedEstablishedImplicitlySuspendedImplicitly

SuspendedExplicitly

SuspendedExplicitly

Suspended

ClosedClosedConnected to Server (DSS-EstablishmentPhase(Client) )

Connected from Client (DSS-EstablishmentPhase(Server) )

Lost IP address

Get IP address (Reconnect to CH, DSS-

ImplicitResume Phase)

Reconnected from MH(DSS-ImplicitResume Phase)

Called suspend()suspend() (send SUSPEND_SIGNAL, DSS-ExplicitSuspend Phase)

Called resume()resume() (Reconnect to CH, DSS- ExplicitResume Phase)

reconnected from MH(DSS-ExplicitResume Phase)

received SUSPEND_SIGNAL (DSS-ExplicitSuspend Phase)

DataSocket broken-pipe

Reconnected from MH(DSS-ImplicitResume Phase)

Called close()close()(close connection)

Called close()close()or timedout

(close connection)

Called close()close()(close connection)

Called close()close()(close connection)

Called close()close()or timedout

(close connection)

Normal Transitions for CHNormal Transitions for MH

Normal Transitions for ClientNormal Transitions for Server

Transition trigger(action)

START POINTSTART POINT

StateState

DSS(1) Establishment Phase

ClientClient ServerServerDataDataSocketSocket

ControlControlSocketSocket

connectconnect accept()accept()

ControlSocket port, AuthenticationSEED1

accept()accept()connect()

ACK

AuthenticationSEED1

DS

S-E

sta

blis

hm

ent

Ph

as

e

RedirectionRedirectionServSocketServSocket

RedirectionServer port, Next_SEED

Data

ALW ACK

DataDataSocketSocket

ControlControlSocketSocket

RedirectionRedirectionServSocketServSocket

CreateCreateSocketSocket

CreateCreateSocketSocket

CreateCreateSocketSocket

CreateCreateSocketSocket

DSS(2) Explicit Suspend Phase

Mobile HostMobile Host Correspondent HostCorrespondent HostDataDataSocketSocket

ControlControlSocketSocket

lock

ACK

SUSPEND_SIGNAL

DSS

-Exp

licitS

uspe

nd P

hase

RedirectionRedirectionServSocketServSocket

WRITE_COUNTER

DataDataSocketSocket

ControlControlSocketSocket

RedirectionRedirectionServSocketServSocket

lock

Compute DIFF Compute DIFF

Invoke Suspend SubPhase(if DIFF>0)

Invoke Suspend SubPhase(if DIFF>0)

ACK (DIFF_IS_ZERO)

CloseClose

Close

Susp

end

SubP

hase

DSS(3) Explicit Resume Phase

ControlControlSocketSocket

connect() accept()

ACK, ControlSocket port, AuthenticationSEED3

accept()connect()

ACK

AuthenticationSEED3

DSS

-Exp

licitR

esum

e Ph

ase

RedirectionRedirectionServSocketServSocket → DataSocket → DataSocket

RedirectionServer port, Next_SEED

Data

ALW ACK

DataDataSocketSocket

ControlControlSocketSocket

RedirectionRedirectionServSocketServSocket

Mobile HostMobile Host Correspondent HostCorrespondent HostNewNewRedirectionRedirectionServSocketServSocket

Next_SEED

unlock unlock

CreateSocketCreate

Socket

CreateSocket

DSS(4) Implicit Redirection

ControlSocket

connect() accept()

ACK, ControlSocket port, AuthenticationSEED3

accept()connect()

ACK

AuthenticationSEED3

DSS

-Impl

icitR

esum

e Ph

ase

RedirectionServSocket → DataSocket

RedirectionServer port, Next_SEED

DataSocket

ControlSocket

RedirectionServSocket

NewRedirectionServSocket

Next_SEED

unlock

READ_COUNTER

unACKed Data retransmit

～ disconnected ～lose IP

get IP

CreateSocket

CreateSocket

CreateSocket

CreateSocket

ControlSocket

connect() accept()

ACK, ControlSocket port, AuthenticationSEED3

accept()connect()

ACK

AuthenticationSEED3

DSS

-Impl

icitR

esum

e Ph

ase

RedirectionServSocket → DataSocket

RedirectionServer port, Next_SEED

DataSocket

ControlSocket

RedirectionServSocket

Mobile HostMobile Host Correspondent HostCorrespondent HostNewRedirectionServSocket

Next_SEED

unlockunlock

READ_COUNTER

unACKed Data retransmit

～ disconnected ～lose IPlose IP

get IPget IP

CreateSocket

CreateSocket

CreateSocket

CreateSocket

Disconnection Recognition in MH

java.net.InetAddressjava.net.InetAddress##getLocalHostgetLocalHost ...IP address based on DNS.

“Checker” Thread as a adhoc solution Disconnection (1)get local IP from

java.net.Socket#getLocalAddressjava.net.Socket#getLocalAddress(2)make Socket to local IP address periodically

Reconnection (1) make Socket to Correspondent Host IP address periodically.

4. MobileSocket Programming

Class Socket sock = new Socket(host, port);Socket sock = new Socket(host, port); MobileMobileSocket sock = new Socket sock = new MobileMobileSocket(host, port);Socket(host, port);

Explicit Redirection (Option) sock.sock.suspend();suspend(); sock. sock.resume();resume();

Adaptation Event (Option) MobilityEvent MobilityEvent Event , , MobilityListener MobilityListener Interface

5. Evaluation

Performance Measurement Explicit Redirection MobileSocket Overhead

Comparison with Related Works

Measurement Environment

Implementation JavaCoreAPI 1.1 jp.ac.keio.sfc.ht.MobileSocketjp.ac.keio.sfc.ht.MobileSocket package

Evaluation Environment Dynabook SS-R590 (Pentium 90MHz, 40MB) for MH S

ony PCG-737 (PentiumMMX 233MHz, 64MB) for CH Closed 10Base-T Network FreeBSD2.2.1R + JDK 1.1.6.V98-9-23 for FreeBSD

Performance Results at MH

Redirection Time (ms)Explicit Suspending 46.67Explicit Resuming 270.28Implicit Resuming 317.78

Explicit Redirection Performance

Explicit Suspending

Steps Time (ms) %manage phase transition 1.76 3.77lock Socket 7.40 15.86kill sub-thread 8.12 17.40send SUSPEND_SIGNAL 1.17 2.50send WRITE_COUNTER 5.35 11.46receive ACK from CH 11.01 23.59receive port number 1.11 2.38receive auth seed 1.85 3.96close Socket 3.28 7.03prepare info of next Socket 1.02 2.19misc 4.60 9.86Total 46.67 100.00

Steps Time (ms) %make new Socket 80.75 29.88switch Socket in stream 0.36 0.13auth check for DataSocket 2.95 1.09receive port of ControlSocket 1.11 0.41receive auth seed 1.89 0.70make new ControlSocket 80.80 29.90auth check for ControlSocket 3.30 1.22make new NextServerSocket 60.44 22.36exchange next port and seed 6.62 2.45restart sub thread 26.56 9.83manage phase transition 0.90 0.33misc 4.60 1.70Total 270.28 100.00

Explicit Redirection Performance Explicit Resuming

Steps Time (ms) %make new Socket 80.75 29.88switch Socket in stream 0.36 0.13auth check for DataSocket 2.95 1.09receive port of ControlSocket 1.11 0.41receive auth seed 1.89 0.70make new ControlSocket 80.80 29.90auth check for ControlSocket 3.30 1.22make new NextServerSocket 60.44 22.36exchange next port and seed 6.62 2.45restart sub thread 26.56 9.83manage phase transition 0.90 0.33misc 4.60 1.70Total 270.28 100.00

82.14%

Inside Socket Creation

Comparison with Related Works

Name Layer Connection Implementation Continuity MH CH Others

Mobile-IP IP Limited K HA,FAPMI (+M-IP) IP Limited K K HA,FAMSOCKS TCP Limited U Proxy TCP-R TCP Yes K K -VNC Screen Yes U ServerMobileSocket Socket Yes U U -

6. Conclusion

Conclusion Application Layer Mobility and Connection Continuity User-Level library in Java Implicit & Explicit Redirection for Conventional Apps. & Mobile Apps.

Future Work UDP & Multicast Socket More Optimization

Fin.Thank you for your attention...

Eval.1 MobileSocket Overhead

Conventional Java.net.Socket 100MobileSocket (contains Mobility Support)

80? 90?

Eval.2 Socket Creation Overhead

Why is Socket Creation so heavy in Java? Where is bottle neck?C & Java

Java 80.4ms (71ms object constructor) C

Eval.3 ALW

In the case of large size ALW?Buffer overflow? Lock?Defined buffer size?ALW size and Transfer bandwidth

could not evaluate because of bug in JDK FreeBSD

Or Solaris ？

read & write mechanism

Adaptation in Application

Java Event

DSS Time Sequence

Client Server

connect

MobilityPreparation

DSS-EstablishmentPhase

user data EstablishedStateEstablishedState

ClosedStateClosedState

Explicit Redirection Implicit Redirection

Connection Establishment

MH

ALWAdjustment

DSS-Explicit SuspendPhase

disconnectExplicitySuspended StateExplicitySuspended State

CHSuspend()

resume()

connect

MobilityPreparation

user data EstablishedStateEstablishedState

DSS-Explicit ResumePhase

EstablishedStateEstablishedState

Explicit Redirection

MH

ImplicitlySuspended StateImplicitlySuspended State

CH

connect

ALWAdjustment

user data EstablishedStateEstablishedState

DSS-Implicit ResumePhase

EstablishedStateEstablishedState

lose IP(Disconnect)

Brokenpipe

Implicit Redirection

MobilityPreparation