MobileSocket Toward Continuous Operation for Java Applications

1
MobileSocketToward Continuous Operation for Java
Applications

• Tadashi OKOSHIGraduate School of Media and
  GovernanceKeio University, JAPAN
• slash_at_ht.sfc.keio.ac.jp

Eighth International Conference on Computer
Communication and NetworksIEEE ICCCN99 October
11-13, 1999 _at_Boston, USA
2
Research Abstract

• Goal Communication Continuity
  for network applications for users
  Work Continuity
• MobileSocket
• Is an application layer approachimplemented as
  an user-level library.
• Is effective for
• Conventional Network Application
• Java Mobile Applications

3
With MobileSocket library

• Java network applications can continue their
  communication with the one continuous socket
  connection, even after the mobile hosts
  relocation.
• No need to modify source code
• Additional APIs for adaptation

4
Todays Outline

• 1. Research Background
• 2. Communication Continuity
• MobileSocket 3. Design 4. Implementation 5.
  Programming Applications 6. Evaluation
• 7. Conclusion Future Work

5
1. Background

• Mobile Computing Environment
• Mobile hosts and users move around network even
  during applications are communicating with the
  remote.

A
Internet
B
A
Mobile Host
6
1. Background (Contd)

• Research Goal
• To realize users Continuous Operationsupported
  by the continuous behavior of applications
• For network applications
• Communication Continuity with remote

7
2. Communication Continuity

• Communication Continuity consists of
• Mobility
• Virtual Circuit Continuity
• Other Issues

8
Mobility

• Capability of the protocol functionality in the
  both communication endpoints to identify each
  other independent of the location changes of the
  endpoints.
• E.g. Mobile IP

Identify each other
(Location Transparent ID)
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Virtual Circuit Continuity

• Capability of keeping a virtual circuit
  connection alive, retaining reliability and the
  byte stream consistency independent of the
  location changes of the endpoints.
• E.g. TCP-R

Keep a virtual circuit connection
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Toward Communication Continuity

• For applications with
• Datagram communication (e.g.UDP/IP)
• Mobility support
• Virtual circuit communication (e.g.TCP/IP)
• Mobility support
• Virtual circuit continuity support

? Both Mobility and VC Continuity supports
are the requirements for communication
continuity.
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Other Issues for CommunicationContinuity Support

• 2) Simplified and minimized implementation
• 3) Avoidance of modification in existing
  applications
• 4) Adaptation interfaces for
  MobileSocket-aware applications

12
3. MobileSocket Design

• (1) mobility and connection continuity
  support in application layer
• Dynamic Socket Switching (DSS)
• Application Layer Window (ALW)
• (2) User-level library in Java
• (3) Supports both implicit explicit
  redirection operations
• (4) Adaptation APIs for applications

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(1) Application Layer Approach
Application
Application
MSOCK
Socket Layer
TCP Layer
TCP-R
IP Layer
Mobile IP
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Dynamic Socket Switching
Internal SocketConnection (1)
Application (MobileHost)
Application (CorrespondentHost)
MobileSocket Layer
MH1
CH
Socket Layer
MH1
CH
TCP Layer
MH1
CH
IP Layer
IPMH1
IPCH
Before
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Dynamic Socket Switching
Application (MobileHost)
Application (CorrespondentHost)
MobileSocket Layer
MH1
CH
Socket Layer
MH1
CH
MH2
TCP Layer
MH1
CH
MH2
IP Layer
IPMH1
IPMH2
IPCH
Relocation
After
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Application Layer Window (ALW)

• User-level sliding window inside library
• Provides Byte Stream Consistency

Application
Application
write()
read()
Data
Data
read
store
write
ACK
ALW_COUNTER
ACK
send
flush
count
recv
ALW
MobileSocketin Sender
MobileSocketin Receiver
Data
Data
Data
DataSocket
ACK
ControlSocket
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(2) User-Level Library
(MSOCKS)
(TCP-R)
(Mobile-IP)
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(3) Connection Redirection Schemes

• Implicit Redirection
• Mechanism by which a connection is automatically
  redirected such that application is unaware of
  the relocation.
• No need to modify and insert any additional lines
  to applications
• No adaptability in applications behavior
• Explicit Redirection

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(4) Explicit Redirection Adaptation
Interfaces

• Implicit Redirection
• Explicit Redirection
• Mechanism by which the application programmers
  can explicitly specify where the connection
  redirection takes place
• Realized by specific APIs (suspend() resume()
  )
• Adaptive behavior of application
• Need to modify applications source code

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4. MobileSocket Implementation

• State Transition Diagram
• Time Sequence
• Connection Establishment
• Implicit Redirection
• Explicit Redirection

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START POINT
Closed
Connected to Server (DSS-EstablishmentPhase(Clien
t) )
Connected from Client (DSS-EstablishmentPhase(Ser
ver) )
Called suspend() (send SUSPEND_SIGNAL,
DSS-ExplicitSuspend Phase)
Lost IP address
Called resume() (Reconnect to CH, DSS-
ExplicitResume Phase)
Get IP address (Reconnect to CH,
DSS-ImplicitResume Phase)
Called close()(close connection)
Established
ImplicitlySuspended
ExplicitlySuspended
reconnected from MH(DSS-ExplicitResume
Phase)
Reconnected from MH(DSS-ImplicitResume Phase)
Called close() or timedout(close connection)
DataSocket broken-pipe
received SUSPEND_SIGNAL (DSS-ExplicitSuspend
Phase)
Reconnected from MH(DSS-ImplicitResume Phase)
Called close()(close connection)
Called close() or timedout(close connection)
Called close()(close connection)
Normal Transitions for CH
Normal Transitions for MH
Transition trigger(action)
State
Normal Transitions for Client
Normal Transitions for Server
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DSS(1) Establishment Phase
23
Client
Server
DataSocket
ControlSocket
RedirectionServSocket
DataSocket
ControlSocket
RedirectionServSocket
accept()
connect
ControlSocket port, AuthenticationSEED1
CreateSocket
CreateSocket
connect()
accept()
AuthenticationSEED1
DSS-Establishment Phase
ACK
CreateSocket
CreateSocket
RedirectionServer port, Next_SEED
Data
ALW ACK
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DSS(2) Explicit Suspend Phase
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Mobile Host
Correspondent Host
DataSocket
ControlSocket
RedirectionServSocket
DataSocket
ControlSocket
RedirectionServSocket
SUSPEND_SIGNAL
lock
lock
ACK
WRITE_COUNTER
Compute DIFF
Compute DIFF
DSS-ExplicitSuspend Phase
Invoke Suspend SubPhase(if DIFFgt0)
Invoke Suspend SubPhase(if DIFFgt0)
Suspend SubPhase
ACK (DIFF_IS_ZERO)
Close
Close
Close
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DSS(3) Explicit Resume Phase
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Mobile Host
Correspondent Host
RedirectionServSocket ? DataSocket
New RedirectionServSocket
ControlSocket
DataSocket
ControlSocket
RedirectionServSocket
connect()
accept()
Next_SEED
ACK, ControlSocket port, AuthenticationSEED3
connect()
CreateSocket
accept()
AuthenticationSEED3
DSS-ExplicitResume Phase
ACK
CreateSocket
CreateSocket
RedirectionServer port, Next_SEED
unlock
unlock
Data
ALW ACK
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DSS(4) Implicit Redirection
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Correspondent Host
Mobile Host
RedirectionServSocket ? DataSocket
RedirectionServSocket ? DataSocket
New RedirectionServSocket
New RedirectionServSocket
ControlSocket
DataSocket
ControlSocket
RedirectionServSocket
ControlSocket
DataSocket
ControlSocket
RedirectionServSocket
lose IP
lose IP
disconnected
disconnected
get IP
get IP
accept()
accept()
connect()
connect()
Next_SEED
Next_SEED
CreateSocket
CreateSocket
ACK, ControlSocket port, AuthenticationSEED3
ACK, ControlSocket port, AuthenticationSEED3
connect()
connect()
CreateSocket
CreateSocket
accept()
accept()
AuthenticationSEED3
AuthenticationSEED3
ACK
ACK
DSS-ImplicitResume Phase
DSS-ImplicitResume Phase
CreateSocket
CreateSocket
CreateSocket
CreateSocket
RedirectionServer port, Next_SEED
RedirectionServer port, Next_SEED
READ_COUNTER
READ_COUNTER
unACKed Data retransmit
unACKed Data retransmit
unlock
unlock
unlock
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Disconnection Recognition in MH

• java.net.InetAddressgetLocalHost returns IP
  address based on DNS.
• Checker Thread as a adhoc solution
• Disconnection (1)get local IP from
  java.net.SocketgetLocalAddress (2)make Socket
  to local IP address periodically.
• Reconnection (1) make Socket to Correspondent
  Host IP address periodically.

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5. Programming Applications

• Class Socket sock new Socket(host, port)
  MobileSocket sock new MobileSocket(host, port)
• Explicit Redirection (Option) sock.suspend()
  sock.resume()
• Adaptation Event (Option) MobilityEvent Event ,
  MobilityListener Interface

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Applications with MobileSocket

• Serializable MobileSocket classfor Mobile
  Applications and Agents

AppA
MSockA (SocketX)
AppB
Host-A
Host-B
AppA
MSockA (SocketY)
ObjectSerialization
Host-C
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Applications with MobileSocket

• MobileSocket Exchanging

AppA
AppB
MSockA
MSockB
Host-A
Host-B
MSockA
Send MobileSocket Objectvia ObjectSerialization
AppC
Host-C
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6. Evaluation

• Performance Measurement
• Explicit Redirection
• Comparison with Related Works

35
Measurement Environment

• Implementation
• JavaCoreAPI 1.1
• jp.ac.keio.sfc.ht.MobileSocket package
• Evaluation Environment
• Dynabook SS-R590 (Pentium 90MHz, 40MB) for MH
  Sony PCG-737 (PentiumMMX 233MHz, 64MB) for CH
• Closed 10Base-T Network
• FreeBSD2.2.1R JDK 1.1.6.V98-9-23 for FreeBSD

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Performance Results at MH
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Explicit Redirection Performance

• Explicit Suspending

38
Explicit Redirection Performance

• Explicit Resuming

82.14
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Comparison with Related Works
Name Layer Connection Implementation
Continuity MH CH Others Mobile-IP IP
Limited K HA,FA TCP-R TCP Yes K K
- MSOCKS Socket Limited U Proxy
MobileSocket Socket Yes U U -
upper
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7. Conclusion

• Conclusion
• Application Layer Mobility and Connection
  Continuity
• User-Level library in Java
• Implicit Explicit Redirection
• for Conventional Apps. Mobile Apps.
• Future Work
• More Optimization
• Security Issues

41
Fin
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Eval.1 MobileSocket Overhead

• Conventional Java.net.Socket 100
• MobileSocket (contains Mobility
  Support) 80? 90?

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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

44
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?

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read write mechanism
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Adaptation in Application

• Java Event

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DSS Time Sequence
Connection Establishment
Server
Client
ClosedState
connect
DSS-EstablishmentPhase
MobilityPreparation
user data
EstablishedState
Explicit Redirection
Implicit Redirection
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Explicit Redirection
EstablishedState
MH
CH
Suspend()
ALWAdjustment
DSS-Explicit SuspendPhase
disconnect
ExplicitySuspended State
resume()
connect
MobilityPreparation
DSS-Explicit ResumePhase
user data
EstablishedState
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Implicit Redirection
MH
CH
EstablishedState
lose IP(Disconnect)
Brokenpipe
ImplicitlySuspended State
connect
DSS-Implicit ResumePhase
MobilityPreparation
ALW Adjustment
user data
EstablishedState
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Mobile Computing Environment

• Work Continuity for users

?
A
Internet
B
A
Mobile Host
51
MobileSocket Applications (1)

• Java network applications

A
Internet
B
A
Mobile Host
52
MobileSocket Applications (2)

• Java Mobile Applications

AppA
MSockA (SocketX)
AppB
Host-A
Host-B
AppA
MSockA (SocketY)
ObjectSerialization
Host-C
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MobileSocket Applications (3)

• Even Exchanging Socket...

AppA
AppB
MSockA
MSockB
Host-A
Host-B
MSockA
Send MobileSocket Objectvia ObjectSerialization
AppC
Host-C