Optimized Communication for Mobile Applications

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Optimized Communication for Mobile

Applications

Thesis Proposal

Sangyoon Oh

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Why Interesting?

z Recent prominent data sharing of mobile computing with other distributed system.

z e.g. Packet-based, Always-on Cellular

z SOAP Interoperability Æ Connect disparate and distributed resources.

z Prospective of popularity

z Open Standard Community (W3C), Industry (Nokia, Sun..)

z W3C’s XML Binary Characterization WG

Å result of the Binary Interchange Workshop.

z Mobile computing demands support for

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Problems

z Performance Overhead in Web Services

z XML – uses considerable resources for transmit and parsing.

z Information storing as Text

z Tagged Element in document (Universal End-to-End

presentation format)

Æ Parsing and Increase Size

z Mobile environment

z Battery-constraint, Limited Computation

z _{High-Latency, intermittent communication}

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Research Statement

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Purpose of Research

z Purpose of Research:

To design and develop an optimized communication framework preserving SOAP semantics for mobile computing.

z Prospect of Research

z Separate data presentation format and data content

z Interoperability: platform and language ÅXML’s universality

z Interoperability and performance

z Loss of self description

z Saving parsing computation and data binding >> Latency

Saving

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Related Literature Survey

z

Sun’s Fast Web Services and Fast

Infoset Project

z

MTOM/XOP of W3C

z

DFDL of Global Grid Forum

z

Extreme! Lab’s research on SOAP

Performance

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Classification of SOAP Alternatives

z Some data doesn’t fit in XML serialization

Æ MTOM/XOP

z _{Media data}

z Standard format with compression z JPEG, GIF, MP3

z Data that includes digital signature

z Binary integrity would not be preserved after serialized into XML

format

z Some Application domain use a binary representation to avoiding verbose XML encoding.

Æ Fast Web Services/Fast Infoset, Extreme! Lab

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Summary of Projects

Extreme! Lab Properties Negotiation, Binary Application Protocols Scientific Data QoS Target Lack of mobile issues

MTOM/XOP Fast Web Services

Support binary contents

GZip for XML

Media File, Data that includes digital

signature

Java Application (No changes on Application level) Performance, Optimized message scheme for in-memory representation

Fast Infoset is not interoperable,

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Sun’s Fast Web Services and Fast

Infoset Project

z

Fast Web Services make use of Fast

Infoset (Binary encoding of XML

Infosets) for carrying SOAP messages.

z

Fast Infoset: specifies a representation of

an instance of the XML Infoset using binary

encoding.

z

Use ASN. 1. for binary encoding

z Binary Encoding Æ Packed Encoding Rule

(PER) – Octet

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Fast Infoset

z

No end tags

z

Indexing repeated

string

z

Indexing qualified

names

PERed

Fast Infoset

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Fast Infoset: Example

<root>

Local Name Content

0 root

one

1 tag

two

2 anotherTag

{0}<root>

{1}<tag>{0}one

[1]<>{1}two

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MTOM/XOP

z

MTOM

(Message Transmission Optimization Mechanism) and

XOP

(XML-binary Optimized Packaging)

z

By W3C XML Protocol Working Group

z

MTOM describes how XOP is layered into

SOAP-HTTP.

z

Serialization of XML: Looks like MIME

z

Still Preserve “XML structure”

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XOP: Example

--MIME_Boundary Content-ID: <[email protected]> Content-Type: application/xop+xml;charset=UTF-8;type="application/soap+xml" Content-Transfer-Encoding: binary <soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope" xmlns:xmlmime="http://www.w3.org/2004/06/xmlmime" xmlns:xop="http://www.w3.org/2004/08/xop/include"> <soap:Header></soap:Header> <soap:Body><ns1:EchoTest xmlns:ns1="http://example.org/mtom/data"> <ns1:Data><xop:Include href="cid:thismessage:/frog.jpg"></xop:Include> </ns1:Data></ns1:EchoTest> </soap:Body> </soap:Envelope> --MIME_Boundary Content-ID: <thismessage:/frog.jpg> Content-Type: application/octet-stream Content-Transfer-Encoding: binary

ÿØÿà JFIF ÿÛC

$.' ",# ( 7),01444 '9=82<.342ÿÛC

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Data Format Description Language

(DFDL)

z Define an XML-based language for describing the structure of binary and character encoded data

z _{DFDL Syntax allows a description of abstract data model}

using XSD.

z Data file or data stream

z Provide Processing Library

z Maybe as Web Services, e.g. OGSA Virtual Data Service.

z Process binary data to structured output XML Abstract Data Model

z _{Data structure, Complex-type}Å _schema

z _{Lower Layer (Mapping): physical representation, base-type (4}

byte integer, little-endian format…)

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DFDL Overview

Data Model

•

Structure

•

Primitives

Fortran C/C++ Java

Binary file Text file Data stream API

Data Model

Mapping _{Integers should be read as 4}

bytes, little endian format A structure called “spectrum” that is a 200 value vector of integers

Vector myspectrum =

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DFDL: Example

Example XML Representation A₁

<?xml version="1.0" encoding="UTF-8" ?>

<DFDLxmlns="DFDL" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xsi:noNamespaceSchemaLocation="C:\RECORDS\projects\BFD-DFDL\jdm1\NewDFDLType.xsd">

<point>

<point>

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DFDL: Example

Example Description File in DFDL for XML A1

<?xml version="1.0" encoding="UTF-8"?>

<xs:schema elementFormDefault="qualified" attributeFormDefault="unqualified" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns="DFDL">

<xs:complexType name="complexNumber">

<xs:sequence>

<xs:element name="real" type="xs:float"/> <xs:element name="imaginary" type="xs:float"/> </xs:sequence> </xs:complexType> <xs:element name="DFDL"> <xs:complexType> <xs:sequence> <xs:element name="vector"> <xs:complexType> <xs:sequence>

<xs:element name="point" type="complexNumber" maxOccurs="10"/>

</xs:sequence> </xs:complexType> </xs:element> </xs:sequence> </xs:complexType> </xs:element> <!-- Notes:

New DFDL types are simply new types defined in XML Schema

To be usable, new types must be associated with one or more transforms. By default, a transform that is the equivalent of reading constituent elements is available.

In this example, complexNumber can be created by sequentially reading two floats using the default transform, so no explicit specification of the transform is needed (see ExplicitTransformSpecification.xsd for this case). -->

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SOAP Performance Research

Extreme! Lab

z Research of SOAP performance for scientific computing

z _{Schema-specific parsing}

z _{Persistence Connection and Chunking (Streaming) of}

messages

z _{ASCII-Double Conversion}Å _{the most critical overhead}

z Target: Large Files with many small objects (million floats)

z High performance communication Approach (Recommendation)

z Use SOAP as an initial mechanism for negotiating faster

protocol

z _{Use multiple communication protocol to handle wide range of}

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Architecture Requirements

z Mobile computing issues

z Reliable Communication Model

z Simpler Security Model

z Compatible with J2ME platform

z Flexible Representation preserving SOAP Semantics

z Binary encoding

z Negotiation

z Quality of Service (Reliability and Security)

Æ Expecting to reduce parse time, bandwidth usage

z Work best for a stream

z _{Designed for on high-frequency small messages}

z Not limited to proxy architecture

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Handheld Messaging Service

101 102 103 104 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 Payload (byte) R ound Tr ip Ti m e (s e c ) HHMS RPC

z General mobile

communication framework by CGL

z Provides a core pub/sub API for mobile application.

z Lightweight user library

z Server-side gateway

z TCP and HTTP transport

z HHFR is a part of HHMS

100 101 102 0 50 100 150 200 250 300 350 400 450

Number of Clients

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Overview Architecture

Simple Scenario of a Stream

1. Mobile application request

Negotiation for stream characteristics

2. Gateway response 3. Gateway generates

encoder/decoder

4. Establish Flexible

Representation stream

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Message Generation

z

Works best in a Stream in Web Services

z Unchanged SOAP Header used throughout the

stream

z Data Structure and SOAP message header Å

beginning of stream (Negotiation)

z SOAP body of changing content Å Binary encoding

z

Use DFDL to define message structure

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Message Generation

z

Pointer (URI)

1)

Pointer to Context Store

(Representation

Specification)

2)

Pointer to Method used e.g.

HHFR (In SOAP Header)

z

Context store

z

SOAP Header

z

Stream Info

z

DFDL schema

Message block

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Negotiation

z

Two end-points exchange characteristics of

stream.

z

Negotiate in a conventional SOAP message.

z Data structure in DFDL, reliable messaging

scheme, security model, and transport protocol

z In pre-defined negotiation schema

z

Current ad-hoc scheme to store Context

Information

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Handlers

z

Context Handler

z Filter: mapping presentation format

z Context store: SOAP Header, Stream (Session)

Info and DFDL

z

Reliability Handler

z Reliable Messaging processor

z WS-Reliable Messaging compatible

z Trace messages and assure message delivery

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Handlers

z

Security Handler

z

Binary encoding

z WS-Security Æ very careful to apply XML level

security

z

Traditional encryption

Æ

HTTPS or

Message block encryption with lightweight

library

z E.g. Bouncy Castle

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Research Issues

z

Having on-the-wire representation of SOAP

Infoset for wireless communication

z

Performance vs. Interoperability

z

Break-even point

z SOAP and Handheld Flexible Representation

z

Performance vs. Quality of Service

z reliability and security

z

Application Domain

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Contributions

z We will show how to improve SOAP message transmission performance without sacrificing its interoperability.

z A novel approach to optimize message transmission by designing scheme which is message-based and capitalizing SOAP message structure.

z We will experiment the idea - Handheld Flexible

Representation (HHFR) by building a prototype, for mobile applications in stream specific application domains.

Optimized Communication for Mobile Applications