Understanding the WebDAV Protocol

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Understanding The WebDAV ProtocolAlex
HopmannProgram ManagerExchange Server Product
UnitMicrosoft Corporation
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(No Transcript)
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Better Living Through HTTP, XML And Rich Storage
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Agenda

• HTTP 1.1
• The WebDAV Extensions
• Using XMLHTTP in Internet Explorer 5

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Audience

• Administrators
• Understand your network traffic
• Developers
• Building web components to talk to Exchange

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HTTP 1.1

• HyperText Transfer Protocol
• IETF RFC 2616
• Most notably the protocol used to retrieve
  content for web browsers
• Widely implemented and deployed today

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HTTP 1.1 Protocol Basics

• RequestMETHOD URI HTTP/1.1HeaderName
  HeaderValueContent-Length
  21 Request Body
• ResponseHTTP/1.1 Status StatusTextHeader
  Name HeaderValue Response Body
  

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HTTP GET

• RequestGET /myfile.gif HTTP/1.1host
  www.myserver.comaccept /Content-Lengt
  h 0
• ResponseHTTP/1.1 200 OKContent-type
  text/htmlContent-Length
  8274 xxxxxxxxxxxxxxxxxxxxxxxxxx
  . . .

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HTTP 1.1

• Supported methods
• GET -- retrieve a resource
• PUT -- write a resource to server
• DELETE -- remove a resource
• OPTIONS -- discover server capabilities
• HEAD -- Get header information
• POST Submit form / new item

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Key HTTP Features

• Scalability
• Persistent Connections
• Authentication
• Connection Security
• Proxy and Cache Support
• Virtual Servers
• Flexible Methods
• Content Negotiation

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HTTP And Scalability

• Most widely deployed and scale proven application
  today
• Hotmail has 40 million users
• Big web sites run a billion requests per year
• How?
• Simplicity
• The right kind of state

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HTTP And Persistent Connections

• Performance Optimization in HTTP 1.1
• Persistent connections are not the same thing as
  maintaining state
• Any request / response pair is independent from
  others
• Proxies can aggregate requests from multiple
  users on one connection

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HTTP And Authentication

• Flexible framework for multiple authentication
  techniques
• Basic HTTP included clear-text password (basic)
• Microsoft NTLM authentication
• Windows 2000 supports digest and kerberos

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HTTP And Connection Security

• SSL Secure Sockets Layer
• Basic security approach is secure tunnel
• Transparent to rest of protocol
• Can also transport already secured objects (ex
  S/MIME)

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Proxy And Cache Support

• HTTP is one of the first protocols that provided
  for proxies in the basic framework
• Proxy and cache support leads to basic techniques
  for scalable web services

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Virtual Servers

• HTTP makes it easy to separate the physical
  machine from the greater namespace.
• The HOST header
• Multiple virtual servers on one physical machine.
• Multiple physical machines supporting one
  namespace
• Exchange 2000 Front End / Back End

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Content Negotiation

• HTTP is based on MIME
• Initially the web was just HTML
• Then image/gif
• Then image/jpeg, text/css
• Now text/xml and whatever comes next
• Client can request specific content-type via
  ACCEPT header

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Flexible Methods And Headers

• New types of methods and headers can be defined
• OPTIONS method used to determine what extensions
  a server supports
• HTTP/1.1 200 OK
• Server Microsoft-IIS/5.0
• Date Tue, 05 Oct 1999 190144 GMT
• Content-Length 0
• Accept-Ranges bytes
• DAV 1, 2
• Public OPTIONS, TRACE, GET, HEAD, DELETE, PUT,
  POST, COPY, MOVE, MKCOL, PROPFIND, PROPPATCH,
  LOCK, UNLOCK, SEARCH

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WebDAV

• Web Distributed Authoring and Versioning
• IETF RFC 2518
• Most notably the protocol extension to HTTP that
  makes the web read/write
• No versioning!
• Its just the good old Internet
• Supported by Office 2000, Internet Explorer 5.0,
  Windows 2000, IIS 5, Exchange 2000 Server.

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WebDAV Model

• Resources
• Anything identified by a URL
• Collections
• Anything that contains resources
• Is a resource
• Properties
• Associated with resources.
• Represented by XML.

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WebDAV Methods Part 1

• Supported methods
• MOVE move a resource / collection
• COPY copy a resource / collection
• LOCK lock a resource
• UNLOCK unlock a resource
• MKCOL make a collection

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Example MOVE

• request
• MOVE /public/docs/test.doc HTTP/1.1
• Destination /public/pch/test.doc
• HOST ptdemo
• depth infinity
• Content-Length 0
• response
• HTTP/1.1 201 Created
• Server Microsoft-IIS/5.0
• Date Fri, 31 Jul 1999 235305 GMT
• Location http//public/pch/test.doc
• Content-Length 0

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Properties

• Supported methods
• PROPFIND enumerate properties
• PROPPATCH set / remove properties
• SEARCH query properties
• Superset of PROPFIND capabilities
• Properties use XML model
• XML-Namespaces
• Actual XML representation

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Example Properties

• DAVcreationdate
• DAVdisplayname
• DAVgetcontentlength
• DAV is an XML-Namespace
• You can define new namespaces for custom
  properties

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Example PROPFIND

• PROPFIND /public/pch/test.doc HTTP/1.1
• Host ptdemo
• Depth 0
• Content-Type text/xml
• Content-Length 104

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Building Apps With HTTP

• OLEDB / ADO
• Version 2.5 provides hierarchy support
• Bind via normal URLs
• XMLHTTP
• Simple scripting component
• use in web pages or client apps

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Using MSDAIPP With ADO

• MSDAIPP Microsoft Data Access for Internet
  Publishing
• Same provider used by Web Folders
• C new ActiveXObject("ADODB.Connection")
• C.Provider "MSDAIPP.DSO"
• C.ConnectionString "http//servername/"
• C.Open()
• R new ActiveXObject("ADODB.Recordset")
• R.Open(SQLStatement, C, 0, 2, 512)

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Iterating Over The Rowset

• while(!R.eof)
• outputhere.innerHTML R.Fields("DAVdisplayname"
  ) "   size " R.Fields("DAVgetcontentlength"
  ) "
  "
• R.movenext()

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XMLHTTP

• Simple scripting interface for HTTP
• open(method, url, async, user, pass)
• setRequestHeader(header, value)
• send(value)
• getResponseHeader(header)
• responseText
• responseXML
• onreadystatechange
• readyState

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Asynchronous Operation

• Avoid locking client
• Set a callback routine
• When readyState 4 response is
  availablefunction requestdone()
• if(httprequest null httprequest.readyState
  ! 4)
• returnhttprequest null
• // do something here

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XMLHTTP Example And Demo

• function doquery()
• xsldest.innerHTML "loading..."
• request new ActiveXObject("microsoft.xmlhttp")
• request.open("PROPFIND", urlid.value, false)
• request.setRequestHeader("depth", "1")
• request.send("")
• xsldest.innerHTML request.responseXML.transform
  Node(calxsl.documentElement)

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Other Sessions

• 5-303 Wednesday 1030 am Building Web Solutions
  with XML and XSL
• 5-302 Wednesday 115 pm Building Solutions for
  Internet Explorer 5
• 5-305 Thursday 1030 am Building Web
  Applications Using Exchange 2000 Outlook Web
  Access Components

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Web References

• Information on Microsoft Standardshttp//msdn.m
  icrosoft.com/standards/
• Information on XML http//msdn.microsoft.com/xml/
  
• XMLHTTPhttp//msdn.microsoft.com/xml/reference/sc
  riptref/XMLHttpRequest_object.asp

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Questions?

• HTTP is great for scalable, efficient
  applications
• WebDAV makes it richer and non-static
• Microsoft provides easy tools to build
  applications using this technology

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