T-110.5140 Network Application Frameworks and XML Summary and Conclusions 25.04.2006 Sasu Tarkoma

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T-110.5140 Network Application Frameworks and XML
Summary and Conclusions25.04.2006Sasu
Tarkoma
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Topics Covered

• Distributed systems security
• Multi-addressing Mobility and multi-homing
• Building applications with XML
• Distributed objects
• Role of directory services
• Mobile and wireless applications
• XML-based presentation and RPC
• Scalability and performance issues

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Interconnections
Network
Security
Directories

• Interconnections applicable on many levels
• Network-level operation
• DNS, overlay lookup, IPsec
• Application-level operation
• UDDI, SSL, WS-Security

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Mobility and Routing
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Naming, Addressing, and Routing
How to identify and name a node? Frequent
updates? One or two new name spaces?
NAMING
unicast to a specific node broadcast to all
nodes multicast to a subset of nodes anycast to
any one in some subset (IPv6)
ROUTING
ADDRESSING
How to route information to the nodes address?
NAT traversal? Overlay vs. network routing
Where is the node located? Differences
(IPv4/IPv6) Multi-addressing?
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Routing vs. mobility

• Topology data aggregation is necessary
• Cannot track all hosts in the world
• IP addresses determined by topology
• Network gives the routing prefix
• Mobile hosts must change their IP addresses
• Causes sockets / connections to break
• How to communicate address changes?
• Goal of a mobility protocol
• Transport and applications do not see address
  changes

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Rendezvous

• How to find the moving end-point?
• Tackling double jump
• What if both hosts move at the same time?
• Requires a rendezvous point
• Mobility management is needed!
• Initial rendezvous
• Can be based on directories
• Requires fast updates to directories
• Does not work well for DNS

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Identity/Locator split

• New name space for IDs
• Maybe based on DNS
• Maybe a separate namespace
• Maybe IP addresses are used for location
• Good for hiding IP versions
• Communication end-points (sockets) bound to
  identifiers

identifier
ID Layer
locator
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Host Identity Protocol

• New cryptographic namespace
• Connection endpoints mapped to 128 bit host
  identity tags (hashes of public keys)
• Mapping at HIP layer
• 4-phase Base Exchange with cryptographic puzzle
  for DoS prevention
• IPSec for network-level security

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Upper layer view

• IP connectivity problematic today
• Broken by firewalls, NATs, mobility
• Two versions of IP IPv4 and IPv6
• HIP has a potential remedy
• Restores end-to-end connectivity (NAT traversal
  possible but may require changes / tunnelling)
• Adds opportunistic security
• Handles mobility and multi-homing
• Requires DHT based overlay (currently missing)
• Where is the network state?
• Routers know addresses
• Like today
• DHT knows HITs / SIDs
• Lease based storage
• Middleboxes know SPIs
• Soft state

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Lessons to learn

• Hierarchical routing likely to stay
• Addresses carry topological information
• Efficient and well established
• Applications face changing connectivity
• QoS varies
• periods of non-connectivity
• Identifiers and locators likely to split
• Mobility management is needed
• Probably changes in directory services
• Overlays have been proposed

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Summary

• Topology based routing is necessary
• Mobility causes address changes
• Address changes must be signalled end-to-end
• Mobility management needed
• Initial rendezvous maybe a directory service
• Double jump problem rendezvous needed
• Many engineering trade-offs

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Distributed Hash Tables and Overlays
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Overlay Networks

• Origin in Peer-to-Peer (P2P)
• Builds upon Distributed Hash Tables (DHTs)
• Easy to deploy
• No changes to routers or TCP/IP stack
• Typically on application layer
• Overlay properties
• Resilience
• Fault-tolerance
• Scalability

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Some DHT applications

• File sharing
• Web caching
• Censor-resistant data storage
• Event notification
• Naming systems
• Query and indexing
• Communication primitives
• Backup storage
• Web archive

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Applications for DHTs

• DHTs are used as a basic building block for an
  application-level infrastructure
• Internet Indirection Infrastructure (i3)
• New forwarding infrastructure based on Chord
• DOA (Delegation Oriented Architecture)
• New naming and addressing infrastructure based on
  overlays

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Summary

• Mobility and multi-homing require directories
• Scalability, low-latency updates
• Overlay networks have been proposed
• Searching, storing, routing, notification,..
• Lookup (Chord, Tapestry, Pastry), coordination
  primitives (i3), middlebox support (DOA)
• Logarithmic scalability, decentralised,
• Host/identity split and overlays for directories
  seem good candidates for solving many of the
  issues with mobility and multi-homing

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Middleware
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Middleware

• Widely used and popular term
• Fuzzy term
• One definition
• A set of service elements above the operating
  system and the communications stack
• Second definition
• Software that provides a programming model above
  the basic building blocks of processes and
  message passing (Colouris, Dollimore, Kindberg,
  2001)

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Why Middleware?

• Application development is complex and
  time-consuming
• Should every developer code their own protocols
  for directories, transactions, ..?
• How to cope with heterogeneous environments?
• Networks, operating systems, hardware,
  programming languages
• Middleware is needed
• To cut down development time
• Rapid application development
• Simplify the development of applications
• Support heterogeneous environments and mask
  differences in OS/languages/hardware

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Middleware cont.

• Middleware services include
• directory, trading, brokering
• remote invocation (RPC) facilities
• transactions
• persistent repositories
• location and failure transparency
• messaging
• Security
• Network stack (transport and below) is not part
  of middleware

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Transparencies

• Location transparency
• RPC and RMI used without knowledge of the
  location of the invoked procedure / object
• transport protocol transparency
• RPC may be implemented using any transport
  protocol
• transparency of OS and hardware
• RPC/RMI uses external data representation
• Presentation is important
• XML is becoming increasingly important
• transparency of programming languages
• language independent definition of procedures
  CORBA IDL

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Network Application Framework

• Network Application Framework is middleware
• Contains services for distributed applications
• Middleware as a term is fuzzier and larger
• In this course, we focus on network application
  frameworks and XML
• objects (discovery, representation)
• directories (overlays,..)
• network
• security

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Examples

• Middleware
• CORBA
• Message-oriented Middleware
• Event Systems tuple spaces
• Java Message Service
• Java 2 Enterprise Edition (J2EE)
• .NET
• Mobile middleware
• WAE
• J2ME
• Wireless CORBA
• FUEGO

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Mobile Middleware I

• Middleware is typically designed and implemented
  for fixed-network hosts
• High bandwidth, low latency, reliable
  communication
• Persistent storage and sufficient computing power
• No mobility
• Mobile environment requires new solutions
• Existing middleware services do not scale
• Previous lectures mobility is challenging
• Small devices / embedded systems pose totally
  different challenges

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Mobile Middleware II

• Goals for middleware
• fault-tolerance, adaptability, heterogeneity,scala
  bility, resource sharing
• Mobile middleware
• dynamically changing context
• decoupled
• events, tuple spaces
• Basic solution for wireless
• Use a proxy

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Summary

• Middleware
• for application development and deployment
• for supporting heterogeneous environments
• Main communication paradigms RPC/RMI,
  asynchronous events (publish/subscribe)
• J2EE, CORBA, ..
• Mobile middleware
• Desktop middleware not usable on small, mobile
  devices
• Special solutions are needed
• J2ME, Wireless CORBA, ..

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Web Services
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Standardization

• W3C Web Services
• XML Protocol Working Group
• SOAP
• Web Services Addressing Working Group
• Web Services Choreography Working Group
• Web Services Description Working Group
• WSDL
• OASIS
• E-business standards, UDDI
• WS-I (Web Service Interoperability Org.)
• Binding profiles,..

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Web Service Architecture

• The three major roles in web services
• Service provider
• Provider of the WS
• Service Requestor
• Any consumer / client
• Service Registry
• logically centralized directory of services
• A protocol stack is needed to support these roles

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Web Services Protocol Stack

• Message Transport
• Responsible for transporting messages
• HTTP, BEEP
• XML Messaging
• Responsible for encoding messages in common XML
  format
• XML-RPC, SOAP
• Service Description
• Responsible for describing an interface to a
  specific web service
• WSDL
• Service discovery
• Responsible for service discovery and search
• UDDI

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WS Protocol Stack
Discovery UDDI
Description WSDL
XML Messaging SOAP, XML-RPC, XML
Transport HTTP, FTP, BEEP, SMTP, JMS
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What is WSDL?

• WSDL Web Service Description Language
• An XML language used to describe and locate web
  services
• location of web service
• methods that are available
• data type information and XML messages
• Commonly used to describe SOAP-based services
• W3C standard (work in progress)
• Initial input WSDL 1.1 as W3C Note
• Current version 2.0 (last call)
• Some differences between 1.1 and 2.0
• WSDL 1.1 in WS-I Basic Profile 1.0 and 1.1.

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WSDL Overview
ltdefinitionsgt ROOT WSDL element
lttypesgt The data types that are used
ltmessagegt What messages are transmitted?
ltportTypegt The supported operations
ltbindinggt The binding to concrete protocols
ltservicegt Reference to actual location
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Mapping SOAP to WSDL


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Putting it together
Source http//msdn.microsoft.com/
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SOAP Message Structure

• Optional header contains blocks of information
  regarding how to process the message
• Routing and delivery settings
• Authentication/authorization assertions
• Transaction contexts
• Body is a mandatory element and contains the
  actual message to be delivered and processed (and
  fault information)

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What is UDDI?

• Universal Description Discovery and Integration
• Industry-wide initiative supporting web services
• Specifications
• Schemas for service description
• Schemas for business (service implementers)
  description
• Developed on industry standards
• Applies equally to XML and non-XML web services
• Implementation
• Public web service registry and development
  resources
• SOAP-based programming protocol for registering
  and discovering Web services
• XML schema for SOAP messages
• a description of the API
• UDDI does not directly specify how pricing,
  deadlines, etc. are handled/matched
• Advanced discovery via portals and marketplaces

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Web Services Security
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Need for XML security

• XML document can be encrypted using SSL or IPSec
• this cannot handle the different parts of the
  document
• documents may be routed hop-by-hop
• different entities must process different parts
  of the document
• SSL/TLS/IPSec provide message integrity and
  privacy only when the message is in transit
• We also need to encrypt and authenticate the
  document in arbitrary sequences and to involve
  multiple parties

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High-level view to WS security

• Security is as strong as the weakest link
• The options for an attacker are
• Attack the Web Service directly
• Using unexpected XML
• Attack the Web Services platform
• Attack a WS security tool
• Attack the underlying operating system or network
  connection

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Application-layer Security

• Identity-based security
• Authentication and authorization information
  shared across security domains
• Content-based security
• Protecting against buffer overflow and CGI-like
  attacks
• Must have knowledge about the applications to
  which these messages are directed
• Accountability or non-repudation
• Need message level security
• Maintain integrity, archived audit trails
• The standards and specifications mentioned
  earlier address these issues

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Standardization landscape

• Who are specifying the basic standards?
• Who are specifying the higher level standards?
• Who is implementing the standards?

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Who are specifying the standards?

• Joint IETF/W3C
• XML Signature (www.w3.org/Signature)
• W3C
• XML Encryption (www.w3.org/Encryption/2001)
• XML Key Management (XKMS) (www.w3.org/2001/XKMS)
• OASIS
• WS-Security
• SOAP Message Security specification etc.
• SAML Security Assertion Markup Language
• XACML Extensible Access Control Markup language
• Electronic Business XML (ebXML) (with UN/CEFACT)
• Web Services Interoperability Organization (WS-I)
• Basic security

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Standardization Groups
Extensible Rights Markup Language
XrML
Provisioning
XML Common Biometric Format (XCBF)
eXtensible Access Control Markup Language (XACML)
XML Key Management Specification
WS-Security
Biometrics
XML Encryption
XML Signature
XKMS
XACML
SAML
Security Assertion Markup language
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Basic XML Security

• XML Digital Signatures (XMLDSIG)
• XML Encryption
• XML Canonicalization
• XML Key Management

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Web Services Security Requirements

• Access control to Web services
• WS-Security, XML-Signature
• SAML Issuing and validation of SAML assertions
• Digital certificate validation
• Content-filtering XML
• Filters based on data format (XSD)
• Filters based on content (XPath)
• Filters based on integrity (XML Signature)

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Functional point of view
Management Console Design and Deploy Security po
licies
ID Management LDAP PKI Single Sign-On
Authorization
Authentication
Content Checking
Reporting Activity Alerting Secure logging
Integrity
Validation
Routing
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Security Contexts in Web Services

• Remember Web Services goals
• Re-use existing services
• Combine services from several domains
• Security result Must support several security
  domains
• SOAP intermediaries
• Reusing security tokens from one message in
  another message

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Summary

• Security contexts
• Security needed within and between contexts
• XML validation, encryption, and authentication
  needed between security contexts!
• WS security standard revisited
• SOAP header carries security information (and
  other info as well)
• Selective processing
• SAML
• Statements about authorization, authentication,
  attributes
• SAML WS-Security XACML
• Implementations available

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Putting it together
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With identity/locator split overlays?
CONTROL
Upper layers
DNS names, custom identifiers
Overlay
Overlay addresses
Host Identities
Congestion
IP addresses
ID Layer
IP addresses
End-to-end
DATA
Routing
Routing paths
Routing paths
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Discussion
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Important Dates

• Exam on Tuesday 16.5. 9-12 in T1.
• Deadline for the second assignment 12.5.