Transcript
T-110.5140 Network Application Frameworks and XML Introduction and overview 2.2.2009
Contents
Introduction
Overview
Sasu Tarkoma
Based on slides by Pekka Nikander
Starting Point
Assume that you already know details of
TCP/IP and underlying technology Basics of cryptography and cryptographic protocols Java, C++, and OO programming Basic client/server programming
Distributed objects and distributed security XML and Web services Architectural overview and understanding New directions in research and standardization
Course focus and goals
Connections between aspects Examples
Distributed systems security Multi-addressing: Mobility and multihoming Building applications with XML
Distributed objects Role of directory services Mobile and wireless applications XML-based presentation and RPC
Scalability and performance issues
Course Info
General overview of all aspects involved Ability to implement distributed systems
Networking: naming, addressing, routing Multi-addressing:Mobility, multi-homing Security: Trust, risks, protocols, keys Objects: Encapsulation, XML, frameworks Performance: bandwidth, delay, bottlenecks
Topics Covered
Adding to these
Starting point, topics, goals
Hands-on experience with CORBA, SOAP (web services), XML, network-level security
Understanding of
Distributed object-oriented systems Crypto based security in distributed systems XML and how it is used in practise Performance issues Architecture and why does it matter
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Course Info
Course structure Lectures on Mondays 12.15-14 in T3 Two assignments as pair-work Final exam on Tuesday 12.5. 9-12 in T1
Study materials for the course
Lectures
Assignments
Lecture slides and handouts, scientific papers, and relevant standards
Contact information
Background
Eric Newcomer Understanding Web Services
Eric Greenberg’s book “Network Application Frameworks” Chapter 1-9 and 12
Sanjiva Weerawarana et al. Web Services Platform Architecture. Prentice Hall.
Kari Visala (@hiit.fi) Long Hoang (
[email protected])
Common questions to the newsgroup:
Sasu Tarkoma (@tml.hut.fi)
opinnot.tik.naf
Personal questions by email
[email protected]
Lecture Outline 26 Jan 09 5 Mon 12:15-14:00 T3 About course and assignment About course and assignments. Please attend the first lecture to register for the course. 02 Feb 09 09 Feb 09 16 Feb 09 23 Feb 09 02 Mar 09 09 Mar 09 16 Mar 09 23 Mar 09 30 Mar 09 06 Apr 09 13 Apr 09 20 Apr 09
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Mon Mon Mon Mon Mon Mon Mon Mon Mon Mon Mon Mon
12:15-14:00 12:15-14:00 12:15-14:00 12:15-14:00 12:15-14:00 12:15-14:00 12:15-14:00 12:15-14:00 12:15-14:00 12:15-14:00 12:15-14:00 12:15-14:00
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Overview
Introduction and overview Routing, multi-homing, mobi Distributed Hash Tables (DH Host Identity Protocol Middleware Exam week, no lecture Web services SOAP Securing Web services Service federation Easter, no lecture Summary and conclusions
Please check the news section on the web page for updates!
Networking
Communication between distributed entities What are network entities?
NAMING
How are they named? How are they connected?
Where is state?
Naming, Addressing, Routing I/II
How it is created? How it is removed? How it is maintained?
ADDRESSING
ROUTING
How are resources allocated?
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Naming, Addressing, Routing II
Naming, addressing, and routing may be applied on many levels and for different purposes Naming
Routing Routing
Simply the name of an entity For example: a domain name
For the remainder: we assume that addresses are assigned topologically
Prefix-routing (network part, host part)
Keeps routing tables manageable
Addressing
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The address of an entity For example: geographical location, IPaddress
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Multi-addressing
Correspondent host
Entities may have multiple addresses
In mobility the topological location (access point) changes --> the address changes
Triangular routing
Mobility
Mobile nodes Handover terminology ) )
make-before-break break-before-make
Home link
Server has multiple addresses on different networks for increased reliability Client has multiple addresses
Multi-homing requires support for address change Topology change can cause renumbering
Foreign link Mobile host
Moving networks
Multi-homing
Foreign agent
Home agent
Multi-addressing
Addresses depend on location
Mobility requires support for address change
More flexibility: CIDR
Mobility Example:Mobile IP Triangular Routing
Mobility and Multi-addressing
How information is routed to the entity in distributed environment Examples: IP-routing, overlay-routing
From old prefix to new prefix Changing the IP host addresses of each device within the network
Multi-homing Examples Site multi-homing ISP1
End-host multi-homing
NAT1
Multi-homed site
ISP2
Internet
NAT2 WLAN
GPRS Wireless Host
Related with multi-homing and must be supported by mobility protocols
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Multi-layer Operation
Mobility and multi-homing can be realized on different layers
Network (Mobile IP) Between network and transport (HIP) Transport (SCTP) Application (SIP, Wireless CORBA, overlays)
View points to Distributed Systems
User view point
Developer view point
Requirements
Confidentiality Authentication Authorization ) )
Physical network operated by many parties Not all operators can be trusted Protecting subnets
Information hiding for programmers Extend a familiar paradigm to a distributed environment Psychological drawbacks
Huge difference in latency Completely different fault semantics Synchronization problems
How to name and find objects? Using services provided by third parties?
Connectivity problems
Need for cryptographic protection
Firewalls, NATs, middleboxes )
Objects
Easy to deploy and maintain Scale well Secure
Security
Rules, policies, ACLs ticket-based schemes
Non-repudiation Auditing and logging Availability
Easy to develop and debug Fast time-to-market
Administrator view point
Security Requirements
Services that work 24/7, anywhere Usability, security
Integrity and confidentiality of data Identification, access control, and authorization Key distribution and trust creation/evaluation
Performance
Network Quality of Service (QoS) characteristics
A dynamic phenomenon if packet switched
End-to-end latency Bandwidth Sometimes also jitter matters
Congestion leads to drops or delays
Different paths have different QoS properties Two worlds: wireless and wired
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Delay and failure model
Interconnections
A uni-processor machine works or fails A method call takes a few nanoseconds In a network,
round trip latency may be ~ 100ms a single end-node may fail a path between two end-nodes may fail performance may fall to unacceptably poor level
Network
Security
Objects
Directories
Layered Model Presentation
Object API, serializ.
Layered model Object centric view Network centric view Directories vs. security
Object centric view Network
Security
Presentation Session
“Transaction”, RPC
Transport
Congestion control
Object API to network
Object-level security
End-to-end Internetworking
Objects
Directories
Routing Naming and finding objects
Naming and finding objects
Each object needs to have a name Each type (class) needs to have a name Each method (action) needs to have a name Objects may be mobile, replicated, ephemeral, or permanent
Providing an object API
Mostly a naming related issue How to find the object? How to find type and method meta-data?
How to refer to remote objects? How to move objects over the network? How to synchronize replicated objects? Abstraction of delay and faults
How to find an object? How to maintain a consistent view of types?
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OO security
May implement access control logic
How to trust a remote node? How to represent threads, call history, and permissions over the network?
Large networks are physically vulnerable Cryptography for integrity and confidentiality
Delay and failure mode
Naming, addressing, and directories
Objects
Availability depends on protocol design Privacy depends on protocol design Balance: security vs. ease of administration vs. performance
Chicken and egg with security and directories Security
Network entities are named
Need to solve the key distribution problem Need to have identities and credentials
Directories
Naming, addressing, and directories
DNS names: www.example.org
Names need to be translated to addresses
Not everybody is equally trusted
Security Secure network mgmt
--> {permissions}
Network security
Network
Threads of execution act upon them
Network security
Objects represent reactive data storage
Network centric view
Network knows how to forward to an address
A directory provides translation information Avoid circular design! Make sure that basic networking works even without directories.
Examples
Access control
Long term keys
Networking: IPv4 and IPv6 Directories: DNS Security: IPsec and IKE Objects: Java RMI
Directories
Security mechanisms require access to long term public keys Directory access must be protected
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Networking: IPv4 and IPv6
Concerns with networks
Hosts named and addressed by IP address Two broad classes of state:
Routing and forwarding tables End-to-end state
Reduces traffic Make update distribution slow
IKE
IP Security (IPsec) End-to-end, below congestion control
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Integrity and authenticity (immutable IP header+payload) Problems with NATs (dst mutable)
ESP (Encapsulating Security Payload) )
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Authentication Header (AH) )
Partitioning, replication, caching Access control: reading, modification Representation of relationships Representation of objects
Mostly relies on manual configuration
Security: IPsec
Logical structure: architecture Physical structure: performance
Partitioned into administrative domains Relatively poor security
Actual data storage and structure
Hosts are no longer named with IP addresses
Replicated, hierarchical repository Data cached at end-hosts
Complexity of next-hop lookup QoS facilities, queues, traffic shaping
Concerns with directories
Provides Domain Name to IP address mapping
Traditionally handled at the transport layer
Routing hardware design and cost
Created by routing protocols Converge time: minutes
Directories: DNS
Should always be soft state
Congestion control, reliability, packet drop / retransmission, flow control
IP addresses are assigned topologically Forwarding tables
Non-forwarding,non end-to-end state: NAT
Transport-mode: higher level payload • host-to-host Tunnel-mode: payload is IP packet • network-to-network Mostly in tunnel mode, VPNs
Contains a complex policy control model Does not work for IP control traffic
IPSec separates key management into IKE / IKE v2 Security Association (SA)
relationship between two or more entities that describes how the entities will use security services to communicate securely
Internet Key Exchange (IKE)
negotiates the IPSec security associations (SAs)
IKE creates an authenticated, secure tunnel
negotiates the security association for IPSec
authentication, establishment of shared keys
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Five authentication options
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IPsec and IKE 1.No IPSec SA for Bob
Concerns with security
4. Protected packets are sent to Bob
Right layer to implement? What about multi-layer security? Privacy? DoS protection? Trust management?
Authorization and credentials?
IPSec Alice
IPSec Bob
IKE Alice
IKE Bob
IKE Tunnel
2. Alice’s IKE starts negotiations
How to bootstrap trust?
3. Negotiation completes. IPSec SAs in place
Objects: Java RMI I/II
Java Remote Method Invocation
Objects: Java RMI II
Objects in one VM invoke methods in objects in a remote VM
5. Skeleton calls method 1. Client Obtains Handle
Remote handle
From the registry name facility
By receiving the reference as an argument or return value of a method call
Client needs stubs (generated from interfaces / downloaded, rmic compiler)
Type polymorphism adds interesting semantics
Run-time dispatch instead of compile time
Parameters of method calls are passed as serialized objects (deep copy)
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Object Discovery
Reliability and disaster recovery
Stubs RMI system
Skeletons
Remote Reference Layer 4. Skeleton unmarshals
Transport Transport independence. Connection management. Unicast/multicast object invocation.
Summary
Representation of Object Handle Fault tolerance: Replication, Consistency, etc. Version detection
Marshalling and unmarshalling Transparency vs. efficiency Performance
ClientRemote 7. Stub Stub isunmarshals and object) Server 2. called (rep.result 3. Marshalling 6. Skeleton arguments marshals result passes it to client (type checking)
Dynamic binding
Concerns with objects
Application
Easy to send more data than necessary! Distributed garbage collection
Networking: naming, addressing, routing Multi-addressing:Mobility, multi-homing Security: Trust, risks, protocols, keys Objects: Encapsulation, XML, frameworks Performance: bandwidth, delay, bottlenecks
Semantics: defining objects beyond appearance Supporting heterogeneous environments
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Questions / discussion
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