1. An Architecture for Secure Wide-Area Service Discovery
Todd D. Hodes, Steven E. Czerwinski, Ben Y. Zhao, Anthony D. Joseph, and Randy H. Katz Imrich
Wireless Networks 8, (2002)
MMLAB, Seongil Han

2. Contents Introduction Design concepts Operations Wide-area support
Features and components
Design concepts
Operations
SDS servers and services
Secure communications
Wide-area support
Multi-criteria search
Query filtering

3. Introduction Service discovery system Features Security
Flexible and multi-criteria search
Wide-area deployed
Fault tolerence
Scalability

4. Components Clients Services SDS server
Discover the services, using query
Services
Announce their own descriptions
SDS server
Solicit information from the services and manage queries from clients

5. Design concepts Announcement-based XML service descriptions
‘Soft State’
Periodic multicast announcements and caching
Fast react to faults
XML service descriptions
Flexibility and semantic-rich content
Privacy and authentication
Hybrid of asymmetric and symmetric-key cryptography
Authentication : certificate
Capabilities
Hierarchical organization

6. SDS servers Basic operations Cluster operation and fault tolerance
Send authenticated messages periodically
List of the domain
Multicast address for service announcements
Desired service announcement rate
Contact information for CA and CM
Well-known SDS multicast channel
Cluster operation and fault tolerance
Load balancing, mirrors
Accepting services and clients
Register the services’ description
Process the clients’ queries

7. Services Find the correct SDS server
Listen for SDS server announcements
Not a one-time task
Send the descriptions to SDS server
Proper channel, proper frequency
Contact Capability Manager
Defining the capabilities for individual users

8. Secure SDS communications
Authenticated server announcements
Sign but not encrypt announcements
Timestamp
Secure one-way service description announcements
Hybrid public / symmetric key system
Authenticated RMI
Two-way authenticated and encrypted
Use certificates for authentication ID
Ciphered Secret
Payload
{…, Expire, SK, …}EK
{…datas…}SK

9. Multi-criteria search
Very difficult function
Complex queries and wide-area distribution
Mechanism category
Centralization
Single point of failure
Name-specified mapping
Hashing, only single criteria
Flooding
Scalability

10. Wide-area support Objective Filtered query flooding (query filtering)
Full rechability
Multi-criteria selection
Filtered query flooding (query filtering)
Dynamic construction and adaptation of the neighbor relationship
Set of hierarchical interconnections
Multiple tree with various metrics
Application-level filtering infrastructure
Aggregation and query routing
Bloom-filtered crossed terminals (BCT)

11. Filtering Terminal set Bloom filter Routing
Nth-degree crossed terminal set
Lexigraphic concatenation
Reduction of N ⇔ increase of ‘false positive’
Bloom filter
Routing
Parent based filtering (PBF)
Full indexing
Adaptation of service change
Table rebuilt, per-bit count v1 v1 v2
HIT S1 S2
query
MISS
False
Positive
query

12. Other issues Range query, wildcards Soft-state messaging
BCT supports neither naturally
Known false positives (KFPs) caching
Soft-state messaging
Updates
Differences + fragment of table
Queries
Stateless, always with query
Query replies
Stateless, except for KFPs

13. Summary SDS Complex query Automatic handle of failures Security-minded
XML
Service-specific tag
Powerful query
Soft-state and announcement-based