Abstract
Successive to a preceding study about Service Discovery, this thesis covers the topics Service Description and Service Access. Starting with an analysis and comparison of existing technologies, a new protocol for the service access was developed and an operating
environment, capable of accessing services of any type was programmed. Thereby emphasis is placed on high scalability, extensibility, modularity and comprehensive documentation, to provide easy association with existing or future works.
The first part deals with the various versions of Service Descriptions, followed by a description of the service access methods and concluding with a comprising comparison.
All technologies or protocols qualified for Service Discovery and Access discovered during this diploma thesis are discussed.
The main part comprises the software implementation which was written in Java, including a comprehensive documentation containing, among others, the protocol specification, software architecture, an user guide and proposals for advancements.
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Table of Contents
1 Introduction
1.1 Topic
1.2 Content
1.3 How to Read This Paper
2 General
2.1 Introducing Reflections
2.1.1 A Possible Scenario
2.1.2 Ad Hoc Networking
2.1.3 State of the Art
2.1.4 Future Situation
2.1.5 Reflections About Service Discovery, Description and Access
2.2 The Problem of automated Interaction
2.3 Use Cases
2.3.1 Service Discovery
2.3.2 Service Access
2.4 URLs/URIs/URNs, Namespaces
2.4.1 URI
2.4.2 URL
2.4.3 URN
2.4.4 Comparison URN - URL
2.5 Overview of the Different Techniques
2.5.1 SLPv2
2.5.2 UPnP
2.5.3 Jini
2.5.4 Salutation
2.5.5 JetSend
2.5.6 Inferno
2.5.7 SDP (Bluetooth)
3 Service Description
3.1 SLPv2
3.1.1 The Service-URL, Accessing SLP
3.1.2 Abstract Service Types
3.1.3 Definition of Attributes
3.1.4 Mandatory Attributes
3.1.5 Registration and Standardization of New Service Types
3.1.6 Explanatory Example
3.2 UPnP
3.2.1 Device Description
3.2.2 Service Description
3.2.3 Template Design Process
3.2.4 Example
3.3 Jini
3.3.1 Service Architecture
3.3.2 Remarks
3.3.3 Description
3.4 Salutation
3.4.1 Architecture
3.4.2 Service Description/Capability Exchange
3.4.3 Functional Unit Description
3.4.4 Attribute Description
3.4.5 Description Format
3.5 JetSend
3.6 Inferno
3.7 SDP (Bluetooth)
3.7.1 Structure
3.7.2 Discovery
3.7.3 Service Record
3.7.4 UUIDs
3.7.5 Data Elements
3.7.6 Universal Attributes
4 Service Access
4.1 SLPv2
4.2 UPnP
4.2.1 Control
4.2.2 Example for Control: Action:Invoke
4.2.3 Eventing
4.2.4 Example for an Event:Notify
4.2.5 Security
4.2.6 Summary
4.3 Jini
4.3.1 Considerations
4.3.2 Features
4.3.3 Security
4.3.4 Implementation Example
4.4 Salutation
4.4.1 Open Service
4.4.2 Transfer Data
4.4.3 Close Service
4.4.4 Summary of RPC Calls of the SLM-API
4.4.5 Salutation Architecture
4.5 JetSend
4.6 Inferno
4.6.1 General
4.6.2 External Environment
4.6.3 Styx
4.6.4 Security
4.7 SDP (Bluetooth)
5 Comparison of the Different Protocols
5.1 Features
5.2 (Dis)Advantages of the Protocols
5.2.1 SLPv2
5.2.2 UPnP
5.2.3 Jini
5.2.4 Salutation
5.2.5 JetSend
5.2.6 Inferno
5.2.7 SDP (Bluetooth)
6 Implementation of the SAP Project
6.1 Overview
6.1.1 Motivation
6.1.2 Features
6.1.3 Used Technologies
6.2 SAP Protocol Specification
6.2.1 Common Topics
6.2.2 Answer Message
6.2.3 Features and Limitations
6.2.4 The Tags
6.3 Architecture
6.3.1 External Architecture
6.3.2 Internal Architecture
6.4 Integration with Service Discovery
6.4.1 Common Integration Topics
6.4.2 SLP Integration
7 Conclusions and Outlook
7.1 Conclusions
7.2 Further Development
B Userguide
B.1 User Guide
B.2 General
B.3 Compiling
B.3.1 Compiling the Java Sources
B.3.2 Compiling the C Client
B.3.3 Creating the Documentation
B.4 Running
B.4.1 Easy Approach
B.4.2 Manual Approach
B.5 Usage
B.5.1 Serverside Programs
B.5.2 Clientside Programs
B.6 Usage in External Software
B.7 Module Programming
B.7.1 Modules Written in Java
B.7.2 Modules in Other Languages
B.7.3 Binding Modules to the SAS
B.8 Examples
B.8.1 Addierer
B.8.2 Print
B.8.3 Parport
Objectives and Topics
This thesis investigates technologies for automated service discovery and access in network-centric computing environments, addressing the challenges of heterogeneous systems and proprietary interfaces. The research focuses on designing and implementing a middleware-based Service Access Protocol (SAP) to enable seamless, scalable, and modular access to diverse network services without requiring complex manual configuration.
- Analysis and comparison of existing service discovery and access protocols (e.g., SLP, UPnP, Jini, Salutation).
- Exploration of service description methodologies and templates for cross-platform interoperability.
- Development of the Service Access Protocol (SAP) architecture and its server-side implementation in Java.
- Evaluation of middleware approaches for translating between common protocols and native device-specific interfaces.
- Creation of a documentation framework for protocol specification and software deployment.
Excerpt from the Book
3.2.1 Device Description
The structure and content of a device description and a device template is shown in Figure 3.1 schematically:
The general information contains the URN for the device template specification used, optionally a base URL and other things. The ultimate information about the device is found in the device block, which consists of informations, such as device type, manufacturer, name, informational URLs and a UDN (Unique Device Name). The latter is a universal unique identifier for the device. Actually there are discussions on the UPnP mailing list, how to use this UDN. A service list follows, which contains a number of services, and a list of device for possibly existing embedded (nested) devices.
The service type contains a URN for its template specification, the service ID, which identifies the service and contains a URN as well. Finally there are 3 URL’s for service description (described in the next paragraph), control and eventing (described in Chapter 4.2 about service access).
Summary of Chapters
1 Introduction: Provides the context of network-centric computing, defines the scope of service discovery and access, and outlines the thesis structure.
2 General: Discusses the theoretical framework, including service discovery concepts, use cases, and URI/URL/URN naming schemes.
3 Service Description: Details the methodologies and templates used by various protocols, such as SLPv2, UPnP, Jini, and Bluetooth, to describe service capabilities.
4 Service Access: Examines techniques for interacting with services, focusing on control and eventing mechanisms across different network protocols.
5 Comparison of the Different Protocols: Compares the features, advantages, and disadvantages of the discussed protocols, providing a foundation for selecting appropriate solutions.
6 Implementation of the SAP Project: Describes the design, architecture, and implementation of the custom Service Access Protocol (SAP) and its Java-based server environment.
7 Conclusions and Outlook: Reflects on the future of automated device interaction and suggests potential improvements for the SAP project, such as enhanced event mechanisms.
Keywords
Service Discovery, Service Access, Service Description, Network-Centric Computing, UPnP, SLPv2, Jini, Salutation, Bluetooth, SAP, Middleware, Java, XML, Ad Hoc Networks, Protocol Implementation.
Frequently Asked Questions
What is the core focus of this thesis?
The thesis focuses on the challenges of automated service discovery and service access in network-centric environments, specifically proposing a middleware-based solution to bridge proprietary interface differences.
What are the primary thematic areas covered?
The work covers service description technologies, service access protocols (such as SLP, UPnP, Jini, and Salutation), protocol comparison, and the implementation of a new Service Access Protocol (SAP).
What is the main objective of the proposed SAP?
The objective of SAP is to serve as a scalable and simple middleware protocol that translates generic access requests into the native protocols required by various underlying devices.
Which scientific or technical methods are applied?
The work uses analytical methods to compare existing protocol specifications and utilizes object-oriented design and Java programming to implement the Service Access Server (SAS) and modules.
What is discussed in the main implementation chapter?
Chapter 6 details the SAP architecture, the motivation for its design, the technical features of the SAS, and the integration of services through a modular, driver-like interface.
Which keywords characterize this work?
Key terms include Service Discovery, Service Access, Middleware, SAP, UPnP, SLPv2, Jini, and Ad Hoc Networking.
How does UPnP handle service description?
UPnP uses XML-based descriptions, partitioned into a device description (containing metadata and a list of services) and individual service descriptions (containing actions, state variables, and arguments).
What role does the Service Access Server (SAS) play in the SAP architecture?
The SAS acts as a middleware entity that receives client requests via the SAP protocol, translates these into the specific commands required by target devices or services, and returns the results to the client.
- Quote paper
- Michael Fischer (Author), 2001, Development and Implementation of a Service Access Concept, Munich, GRIN Verlag, https://www.grin.com/document/181
