学习笔记-Resource and Service Discovery in Large-Scale Multi-domain Networks

Resource and Service Discovery in Large-Scale Multi-domain Networks

作者：REAZ AHMED, NOURA LIMAM, JIN XIAO, YOUSSEF IRAQI, AND RAOUF BOUTABA

发表于：IEEE Communications Surveys & Tutorials • 4th Quarter 2007

本文有关的术语定义：

1、服务（service）：

We define a service as a set of functionalities associated with

a process or system that performs a task.

2、资源（resource）:

A resource is defined as an entity that is used or acted

upon by a process or system. A service functionality takes

resources as input.

服务与资源的区别：

We can denote a service by a function f, and a resource by an

input variable x. The outcome of the service is then returned as f(x).

Notice that a service can be invoked by another service. In this case, the outcome of the service f becomes a resource and is used by another service, say g. This is called service composition and the outcome of the service g becomes g(f(x)).

服务的两种类型：

hardware devices as services：

Most of the industrial service discovery approaches like (Jini, SLP, UPnP etc.) use hardware devices like printer, fax machine, etc. as networked services.

software founction as services:

On the other hand, the majority of WebService discovery

approaches consider a software component, performing a specific functionality, as a service.

服务发现协议的评价标准：

architecture，effectiveness, fault tolerance, performance, security,and platform- and network-dependence.

标准一：architecture

how information is distributed,and therefore accessed-信息如何组织和如何获取。

主要分成两类：集中式centralized和分散式decentralized

The architecture of discovery systems ranges from centralized to

fully decentralized.

标准二：effectiveness

how well the system can discover services;

信息检索领域使用precision和recall评价effectiveness

Information retrieval literature uses precision and recall to describe the effectiveness of data retrieval operations.

本文作者使用completeness和correctness评价effectiveness

Completeness：

Completeness is the ability of a service-discovery process to return all matching service instances registered in a service directory.

Correctness：

The other criterion, correctness, denotes the validity of the results of service discovery: when a service is discovered, how closely does it match the user’s request?

标准三：Fault tolerance

Fault tolerance deals with the behavior and robustness of the

discovery process under erroneous conditions.

主要考虑两个方面：

1、 how does the system behave under erroneous conditions（Robustness）

2、how well does the system recover from errors（Recovery）.

标准四：PERFORMANCE

we examine the amount of communication overhead involved in the discovery process, which affects both the utilization of underlying network resources and the latency of query response. We also look at the treatment of load balancing.

标准五：Security

user authentication/ authorization,data integrity, and privacy of sensitive data.

标准六：SCALABILITY

This criterion examines the targeted infrastructure size of each systems and allows us to evaluate the ability of discovery systems to cope with large scale networks.

标准七：PLATFORM AND NETWORK INDEPENDENCE

software platforms or network technologies

标准八：INTEROPERABILITY WITH OTHER DISCOVERY SERVICES

服务发现协议介绍（TECHNOLOGY OVERVIEW）

服务发现的过程：

We view service discovery as a four-step process (Fig. 1);

1、Bootstrapping

where clients and services attempt to initiate the discovery process via establishing the first point of contact within the system

2、Service advertisement

where a service provider publishes information about the provided services

3、Querying

where a client looks for a desired service

4、Service handle retrieval

the final step in the discovery mechanism, where a client receives the means to access the requested service