By Ken North
Computing is sometimes like pop music in the rush to embrace the label
"new". Someone promoting a singer or group is more likely to talk about a
"new sound" than a classic sound or a traditional beat. Despite all of the
hype about new sounds, most popular tunes are based on a three- or
four-chord progression. Music doesn't really re-invent itself every few
months. Although publicists are beating the "new sound" drum, many artists
openly acknowledge their musical roots. They give credit to the musicians,
songwriters and composers who music was an influence on them.
If I have been able to see farther, it was only because I stood on the
shoulders of giants.
- Sir Isaac Newton, 1675
The software field seems to be operating on a different set of rules,
perhaps because of the rush to patent ...
To his credit, Ian Foster is reluctant to be called the father of grid
computing. Perhaps it's because he comes from an academic background with a
tradition of giving credit where credit is due.
The history of grid computing, or utility computing, includes events such
as formation of the Global Grid Forum, Enterprise Grid Alliance and Globus Alliance.
Will historians begin the history grid computing with the formation of those
alliances, or were there other seminal events that marked the beginnings of
grid computing?
There is no consensus among scholars and technology writers about the
origins of grid computing. Perhaps the different opinions are due to
terminology and that some authors use utility computing while others prefer
grid computing. Except for persons who confuse grids with clusters, authors
are often in agreement about the concept of grids:
Grids enable the sharing, selection, and aggregation of a wide variety of
geographically distributed computational resources ... and presents them as
a single, unified resource for solving large-scale compute and data
intensive computing applications. 1
Grid computing can be differentiated from almost all distributed
computing paradigms by this defining characteristic: The essence of grid
computing lies in the efficient and optimal utilization of a wide range of
heterogeneous, loosely coupled resources in an organization tied to
sophisticated workload management capabilities or information
virtualization. (Note that an organization can span multiple
departments, physical locations, and so on. We use term "organization" here
in the abstract sense.) 2
To avoid confusion
As grid technology emerged, an important research paper defined an open
architecture for grid services. That paper provided the genesis for further
refinement of the services model, with security services playing an
important role.
Several generations of technical documents have emerged to describe an
architecture and infrastructure for grid services. A de facto model has
emerged for grid services
authentication. There have also been parallel developments in security for
web services and several releases of a tool set for grid developers.
Ian Foster, Joseph Kesselman, Jeffrey Nick and Steve Tuecke wrote an
important paper about the
Physiology of the Grid and the Open Grid Services Architecture (OGSA).
The Global Grid Forum's
OGSA
1.0 document specifies security services for enforcing the security
policy related to authentication, message integrity, confidentiality and
privacy, auditing, intrusion prevention, access control and so on.
For user authentication, delegation and single sign-on, the OGSA uses
the Grid Security Infrastructure (GSI) protocol. GSI provides a vehicle
for using X.509 certificates with public key-based authentication
protocols, such as the Transport Layer Security (TLS) protocol. Another
key OGSA characteristic is the use of the Web Services Description
Language (WSDL) and the Simple Object Access Protocol (SOAP) for grid
services.
Building on OGSA, the Globus Alliance chartered a working group that
defined the Open Grid Services Infrastructure (OGSI). The
OGSI 1.0
proposed recommendation defines how to create, manage and communicate
among grid services. It excludes details of grid services security and
refers the reader to other specifications for communication protocols,
policy management and platform-specific security.
As OGSA and OGSI were evolving, there was much work being done in the
web services community to define specifications related to the creation
of secure, interoperable web services. Key participants in the Globus
Alliance and grid community recognized the merit of aligning grid
services technologies with the work being done to evolve web services
technology.
WSRF and Web Services Security
Technology
By 2004, Globus announced the Web Services Resource Framework (WSRF)
would be a re-factoring of OGSI to exploit the standards being developed
for web services. Because the OGSA, OGSI and WSRF leverage XML-based
technologies (e.g., SOAP), it's possible to exploit technologies for
creating web services when building grid services.
OASIS published the WS-Security specification as a standard for
creating secure message exchanges that offer authentication,
confidentiality, encryption and message integrity. OASIS also published
the Security Assertions Markup Language (SAML)
The WS-Policy specification defines fundamentals used for creating
security policies, such as the type of security tokens a service will
accept.
IBM and Microsoft have submitted the WS-Trust, WS-SecureConversation
and WS-SecurityPolicy specifications to OASIS for standardization.
WS-Trust provides for the issuing and exchange of tokens for
establishing trust among communicating parties, including Kerberos
tickets and X.509 certificates. WS-SecurityPolicy provides a vehicle for
expressing policy assertions.
Globus Toolkit
The Globus Alliance has provided several release of a toolkit for
developing grid software. Globus Toolkit 4.0 provide an authorization
framework, message-level security and transport-level security. To
protect the security of SOAP messages, GT4 provides an implementation of
the WS-Security standard and the WS-SecureConversation specification.
The authorization and authentication tools are suitable for using
with or without web services frameworks. Globus provides Java classes
and libraries that support certificate-based authentication. It also
provides components for access controls and managing credentials.
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