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power of expensive supercomputers which oth-
erwise would have been impossible.
There are four factors behind the growing
interest in grid computing: the evolution of key
standards such as TCP/IP and Ethernet in network-
ing; the ever-increasing bandwidth on networks
reaching into the gigabit range; the increasing
availability of idle megaflops on networked PCs,
workstations and servers; and the emergence of
Web services as a logical and open choice of
software computing tasks (Prabhakar, Ribbens
and Bora, 2002; Naedela, 2003). Grid scheduling
software considers a job composed of tasks; finds
suitable processors and other critical resources
on the network; distributes the tasks; monitors
their progress and reschedules any tasks that fail.
Finally, the grid scheduler aggregates the results
of the tasks so that the job is completed.
Grid computing has extensively supported col-
laborated science projects on the internet. Most
of these projects have stringent security require-
ments. To a certain extent, the security may be
provided by the application itself, but more usually
it should be ensured and supported by the grid
environment. The dynamic and multi-institutional
nature of these environments introduces challeng-
ing security issues that demand new technical
approaches for solutions. Scheduling algorithms
play an important role in any distributed system.
In an environment where security is of concern,
responsibility is delegated to the scheduler to
schedule the task on the resource that can meet the
security requirement of the task. Such a scheduler
is referred as the security aware scheduler (Jones,
2003; Tonelloto and Yahyapour, 2006). The goal of
a security aware scheduler is to meet the desired
security requirements as well as providing a high
level of performance metric e.g. site utilization
and makespan.
The most common public key authentication
protocol used in the grid today is the Transport
Layer Security (TLS) (Dierks and Allen, 2007;
Apostolopoulos, Peris and Debanjan, 1999) pro-
tocol that was derived from the Secure Sockets
Layer (SSL) (Freier, Karlton and Kocher, 1996).
Different versions of SSL/TLS provide differ-
ent level of security. Different version supports
various cipher suites (security algorithms) for
different security services like authentication,
encryption and integrity. Thus it is the job of
scheduler to allocate the tasks on the resources
which supports the required security version and
even supports required algorithm on a particular
version to satisfy the demand.
Various grid scheduling models (algorithms)
have been proposed in the past, but addressing
little about security-aware scheduling. In this
article, the thrust is security-aware scheduling
model to optimize performance characteristics
such as makespan (completion time of the entire
job set) and site utilization along with the security
demand of the task. The model is to consider the
constraints exerted by both the job and the grid
environment. In the proposed model, security
prioritization is incorporated in MinMin schedul-
ing strategy, resulting in renaming the model as
Security Prioritized MinMin (SPMinMin).
The next section discusses the related work
done in this field. Section 3 explains the proposed
grid scheduling SPMinMin model. Section 4
shows some experiments and the observations over
the results. Finally, section 5 concludes the work.
RELATED WORK
Often, grids are formed with resources owned by
many organizations and thus are not dedicated to
specific users. There are many important issues
that a job scheduler should address for such a
heterogeneous environment with multiple users.
The grid resources have different security capabil-
ity and computational power. The assignment of
a task to a machine on which the task executes
can significantly affect the overall performance.
Resource contention should also be considered
while scheduling tasks on grid resources with
multiple users. Further, grid, being a non-dedicated
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