Flow Networking in Grid Simulations - Grid Computing: Infrastructure, Service, and Applications - page 382

15.6 The New GridSim Flow Networking Architecture
In order to implement the l ow-level networking model described previ-
ously, we need to make some fundamental changes to the existing packet-
level network implementation in GridSim. More specii cally, we need to
replace the entire networking stack with l ow-aware components due to
the signii cant differences between the two approaches.
Figure 15.3 depicts a high-level class diagram showing the l ow-aware
networking stack that is to be added to GridSim to enable l ow-level net-
work functionality. The new support components are shown as dotted
boxes to differentiate them from the existing packet networking stack. A
summary of these additions (and changes) is listed in Table 15.1 . Figure 15.4
shows an example GridSim topology that utilizes the new l ow model.
To k e e p t he l ow-level network functionality logically separated, a new
package was added, namely gridsim.net.l ow. This will encapsulate all of
the l ow-level networking functionality to be added. A new interface,
NetIO, was created to provide a common set of functions for the existing
input and output classes, as well as the new l ow-aware FlowInput and
FlowOutput classes. These l ow-aware input and output classes are auto-
matically generated for GridSim entities by calling GridSim.initNetwork-
Type (GridSimTags.NET_FLOW_LEVEL), before initializing a GridSim
simulation.
The FlowOutput class performs a similar function to the existing out-
put class, but instead of packetizing data that are sent by GridSim enti-
ties into MTU-sized chunks (as described previously), it creates a single
FlowPacket that will represent an active l ow for its lifetime. The Flow-
Output class also supports background trafi c, creating junk l ows to
simulate load on links and the Grid Information Service (GIS), which
is an entity that provides grid resource registration, indexing and dis-
covery services. These two features were available in the NetPacket
implementation and are dependent on by GridSim users worldwide for
simulating complex scenarios and topologies, and thus were supported
in the l ow implementation.
We still require an entity to represent the network l ow. As such, for
convenience we will leverage a subset of the existing packet implementa-
tion, extending it to create a FlowPacket class. This allows us to utilize the
existing features of the packet class, while adding logic that will support
an accurate l ow-networking model for GridSim. A l ow is then simply
represented by a single FlowPacket, which exists as long as the l ow is
active. As it traverses along a GridSim topology from its source to destina-
tion, it maintains a list of the FlowLink entities it passes over, and more
specii cally the latency and bandwidth available on each of these links.
As a FlowPacket traverses a FlowLink, it is registered as an active l ow
on that link for the purpose of computing the bandwidth a FlowLink