Generated Topology (discussion and options)

The generator can create the topology as desired, and changing it is quite simple: change the templates.
But there is a modeling decision to be taken: ¿what should we generate?
All options would work, but from the M&S perspective: ¿which one is more convenient?

The decition will impact how to code the atomic models, how to develop the templates, the configuration, metrics, etc, etc.

Old ATLAS model

Before we had used VDEVS models to represent several nodes in the network. This has the advantage of being a simple solution to represent multiple similar models, but has several disadvantages:

  1. For this to work Indexer models are required in order for packets from one queue to go to the adequate next queue.
    1. These Indexer models have the routing logic
    2. They have the indexes hardcoded in c++
  2. visualy does not give you a good idea of the topology
  3. There is no real concept of a switch/router. Each model represents and egressport. There are ~9000 egressports for the ToR switches, but which ones are from the same switch? (this can be answered only looking at the indexes in the c++ models and making calculations)

Phase I model

In order to have a better representation of the topology, for the PhaseI model we created the router, links models

good:

  1. This provide a better visual idea of the network
bad:
  1. The router model is not really a router node. It is just the routing logic (it could be inside a host or a switch)
  2. The link model is not really a just the cable (which applies a delay). It has also the queue which represents the egressport queue. It is weird to have the egress port in the link!
  3. It is not so simple to create. Specially adding a new connection one should add the Link model and the connections

proposed model to generate

This would be the ideal topology to build:

Good:

  1. Only hosts and switches. Connections with PowerDEVS links. Topology very easy to understand visually
  2. Links are inside the port model, which is not as weird as queues inside the link.
  3. Host ports use normal queues. Switch ports use priorityQueues
  4. It is hard to build by hand, but easy to generate
bad:
  1. It is not feasible exactly like this. PowerDEVS links are directed one-way links, so we should duplicate the links. Hosts and routers would need to have both incomming and outgoing links.
    The visual effect is not so nice (removed one router for simplification):
    This is a limitation in the way PowerDEVS renders the views.

-- MatiasAlejandroBonaventura - 2016-09-30

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Topic revision: r1 - 2016-09-30 - MatiasAlejandroBonaventura
 
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