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Topology Processing Framework:MLMT

The project aim is to provide Yang models for both the multi-layer and the multi-technology topology view, both augmenting the network-topology Yang data model already in use inside OpenDaylight architecture.

The multi-layer topology shall include each single building topology view by associating it to specific layers and shall build up the correlation across them in terms of basic network elements (node, termination-point, links). In that way, a global topology graph embracing multiple network layers shall be available.

A multi-technology topology shall result as an extension of the network-topology model in order to describe all the cross-technologies information in a normalized fashion. The constraints model shall be able to also capture application driven constraints, in compliance with the SDN paradigm, and in addition to native and controller specific ones. This will contribute in providing a normalized view of the network.

The OpenDaylight Yang data models related to network-topologies and its augmentations are described at the following link:

https://wiki.opendaylight.org/view/YANG_Tools:Available_Models

The proposal aims to reuse those models and preserving the currently available implementations.

Further, at northbound interface level, the Operator will have the chance to specify which topologies are to be included within the multi-layer topology to make the approach flexible and configurable based on specific needs.

No updates to OpenDaylight inventory model are planned.

Let us see how the multi-layer and multi-technology view can be built starting from the following sample network comprising four photonic nodes and three IP routers.

Herein shown is the physical topology used in this example.

Sample net.jpg
Fig. 1 - Sample network physical topology

The photonic plug-in is aware of:

Four photonic nodes.jpg
Fig. 2 - Photonic topology

IP router plugin is aware of:


Three ip nodes.jpg
Fig. 3 - Initial IP topology

And eventually, as soon as the control plane is notified of the forwarding adjacency is, an additional link is added to the layer-3 topology, as herein shown:

Three ip nodes and adj.jpg
Fig. 4 - Resulting IP topology

Further, the links connecting nodes belonging to different technologies (in this example, photonic and IP) are reported in a specific topology, the inter-technology topology herein depicted:

Inter-tech.jpg
Fig. 5 - Inter-technology topology

If those nodes do not share any discovery mechanism, no plug-in can advertise them and hence they need explicit provisioning at configuration level. In general that could be the case whenever interconnected nodes do not share any plugin.

As a whole, the resulting topologies are:


Resulting topo.jpg
Fig. 6 - Layer topologies


The picture above shows all three layers (photonic, inter-technology and IP) each one exported by its own specific topology model.

The resulting multi-layer and multi-technology topology is shown in the picture below. Four photonic nodes are building up the layer 0 network and three IP routers the layer-3 network. Inter-technology links and termination points allow the communication across layers.

Mlmt topo circle.jpg
Fig. 7 - Resulting normalized topology with Forwarding Adjacency


In that way, instead of targeting layer by layer individually, the Operator shall have already available northbound the normalized topology view of the network as determined by the multi-layer and multi-technology model.

The set of new defined Yang data model shall be:

  • multi-layer-topology.yang, which shall augment the current network-topology.yang to include references to underlying topologies
  • multi-technology-topology.yang, which shall augment the current network-topology.yang to include the multi-technology information inside node, termination-point, link related attributes

The set of data storages involved shall be:

  • A configured network-topology storage where the Operator specifies the topologies that intend to include inside the multi-layer topology. That will be based on current network-topology Yang model and will take advantage of the underlay-topology data node
  • An operative network-topology storage augmented as based on proposed Yang data model, which will be populated based on advertised nodes, termination points, links and forwarding adjacencies. Forwarding adjacencies will be correlated to underlying services. Inter-technology information will augment the nodes, termination-points, links attributes information.