The TMN model suffers from modern network anxiety

As the TMN diagram below describes, each layer up in the network management stack abstracts but connects (as described in more detail in “What an OSS shouldn’t do“). That is, each higher layer reduces the amount if information/control within a domain that it’s responsible for, but it assumes a broader responsibility for connecting multiple domains together.
OSS abstract and connect

There’s just one problem with the diagram. It’s a little dated when we take modern virtualised infrastructure into account.

In the old days, despite what the layers may imply, it was common for an OSS to actually touch every layer of the pyramid to resolve faults. That is, OSS regularly connected to NMS, EMS and even devices (NE) to gather network health data. The services defined at the top of the stack (BSS) could be traced to the exact devices (NE / NEL) via the circuits that traversed them, regardless of the layers of abstraction. It helped for root-cause analysis (RCA) and service impact analysis (SIA).

But with modern networks, the infrastructure is virtualised, load-balanced and since they’re packet-switched, they’re completely circuitless (I’m excluding virtual circuits here by the way). The bottom three layers of the diagram could effectively be replaced with a cloud icon, a cloud that the OSS has little chance of peering into (see yellow cloud in the diagram later in this post).

The concept of virtualisation adds many sub-layers of complexity too by the way, as higlighted in the diagram below.

ONAP triptych

So now the customer services at the top of the pyramid (BSS / BML) are quite separated from the resources at the bottom, other than to say the services consume from a known pool of resources. Fault resolution becomes more abstracted as a result.

But what’s interesting is that there’s another layer that’s not shown on the typical TMN model above. That is the physical network inventory (PNI) layer. The cables, splices, joints, patch panels, equipment cards, etc that underpin every network. Yes, even virtual networks.

In the old networks the OSS touched every layer, including the missing layer. That functionality was provided by PNI management. Fault resolution also occurred at this layer through tickets of work conducted by the field workforce (Workforce Management – WFM).

In new networks, OSS/BSS tie services to resource pools (the top two layers). They also still manage PNI / WFM (the bottom, physical layer). But then there’s potentially an invisible cloud in the middle. Three distinctly different pieces, probably each managed by a different business unit or operational group.
BSS OSS cloud abstract

Just wondering – has your OSS/BSS developed control anxiety issues from losing some of the control that it once had?

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