Add "Best Effort" Service Level

[eric-murray]

Problem description
The currently defined service levels (C2 and `STREAM_4K") imply a certain "guarantee" from the mobile operator that the predicted service level will be met. This will tend to make the predictions conservative, and hence the connected device is likely to have better coverage than predicted.

An API consumer may not need a service level guarantee, and is rather more interested in a qualitative assessment of the coverage that their devices are likely to experience.

Possible evolution
Introduce a BEST_EFFORT service level with no specific service level requirements. This more closely reflects how mobile operators currently do coverage predictions. The existing connectivity levels of GC, MC, NC and ND will still apply to this new service level, and mobile operators usually anyway have an equivalent rating for their published coverage maps, making for a simple implementation.

Alternative solution
None

Additional context
None

[VGF-TEF]

Hi Eric. It would be nice to continue the discussion on this proposal after this release and once we fully understand the implications.

We do understand the problem you are trying to address, and we can agree that not all use cases require a guaranteed level of service. However, what is not yet clear to us is the logic behind the proposal. Specifically, how a service level with no defined KPI requirements would be calculated or mapped to the existing connectivity levels (GC, MC, NC, ND). Without a clear reference point or threshold, we are not sure how these levels would be calculated or validated.

Could you please let us know how you would address the last point? Just for general understanding. Thanks.

[eric-murray]

@VGF-TEF

The key point to understand here is that Vodafone cannot implement this API for Telefonica connectivity, and vice versa. So we do not need to agree on what is "good connectivity", "medium connectivity" or "no connectivity" for a best effort service, because it is "our" best effort and not "your" best effort.

The same banding as coverage checkers could be used which, for Vodafone, is "Good", "Limited" and "No Coverage". Consumers have an intuitive understanding of what this means, even if it is not rigorously defined.

And, as I mentioned in the meeting yesterday, any CSP can return "ND" if they are not prepared to give a qualitative assessment of their coverage.

[eric-murray]

A related point is that you anyway do not have clear reference points for "C2" and "STREAM_4K". C2 for a drone will be very different to C2 for a car. 4K video could be encoded using VP9, or could be sent raw. These have very different connectivity requirements.

[eric-murray]

Closed by #27