Add additional HA requirements from https://github.com/Azure/DASH/pull/56/ into high-availability-and-scale.md

[chrispsommers]

#56 contains the following content in the proposal document. If this is indeed the case, these requirements should go into https://github.com/Azure/DASH/blob/main/documentation/high-avail/design/high-availability-and-scale.md

Microsoft has provided some additional requirements:

1. HA Interoperability is required between vendors
   • Pairing cards from different vendors is not the typical deployment, but must work
2. The HA packet format and protocol must be public
   • This allows sniffed/mirrored HA messages to be analyzed
   • No vendor-private protocol is allowed
3. The HA protocol for syncing active flows could have a base mode and optional modes
   • Additional modes could be defined, for example to the reduce PPS/bps needed for the active sync messages
   • A vendor only needs to support the base mode
   • Any optional modes must also be public
4. The HA protocol does not need to reliably sync 100% of the flows between cards
   • Ideally all flows are synced. But is ok if a small number of flows (hundreds out of 10s of millions) are missed.

[chrispsommers]

Hi @budgrise we triaged this and the consensus is: could you take the additional "MSFT requirements" captured above, which must have arisen from some conversation and do a PR to add it to the defining HA doc https://github.com/Azure/DASH/blob/main/documentation/high-avail/design/high-availability-and-scale.md? This way MSFT can review and hopefully just get it into the existing spec while we debate the new content you've proposed. Thanks.

[mmiele]

Please, see also Xsight HA proposal.

[mgheorghe]

@r12f will you be able to review this to see if those are still the correct requirements so we can close this issue?

in https://github.com/sonic-net/DASH/blob/main/documentation/high-avail/high-availability-and-scale.md i see
anything pending for this item ?

[r12f]

thanks @mgheorghe for bringing it up! will check on this one.