[SDL 0141] Supporting simultaneous multiple transports

[theresalech]

Note that separate discussions will need to take place to confirm proxy implementation details for this proposal.

Proposal: Supporting simultaneous multiple transports

This proposal aims to support multiple transports between Core and Proxy.

Review: smartdevicelink/sdl_evolution#405

Steering Committee Decision:

The Steering Committee has voted to accept this proposal with revisions. The revisions are as follows:

• Introduce a new Control Frame, RegisterSecondaryTransport, which will be used once a Secondary Transport is connected to notify Core that the Proxy has established a connection and tell Core which session is registering.
• Rename Transport Config Update to TransportEventUpdate. The original parameters will be refactored to a flat structure.
• StartServiceACK for the RPC service will contain a Secondary Transport param that will contain an array of potential secondary transports instead of a single value. The service to transport priority parameters will become flat instead of document style; each service param will contain an ordered array in terms of priority of potential transports.
• Proxy connection retry strategy will include the new TransportEventUpdate Control Frame. When a connection is interrupted/ended, a TransportEventUpdate control frame will be sent to the proxy on the primary transport. If the proxy is to retry (in case of WiFi), it will include the IP address and Port. If the proxy is not to retry, the frame will contain either empty strings for IP address and port or not include the parameters at all.
• Will recommend, but not require, using 5GHz
• Proxy implementations will be discussed outside of this proposal.

The proposal .md was updated on March 16, 2018 to include the agreed upon revisions.

[theresalech]

Closed via #947