If all USSs in an ecosystem use the v1 API, then everything is fine. If all USSs in an ecosystem use the v2 API, then everything is fine. If some USSs in an ecosystem use v1 while others use v2, there may be interoperability problems. To avoid accidentally missing ISAs, this DSS implementation stores v1 and v2 ISAs alongside each other. The URL field for v1 ISAs contains the /flights resource URL (e.g., https://example.com/v1/uss/flights), but this same URL field contains the base URL (e.g., http://example.com/rid/v2) for v2 ISAs. This means a v1 USS may try to query http://example.com/rid/v2 if reading a v2 USS's ISA, or a v2 USS may try to query http://example.com/v1/uss/flights/uss/flights if reading a v1 USS's ISA. This issue is somewhat intentional because even though v1 and v2 both have a /flights endpoint, the communications protocol for these two endpoints is not compatible. If v1 and v2 ISAs are going to co-exist in the same ecosystem, then every USS in that ecosystem must infer the USS-USS communications protocol based on the content of the URL field (flights_url and identification_service_area_url in v1 and uss_base_url in v2).
If a USS in a mixed-version ecosystem reads a v1 ISA, it must communicate with the managing USS in the following ways:
If the flights_url |
Then reach /flights URL at |
Using data exchange protocol |
|---|---|---|
| Ends with "/flights" | flights_url without any changes |
F3411-19 (v1) |
| Does not end with "/flights" | flights_url + "/uss/flights" |
F3411-xx (v2) |
If a USS in a mixed-version ecosystem makes a change to a v1 ISA, the response will contain a list of SubscriberToNotify. The POST notification should be sent differently depending on the contents of the url field:
If the url |
Then reach /identification_service_areas URL at |
Using data exchange protocol |
|---|---|---|
| Ends with "/identification_service_areas" | url + "/" + ISA ID |
F3411-19 (v1) |
| Does not end with "/identification_service_areas" | url + "/uss/identification_service_areas/" + ISA ID |
F3411-xx (v2) |
If a USS in a mixed-version ecosystem reads a v2 ISA, it must communicate with the managing USS in the following ways:
If the uss_base_url |
Then reach /flights URL at |
Using data exchange protocol |
|---|---|---|
| Ends with "/flights" | uss_base_url without any changes |
F3411-19 (v1) |
| Does not end with "/flights" | uss_base_url + "/uss/flights" |
F3411-xx (v2) |
If a USS in a mixed-version ecosystem makes a change to a v2 ISA, the response will contain a list of SubscriberToNotify. The POST notification should be sent differently depending on the contents of the url field:
If the url |
Then reach /identification_service_areas URL at |
Using data exchange protocol |
|---|---|---|
| Ends with "/identification_service_areas" | url + "/" + ISA ID |
F3411-19 (v1) |
| Does not end with "/identification_service_areas" | url + "/uss/identification_service_areas/" + ISA ID |
F3411-xx (v2) |