HTTP protocol standard
The Web Services API has been designed in accordance with the HTTP version 1.1 protocol, as defined in the W3C internet standards document RFC 2616, Hypertext Transfer Protocol – HTTP/1.1, June 1999. This RFC can be found in HTML format on the World Wide Web at: http://www.w3.org/Protocols/rfc2616/rfc2616.html
The API requires that all clients interact using the HTTP/1.1 or HTTP/2 protocols. The API does not support clients that use HTTP/1.0.
Note: While the API does not specifically assume or exclude any particular client user agent, its
use and interpretation of HTTP elements has been designed presuming that the client application
interacting with the API is a programmatic web application client or HTTP-capable scripting client
rather than a standard browser-based application. Additionally, the introduction
of multiplexing in HTTP/2 provides support for many concurrent requests over a single connection.
Clients utilizing this support should take care to limit concurrent requests to a reasonable number
to avoid running into HTTP status code 503 (Service Unavailable) errors.