Why isn't WEBSOCKET_XHR the default?

Vaadin 6 / 7 / 8
1

Concerning the
@Push
 annotation.

I’m just wondering why
WEBSOCKET_XHR
 isn’t the default with the
@Push
 annotation ? If I understood correctly then if the setting is the default of
WEBSOCKET
 then there’s will be no ServletRequest. I can’t really comprehend the implication of that but it sounds severe to me.

I’m doing container-based authentication so I believe I would need
transport=WEBSOCKET_XHR
 and then I came to think why you wouldn’t want
transport=WEBSOCKET_XHR
 rather than
transport=WEBSOCKET
 in almost all cases ?

2

How does WEBSOCKET differ from WEBSOCKET_XHR for push transport? Is one better than the other? Is one more reliable for clients that may be behind firewalls/proxies?