[hybi] Multiplexing: even/odd client/server channel open

[Scott Ferguson <[e-mail]>]

In the current draft, only the client can open channels and it can open 
any channel id.

In http-ng (and spdy, I believe), half the channel ids (even) are 
reserved to the client and half the channel ids (odd) are reserved to 
the server.

This splitting of the channel space allows either end to open a new 
channel without collision. Since spdy is already experimenting with the 
use of server-initiated channels, it's not unreasonable to suppose that 
some websocket applications may want similar capabilities. (Presumably 
non-browser apps or spdy-over-websocket.)

Alternatively, the odd channels could be reserved for future expansion 
without adding server-initiated channels now, allowing a later version 
of mux to add server-initiated channels.

I didn't see a previous discussion on this topic, but I skimmed fairly 
quickly, so disregard if it's been discussed already.

I'd think reserving odd channel ids would be a straightforward 
improvement to avoid locking in the client-only limitation of the 
current draft, even if it was decided that server initiated channels 
should be avoided for the current spec.

-- Scott