[hybi] WebSocket and metadata (Was: BWTP Proposal - Bidirection Web Transfer Protocol)

[Ian Hickson <ian at hixie.ch>]

On Tue, 16 Jun 2009, Salvatore Loreto wrote:
>
> It would be interesting understand why WebSocket does not have defined 
> 'meta'; if there is any specific reason why there aren't.

The WebSocket protocol is designed on the principle that there should be 
minimal framing (the only framing that exists is to make the protocol 
frame-based instead of stream-based, and to support a distinction between 
Unicode text and binary frames). It is expected that metadata would be 
layered on top of WebSocket by the application layer, in the same way that 
metadata is layered on top of TCP/IP by the application layer (HTTP).

Conceptually, WebSocket is really just a layer on top of TCP/IP that adds 
a Web "origin"-based security model for browsers; adds an addressing and 
protocol naming mechanism to support multiple services on one port and 
multiple host names on one IP address; and layers a framing mechanism on 
top of TCP to get back to the IP packet mechanism that TCP is built on, 
but without length limits. Other than that, it adds nothing. Basically it 
is intended to be as close as possible to just exposing raw TCP/IP to 
script as possible given the constraints of the Web. (It's also designed 
in such a way that its servers can share a port with HTTP servers, by 
having its handshake be a valid HTTP Upgrade handshake also.)

HTH,
-- 
Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'