[whatwg] Case-sensitivity of "WebSocket" in Upgrade field

[Simon Pieters]

WebSocket establish a WebSocket connection:

[[
41. ...
If the entry's name is "upgrade"
If the value is not exactly equal to the string "WebSocket", then fail the  
WebSocket connection and abort these steps.
]]

Reading the client's opening handshake:

[[
Upgrade
Invariant part of the handshake. Will always have a value that is an ASCII  
case-insensitive match for the string "WebSocket".

Can be safely ignored, though the server should abort the WebSocket  
connection if this field is absent or has a different value, to avoid  
vulnerability to cross-protocol attacks.
]]

Why should the client compare case-sensitively but the server  
case-insensitively?

-- 
Simon Pieters
Opera Software