Re: [hybi] method of allocation of reserved bits to extensions

[Greg Wilkins <[e-mail]>]

Brodie,

this is good. But I think we also need to say the same for op-codes.

I think each extension needs to say how many bits, data op-codes and
control op-codes it needs and then these should all be allocated in
order.

This will mean a minor inconvenience to developers of extensions, as
they need to not have constant op-codes, but it is not a difficult
thing we ask and it will give us interoperability of extensions.

cheers





On 28 April 2011 12:57, Brodie Thiesfield <[e-mail]> wrote:
> If we accept Greg's suggestion, then the following text can be a base:
>
>
>
> 8.2 Allocating Reserved Bits
>
> An extension may require the use of a reserved bit in the framing for
> proper operation. Because both the server and client must know all
> extension requirements before negotiating their use, requirements for
> use of reserved frame bit are known.
>
> The server and client will allocate reserved frame bits in a
> predefined order. The order for the reserved bits is defined as the
> number of the reserved bit as defined in section 4.2, i.e. RSV1 ->
> RSV2 -> RSV3. The order of the extensions is defined by the order of
> the extensions in the the Sec-WebSockets-Extensions response header.
>
> Example;
>
> The client requests the following 3 extensions:
> Sec-WebSocket-Extensions: deflate-frame, sign-frame, mux-o-magic
>
> The server supports all extensions and sends the response header:
> Sec-WebSocket-Extensions: deflate-frame, sign-frame, mux-o-magic
>
> If the deflate-frame extension requires 1 reserved bit and the
> mux-o-magic extension requires 2 reserved bits, then the bits are
> allocated as:
>
> deflate-frame: RSV1
> mux-o-magic: RSV2, RSV3
>
> If the server response used a different ordering of extensions, the
> allocated bits will be different according to the response extension
> ordering.
>
> For example, given the following server response header:
> Sec-WebSocket-Extensions: mux-o-magic, deflate-frame, sign-frame
>
> The reserved bits would be allocated as:
> mux-o-magic: RSV1, RSV2
> deflate-frame: RSV3
>
> If there are no available reserved bits to be allocated to an
> extension the server MUST NOT agree to use the extension.
>