[hybi] Ping/Pong body (was Re: TSV-Directorate review of draft-ietf-hybi-thewebsocketprotocol-07)

[Takeshi Yoshino <[e-mail]>]

(Detaching from TSV review thread)

Greg,

I see. Sounds ok to use assignment like that. As you said "it's over
reliable transport" in reply to my message, we don't need to use sequence
number as ping/ICMP does since there's no loss or reorder. Maybe just \x00
(reply to ping) or \x01 (unsolicited) would be fine.

Basically, I don't think it's good idea to make it duty of implementor or
service designer to choose body for Ping and unsolicited Pong properly. That
should be covered by the spec to reduce what to be cared by user if
possible. What do you think about specifying some rule for the body strings
to be used for Ping and unsolicited Pong in the spec?

- application data of Ping must start with \x00
- application data of in-reply-to Pong MUST have the same body as the
received Ping
- application data of unsolicited Pong must start with \x01

I think the following is clearer.

- when received Normal-Ping (Ping with its application data starting with
\x00), reply with Pong with the same body
- when received NOP-Ping (Ping with its application data starting with
\x01), just ignore it

On Fri, May 13, 2011 at 07:29, Greg Wilkins <[e-mail]> wrote:

> Takeshi,
>
> what I have seen before is the use of sequence numbers where the
> client side uses even and the server side uses odd, so can tell by the
> seq number in a pong where it was generated and thus tell if it is a
> response or unsolicited.
>
> cheers
>
>
> On 13 May 2011 04:36, Takeshi Yoshino <[e-mail]> wrote:
> >>   Obviously there is a chance that a unsolicited pong matches a ping,
> >> but some careful design of payloads can easily fix that.
> >
> > I see. Coordinating body value assignment so that unsolicited one and
> reply
> > one don't conflict each other (e.g. "ABC" and "XYZ" as you said) is one
> > possible solution.
> > This should be discussed well when we add some keep alive feature to
> browser
> > that sends Ping to the server. If we prepare some API for JavaScript to
> tell
> > the browser what string to use for Ping, service designers may coordinate
> > assignment by themselves. If we don't, we should reserve some string to
> be
> > used for Ping/unsolicited Pong by browsers to avoid collision.
> > ----
> > Isn't it simpler to reserve some string, say "NOOP" (or "\x00" to save
> > bytes), for Ping body and require endpoints to ignore such Ping rather
> than
> > diverting Pong for heartbeat?
> > Thanks,
> > Takeshi
>