Subject: [hybi] Sender-Receiver Latency

From: "Bob Gezelter" <[email-masked]>
Date: Tue, 16 Aug 2011 07:15:15 -0700

Concerning a message from Andy Green <[email-masked]> to Bruce
Atherton <[email-masked]> on Tue, 16 Aug 2011 06:43:50 +0100
entitled "Re: [hybi] CONSENSUS CALL / Frame too big not possible to
occur"

Breaking the latency discussion into sender vs. receiver latency is not,
IMHO, particularly constructive. There are multiple sets of queued
interfaces between when a sender application hands a message to the API
and when the response is received by the sender. 

It is this round-trip delay that is measured by the applicable timeout.
A huge frame (e.g., many seconds of channel time) causes a timeout,
regardless of whether it interferes with the transmission of the
original request, or whether it delays the reverse direction response.
The next effect is the same: a failed request. This is the phenomenon
referred to in military communications circles as "a message not
received is was as if never sent" (For the literary minded, the quote is
from Edward Beach's "Dust on the Sea" (1972); similar references occur
in other places, both fiction and non-fiction).

This is one of the reasons for keeping frames relatively small relative
to transmission bandwidth. In the case of multiplexing, it is also the
reason for doing frame-based multiplexing as opposed to message-based
multiplexing.

- Bob Gezelter, http://www.rlgsc.com

---

From: "Andy Green (林安廸)" <[email-masked]>
Date: Tue, 16 Aug 2011 16:26:29 +0100

On 08/16/2011 03:15 PM, Somebody in the thread at some point said:
> Concerning a message from Andy Green<[email-masked]>  to Bruce
> Atherton<[email-masked]>  on Tue, 16 Aug 2011 06:43:50 +0100

You are right.

However, in the mail you're referring to, I am answering the proposal 
that an error code about frames being too big is needed to solve latency 
problems, with the observation that what's needed is timeouts and not 
the error.  So it seems we are in agreement about it.

> in other places, both fiction and non-fiction).

Curiously that sounds a dangerous approach for the military... the 
message may have been anyway intercepted and acted on by others.  It's 
not quite the same as never having sent it.

-Andy