Subject: [Sipping] Re: Cookies vs. State

From: [email-masked]
Date: Fri, 19 Apr 2002 11:46:57 EDT

In a message dated 4/18/02 4:06:56 PM Eastern Daylight Time, [email-masked] 
writes:

> > [Mike] Yes, I've been involved in the design and implementation of 3 
> telephony
> > switching systems, where the presumed requirement was for high
> > reliability/almost no down time. They operated on the principle of
> > active/standby processors and critical peripherals and performed "state"
> > sharing between the two sides in order to support switch-over when the 
> active
> > side failed. I guess coming from this design background, I continue to 
> wonder
> > why so much effort is being put into complex protocols and procedures 
> between
> > devices which have a high failure rate and down time rather than tackling 
> the
> > real problem. Telephone and data switching equipment in the past was 
> designed
> > for low failure and down time and I continue to wonder why I keep getting
> > e-mails from our system administrator that "The LAN or e-mail server will 
> be
> > down for several hours for maintenance".
> 
> Based on your description, you did not implement such a system in software
> (as I queried), but in hardware instead.  It is fundamental to the
> Internet model to use lots of cheap distributed components.  Despite the
> phone systems better reliability during oridinary usage, the Internet
> continues to adapt better to unforseen massive failures.  Your Mileage May
> Vary.
> 

Sorry, I wasn't clear. What I was referring to was completely software. Of 
course it ran on a piece of hardware, which was specially designed for the 
telephony system, since there never was an off-the-shelf computer system that 
could provide the reliablity and functionality required by every telephony 
service provider around the world.

I believe if you query those service providers who you hope will replace 
their existing large telephone switches with internet (SIP) based equipment, 
they will universally tell you that reliability is the primary requirement. 
"Cheap" is nice but is secondary. As for "distributed components", as one of 
the ADs insisted, don't tell me that your favorite solution is the 
requirement. And I firmly believe that past experience in telephone switching 
has shown that distributed systems by themselves are not always the answer.

Mike

---

From: Rohan Mahy <[email-masked]>
Date: Fri, 19 Apr 2002 08:57:24 -0700 (Pacific Daylight Time)

> service provider around the world.

My apologies for mispeaking.  I think others have made my point for me
however about the need for out-of-box redundancy and the complexity of
passing state over the wire.

> has shown that distributed systems by themselves are not always the answer.

We are now significantly off-topic.  If you object to requirements to
build a distributed system, may I suggest the MEGACO Working Group.  If
you don't object, then we can agree to disagree on this philosophical
point and move on with tightening the language on the cookies draft.

thanks,
-rohan

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