Subject: npmps-04

From: [email-masked]
Date: Wed, 13 Dec 2000 06:06:53 +0200

Hello,

please find attached my (intended) slides, the results document, as well as
the v-04 of the npmps draft. Lacking my slides, I forgot the IP version from
the list of additions to the -03 version of the metric. Moreover, I had read
Glenn's answer to Al sloppily, which I apologize. I now realize that Glenn
was not in favour of including error of incT into the actual metric.

After some thought, I came to the conclusion that I support Glenn's proposal
of calling incT a nominal duration of the inter-packet interval and
mentioning the possiblility of error in discussion later. If process
scheduling or some other reason causes marked variations in incT, this
should be treated as a deviation from the norm rather than a part of a
normal measurement arrangement.

The only changes in v-04 to v-03 are as follows:

- changed definition of incT at p. 8 into

   +  incT, nominal duration of inter-packet interval

- added text on incT error into Sec. 4.6:

   +  Error due to variation of incT

- For clarity, I added a mention of packet loss as the second sentence to to
Sec 4.4, which now reads

   The sample metric thus defined is intended to probe the delays and
   the delay variation as experienced by multimedia streams of
   an application. Due to the definition of the metric, also packet loss
   status of packets is recorded. The delay is assumed to be measured at
   transport layer level. Since a range of packet sizes and nominal 
   interval between packets is used, the method probes only a specific 
   time scale of network QoS variations.

For those intested in a computer repair story with a human interest tint,
I'll attach one at the end of the message. For the rest, just read the docs
& the slides and you'll do fine.

	BR,
	   Vilho

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
 Vilho Räisänen                           
 [email-masked]                 
 Senior research engineer                 
 Nokia Research Center, Helsinki, Finland 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

 * * * end of real business * * *

~~ How to boot up a stubborn computer - a small tale of fatherly wisdom ~~

At boot, my laptop reported that it was the modem driver that caused the
crash. From previous experience, I knew that the order in which device
drivers are loaded sometimes makes a difference, at least in some operating
systems. Armed with this piece of what I thought of as profound knowledge, I
booted NT with and without my PCMCIA NIC, without CD-ROM drive and
experimenting with all combinations. I even tried the VGA mode. To no avail.

At this point I remembered my father's tale of a dysfunctional old radio. He
told me having opened the casing, and - lacking training in electronics -
could not do very much more. So he just blew some dust off the valves and
closed it again. Surprise, surprise: now it worked.

Lacking better ideas, I did just the same: I located the modem, opened a
tiny cover and blew some imaginary dust off the printed board. Reassembly,
boot - succcess.