Emergency Services and Service classes

Gary Thom gthom at delta-info.com
Thu May 3 11:06:42 EDT 2001


Frank,

I do not see any conflict between the text that you have quoted and the
figure.

I do not understand how you can say using modulo arithmetic has no effect.
For example, 1 - 2 = -1, but 1 - 2 modulo 2^24 is 2^24 - 1.

The absolute value of the difference between local and received values can
not be used as this would be the same at both ends, hence both would
conclude to being the master (or both the slave).

Best regards

Mike Nilsson

--------------------
Mike Nilsson
Advanced Video Services
> BTexact Technologies
>
Callisto House, B81 Room 102 pp14
Adastral Park, Martlesham Heath, Ipswich, IP5 3RE, UK
Tel:    +44 1473 645413
Mobile: +44 7808 635412
Fax:    +44 1473 646589
Email:  mike.nilsson at bt.com


BTexact Technologies is a trademark of British Telecommunications plc
Registered office: 81 Newgate Street London EC1A 7AJ
Registered in England no. 1800000

This electronic message contains information from British Telecommunications
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> -----Original Message-----
> From: frank.derks at philips.com [SMTP:frank.derks at philips.com]
> Sent: Thursday, May 03, 2001 3:23 PM
> To:   mike.nilsson
> Cc:   itu-sg16
> Subject:      RE: The use of statusDeterminationNumber in
> masterSlaveDeterminat ion
>
> Mike,
>
> the figure only partly solves the problem. The text that I referred
> to does not reflect what is in the figure, so this should be corrected.
>
> Furthermore, since the values that statusDeterminationNumber can take
> on are in the range 0..(2^24-1). The "modulo operation" with 2^24
> has no effect whatsoever.
>
> It would seem that the real intent is that the _absolute_ value of the
> difference between the received statusDeterminationNumber and the
> locally generated statusDeterminationNumber determines which party is
> to become the master and which party is to becomes the slave. If the
> difference is smaller than 2^23 then the party that received the
> masterSlaveDetermination message becomes the master. Otherwise it
> becomes the slave. In the case that the two numbers are equal, the
> result is indeterminate.
>
> Regards,
>
> Frank
>
>
> -----------------------------------------------------
> Frank Derks                    |Tel  +31 35 6893238 |
> ServWare                       |Fax  +31 35 6891030 |
> Philips Business Communications|P.O. Box 32         |
>                                |1200 JD  Hilversum  |
>                                |The Netherlands     |
> ----------------------------------------------------|
> E-mail: mailto:frank.derks at philips.com              |
> WWW: http://www.sopho.philips.com                   |
> -----------------------------------------------------
>
>
>
>
>
> mike.nilsson at bt.com on 03-05-2001 16:04:45
> To:   Frank Derks/HVS/BE/PHILIPS at EMEA2
> cc:
> Subject:      RE: The use if statusDeterminationNumber in
> masterSlaveDeterminat ion
> Classification:
>
>
> Frank,
>
> The answer is in Figure C.4(v) of H.245.
>
> Best regards
>
> Mike Nilsson
>
> --------------------
> Mike Nilsson
> Advanced Video Services
> > BTexact Technologies
> >
> Callisto House, B81 Room 102 pp14
> Adastral Park, Martlesham Heath, Ipswich, IP5 3RE, UK
> Tel:  +44 1473 645413
> Mobile:       +44 7808 635412
> Fax:  +44 1473 646589
> Email:        mike.nilsson at bt.com
>
>
> BTexact Technologies is a trademark of British Telecommunications plc
> Registered office: 81 Newgate Street London EC1A 7AJ
> Registered in England no. 1800000
>
> This electronic message contains information from British
> Telecommunications
> plc which may be privileged or confidential. The information is intended
> to
> be for the use of the individual(s) or entity named above. If you are not
> the intended recipient be aware that any disclosure, copying, distribution
> or use of the contents of this information is prohibited. If you have
> received this electronic message in error, please notify us by telephone
> or
> email (to the numbers or address above) immediately.
>
>
> > -----Original Message-----
> > From:       Frank Derks [SMTP:frank.derks at PHILIPS.COM]
> > Sent:       Thursday, May 03, 2001 1:51 PM
> > To: ITU-SG16 at MAILBAG.INTEL.COM
> > Subject:    The use if statusDeterminationNumber in
> > masterSlaveDetermination
> >
> > C.2.1.4/H.245 states the following:
> >
> > "If the terminal type numbers are the same, the
> statusDeterminationNumbers
> > are compared using modulo arithmetic to determine which is master
> >
> > If both terminals have equal terminalType field values and the
> difference
> > between statusDetermination field values modulo 2^24 is 0 or 2^23, an
> > indeterminate result is obtained"
> >
> > The first sentence states that "modulo arithmetic" must be used to
> compare
> > the numbers. I would say that that's a rather vague way of describing
> how
> > the comparison must be done. Furthermore it does not tell me what the
> > result
> > must be for a terminal to be determined to be the master!
> >
> > According to the second sentence, I know how to obtain an indeterminate
> > result. So any result that is not any of the two specified values is not
> > indeterminate, but I still do not know what the meaning of the result
> is.
> > "Modulo arithmetic" is, however, introduced, but it is not clear whether
> > this is the modulo arithmetic referred to in the first sentence.
> > Furthermore,
> > what is the significance of a result of 2^23?
> >
> > I assume that the same rules that apply to the comparison of the
> > terminalType
> > field apply (i.e. the terminal with the higher value becomes the
> master),
> > but this is not stated explicitly.
> >
> > Regards,
> >
> > Frank
> >
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > For help on this mail list, send "HELP ITU-SG16" in a message to
> > listserv at mailbag.intel.com
>
>
>

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