Errors / ambiguities / problems found in specs at lastweek'sinterop

Chris Wayman Purvis cwp at ISDN-COMMS.CO.UK
Mon Mar 13 12:38:14 EST 2000


Gene,

It Simply Doesn't Work Like That.

The endpoint WOULD be honouring the request if it sent RRQs "too frequently",
by sending keepalive RRQs at least as often as requested - which is what the
time the gatekeeper gives in RCF asks of it.
In principle endpoints should give a time they think is incredibly long in RRQ
(essentially they're saying "my timers will get confused if you ask them to run
longer than this!"), and the gatekeeper cuts them down to size, saying "if you
want to live in MY zone you'll behave yourself and renew your registration at
least THIS often.".  There is NO way in the standard that a gatekeeper can ask
an endpoint not to send it RRQs at more than a certain frequency - and for good
reasons.  And it would look a little odd if you were allowed to send "normal"
RRQs arbitrarily frequently, but keepAlives mustn't be more than a fixed
frequency.

If an endpoint's threatening to send keep-alives every few seconds, as you
describe, and this is likely to cause you problems, my advice would be to
reject the RRQ...

Chris

Gene Schroeder wrote:
>
> One common reason the gatekeeper might want to increase the registration TTL
> is to control the rate of incoming keep-alive RRQs.  If a gatekeeper has
> many endpoints registered, and these endpoints select a very low TTL (say a
> few seconds), then the gatekeeper will be forced into processing a high rate
> of keep-alive RRQs.  If the gatekeeper does not require nor need such timely
> information on endpoint status, then IMHO it should be able to specify a
> higher TTL in the RCF.  And it seems the endpoint should honor this request,
> just as if it would honor a lower TTL.
>
> Regards
> Gene Schroeder
> elemedia
>
> > -----Original Message-----
> > From: Mailing list for parties associated with ITU-T Study Group 16
> > [mailto:ITU-SG16 at mailbag.cps.intel.com]On Behalf Of Chris Wayman Purvis
> > Sent: Monday, March 13, 2000 9:02 AM
> > To: ITU-SG16 at mailbag.cps.intel.com
> > Subject: Re: Errors / ambiguities / problems found in specs at last
> > week'sinterop
> >
> >
> > Comments inline:
> >
> > "Johan Gerhardsson (ETX)" wrote:
> > >
> > > Hi folks,
> > >
> > > To clarify things:
> > >
> > > It seems that my writing was a bit sloppy when I wrote the
> > problems about TTL and SEQUENCE OF... on the interop. I intended
> > to describe two different problems:
> > >
> > > 1) GK cannot increase TTL in RCF.
> >
> > This is true.
> >
> > > 2) Mandatory parameters of type SEQUENCE OF ... can have empty list.
> >
> > This is also true.
> >
> > > 1)
> > > h323v2, 7.2.2:
> > > "The Gatekeeper may respond with an RCF containing the same
> > timeToLive or a shorter timeToLive.".
> > > As I see it, according to this, a GK is not allowed to increase
> > the timeToLive value proposed by the endpoint in RRQ, regardless
> > if the endpoint makes a full registration or a keep-alive registration.
> > >
> > > I think it should be possible for the gk to do it.
> >
> > I disagree.  As the endpoint is permitted to renew its
> > registration any time up
> > to the assigned time to live, allowing the GK to increase time to
> > live would
> > have no effect whatsoever (the endpoint would send keepalives at whatever
> > frequency it always wanted to).  There would be no effect, so
> > there's no reason
> > to change.
> >
> > As for your second point about SEQUENCE OF being permitted to
> > have an empty
> > list, this has always been the case.  Is there a specific problem
> > with this?
> > It looks more like a (true) observation than a problem to me!  I
> > doubt you'll
> > get ASN.1 changed in existing stuff to make things SEQUENCE
> > [1..something] OF
> > rather than SEQUENCE OF (even if such a structure is permitted - any ASN.1
> > experts wish to comment?).
> >
> > Chris
> > --
> > Dr Chris Purvis -- Development Manager
> > ISDN Communications Ltd, The Stable Block, Ronans, Chavey Down Road
> > Winkfield Row, Berkshire.  RG42 6LY  ENGLAND
> > Phone: +44 1344 899 007
> > Fax:   +44 1344 899 001
> >

--
Dr Chris Purvis -- Development Manager
ISDN Communications Ltd, The Stable Block, Ronans, Chavey Down Road
Winkfield Row, Berkshire.  RG42 6LY  ENGLAND
Phone: +44 1344 899 007
Fax:   +44 1344 899 001



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