Re: [MEDIACTRL] MRB seqnumber
Lorenzo Miniero <lorenzo@meetecho.com> Thu, 14 February 2013 10:11 UTC
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Date: Thu, 14 Feb 2013 11:11:41 +0100
From: Lorenzo Miniero <lorenzo@meetecho.com>
To: Chris Boulton <chris-standards@ns-technologies.com>
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Cc: mediactrl@ietf.org
Subject: Re: [MEDIACTRL] MRB seqnumber
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On Wed, 13 Feb 2013 12:57:01 +0000 Chris Boulton <chris-standards@ns-technologies.com> wrote: > All, > > After some discussion we have agreed that the text needs to change > slightly to address the comment submitted and other queries we have > received. The change would result in subscription reading something like: > > seqnumber: indicates a sequence number to be used in conjunction > with the subscription session id to identify a specific > subscription command. The first subscription MUST contain a > non-zero number > 'seqnumber', and following subscriptions MUST contain a higher > number that the > previous 'seqnumber' value. If a subsequent 'seqnumber' is not > higher, a XXX response code is generated > as per section 5.1.4. The attribute MUST be present. > > This also applies to the notification text in section 5.1.5 and the > following text is proposed: > > seqnumber: indicates a sequence number to be used in conjunction > with the subscription session id to identify a specific > notification update. The first notification update MUST contain > a non-zero number > 'seqnumber', and following notification updates MUST contain a > higher number that the > previous 'seqnumber' value. If a subsequent 'seqnumber' is not > higher the situation should > be considered an error by the entity receiving the notification > update. It is implementation > specific how the receiving entity deals with this situation. The > attribute MUST be present. > > Please let me know if you are OK with these changes. > Of course I support them all: +1 from me as well. L. > Thanks. > > Chris. > > > On 12/02/2013 23:02, Eric Burger wrote: > > The MRB document talks about a seqnumber in a subscription request and notification response. For your laziness, I have included the entirety of the text defining both uses: > > > > 5.1.3.1. <subscription> > > [...] > > seqnumber: indicates a sequence number to be used in conjunction > > with the subscription session id to identify a specific > > subscription command. The first subscription MUST have 1 as > > 'seqnumber', and following subscriptions MUST increment by 1 the > > previous 'seqnumber' value. The attribute MUST be present. > > > > [...] > > > > 5.1.5. <mrbnotification> > > [...] > > seqnumber: indicates a sequence number to be used in conjunction > > with the subscription session id to identify a specific > > notification update. The first notification MUST have 1 as > > 'seqnumber', and following notifications MUST increment by 1 the > > previous 'seqnumber' value. The attribute MUST be present. > > > > It's important to point out that the 'seqnumber' that appears in a > > <mrbnotification> is not related to the 'seqnumber' appearing in a > > <mrbsubscription>. In fact, the latter is associated with > > subscriptions and would increase at every command issued by the MRB, > > while the former is associated with the asynchronous notifications > > the Media Server would trigger according to the subscription, and as > > such would increase at every notification message to enable the MRB > > keep track of them. > > [...] > > > > > > The AD's are having trouble wrapping their heads around the use of seqnumber. Upon closer inspection, this chair has trouble wrapping his head around the utility of seqnumber. > > > > On the subscribe side, what does it mean in a TCP/DTLS environment, where there is no issue of out-of-sequence request delivery, for there to be an out-of-sequence request? Can anyone tell me the value of seqnumber in this environment? In particular, what does a server do if it gets an out of order request (which cannot happen) or a request gets lost (which cannot happen)? > > > > On the notification side, I *think* I *might* see a value of having monotonically increasing response sequence numbers. If for some reason the server loses a request, the client might figure out that, for a given id, no response ever came. However, in a TCP/DTLS environment, where there is no issue of out-of-sequence notification delivery, what does it mean for the client to receive an out-of-order response (which cannot happen) or a request gets lost (which cannot happen)? > > > > <chair hat off> > > Unless there is a reason to keep seqnumber, my vote is to take it out altogether. > > > > If there is a reason to keep seqnumber, then we need to describe what a server does if it gets a request "out of sequence" and what a client does if it gets a response "out of sequence." > > > > Also, if we keep it, I would offer having two attributes that are unrelated having the same name is confusing at best, and will lead to implementation errors at worst. Thus, I would propose we give them different names, like reqseq and respseq. > > > > > > <chair hat on> > > This is the LAST issue holding up publication. Prompt discussion and resolution is strongly desired. > > > > > > _______________________________________________ > > MEDIACTRL mailing list > > MEDIACTRL@ietf.org > > https://www.ietf.org/mailman/listinfo/mediactrl > > Supplemental Web Site: > > http://www.standardstrack.com/ietf/mediactrl > > > -- > Chris Boulton > CTO & Co-founder > NS-Technologies <http://www.ns-technologies.com> > m: +44.7876.476681 -- Lorenzo Miniero, COB Meetecho s.r.l. Web Conferencing and Collaboration Tools http://www.meetecho.com
- [MEDIACTRL] MRB seqnumber Eric Burger
- Re: [MEDIACTRL] MRB seqnumber Chris Boulton
- Re: [MEDIACTRL] MRB seqnumber Scott McGlashan
- Re: [MEDIACTRL] MRB seqnumber Lorenzo Miniero
- Re: [MEDIACTRL] MRB seqnumber Simon Pietro Romano
- Re: [MEDIACTRL] MRB seqnumber Burger Eric
- Re: [MEDIACTRL] MRB seqnumber Tobia Castaldi UniNa