Thanks for taking the time to reply. The problem is one of scalability and the need for reliability. Subscribe Notify model has a built in assumption of reliability because NOTIFY is a transaction. This means that a single state agent cannot handle too many subcribers as it will be over come with OK reply implosion. We can of course handle this by using a hierarchy of User Agents (State Agents) that rebroadcast state. However, the nature of my application is to monitor temporal data in a scalable fashion and stale data is not meaningful.
In my application, I want to construct what essentially amounts to an application layer multicast. The application consists of several state monitors (UAs) that are all members of the muticast group. Each User Agent also has some state information that it would like to publish to all other members of the group. There are no reliability requirements as state information is re-broadcast periodically. ( Indeed one could construct a reliable scheme using Negative Acknowledgement if desired to retrieve missing state updates). Group membership is unknown and dynamically changes and I want to make as few infrastructural assumptions as possible. I want to use SIP routing and SIP messages as these work nicely but I dont need the reliability that is implicit in a SIP transaction at the state agent because of the nature of my application and because of scalability issues above and because of the periodic nature of the multicast, I can get missing data using a negative acknowledgement scheme. In other words I can essentially do with SIP what is done in Scalable Reliable Multicast (SRM - see http://www.icir.org/floyd/srm.html ) but at an application layer and exploit all the nice features of SIP such as application layer routing and mobility of the group members as well as the large scale scalability and decentralized control of SRM.
My question is is there a method that has no reliability semantics associated with it that can be used for this purpose (ie. is there a draft in the works for this) or should I invent one (maybe propose a draft in the future if this all works out).
Regards,
Ranga.
[EMAIL PROTECTED] wrote:
Hi Ranga,
There's not a lot I can deduce from your description below - what sort of problems are you having exactly using SUBS/NOT?
From what i can gather, your setup includes a state agent at each member of the "multicast" group. Have you considered a different model that has a dedicated state agent for which the members PUBLISH their state, and who then takes care of distributing that state?
Cheers, Aki
> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED] Behalf Of ext M.
> Ranganathan
> Sent: 12 January, 2004 15:07
> To: [EMAIL PROTECTED]
> Subject: [Sip-implementors] Should I be using NOTIFY for this?
> > > Hello and a belated happy 2004.
> > I am designing a distributed system where I would like to propagate > state information within a "multicast" group. Each member of the > mutlciast group is interested in knowing about the state of > the others > and each member periodically sends out state update notifications. I > should like to design this on top of SIP as SIP gives me the > necessary > application layer routing and request proxying that allows > me to deploy > such an application on the internet. I am wondering if SUBSCRIBE / > NOTIFY is the best model for this as NOTIFY is a transaction > and that > could lead to response Implosion. Is there any other method already > defined that is in effect a one way notify (ie. not a transaction).
> > > For my application, the state is temporal data (stale state is > meaningless) so Reliability is not a major concern and I can > use error > correction and Negative Acknowledgement ( like in Scalable Reliable > Multicast ) for Reliablity should I need it.
> > > Thanks and best regards!
> > Ranga.
> > -- > M. Ranganathan > > Advanced Networking Technologies Divsion,
> National Institute of Standards and Technology (NIST),
> 100 Bureau Drive, Stop 8920, Gaithersburg, MD 20899. > > tel:301 975 3664 , fax:301 590 0932 , > http://www.antd.nist.gov/~mranga
> > Advanced Networking Technologies For the People! > > > > _______________________________________________
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M. Ranganathan
Advanced Networking Technologies Divsion,
National Institute of Standards and Technology (NIST),
100 Bureau Drive, Stop 8920, Gaithersburg, MD 20899.
tel:301 975 3664 , fax:301 590 0932 , http://www.antd.nist.gov/~mranga
Advanced Networking Technologies For the People!
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