Subject: [Sipping] Comments to draft-garcia-sipping-resource-sharing-framework-01

From: "Willekens, Marc" <[email-masked]>
Date: Fri, 9 Mar 2007 17:29:48 +0100

Hi,
 
Some specific comments/question/remarks to the draft:
http://www.ietf.org/internet-drafts/draft-garcia-sipping-resource-sharing-framework-01.txt <http://www.ietf.org/internet-drafts/draft-garcia-sipping-resource-sharing-framework-01.txt> 

[Page 3], 1 Introduction, §1

What about notifications for a state change of a resource? Is it something as: 

- Subscriptions to new files becoming available?

- Subscriptions to changes of the content of a certain file?

- Subscriptions to resources exceeding a certain threshold? E.g. subscribe to get a notification when the temperature sensor resource of a certain device comes above a certain threshold?

- Subscriptions to a list of printers and get a notification when a printer becomes idle or busy?

[Page 3], 1 Introduction, §2

"The resource metadata is stored in the peer nodes."

Is it stored in all the peer nodes, or in the super-nodes? Is this info replicated over the different nodes with the same content, or is the content (metadata) split-up in different parts and stored in a distributed way over the different nodes with the ability to recover the complete content when one of the nodes fails?

In the example, how does Bob know he can use the keyword "vacation"?  Is this only related to the content made available by Alice or is it valid to every resource made available by every part of the p2p community with the keyword "vacation"? 

Is the search criteria sent to the super-nodes or to all nodes? I assume to the super-nodes, else the question can be posed why Bob has not received the information as a peer-node from the Publish from Alice to the p2p network? What's the difference for all the received notifications from the different peer nodes by Bob? Do they all refer to the same content made available by Alice?

And what is actually stored in the network: only the metadata or also the content itself? What's the advantage when only the metadata is stored in the p2p network but the actual content is kept in the device of Alice?

[Page 3], 1 Introduction, §3

What's the centralized server? Is this really a central server, or is it distributable function which is provided by one of the peer nodes? E.g. all or a subset of the nodes which can fulfill the role of centralized server but only one of them actually performing this function and automatically taken over by another node when the actually performing server becomes unavailable?

The central server can have an advantage to aggregate the metadata. But what's about the main content? Is it also stored in the central server or is it kept in the end-device, or will it also become part of the p2p network to allow a more efficient retrieval of the information without placing a burden on the specific end device? 

[Page 4], 1 Introduction, §4

Hybrid approach: same question: where will the main content be kept? If it is kept in the secondary nodes, then there is still a burden on these devices even if SIP is used to minimize the protocol implementation in endpoints with limited resources.

[Page 4], 2 Definitions, §1

"Resource directory: a device storing the resource descriptors...".

Are a resource and a resource directory always bound to device? Is it not the intention to use the p2p concept to decouple the constraint of a resource strictly bound to a device?

[Page 5], 3.1 File publication, §2

"The actual files are not transmitted until someone requests them".

When they are requested, the resource will be retrieved from the end-device and then made available in the p2p network? Or is every request for the resource made towards the end-device? In last case, there can be a big burden on the end-device when many community members want to retrieve the pictures.

[Page 6], 3.2 File Search, §1

"... search results back to Bob's SIP UA in a series of notifications".

What is meant with a series of notifications? Does the ESC not make any kind of aggregations of different notifications?

Are the thumbnails also part of the metadata generated by the source (Alice phone)? Or are these thumbnails generated by a function in the p2p network?  

[Page 6], 3.3 File Directory..., §1

"In this case he can just subscribe to the presence information of Alice and his other friends".

Is it "his other friends" or can it can it also be "her" (i.e.) Alice friends?

[Page 6], 3.3 File Directory..., §2

What will be the influence on generated network traffic with this concept?  Is this not generating too many PUBLISH and NOTIFY messages?

[Page 7], 3.4 File Download..., §1

"Bob's SIP UA sends a download request to Alice's SIP UA."

How will this be done? Which protocol will be used for this (MSRP)? Will it be a new method in a SIP message? Is the download request send directly to Alice's SIP UA. Maybe you can add a reference to §7.

"Alice's terminal will automatically approve the request ..."

How is this done? What kind of authentication is used to approve the request? Make reference to draft-garcia-sipping-resource-event-package §3.6.1, 3.6.2?

[Page 7], 4 Resource publication.., §1

Is it one out of two type of PUBLISH methods or can both methods also be provided in parallel?  Are these then 2 separate PUBLISH methods from the end-device to the ESC?

[Page 8], 4.1.1 Initial resource metadata publication, §3

Why is the size of the file part of the invariant part and the file name, creation/modification data part of the instance-specific part? Can you clarify this? What about the identical copy of the file? Is the EPA sending different copies of the same file to the ESC? Why and for what purpose?

[Page 9], 4.1.3 Actions performed by the ESC, §1

Is the given example the "hybrid approach" by which the ESC is part of a p2p network and the EPA in the UE device is only the access towards the p2p network but not forming part of it? How can the relation and addressing be done between the EPA and the ESC?

[Page 10], 4.2 Resource Publication, §3

Is the ESC is this case the "presence server"?

[Page 11], 5 Search operation, §1

Is the search operation only a "pull" method or can it also be a "push method with a Subscription for a certain amount of time, e.g. when new resources are added which also fulfills the search criteria?

Maybe you can add a reference to  document draft-garcia-sipping-resource-event-package §3.4.

[Page 13], 5.3 Propagating searches, §1

How is the distribution of the metadata done? Distribution for different resources or can the distribution also be done for one specific resource? And what is distributed? The whole set of metadata or are only certain parts of the metadata distributed over different nodes?

[Page 14], 5.4 Terminating a search request, §2

Does not imply that a SUBSCRIBE for a pull method can't be used? 

[Page 16], 6 Directory operations, §1

The resource is bound to the device of a presentity. What if the presentity has the same resource available on different devices?

[Page 18], 8 Security considerations, §1

How can all the policing and authorization be done on limited end-devices? How can a DoS attack be avoided?

Best regards,
Marc Willekens.
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