I believe that this is now a question for the WG (since it is a WG
document), and should receive comments from more WG participants
than just one of the draft's editors.

However, I can give my personal opinions (my initial thoughts at
least) on that may need further
consideration before being incorporated.  I don't mean to imply that
_if_ something were to be included we must have all of the details
worked out, but we should be reasonably comfortable with the scope of
such a mechanism.

(1) For what entities can an ALTO Client register for notifications?
Network map changes? Cost map changes? Changes to only a subset of the
maps (e.g., as returned by the Map Filtering Service)?  Endpoint
properties? Endpoint costs?  How specific or general do you envision
this notification mechanism to be?

(2) How "persistent" is the registration for notifications?  Does an
ALTO Client simply register for the _next_ network event, and is
expected to re-register after receiving this particular notification?
Or, does an ALTO Client register for notifications for all future
network events (in which case, a mechanism for un-registering must
also be provided)?

(3) What happens if the ALTO Server cannot reach a particular client
that registered for notifications -- is it permanently removed from
the notification list?  What if there is a network failure between the
ALTO Server and ALTO Client - is the ALTO Client expected to somehow
detect this and re-register for notifications?

(4) I see in the draft that you mention "In order to improve the ALTO
server's efficiency, only P2P tracker and application server will be
notified by ALTO server."  How do does the ALTO Server know which ALTO
Clients are P2P trackers or application servers?  Is there a whitelist
maintained by the ALTO Service's provider?

You also mention below that "For tracker-less application, if one PID
head was elected as described in draft
http://tools.ietf.org/id/draft-ikpark-alto-virtual-p2ptracker-00.txt
the notification mechanism can also applied to it."  Looking back at
this draft, I think you are assuming that the ALTO Server maintains
state information about the particular P2P swarms -- this would
require a radical shift from the current direction of the ALTO
Protocol and the multiple solution proposals that fed into it.  My
personal preference would be to keep P2P swarm information out of the
ALTO Server; an alternative method for the P2P application would be to
utilize a different mechanism such as a DHT.

Another architecture for providing notifications (if they are needed
in only certain deployment scenarios) is to define it as a separate
protocol.  "Notification servers" could be deployed separately (either
physically or logically separate) from the ALTO Servers. Notification
servers could be responsible for performing more frequently polling
the ALTO Server to look for changes, and a notification mechanism can
operate between the Notification Servers and ALTO Clients.  The same
protocol could even be used between Notification Servers, and be used
for distributing notifications in a distribution-tree-like fashion.
Of course, this would not provide "realtime" notifications (in the
sense that it still operates as a polling mechanism), but I just
mention it as another possibility for consideration that might satisfy
your particular design goals.

Thanks,
--
Richard Alimi
Department of Computer Science
Yale University

2010/4/16 wangaijun <[email protected]>:
> Hi Alimi,
>
> We have discussed about our
> draft(http://tools.ietf.org/id/draft-sun-alto-notification-00.txt) for short
> time in IETF meeting in Anaheim. It a pity we did not get the chance to
> illustrate the prepared ppt(see attached file)in this meeting.
>
> After this meeting, I discussed your comments with my colleagues, and we
> still think the "server notification" mechanism should be incorporated into
> the current ALTO protocol. It may act as one optional implementation, and
> mainly aim at the tracker-based environment. For tracker-less application,
> if one PID head was elected as described in draft
> http://tools.ietf.org/id/draft-ikpark-alto-virtual-p2ptracker-00.txt,
> the notification mechanism can also applied to it, on the assumption that it
> has the public IP address. These implementation can certainly reduce the
> burden of the ALTO server and let the ALTO clients get the ALTO information
> timely. This eventually will let the p2p traffic to keep up with the
> adjustment pace of ISP's policy.
>
> Wait for you and other interested persons' comments. If possible, we can
> discuss it in the coming " Interim Virtual Meeting " or next IETF plenary
> meeting.
>
> Best regards.
>
> 王爱俊
> 网络业务研究部 基础网络研究室
> 中国电信 北京研究院
> Tel: 010-58552347
>
> Wang Aijun
> Network Infrastructure Research Division
> Network and Service Research Department
> China Telecom Coporation Beijing Research Institute
>
>
>
>
> Today's Topics:
>
>   1. Interim Virtual Meeting (Enrico Marocco)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Thu, 15 Apr 2010 15:36:11 +0200
> From: Enrico Marocco <[email protected]>
> Subject: [alto] Interim Virtual Meeting
> To: "[email protected]" <[email protected]>
> Cc: "Vijay K. Gurbani" <[email protected]>
> Message-ID: <[email protected]>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Hi all,
>
> as mentioned during the last meeting, we plan to have an interim WebEx
> meeting between Anaheim and Maastricht. The date we have identified is
> June 16, but it may still be subject to change.
>
> In particular, we would like to focus the meeting on progressing the
> work on the protocol document, info redistribution, deployment
> considerations and v4/v6 issues. If anyone would like to propose other
> topics, please check well in advance with the chairs.
>
> An official email from the IETF secretariat will follow in the following
> weeks.
>
> --
> Ciao,
> Enrico
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