Re: [CDNi] CDNI Metadata Interface

Hi Susan,

  responses inline:

> -----Original Message-----
> From: HeXiaoyan [mailto:hexiaoyan@huawei.com]
> Sent: Friday, October 14, 2011 5:35 AM
> To: Kevin J Ma; cdni@ietf.org
> Subject: RE: [CDNi] CDNI Metadata Interface
> 
> Hi Kevin,
> Thanks for the response. Some further concern,
> - I don't quite understand the restriction that require metadata of all
> hostnames in one Domain have same value. The case exist that for a
> specific
> metadata different hostnames often have different value. Compare with
> creating multiple Domains with less hostname sharing the same metadata, I
> think link metadata to hostname not Domain is more simpler.

>From a conceptual perspective, it could be argued that the domain
object is extraneous.  As an implementation detail, however, the
multi-table joins, imo, were simplified by having a central object
to define the domain, so I added one.  From an operator perspective,
having a way to group multiple hostnames also seems useful, even
though, in the degenerate case, you could just have one hostname per
domain.  If there is a concensus view that the domain is unnecessary,
it could be removed.

> -I interpret the role of the Agent object is to identify entities
> communicated (correct me if I'm wrong), other interfaces in CDNI e.g.
> Logging interface needs such an parameter as well, a universal solution
> for
> that would be good, do you think the Agent object introduced in your draft
> could also be applicable for other interfaces?

I agree that the other interfaces (control/logging) will require some
type of authentication and security.  The agent concept could certainly
be extended to other interfaces, and I agree that it would be good to
have the same solution for all interfaces

thanx.

--  Kevin J. Ma

> Best Regards
> Xiaoyan(Susan) He
> 
> -----Original Message-----
> From: Kevin J Ma [mailto:kevin.ma@azukisystems.com]
> Sent: Tuesday, October 11, 2011 11:30 PM
> To: HeXiaoyan; cdni@ietf.org
> Subject: RE: [CDNi] CDNI Metadata Interface
> 
> Hi Susan,
> 
>   thanx for the comments, responses inline:
> 
> > -----Original Message-----
> > From: HeXiaoyan [mailto:hexiaoyan@huawei.com]
> > Sent: Tuesday, October 11, 2011 5:28 AM
> > To: Kevin J Ma; cdni@ietf.org
> > Subject: RE: [CDNi] CDNI Metadata Interface
> >
> > Hi Kevin,
> > Some quick questions and comments on this draft,
> > >The Metadata objects are each associated with a URI within the Domain
> and
> > accessible through any of the Hostnames...
> > - Could you further explain or give an example how a metadata is
> accessed
> > by
> > a Hostname within the Domain? And a further question is how the data
> model
> > works if a metadata is only associated with a specific Hostname within
> one
> > Doman?
> 
> I was assuming that metadata would be valid for all hostnames.  If a
> hostname
> needed separate metadata, a new domain would be required.  I was thinking
> of
> hostname as a first level restriction.  My implementation does something
> along
> the lines of the following (where hostname is checked before metadata
> lookup):
> 
>   domain = get_param_from_query_string(getenv("QUERY_STRING"), "domain")
>   if (!db_verify_hostname_for_domain(getenv("SERVER_NAME"), domain))
>     return error
>   metadata = db_get_metadata_by_uri_domain_agent(getenv("REQUEST_URI"),
>                                                  domain,
> getenv("REMOTE_USER"))
>   xml = generate_xml_for_metadata(metadata)
>   return xml
> 
> > - The relationship between Agent objects and Metadata objects is a
> > one-to-one relationship, does this mean one agent can only access one
> > Metadata within one Domain?
> 
> That is a typo in the doc, good catch, thanx!  It should be one to many.
> Each metadata must be associated with a single agent, but an agent can be
> associated with multiple metadata.  Agent-1 could have metadatas A, B, and
> C, while agent-2 could have a separate value for metadatas A and B, and
> also
> have its own metadata D (that agent-1 does not have access to)
> 
> > > The association of each Metadata to an Agent allows different Agents
> to
> > retrieve different Metadata values for a given URI in the given Domain.
> > - Don't understand why each Metadata object needs to be bind with an
> Agent
> > explicitly, IMO, whether to return different value to different Agents
> is
> > an
> > inside process of the upCDN, what downCDN needs to do is just transmit
> its
> > identifier to the upCDN when retrieve a Metadata.
> 
> I think the fact that a uCDN would want/need to give out different values
> to
> different dCDNs requires that there be a way to represent and store that
> information.  Having it explicitly in the model, i think, simplifies the
> implementation and guarantees that all implementation give this issue
> proper
> consideration.
> 
> > - Which entity is responsible for creating the Agent objects within one
> > Domain? Does the CP can 'see' the downCDNs and creates corresponding
> Agent
> > objects and other CDNs on the way just transmitted it or each upCDN
> > located
> > in the cascaded path creates a Agent object for each its downCDN?
> 
> This is a good question.  Different agents would need to be create by
> different
> entities, as you mention.  I would expect each CDN to create agents to
> represent
> those (outside that CDN) who need access to the metadata interface.
> 
> thanx!
> 
> --  Kevin J. Ma
> 
> > Thanks.
> > Best Regards
> > Xiaoyan(Susan) He
> >
> > -----Original Message-----
> > From: cdni-bounces@ietf.org [mailto:cdni-bounces@ietf.org] On Behalf Of
> > Kevin J Ma
> > Sent: Friday, October 07, 2011 1:21 PM
> > To: cdni@ietf.org
> > Subject: [CDNi] CDNI Metadata Interface
> >
> > Hi all,
> >
> >   Just uploaded a new I-D with a proposed metadata model and API:
> >
> >     http://www.ietf.org/internet-drafts/draft-ma-cdni-metadata-00.txt
> >
> >   The model takes a rather generic approach to metadata representation
> >   to support opaque metadata and addresses some of the security issues
> >   associated with metadata retrieval.  Comments welcome.
> >
> > thanx.
> >
> > --  Kevin J. Ma
> >
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