[Nmc-wg] Transport protocol

Fri Feb 19 03:27:42 CST 2010

>
> This sounds more like you agree with what I just said... So, I'm pretty
> sure I don't understand your point.

I'll try to clarify;

In an abstract formal way what I'm trying to say is:
you are free to choose any transport, (NMC is at it's core protocol
agnostic)
but:
- if you choose SOAP you must adhere to set of rules x as specified by the
binding document to be NMC compliant
- if you choose HTTP-POST you must adhere to set of rules Y as specified by
the binding document to be NMC compliant
... where there are maintenance updates for future, at this time unknown or
unforeseen transport.

This mirrors SAML which at it's core is protocol agnostic, so you have
freedom to choose whatever transport you want.
But if you choose SOAP you MUST adhere to rules defined in
http://docs.oasis-open.org/security/saml/v2.0/saml-bindings-2.0-os.pdf

The rationale for this is what I've have been trying to explain, but perhaps
it's best to quote others:

The reason for at it's core being protocol agnostic:
Jason: "The strength of this work should lie in the specification and
meaning of the XML - if it travels over pigeons or
wires should not be a primary concern."
Nina: "There are number of (non-perfsonar) services nowadays that offer both
SOAP and REST interface. The goal
of this duality is not interoperability, but flexibility and ease of
adoption. A service can offer both, and let the clients
decide which one to use. This might be a reasonable goal for NMC."
I would add; that if say, for example, spdy(
http://dev.chromium.org/spdy/spdy-whitepaper) would ever catch on we
wouldn't want us to be tied to http....

The reason for being protocol specific is that this ensures
interoperability, but this conflicts obviously with the former.
The typical way to solve this conflict is to separate the two leaving only
the protocol specific bits to be rewritten should
a new transport come along. This solves the forward compatibility problem,
but doesn't solve the situation when there
is not a single transport being embraced(a situation that will never exist
in my opinion, for communication between
two services hosted on the same node if performance is critical one would
always opt for IPC/shared memory). That
situation can be solved by having multiply optinal protocol specific bits.
aka multiply bindings.

This is also what I think Roman was getting at;

I agree. I would not put such specifics of the WS in base and even
> extension documents. Maybe third type of document describing an
> implementation could have them (I can imagine that pS services have more
> interfaces than one - SOAP, REST, etc. - in the future )?
>
> - base doc
>  -- extension doc (e.g. for MA)
>  --- transport implementation doc (including, for example WS info)
>
> (lower level doc refers to upper level doc)

Like I said in the conference call, and I think we all agree is the base
document should be protocol agnostic and as that
is our main concern right now perhaps. Beyond that I'd like to keep the
option open, so it's best to let this sudder, and
revisit this at a later time. / put this on the back burner. (feel free to
speak up if you disagree)

- Michael

On Fri, Feb 19, 2010 at 7:18 AM, Nina Jeliazkova <nina at acad.bg> wrote:

>  Jeff W.Boote wrote:
>
> A protocol specification should indicate more than the valid messages. It
> should also define the context in which those messages are valid. If it is
> possible to cleanly separate the messages from some of the underlying
> support we receive from soap/http than we should structure it that way. (I
> believe to a large degree this is possible.)
>
>  But, I also think it is absolutely reasonable for us to indicate
> specifically which lower layer transport we are using once we get to some of
> the more intricate issues. For example, I would much rather depend on soap
> and/or http for authentication headers than define that in our messages. If
> we separate this cleanly, I think we can indicate that we are only doing a
> 'full' protocol specification for using these messages in a soap/http
> context and that future protocol specifications can indicate how they are
> applicable for other transports.
>
>  Will this strategy work for people?
>
> Perhaps indeed the protocol should be documented on different levels.  My
> view is currently
> - I am reluctant of locking everything down to SOAP, on the basis of
> existing implementation.
> - There are number of (non-perfsonar) services nowadays that offer both
> SOAP and REST interface. The goal of this duality is not interoperability,
> but flexibility and ease of adoption. A service can offer both, and let the
> clients decide which one to use. This might be a reasonable goal for NMC.
> - Security related (and perhaps other) solutions may rely on transport
> protocol, and this should be documented , yet not locking the possible
> solutions to a single protocol.
>
> Best regards,
> Nina
>
>
>   On Feb 18, 2010, at 4:44 PM, Michael Bischoff wrote:
>
>  If implementation A uses SOAP based webservices and
>
>  implementation B uses RESTful webservices they do not operate. So I
>
>  think it should be specified, preferably in a different (short)
>
>  document.
>
>
>  On that basis I disagree. There might well be a implementation C that
> provides both a SOAP and RESTfull interface. Since that just starts the
> best of breed game as far as transport is concerned. Freedom here
> promotes adoption.
>
>
>  I do not believe this is true, but perhaps I don't understand what you
> are trying to say. In my opinion, freedom to 'do it however you want' does
> not promote adoption, it hinders interoperability which in turn makes
> development difficult and implementations buggy. This hinders adoption in
> the long run.
>
>   My issue with not specifying it is that there might be two
> implementations
> who both have a SOAP-based interface but bind it differently. That leads to
> a bickering game, where no one benefits - which is a treat to adoption
>
>
>  This sounds more like you agree with what I just said... So, I'm pretty
> sure I don't understand your point.
>
>  jeff
>
>
>  - Michael
>
> On Thu, Feb 18, 2010 at 8:57 PM, Freek Dijkstra <Freek.Dijkstra at sara.nl>wrote:
>
>> Jason wrote:
>>
>> > Specifying details regarding a specific implementation of an NMC-
>> > capable
>> > framework (like perfSONAR or something completely different) does not
>> > seem correct to me.  I still believe that we do not want to box
>> > ourselves in by saying "use SOAP over HTTP because that's what the
>> > first
>> > generation used".  The strength of this work should lie in the
>> > specification and meaning of the XML
>>
>>  I agree with your second statement. However, I also believe that our
>> aim is to define a standard so that different implementations can work
>> together. If implementation A uses SOAP based webservices and
>> implementation B uses RESTful webservices they do not operate. So I
>> think it should be specified, preferably in a different (short)
>> document. Otherwise you may just as well argue that "you do not need
>> to specify the XML syntax, just because that's what the first
>> generation uses"
>>
>> Regards,
>> Freek
>>
>>
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>>
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