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a question ONES again?

2003-04-05 09:37:44

I went through a very interesting real life "something" which very much looks like an OPES but has none of its attributes and makes big real money (a ONES?). The box is on the edge of the network since it is actually a gateway to X.25 Minitel protocol. So there is protocol conversion at lowest layer as well.

That box reads a web page and transforms it in a Minitel page on the fly. Since in France there are still more Minitel users than Internet users, I think the example is relevant.

The interest is that other OPES could be added to transform the page not only from HTML to Minitel format, from TCP/IP to stable cheap X.25, from free access services to pay network access with good return for the content provider, but also from French into English, etc...

I note that these services have an interesting specificity: no callout protocol the way it is proposed in here. But a much more simple "callout path". Depending on the load of the next Service Processors and on the next rule to apply the precedeing dispatcher send the whole traffic to a processor or to another, dasy chaining with all the possible loop, redirect, etc. that an X.25 native net can provide including multitarget, closed user groups, etc..

I discussed with the people there and the way they are able to support 128 users with a simple cheap X25 board and asked them about a simple architecture where I could use an X.25 edge network, daisy chaining with as much PC I would like (standard plug, stable and secure flow, flow control, simply formated extremely fast exchanges, easy priority support), looping back into the old internet in good old TCP/IP once the whole bunch of sophisticated OPES have been performed.

I am waiting for a price from them (we developped that interface in 1983 so one probably improved since then). We discussed an interesting feature BTW: the Gatekeeper. To be able to store at the entrance of the X25 system (first dispatcher) everything confidential which may not interest the OPES operators and restore them at the output. Obviously the X.25 system can be used as a star network or a mshed network (the processed documents proceeding along a dasychaining or coming back to the same dispatcher until cleared).

Comments welcome. jfc

On 21:44 04/04/03, Reinaldo said:

----- Original Message -----
From: "Alex Rousskov" <rousskov(_at_)measurement-factory(_dot_)com>
To: "OPES WG (E-mail)" <ietf-openproxy(_at_)imc(_dot_)org>
Sent: Friday, April 04, 2003 11:19 AM
Subject: RE: Comments on ocp-00

> On Fri, 4 Apr 2003, Martin Stecher wrote:
> > > a) Thus, somebody needs to tell OPES processor
> > >   and callout server what is an "application message"
> > >   definition that they should both use during OCP
> > >   communications. Should OCP support auto-negotiation or
> > >   rely on out-of-band (e.g., manual) configuration?
> >
> > How about this:
> > We discussed that we probably end with multiple application
> > protocol bindings of the OCP. One application protocol binding
> > could be a generic binding which is not really related to any
> > Internet protocol but handles data as if it was a file on disk.
> > Application messages could have a very simple and generic format
> > here. Many callout services may want to support this protocol
> > binding and an OPES processor may have pre-processing code to
> > translate Internet protocol data to that simple format.
> > Other protocol bindings will handle native HTTP and SMTP messages.
> > Every application protocol binding defines a fixed application
> > message format.
> I think both Reinaldo Penno and myself want a scheme very similar to
> what you described above. There will be a set of supported application
> protocols and message encodings. Known message "formats" will be
> documented. OPES agents will support some subset of them. It is
> probably a good idea to document a scheme where OCP sees only message
> payloads and is unaware of the actual application protocol (still, one
> would need to agree on things like payload encoding).
> > Negotiations between OPES processors and callout services is then
> > limited to exchange supported application protocol bindings.
> This is the only uncertain area. You are, essentially, voting for
> supporting auto-negotiations (over a finite set of known
> protocols/encodings, of course). If nobody objects to this automation,
> OCP will implement auto-negotiation. My understanding is that Reinaldo
> is already working on specific messages to handle that.


Are we talking about the same thing? This is already a MUST on the
requirements draft. We have several parameters that need to be negotiated
that have (a priori) nothing to do with the application protocol/bindings
OCP will be carrying.  They are go from basic things like version number to
performance, security, etc.

"  Capabilities and parameters that could be negotiated between an OPES
   processor and a callout server include (but are not limited to):
   callout protocol version, fail-over behavior, heartbeat rate for
   keep-alive messages, security-related parameters etc.

and yeah, I'm already working on that...



My statements

> > > e) Do we need to group processing of a single application
> > >    message together using OCP transaction concept? Should
> > >    OCP transaction mean something else? Do we need OCP
> > >    transactions at all?
> >
> > Yes, I think so.
> > In most cases not more than one application message will be
> > transferred from CLIENT to SERVER and back within a transaction.
> > But we have two examples where multiple messages make sense:
> > 1. Allowing the SERVER to return different SMTP messages for
> > one email to multiple recipients it received from the CLIENT.
> > 2. Pre-processing of a message at CLIENT which results in
> > multiple application messages, e.g. MIME sections of an email
> > to be transferred as multiple application messages
> >
> > The first case requires to have the messages being wrapped into
> > a single transaction.
> > The second case could benefit from a transaction wrapping
> > because the SERVER may want to know which MIME sections belong
> > together.
> The current draft does not support the second case in a situation where
> both cases happen at the same time (e.g., multiple responses to a
> pre-processed message part). This combination can be supported within one
> OCP transaction only if server responses specify which pre-processed
> application message [part] they are adapting. That is, an
> app-message-start message from a callout server will have to include a
> second am-id parameter, carrying the am-id of the corresponding
> application message part from the processor. While possible, this
> defeats the purpose of having an OCP transaction -- since all server
> responses have to carry two am-ids, the transaction wrapping is useless
> for anything other than aborting the whole thing with one message.
> I think the second case must be supported by generating multiple
> (possibly interleaved) OCP transactions, one for each pre-processed part.
> The overhead, if any, will be minimal, and the only missing
> functionality would be an ability to abort all parts with one message. We
> can add 'xaction-ends' to support the latter if needed.
> > I agree with Alex that the transaction overhead could (and should)
> > be limited to a minimum so that no additional transport layer packet
> > is needed. For the normal case the xaction-start app-message-start
> > couple could almost look like a single message I think.
> > But let's keep the xaction-start message two allow support of above
> > cases.
> Yes, there is not much difference between parsing two simple messages
> with 1 attribute and one complex message with 2 attributes.
> > - The sentence "A SERVER MUST NOT send this message" should also
> >   be added to the connection-service message and maybe also to
> >   connection-priority
> Ack.
> > - I am not sure whether the ability to change the service with
> >   connection-service and within xaction-start is really needed.
> >   It increases the implementation requirements for a callout
> >   server but is it really needed?
> >   Setting a service will usually also mean to negotiate further
> >   parameters.
> >   Couldn't we just put this into connection-start?
> >   Using different services will then mean to start different
> >   connections. Isn't this just ok?
> Yeah, that will work. The rationale was that you can use the
> connection to specify common/default services and then overwrite that
> on a transaction basis. You make a good point regarding associated
> negotiations though. Will add this question to the to-do list. The
> answer will probably depend on what kind of negotiations we would end
> up supporting.
> > - I forget about the motivation of the "ack" flag and data-ack
> >   messsage. I thought we wanted to have this done by the
> >   transport layer binding. Can you point me to the thread in
> >   which this has been discussed?
> Ack/Data-ack sequence is useful if one side wants to track (or debug)
> progress in receiving/parsing OCP messages on the other side. Perhaps
> OPES processor can optimize its buffer management by knowing how fast
> the callout server is reading the data. Do you think that enough
> motivation to support the ack/data-ack pair?
> > - Isn't there a problem with data-pause?
> >   If the SERVER sends data-pause to the CLIENT, the CLIENT
> >   MUST stop sending but before the CLIENT receives and
> >   processes this message it may already have sent additional
> >   data-have messages. The SERVER will then receive unexpected
> >   data any MAY abort.
> Indeed. I've added the "MAY abort" part at the last minute and
> missed the bug. Will fix.
> >   Second problem: A CLIENT may not be able to pause as long
> >   as the server likes it to pause. If it is not able to keep
> >   a copy of the complete message and if it is not be able to
> >   pause the origin server for the same time, it may easily run
> >   into an internal buffer overflow problem.
> I do not think that can happen because the CLIENT can always stop
> reading incoming data if it has no place to put it. Right?
> There is a deadlock problem, however (see the "copying commitment and
> deadlock" thread on this list). That problem is on the to-do list.
> >   How about defining that data-pause MUST NOT be send by the
> >   SERVER but adding a new message data-pause-request which is
> >   only to be sent by the SERVER. Upon receiving this message
> >   the CLIENT MAY pause by sending data-pause to the SERVER.
> The above logic is what data-pause from the SERVER was supposed to mean.
> We can fix the current definition or use data-pause-request instead.
> Will fix.
> Thanks a lot for the comments,
> Alex.

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