Re: [Dime] DOIC: Self-Contained OLRs

[Jouni Korhonen <[e-mail]>]

My understanding (and current editing) has already been towards
what Lionel said below.

- Jouni


On Dec 2, 2013, at 4:19 PM, [e-mail] wrote:

> I agree with last part. It was the reason I've reconsidered my position on the need for the Report-Type.
>  
> Ulrich, I think that what you are considering as out of context is just a matter of interpretation.
> When sending a request, a client is always targeting a server, even if Destination-Host is not in the answer. So receiving a host-based OLR in response is not "out of context".
> Receiving a Realm-based OLR in addition to a host-based OLR in answer to a request sent to the Realm is correct as soon as the client receives a positive answer from a server.
> Receiving a Realm-based OLR in addition to a host-based OLR in answer to a request to a specific server could be seen as a "kind of optimization" offered by the use of the Report-Type. But there is nothing wrong. It is only to comply with the Diameter routing principle: subsequent requests from the client could include a destination-host or not. So the client needs to know which reduction to apply from a previous answer.
>  
> In any case, the client needs to store the OLR received according to the Report-type. And having the report type avoids the client to "guess" the context based on the type of request.
>  
> Regards,
>  
> Lionel
>  
>  
> De : Nirav Salot (nsalot) [mailto:[e-mail]] 
> Envoyé : lundi 2 décembre 2013 14:58
> À : Wiehe, Ulrich (NSN - DE/Munich)
> Cc : [e-mail] list; ext Jouni Korhonen; MORAND Lionel IMT/OLN; Ben Campbell
> Objet : RE: [Dime] DOIC: Self-Contained OLRs
>  
> Ulrich,
> 
> Wouldn't that make reacting node's implementation more complex if it has to remember what was sent in the request while processing the response?
> 
> I would prefer to derive the context of the OLR based on the message which contains the OLR.
> 
> Back to the topic of this thread, I don't think we need to define an "optional" optimization at this stage. Either it is respected by all the nodes supporting the solution or we drop that optimization.
> 
> Regards,
> Nirav.
> 
> On Dec 2, 2013 5:27 PM, "Wiehe, Ulrich (NSN - DE/Munich)" <[e-mail]> wrote:
> Nirav,
> 
> If the reacting node sends a request without Destination Host, a realm-type OLR in the answer would be in-context whereas a host-type OLR in the answer would be out of context.
> 
> Similarly, if the reacting node sends a request containing Destination Host, a realm-type OLR in the answer would be out-of-context and a host-type OLR in the answer would be in-context.
> 
> Ulrich
> 
> 
> 
> -----Original Message-----
> From: ext Nirav Salot (nsalot) [mailto:[e-mail]] 
> Sent: Monday, December 02, 2013 12:25 PM
> To: Wiehe, Ulrich (NSN - DE/Munich); ext [e-mail]; ext Jouni Korhonen; Ben Campbell
> Cc: [e-mail] list
> Subject: RE: [Dime] DOIC: Self-Contained OLRs
> 
> Ulrich,
> 
> I have a basic question.
> 
> When the reacting node sends realm-routed request and it receives (only one) OLR in the response message (which also contains the origin-host), is this OLR applicable for realm or host?
> I am trying to understand which is out-of-context OLR here: realm-type or host-type?
> 
> Regards,
> Nirav.
> 
> -----Original Message-----
> From: Wiehe, Ulrich (NSN - DE/Munich) [mailto:[e-mail]] 
> Sent: Monday, December 02, 2013 4:30 PM
> To: Nirav Salot (nsalot); ext [e-mail]; ext Jouni Korhonen; Ben Campbell
> Cc: [e-mail] list
> Subject: RE: [Dime] DOIC: Self-Contained OLRs
> 
> Hi Nirav,
> 
> please see inline.
> 
> Regards
> Ulrich
> 
> -----Original Message-----
> From: ext Nirav Salot (nsalot) [mailto:[e-mail]]
> Sent: Monday, December 02, 2013 7:05 AM
> To: Wiehe, Ulrich (NSN - DE/Munich); ext [e-mail]; ext Jouni Korhonen; Ben Campbell
> Cc: [e-mail] list
> Subject: RE: [Dime] DOIC: Self-Contained OLRs
> 
> Ulrich,
> 
> When the client sends request containing destination-realm (and not containing destination-host), it gets back answer containing origin-host (set by the actual server) as well as host-type OLR.
> So purely from the response message perspective, the host-type OLR in this response message is not out-of-context information. 
> [Wiehe, Ulrich (NSN - DE/Munich)] But we do not purely take the response message perspective. The client sends a request of type x (destination host =x1, destination realm =x2 application= x3) and gets back an OLR in the answer which says "please throttle request of the type you just sent". The client either remembers, or deduces from info received in the answer, what the type x was. E.g. it deduces from the value of Origin Realm in the answer the value of Destination Realm in the request; it deduces from the value of Report-Type in the answer whether Destination Host was present in the request...
> 
> On the other hand, we discussed - as part of Maria Cruz's alternative solution - to define the response message's context based on the request message. And hence if the request message was sent to destination-realm, the corresponding response message can only contain realm-type OLR.
> But this requires the client to remember the context of the request while processing the response and hence it was considered as introducing unnecessary complexity. 
> [Wiehe, Ulrich (NSN - DE/Munich)] I agree. This means: the report-type AVP is needed to let the client deduce from information received in the answer whether the request contained a destination host. It does not mean that we need two OLRs in one answer.
> 
> If we strictly want to ensure that the realm-type OLR is not sent out-of-context [Wiehe, Ulrich (NSN - DE/Munich)] That was not my proposal. My proposal was to clearly mark out-of-context OLRs in answer messages (if we allow including out-of-context OLRs)
> 
> , then we should agree to Lionel's alternative solution - to send realm-type OLR only when the destination-realm based request is rejected. So basically, realm-type OLR is never included in a response message which contains origin-host AVP. (And I am ready to reconsider the same if we want to ensure the context of the response message and the OLR it contains).
> 
> However, as per our current agreement, we are introducing Report-Type AVP [Wiehe, Ulrich (NSN - DE/Munich)] I agree  to allow the inclusion of host-type and realm-type OLRs in the response message.
> [Wiehe, Ulrich (NSN - DE/Munich)] That is not the reason; even if only one OLR is in the answer, report-type would still be needed.
> If we say that the client can ignore one of the OLRs [Wiehe, Ulrich (NSN - DE/Munich)] only the out-of-context one
> 
> , then what is the point of including two OLRs [Wiehe, Ulrich (NSN - DE/Munich)] The in-context-OLR must be included by the reporting node and must be processed by the reacting node; the out-of-context OLR may be included as optimization by the reporting node or any agent (if the reporting node or agent wants to offer this optimization), and may be processed by the reacting node (if the reacting node wants to make use of this optimization).
> 
>  and what is the point of defining Report-Type AVP?
> [Wiehe, Ulrich (NSN - DE/Munich)] to let the reacting node deduce from information received in the answer whether the corresponding request contained a destination host (so there is no need to remember).
> 
> 
> In summary, if we define Report-Type AVP and corresponding handling at the reacting node, the reacting node must act accordingly and not ignore it.
> [Wiehe, Ulrich (NSN - DE/Munich)]  What goes wrong when out-of -context OLR is ignored?
> 
> Otherwise, if we argue that the Report-Type AVP is just an optimization (to allow the inclusion of realm-type OLR) and the reacting node can ignore it, then lets not define this optimization since it has no value if it is ignored.
> [Wiehe, Ulrich (NSN - DE/Munich)] Not the Report-Type AVP is the optimization but the incusion of out-of-context OLRs. And I'm ok not to proceed with this optimization as it is not needed.
> 
> Regards,
> Nirav.
> 
> -----Original Message-----
> From: Wiehe, Ulrich (NSN - DE/Munich) [mailto:[e-mail]]
> Sent: Monday, December 02, 2013 1:08 AM
> To: Nirav Salot (nsalot); ext [e-mail]; ext Jouni Korhonen; Ben Campbell
> Cc: [e-mail] list
> Subject: RE: [Dime] DOIC: Self-Contained OLRs
> 
> Hi Nirav,
> 
> When the client sends a request that contains only destination realm but no destination host an gets back an answer containing a host-type OLR, this OLR is out-of-context.
> Similary, when the client sends a request containing destination host and gets back an answer containing a realm-type OLR, this OLR is out-of-context.
> There is nothing wrong with storing such out-of-context OLRs at the client, but it is simply not needed as the client will learn this OLR from responses received within the context.
> 
> Best regards
> Ulrich 
> 
> 
> -----Original Message-----
> From: ext Nirav Salot (nsalot) [mailto:[e-mail]]
> Sent: Friday, November 29, 2013 4:49 PM
> To: Wiehe, Ulrich (NSN - DE/Munich); ext [e-mail]; ext Jouni Korhonen; Ben Campbell
> Cc: [e-mail] list
> Subject: RE: [Dime] DOIC: Self-Contained OLRs
> 
> Hi Ulrich,
> 
> If an additional OLR is present with a different ReportType, why it should be ignored by the reacting node?
> 
> Regards,
> Nirav.
> 
> -----Original Message-----
> From: DiME [mailto:[e-mail]] On Behalf Of Wiehe, Ulrich (NSN - DE/Munich)
> Sent: Friday, November 29, 2013 5:36 PM
> To: ext [e-mail]; ext Jouni Korhonen; Ben Campbell
> Cc: [e-mail] list
> Subject: Re: [Dime] DOIC: Self-Contained OLRs
> 
> Hi Lionel,
> 
> there is nothing missing exept the clarification that everything works fine when only one OLR (the OLR created by the reporting endpoint) is present in the answer and additional OLRs (not created by the reporting endpoint) may just be present as an optional optimization i.e. optionally inserted by the reporting endpoint and optionally ignored by the reacting endpoint.
> 
> Ulrich
>  
> 
> -----Original Message-----
> From: ext [e-mail] [mailto:[e-mail]]
> Sent: Friday, November 29, 2013 11:13 AM
> To: Wiehe, Ulrich (NSN - DE/Munich); ext Jouni Korhonen; Ben Campbell
> Cc: [e-mail] list
> Subject: RE: [Dime] DOIC: Self-Contained OLRs
> 
> Hi Ulrich,
> 
> Using the Report Type "host report", you know that the OLR applies for subsequent request towards the origin-host of the answer containing the OLR. Using the report Type "Realm report", you know that the OLR has to be used as soon as a request needs to be sent without destination-realm. 
> 
> It is not so important to know what the type of request was and which node inserts this information. It can be any node having sufficient knowledge of the realm overload status. An agent in the path could be this one but, for instance, future development could allow a distributed server architecture to provide the same information.
> 
> I'm not sure of what is missing in this reasoning...
> 
> Lionel
> 
> -----Message d'origine-----
> De : Wiehe, Ulrich (NSN - DE/Munich) [mailto:[e-mail]] Envoyé : jeudi 28 novembre 2013 11:30 À : MORAND Lionel IMT/OLN; ext Jouni Korhonen; Ben Campbell Cc : [e-mail] list Objet : RE: [Dime] DOIC: Self-Contained OLRs
> 
> Lionel,
> 
> my understanding was that _the_ reporting end point provides _the_ OLR.
> 
> If we go for two OLRs in the answer we should indicate which OLR is the actual OLR created by the reporting end point and which OLR is an additional OLR created by another node.
> 
> We have two cases:
> a) The request sent by the client (reacting end point) contains no Destination Host. The agent (reporting node) (after forwarding the request to the selected server and receiving the answer) returns a realm-type OLR as the actual reporting-node-created OLR and optionally in addition a host-type OLR as learned from the selected server.  The client may ignore the additional OLR.
> b) The request sent by the client (reacting endpoint) contains the Destination Host. The Server (reporting node) returns a host-type OLR as the actual reporting-node-created OLR in the answer. The agent may optionally insert a realm-type OLR as additional OLR to the answer. The client may ignore the additional OLR.
> 
> Ulrich
> 
> 
> 
> -----Original Message-----
> From: ext [e-mail] [mailto:[e-mail]]
> Sent: Thursday, November 28, 2013 10:31 AM
> To: Wiehe, Ulrich (NSN - DE/Munich); ext Jouni Korhonen; Ben Campbell
> Cc: [e-mail] list
> Subject: RE: [Dime] DOIC: Self-Contained OLRs
> 
> Hi,
> 
> There is no assumption on which entity is providing the realm overload status. It could be provided an agent inserting this info in answers received from a server behind but also from a server that would know this info by some internal magic.
> But in any case, if we assume that the client will received a successful answer from the server for an initial request with only Dest-Realm AVP, it should be possible to have both report types in the answer: one for the server itself, one for the realm for new request sent to the realm with only Dest-Realm AVP.
> 
> Lionel
> 
> -----Message d'origine-----
> De : DiME [mailto:[e-mail]] De la part de Wiehe, Ulrich (NSN - DE/Munich) Envoyé : jeudi 28 novembre 2013 10:26 À : ext Jouni Korhonen; Ben Campbell Cc : [e-mail] list Objet : Re: [Dime] DOIC: Self-Contained OLRs
> 
> Hi,
> 
> I don't see how the possibility to send more than one OLR in an answer is aligned with the "endpoint principle". If the ReportType is "realm" this indicates to the reacting end point that the reporting end point is an agent (e.g. SFE) rather than a server. If the ReportType is "host" this indicates to the reacting end point that the reporting end point is a server. How can the reporting end point be both agent and server?
> 
> Ulrich
> 
> -----Original Message-----
> From: DiME [mailto:[e-mail]] On Behalf Of ext Jouni Korhonen
> Sent: Wednesday, November 27, 2013 11:44 PM
> To: Ben Campbell
> Cc: [e-mail] list
> Subject: Re: [Dime] DOIC: Self-Contained OLRs
> 
> 
> On Nov 28, 2013, at 12:27 AM, Ben Campbell <[e-mail]> wrote:
> 
> > Hi,
> > 
> > I mentioned in another thread that I prefer putting an explicit 
> > ReportType AVP in an OLR, rather than
> 
> The more I spent time thinking/writing the actual procedures on the endpoints, the more it makes sense to me to keep the ReportType in the OC-OLR. Even if the baseline does not have agent overload etc, the ReportType fits well to the "endpoint principle" we have in the draft. It indeed gives more tools to make a host vs. realm base decision on the reacting node and is plain more clear.
> 
> I skip the rest of the mail.. too much text ;-)
> 
> 
> - Jouni
> 
> 
> 
> 
> 
> > making a responding node infer the type or meaning of the OLR from a Diameter request that corresponds to the answer containing the OLR. My reasons for that go beyond just ReportType, so I'm starting a separate thread.
> > 
> > As currently described, a consumer of an OLR must infer several things from other context. In most cases, that context is in the Diameter answer that carries the OLR. For example, the OLR implicitly refers to the application identified by the Application-Id field of the enclosing answer, the realm identified by Origin-Realm, and so on. This means that the "meaning" of an OLR cannot be determined from the OLR contents alone; OLRs only have meaning in the context of the enclosing answer. If you moved an OLR from one answer to another, it's meaning may change completely.
> > 
> > I think this approach is a mistake. I would greatly prefer that we explicitly include such values in the OLR itself, for multiple reasons:
> > 
> > 1) It's more complex to interpret implicit, contextual values than explicit values. The consumer cannot simply look at the OLR; it must look in various other AVPs to find all the information it needs. For example, I think a common software design for overload control processing to be separated from application processing. The consumer cannot simply hand the OLR to that module and expect things to work. The OC module must not only parse the OLR, but parse any other AVPs that are relevant. As OLR contents get extended (assumedly following the same strategy as the base spec), the number of "context" avps that must be interpreted can grow large. This approach is error prone, and will likely encourage brittle, hard-to-maintain code. Self-contained OLRs would keep all the information related to overload in one place. making for simpler implementations.
> > 
> > 2) It's more complex for the reporting node to send implicit values than explicit values. The sender cannot simply set the context to match the OLR--all those other AVPs have application or protocol layer meanings. Once a reporting node realizes that it is overloade, it has to wait for the right answer that contains the right context before it can send the OLR. This is particularly troublesome for agents, since they will typically have to insert OLRs into answers created by other nodes. 
> > 
> > If the reporting node screws this up, the meaning of the OLR may change significantly. So again, implicit meaning gives us error prone implementations. Self-contained OLRs are simpler to create and send.
> > 
> > 3) Implicit values don't work at all for certain problems. For 
> > example, if an agent needs to originate an OLR, it typically needs to 
> > insert that OLR into an existing Diameter answer created by a server.
> > It can't create its own answer without affecting the application 
> > state. If the responding node assumes the OLR comes from or refers to 
> > the node identified by the Origin-Host AVP in the enclosing answer, 
> > things break. (For examples of when an agent needs to send OLRs that 
> > are distinct from those sent by a server, see Steve's agent overload 
> > draft, or my dh/dr example.)
> > 
> > OTOH, explicit values will work for all cases where we need to associate some arbitrary value with an OLR.
> > 
> > 4) Implicit values seriously constrain the future evolution of Diameter OC standards. For example, lets say we find a good reason to allow OLRs to be sent out of band, or be sent in a dedicated Diameter application. If overload reports were self-contained, one could just reuse the report format we specify here. But if the meaning of an OLR depends on the way it's transported, this won't work. We would have to create a new or significantly modified OLR format if we found a need to transport OLRs in different ways. Self-contained OLRs would allow much greater flexibility.
> > 
> > So, in summary, I think that self-contained OLRs would lead to simpler implementations, less brittle deployments, and more flexibility for future evolution of standards.
> > 
> > Thanks!
> > 
> > Ben.
> > _______________________________________________
> > DiME mailing list
> > [e-mail]
> > https://www.ietf.org/mailman/listinfo/dime
> 
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> Ce message et ses pieces jointes peuvent contenir des informations confidentielles ou privilegiees et ne doivent donc
> pas etre diffuses, exploites ou copies sans autorisation. Si vous avez recu ce message par erreur, veuillez le signaler
> a l'expediteur et le detruire ainsi que les pieces jointes. Les messages electroniques etant susceptibles d'alteration,
> Orange decline toute responsabilite si ce message a ete altere, deforme ou falsifie. Merci.
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