Re: [Dime] [dime] #48: Setting M-Bit gives wrong semantics

Hi

Effectively we should be cautious with M bit for AVPS inside a grouped AVP such as OC-OLR AVP, and as Ben proposed, I am also rather in favour of not using the Mbit inside a DOC group AVP, including application specific AVPs.

In the thread discussion it  was mentioned the use of OC-feature and  also relay node that is application  independent.

Hereafter my  case:

After our IETF draft having become a RFC, IETF standardizes an extension,  which adds a new flag in OC-feature AVP. This extension is not specific to a Diameter application

-          A  relay oonly supporting our IETF draft, will observe that OC-feature value does not fit to what it knows. I expect here that relay will do nothing about DOC as the meaning of the OC-OLR may be different of what it knows. OK? I als othink it applies to a proxy DA

-          If the relay supports the extension, it will recognize  the OC-feature value and will behave according this value. So OK. Should we have some text in the IETF draft?

Now, this is a Diameter  application (eg a 3GPP one) that will define an extension for its own use . Is this application is allowed to use bits of OC-Features AVP to indicate this application specific feature (or even algorithm). How to avoid the application to use the same bits as future IETF extensions? Will we be driven to use another OC-Application-Specific-Feature AVP, or have bits  in OC-Feature  reserved for application specific extensions., or other?  A constraint is that  a relay (application unaware) should nevertheless  detect there is application specific extensions (without knowing their meaning) so to not do DOC actions.

I understand this is not directly linked to our immediate scope, but we may try  to be future proof allowing application specific extensions and Relay node supporting the generic DOC.

Do you agree on this potential issue? If yes may be to analyse what to add in the IETF draft to be future proof.

Best regards

JJacques

De : DiME [mailto:dime-bounces@ietf.org] De la part de Steve Donovan
Envoyé : lundi 24 mars 2014 13:23
À : dime@ietf.org
Objet : Re: [Dime] [dime] #48: Setting M-Bit gives wrong semantics

Do we have proposed wording to be included in the -02 version of the draft on this issue?

Steve
On 3/22/14 12:36 AM, Ben Campbell wrote:

On Mar 21, 2014, at 9:33 PM, Jouni Korhonen <jouni.nospam@gmail.com><mailto:jouni.nospam@gmail.com> wrote:

Ben,

On Mar 22, 2014, at 2:44 AM, Ben Campbell <ben@nostrum.com><mailto:ben@nostrum.com> wrote:

On Mar 21, 2014, at 12:43 PM, Jouni Korhonen <jouni.nospam@gmail.com><mailto:jouni.nospam@gmail.com> wrote:

Consider the case of a Diameter _relay_ that supports DOIC. It is not aware of any application-specific rules about m-bits. It receives an OC-Supported-Features or an OC-OLR that has a mandatory AVP that it doesn't recognize. Logically, it should probably ignore the entire OC-Supported-Features or OC-OLR grouped-AVP. But it won't. Being a relay, it's not going to reject the message. Rather it's likely to try to apply the OC-Supported-Features or OC-OLR incorrectly.

RFC6733 also says that relays perform not do any application level

processing. If a relay supports DOIC and does something goofy that

is left for implementation, we should no care nor try to fix the

situation. The implementation is already bending the rules in that

case.

Hi Jouni,

I'm not talking about the case of the relay doing something goofy. Rather, I mean when a relay tries to perform basic DOIC processing of an OLR as described in the base DOIC spec, but ignores some extension AVP that changes the meaning of the OLR. It's not bending the rules so much as failing to recognize someone else changing the rules.

Ah, I see your point. But if one adds AVPs to the default algorithm

that change he behaviour and does not a) declare it as a new algorithm

or b) add a new supported feature flag, then that is a proprietary

(broken) implementation. We cannot really protect against those..

I think that's reasonable. My original point was that extensions should not try to use the m-bit for that purpose. If they have something that is not backwards compatible, it needs to be negotiated in the feature vector.

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