Re: [Dime] RFC3588 7.2 Misleading ABNF

[Yoshihiro Ohba <yohba at tari.toshiba.com>]

Hi Tolga,

On Thu, Jun 15, 2006 at 12:26:11PM -0400, Tolga Asveren wrote:
> RFC3588 7.2 defines the ABNF to be used for answer messages with a protocol
> error return result. It is quite confusing/misleading/not-optimal (or I got
> it wrong what it should be).
> 
> As the starting assumption, I believe Protocol Errors must be related only
> with routing, i.e. erorrs which are interesting from intermediares point of
> view. Currently there a few errors classiefed as protocl errors, which
> aren't, and hopefully we can have some cleanup there.

Can you eraborate on why protocols errors must be related only to routing?

> 
> 
> I think the idea in 7.2 is:
> a)Protocol error answer message must include the original message, e.g. so
> that a relay agent can route it to some other peer. I assume *[ AVP ] stands
> for that.

Since the node that received the answer message would need to keep the
original request (e.g., to deal with redirect or failover), I don't
see a need for the original message to be included in the protocol
error answer message, but I may be missing something.

> 
> b)Protocol error answer message must include Result-Code, so that an
> intermediary can decide what to do with that answer. This is why we have {
> Result Code }.
> 
> So far so good....
> 
> c) { Origin-Host } { Origin-Realm }
> I assume those are *not* the Origin-Host Origin-Realm AVP of the original
> message -7.4 Error-Reporting hints that they aren't-. Why do we need them?
> If for troubleshooting, I would opt for Error-Reporting-Host AVP. When a
> relay agent receives a protocol error answer, how does it know which
> Origin-Host/Origin-Realm AVP to remove -there is also a pair for the
> original message, which should be kept intact-.

Origin-Host AVP and Error-Reporting-Host AVP may point to different
nodes, since Origin-Host and Origin-Realm AVPs may be replaced by a
proxy.

> 
> d) [ Error-Reporting-Host ]
> It is a good idea to have an AVP for troubleshooting purposes -as specified
> in 7.4-. IMHO, it is better to have this as optional rather than a MUST. I
> think, it is a better idea not ise Origin-Host/Origin-Realm for debugging
> and rely on this specific AVP.

Please see my comment above.

> 
> e) [ Origin-state-Id ] [ Proxy-Info ]
> Why are they explicitly mentioned?

I guess the reason is that those AVPs are generic enough to be
included in any answer message regardless of E-bit.

Yoshihiro Ohba


> 
> 
> Overall, IMO, 7.2 should have said that protocol error answers must include
> the original message, Result-Code AVP and may include Error-Reporting-Host
> AVP.
> 
>     Thanks,
>     Tolga
> 
> 
> 
> 
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