Hi Dhruv, Thank you for your response. The PCE is indeed sending a path that violates the hop-count constraint. The PCRep message contained an ERO with two SR sub-objects, indicating that the ERO path is more than one hop away, despite the PCC's hop-count constraint being set to one.
Could you please clarify the expected behavior of the PCC upon receiving such a PCRep message? I am wondering if this scenario should be interpreted as an error. Regards, Kowsalya On Tue, Nov 25, 2025 at 6:32 PM Dhruv Dhody <[email protected]> wrote: > Hi Kowsalya, > > On Tue, Nov 25, 2025 at 4:55 PM Kowsalya Dhevi < > [email protected]> wrote: > >> Hi All, >> >> Kindly share your insights regarding the following query. >> >> RFC 5440, section 7.8, states that "If no path satisfying the constraints >> could be found by the PCE, the METRIC objects MAY also be present in the >> PCRep message with the NO-PATH object to indicate the constraint metric >> that could be satisfied." >> >> However, I have encountered a scenario where the PCE sent a PCRep message >> with an Explicit Route Object (ERO), even when it could not locate a path >> meeting the constraints. Specifically, the Path Computation Client (PCC) >> sent a PCReq message with a Metric Object for "Hop Counts" set to "1" with >> the B flag enabled. Nevertheless, the PCE responded with a PCRep message >> containing an ERO object but with a different Metric Object "TE Metric". >> >> > Dhruv: Just for my understanding - what is the content of the ERO? > > https://datatracker.ietf.org/doc/html/rfc5440#section-7.5 is clear that > "When a PCE cannot find a path satisfying a set of constraints, it MUST > include a NO-PATH object in the PCRep message." > > The presence of the ERO in PCRep indicates successful path computation. > > > >> In such an instance, I wonder if it is appropriate for the PCC to send a >> PCErr message. If so, I would appreciate it if you could provide the >> appropriate Error-type and Error-value. >> >> > Dhruv: If there is no NO-PATH object present in the PCRep message, the PCC > does not have a way to infer that the path computation failed. This is why > RFC 5440 does not have an explicit error message specified. > > For comparison, Stateful PCE implementations use an empty ERO to signal > "no path" in the PCUpd message (not PCRep). That is why I asked about ERO > content - to understand whether the PCE is sending a path that clearly > violates the hop-count constraint or something else is going on. > > Thanks! > Dhruv > (As a WG participant) > > > >> Regards, >> Kowsalya Dhevi >> >> -- >> > -- .
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