Hello Team, Hope you are doing well.
We have some clarifications required for SR Policy Capabilities and its processing. Please look into it and let us know your views on these points. We are eagerly waiting to get feedback from you guys. Thanks & Regards, Mrinmoy On Tue, Jun 17, 2025 at 8:53 PM Diptiranjan Dash <[email protected]> wrote: > Reminder > > Regards, > Diptiranjan > > On Tue, Jun 17, 2025 at 4:12 PM Diptiranjan Dash < > [email protected]> wrote: > >> Hi Team, >> >> While reviewing the following draft: >> >> draft-ietf-pce-segment-routing-policy-cp-27 - Path Computation Element >> Communication Protocol (PCEP) Extensions for Segment Routing (SR) Policy >> Candidate Paths >> <https://datatracker.ietf.org/doc/draft-ietf-pce-segment-routing-policy-cp/27/> >> >> We came across a few areas that are currently unclear . We request your >> clarification on the following points: >> >> >> >> *1. SR Policy Capabilities: Computation Priority TLV* >> >> >> >> 5.2.1. Computation Priority TLV, page 15: >> >> If the TLV is absent from the LSP >> >> object and the P-flag in the SRPOLICY-CAPABILITY TLV is set to 1, a >> >> default Priority value of 128 is used. >> >> >> >> As per above section, if P-flag is set in SRPOLICY-CAPABILITY TLV and >> Computation Priority TLV is absent then default priority will be 128. Now, >> what would be in the PCReport from PCC? >> >> >> >> 1. Should PCC send a Computation Priority TLV in LSP object with >> priority 128? >> >> 2. Now, as my understanding, if PCE sends any priority update say 50 >> then PCReport will send Computation Priority TLV in the LSP object with >> priority 50. Is that correct? >> >> 3. In later PCUpdates if there is no change in priority, then should >> PCC send Computation Priority TLV in the LSP object of PCReport? >> >> 4. Should PCC send Computation Priority TLV in MBB down PCREports or >> LSP remove PCReports? >> >> >> >> *2. SR Policy Capabilities: Explicit Null Label Policy (ENLP) TLV* >> >> >> >> 5.2.2. Explicit Null Label Policy (ENLP) TLV, page 15: >> >> >> >> If an ENLP TLV is >> >> not present, the decision of whether to push an Explicit NULL label >> >> on a given packet is a matter of local configuration >> >> >> >> 1. Now, as my understanding, if PCE sends ENLP TLV in the LSP object >> then PCC sends it in the LSP object of PCReport. Is that correct? >> >> 2. In later PCUpdates if there is no change in ENLP TLV, then should >> PCC send ENLP TLV in the LSP object of PCReport? >> >> 3. Should PCC send ENLP TLV in MBB down PCREports or LSP remove >> PCReports? >> >> >> >> *3. SR Policy Capabilities: Invalidation TLV* >> >> >> >> 5.2.3. Invalidation TLV, page 16: >> >> >> 1. Now, as my understanding, if PCE sends Invalidation TLV in the LSP >> object then PCC sends it in the LSP object of PCReport. Is that correct? >> >> 2. In later PCUpdates if there is no change in Invalidation TLV, then >> should PCC send Invalidation TLV in the LSP object of PCReport? >> >> 3. Should PCC send Invalidation TLV in MBB down PCREports or LSP >> remove PCReports? >> >> >> >> *4. Another question regarding the below error:* >> >> >> >> 5.1. SR Policy Capability TLV, page 13: >> >> >> >> If a PCEP speaker receives SRPA but the SRPOLICY-CAPABILITY TLV is >> >> not exchanged, then the PCEP speaker MUST send a PCErr message with >> >> Error- Type = 10 ("Reception of an invalid object") and Error-Value = >> >> TBD2 ("Missing SRPOLICY-CAPABILITY TLV") and MUST then close the PCEP >> >> session. >> >> >> >> Suppose PCC does not support SRPA, so didn't send capability TLV in >> open message, but PCE supports and sends it in Open message. >> >> In this situation, my understanding is, the PCEP session should come >> up without any issue. Right? >> >> >> >> >> >> Now, if PCE receives SRPA from PCC, PCE will send Error- Type = 10 >> ("Reception of an invalid object") and Error-Value = >> >> TBD2 ("Missing SRPOLICY-CAPABILITY TLV") and MUST then close the PCEP >> session. It is clear to me. >> >> >> >> But, if PCC receives SRPA from PCE, then which error should be thrown? >> Error- Type = 10 ("Reception of an invalid object") and Error-Value = >> >> TBD2 ("Missing SRPOLICY-CAPABILITY TLV")? But "Missing >> SRPOLICY-CAPABILITY TLV" is not right as it receives SRPOLICY-CAPABILITY >> TLV from PCE, >> >> rather could be some other error like "SRPOLICY not supported". What >> do you think regarding this error? >> >> >> >> Thanks & Regards, >> >> Dipti Ranjan >> >
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