Conveying Vendor-Specific Information in the Path Computation Element (PCE) Communication Protocol (PCEP) extensions for stateful PCE.

The Path Computation Element communication Protocol (PCEP) provides mechanisms for Path Computation Elements (PCEs) to perform path computations in response to Path Computation Clients' (PCCs) requests. A stateful PCE is capable of considering, for the purposes of path computation, not only the network state in terms of links and nodes (referred to as the Traffic Engineering Database or TED) but also the status of active services (previously computed paths, and currently reserved resources, stored in the Label Switched Paths Database (LSPDB). describes general considerations for a stateful PCE deployment and examines its applicability and benefits, as well as its challenges and limitations through a number of use cases. describes a set of extensions to PCEP to provide stateful control. A stateful PCE has access to not only the information carried by the network's Interior Gateway Protocol (IGP), but also the set of active paths and their reserved resources for its computations. The additional state allows the PCE to compute constrained paths while considering individual LSPs and their interactions. describes the setup, maintenance and teardown of PCE-initiated LSPs under the stateful PCE model. These extensions added new messages in PCEP. defined Vendor Information object that can be used to carry arbitrary, proprietary information such as vendor-specific constraints. It also defined VENDOR-INFORMATION-TLV that can be used to carry arbitrary information within any existing or future PCEP object that supports TLVs. This document extend the usage of Vendor Information Object and VENDOR-INFORMATION-TLV to stateful PCE. The VENDOR-INFORMATION-TLV can be carried inside any of the new objects added in PCEP for stateful PCE as per , this document extend the PCEP messages to also include the Vendor Information Object too.

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 when, and only when, they appear in all capitals, as shown here.

A Path Computation LSP State Report message (also referred to as PCRpt message) is a PCEP message sent by a PCC to a PCE to report the current state of an LSP. A PCC that wants to convey proprietary or vendor-specific information or metrics to a PCE does so by including a Vendor Information object in the PCRpt message. The contents and format of the object are described in Section 4 of . The PCE determines how to interpret the information in the Vendor Information object by examining the Enterprise Number it contains. The Vendor Information object is OPTIONAL in a PCRpt message. Multiple instances of the object MAY be used on a single PCRpt message. Different instances of the object can have different Enterprise Numbers. The format of the PCRpt message (with as base) is updated as follows

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Where: ::= [] ::= [] [] Where: ::= [] is defined in [I-D.ietf-pce-stateful-pce]. ]]>

A Path Computation LSP Update Request message (also referred to as PCUpd message) is a PCEP message sent by a PCE to a PCC to update attributes of an LSP. The Vendor Information object can be included in a PCUpd message to convey proprietary or vendor-specific information. The format of the PCUpd message (with as base) is updated as follows

::=

Where: ::= [] ::= [] Where: ::= [] is defined in [I-D.ietf-pce-stateful-pce]. ]]>

A Path Computation LSP Initiate Message (also referred to as PCInitiate message) is a PCEP message sent by a PCE to a PCC to trigger LSP instantiation or deletion. The Vendor Information object can be included in a PCInitiate message to convey proprietary or vendor-specific information.

::=

Where: ::= [] ::= (| ) ::= [] [] [] Where: ::= [] ]]>

<PCE-initiated-lsp-deletion> and <attribute-list> is as per . A legacy implementation that does not recognize the Vendor Information object will act according to the procedures set out in and . An implementation that supports the Vendor Information object, but receives one carrying an Enterprise Number that it does not support, SHOULD ignore the object as per .

The Vendor Information TLV can be used to carry vendor-specific information that applies to a specific PCEP object by including the TLV in the object. This includes objects used in stateful PCE extension such as SRP and LSP object. All the procedures as per section 3 of .

specify the format of VENDOR-INFORMATION Object and VENDOR- INFORMATION-TLV.

There are no IANA consideration.

The protocol extensions defined in this document do not change the nature of PCEP. Therefore, the security considerations set out in , , and apply unchanged. Note that further security considerations for the use of PCEP over TCP are presented in .

Thanks to Avantika, Mahendra Singh Negi, Udayasree Palle and Swapna K for their suggestions.