Conveying Vendor-Specific Information in the Path Computation Element (PCE) Communication Protocol (PCEP) extensions for stateful PCE.Huawei TechnologiesDivyashree Techno Park, WhitefieldBangaloreKarnataka560066Indiadhruv.ietf@gmail.com
Routing
PCE Working Group
A Stateful Path Computation Element (PCE) maintains information on
the current network state, including: computed Label Switched Path
(LSPs), reserved resources within the network, and pending path
computation requests. This information may then be considered when
computing new traffic engineered LSPs, and for associated
and dependent LSPs, received from Path Computation Clients (PCCs).
RFC 7470 defines a facility to carry vendor-specific information
in PCEP.This document extends this capability 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", "MAY",
and "OPTIONAL" in this document are to be interpreted as
described in
.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 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 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.The format of the PCInitiate message (with as base) is updated as follows 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.