Conveying Vendor-Specific Information in
the Path Computation Element (PCE) Communication Protocol (PCEP)
extensions for Stateful PCE.
Huawei Technologies
Huawei Campus, No. 156 Beiqing Rd.
Beijing
100095
China
c.l@huawei.com
Huawei Technologies
H1, Huawei Xiliu Beipo Village, Songshan Lake
Dongguan
Guangdong
523808
China
zhenghaomian@huawei.com
Ciena
385 Terry Fox Drive
Kanata
Ontario
K2K 0L1
Canada
msiva282@gmail.com
Cisco Systems, Inc.
ssidor@cisco.com
Cisco Systems, Inc.
zali@cisco.com
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 the pending path
computation requests. This information may then be considered when
computing new traffic engineered LSPs, and for the associated and the
dependent LSPs, received from a Path Computation Client (PCC).
RFC 7470 defines a facility to carry vendor-specific information in
Path Computation Element Communication Protocol (PCEP).
This document extends this capability for the Stateful PCEP
messages.
Introduction
The Path Computation Element Communication Protocol (PCEP) provides mechanisms for a Path
Computation Element (PCE) to perform path computation in response to a
Path Computation Client (PCC) request.
A Stateful PCE is capable of considering, for the purposes of the
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
(LSP-DB). 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 for
Stateful PCE.
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 extends 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 extends
the stateful PCEP messages to also include the Vendor Information Object
as well.
Requirements Language
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.
Procedures for the Vendor Information Object
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:
::=
Where:
::= []
::= []
[]
Where:
::=
[]
is defined in [RFC8231].
]]>
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 [RFC8231].
]]>
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 an 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:
::=
Where:
::=
[]
::=
(|
)
::=
[]
[]
[]
Where:
::=
[]
and is as per
[RFC8281].
]]>
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, MUST ignore the object in the same way as described
in .
Procedures for the Vendor Information TLV
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 extensions such
as SRP and LSP objects. All the procedures as per section 3 of .
Vendor Information Object and TLV
specify the format of
VENDOR-INFORMATION Object and VENDOR- INFORMATION-TLV.
Manageability Considerations
All manageability requirements and considerations listed in , , , and apply to PCEP protocol extensions
defined in this document. In addition, requirements and considerations
listed in this section apply.
Control of Function and Policy
As stated in , this
capability, the associated vendor-specific information, and policy
SHOULD be made configurable. This information can be used in Stateful
PCEP messages as well.
Information and Data Models
The PCEP YANG module is specified in . Any standard YANG module will not
include details of vendor-specific information. The standard YANG module
MAY be extended to include the use of this information and the
Enterprise Numbers that the object and the TLVs contain.
Liveness Detection and Monitoring
Mechanisms defined in this document do not imply any new liveness
detection and monitoring requirements in addition to those already
listed in .
Verify Correct Operations
Mechanisms defined in this document do not imply any new operation
verification requirements in addition to those already listed in and .
Requirements On Other Protocols
Mechanisms defined in this document do not imply any new
requirements on other protocols.
Impact On Network Operations
Mechanisms defined in and
also apply to PCEP
extensions defined in this document. Further, the mechanism described
in this document can help the operator to request control of the LSPs
at a particular PCE.
IANA Considerations
There are no IANA consideration in this document.
Implementation Status
[NOTE TO RFC EDITOR : This whole section and the reference to RFC
7942 is to be removed before publication as an RFC]
This section records the status of known implementations of the
protocol defined by this specification at the time of posting of this
Internet-Draft, and is based on a proposal described in . The description of implementations
in this section is intended to assist the IETF in its decision processes
in progressing drafts to RFCs. Please note that the listing of any
individual implementation here does not imply endorsement by the IETF.
Furthermore, no effort has been spent to verify the information
presented here that was supplied by IETF contributors. This is not
intended as, and must not be construed to be, a catalog of available
implementations or their features. Readers are advised to note that
other implementations may exist.
According to , "this will
allow reviewers and working groups to assign due consideration to
documents that have the benefit of running code, which may serve as
evidence of valuable experimentation and feedback that have made the
implemented protocols more mature. It is up to the individual working
groups to use this information as they see fit".
Cisco Systems
- Organization: Cisco Systems, Inc.
- Implementation: Cisco IOS-XR PCE and PCC
- Description: Vendor Information Object used in PCRpt, PCUpd and
PCInitiate messages.
- Maturity Level: Production
- Coverage: Full
- Contact: ssidor@cisco.com
Security Considerations
The protocol extensions defined in this document do not change the
nature of PCEP. Therefore, the security considerations set out in , , and apply unchanged.
As stated in , PCEP
implementations SHOULD support the TCP- AO and not use TCP MD5 because of TCP MD5's known
vulnerabilities and weakness. PCEP also support Transport Layer Security
(TLS) as per the
recommendations and best current practices in .
Acknowledgments
Thanks to Avantika, Mahendra Singh Negi, Udayasree Palle, and Swapna K
for their suggestions.
References
Normative References
Informative References