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IETF RFC 8306
Last modified on Friday, December 1st, 2017
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Internet Engineering Task Force (IETF) Q. Zhao
Request for Comments: 8306 D. Dhody, Ed.
Obsoletes: 6006 R. Palleti
Category: Standards Track Huawei Technologies
ISSN: 2070-1721 D. King
Old Dog Consulting
November 2017
Extensions to
the Path Computation Element Communication Protocol (PCEP)
for Point-to-Multipoint Traffic Engineering Label Switched Paths
 Abstract
Point-to-point Multiprotocol Label Switching (MPLS) and Generalized
MPLS (GMPLS) Traffic Engineering Label Switched Paths (TE LSPs) may
be established using signaling techniques, but their paths may first
need to be determined. The Path Computation Element (PCE) has been
identified as an appropriate technology for the determination of the
paths of point-to-multipoint (P2MP) TE LSPs.
This document describes extensions to the PCE Communication Protocol
(PCEP) to handle requests and responses for the computation of paths
for P2MP TE LSPs.
This document obsoletes RFC 6006.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/RFC 8306.
Zhao, et al. Standards Track PAGE 1 
RFC 8306 Extensions to PCEP for P2MP TE LSPs November 2017
Copyright Notice
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document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
This document may contain material from IETF Documents or IETF
Contributions published or made publicly available before November
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material may not have granted the IETF Trust the right to allow
modifications of such material outside the IETF Standards Process.
Without obtaining an adequate license from the person(s) controlling
the copyright in such materials, this document may not be modified
outside the IETF Standards Process, and derivative works of it may
not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other
than English.
Table of Contents
1. Introduction ....................................................4
1.1. Terminology ................................................5
1.2. Requirements Language ......................................5
2. PCC-PCE Communication Requirements ..............................5
3. Protocol Procedures and Extensions ..............................6
3.1. P2MP Capability Advertisement ..............................7
3.1.1. IGP Extensions for P2MP Capability Advertisement ....7
3.1.2. Open Message Extension ..............................7
3.2. Efficient Presentation of P2MP LSPs ........................8
3.3. P2MP Path Computation Request/Reply Message Extensions .....9
3.3.1. The Extension of the RP Object ......................9
3.3.2. The P2MP END-POINTS Object .........................11
3.4. Request Message Format ....................................13
3.5. Reply Message Format ......................................15
Zhao, et al. Standards Track PAGE 2
RFC 8306 Extensions to PCEP for P2MP TE LSPs November 2017
3.6. P2MP Objective Functions and Metric Types .................16
3.6.1. Objective Functions ................................16
3.6.2. METRIC Object-Type Values ..........................17
3.7. Non-Support of P2MP Path Computation ......................17
3.8. Non-Support by Back-Level PCE Implementations .............17
3.9. P2MP TE Path Reoptimization Request .......................17
3.10. Adding and Pruning Leaves to/from the P2MP Tree ..........18
3.11. Discovering Branch Nodes .................................22
3.11.1. Branch Node Object ................................22
3.12. Synchronization of P2MP TE Path Computation Requests .....22
3.13. Request and Response Fragmentation .......................23
3.13.1. Request Fragmentation Procedure ...................24
3.13.2. Response Fragmentation Procedure ..................24
3.13.3. Fragmentation Example .............................24
3.14. UNREACH-DESTINATION Object ...............................25
3.15. P2MP PCEP-ERROR Objects and Types ........................27
3.16. PCEP NO-PATH Indicator ...................................28
4. Manageability Considerations ...................................28
4.1. Control of Function and Policy ............................28
4.2. Information and Data Models ...............................28
4.3. Liveness Detection and Monitoring .........................29
4.4. Verifying Correct Operation ...............................29
4.5. Requirements for Other Protocols and Functional
Components ................................................29
4.6. Impact on Network Operation ...............................29
5. Security Considerations ........................................30
6. IANA Considerations ............................................31
6.1. PCEP TLV Type Indicators ..................................31
6.2. Request Parameter Bit Flags ...............................31
6.3. Objective Functions .......................................31
6.4. METRIC Object-Type Values .................................32
6.5. PCEP Objects ..............................................32
6.6. PCEP-ERROR Objects and Types ..............................34
6.7. PCEP NO-PATH Indicator ....................................35
6.8. SVEC Object Flag ..........................................35
6.9. OSPF PCE Capability Flag ..................................35
7. References .....................................................36
7.1. Normative References ......................................36
7.2. Informative References ....................................37
Appendix A. Summary of Changes from RFC 6006 ......................39
Appendix A.1. RBNF Changes from RFC 6006 ..........................39
Acknowledgements ..................................................41
Contributors ......................................................42
Authors' Addresses ................................................43
Zhao, et al. Standards Track PAGE 3
RFC 8306 Extensions to PCEP for P2MP TE LSPs November 2017
1. Introduction
The Path Computation Element (PCE) as defined in [RFC 4655] is an
entity that is capable of computing a network path or route based on
a network graph and applying computational constraints. A Path
Computation Client (PCC) may make requests to a PCE for paths to be
computed.
[RFC 4875] describes how to set up point-to-multipoint (P2MP) Traffic
Engineering Label Switched Paths (TE LSPs) for use in Multiprotocol
Label Switching (MPLS) and Generalized MPLS (GMPLS) networks.
The PCE has been identified as a suitable application for the
computation of paths for P2MP TE LSPs [RFC 5671].
The PCE Communication Protocol (PCEP) is designed as a communication
protocol between PCCs and PCEs for point-to-point (P2P) path
computations and is defined in [RFC 5440]. However, that
specification does not provide a mechanism to request path
computation of P2MP TE LSPs.
A P2MP LSP is comprised of multiple source-to-leaf (S2L) sub-LSPs.
These S2L sub-LSPs are set up between ingress and egress Label
Switching Routers (LSRs) and are appropriately overlaid to construct
a P2MP TE LSP. During path computation, the P2MP TE LSP may be
determined as a set of S2L sub-LSPs that are computed separately and
combined to give the path of the P2MP LSP, or the entire P2MP TE LSP
may be determined as a P2MP tree in a single computation.
This document relies on the mechanisms of PCEP to request path
computation for P2MP TE LSPs. One Path Computation Request message
from a PCC may request the computation of the whole P2MP TE LSP, or
the request may be limited to a subset of the S2L sub-LSPs. In the
extreme case, the PCC may request the S2L sub-LSPs to be computed
individually; the PCC is responsible for deciding whether to signal
individual S2L sub-LSPs or combine the computation results to signal
the entire P2MP TE LSP. Hence, the PCC may use one Path Computation
Request message or may split the request across multiple path
computation messages.
This document obsoletes [RFC 6006] and incorporates the following
errata:
o Erratum IDs 3819, 3830, 3836, 4867, and 4868 for [RFC 6006]
o Erratum ID 4956 for [RFC 5440]
All changes from [RFC 6006] are listed in Appendix A.
Zhao, et al. Standards Track PAGE 4
RFC 8306 Extensions to PCEP for P2MP TE LSPs November 2017
1.1. Terminology
Terminology used in this document:
TE LSP: Traffic Engineering Label Switched Path.
LSR: Label Switching Router.
OF: Objective Function. A set of one or more optimization criteria
used for the computation of a single path (e.g., path cost
minimization) or for the synchronized computation of a set of
paths (e.g., aggregate bandwidth consumption minimization).
P2MP: Point-to-Multipoint.
P2P: Point-to-Point.
This document also uses the terminology defined in [RFC 4655],
[RFC 4875], and [RFC 5440].
1.2. 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 [RFC 2119] [RFC 8174] when, and only when, they appear in all
capitals, as shown here.
2. PCC-PCE Communication Requirements
This section summarizes the PCC-PCE communication requirements as met
by the protocol extension specified in this document for P2MP MPLS-TE
LSPs. The numbering system in the list below corresponds to the
requirement numbers (e.g., R1, R2) used in [RFC 5862].
1. The PCC MUST be able to specify that the request is a P2MP path
computation request.
2. The PCC MUST be able to specify that objective functions are to
be applied to the P2MP path computation request.
3. The PCE MUST have the capability to reject a P2MP path
computation request and indicate non-support of P2MP path
computation.
4. The PCE MUST provide an indication of non-support of P2MP path
computation by back-level PCE implementations.
Zhao, et al. Standards Track PAGE 5
RFC 8306 Extensions to PCEP for P2MP TE LSPs November 2017
5. A P2MP path computation request MUST be able to list multiple
destinations.
6. A P2MP path computation response MUST be able to carry the path
of a P2MP LSP.
7. By default, the path returned by the PCE SHOULD use the
compressed format.
8. It MUST be possible for a single P2MP path computation request or
response to be conveyed by a sequence of messages.
9. It MUST NOT be possible for a single P2MP path computation
request to specify a set of different constraints, traffic
parameters, or quality-of-service requirements for different
destinations of a P2MP LSP.
10. P2MP path modification and P2MP path diversity MUST be supported.
11. It MUST be possible to reoptimize existing P2MP TE LSPs.
12. It MUST be possible to add and remove P2MP destinations from
existing paths.
13. It MUST be possible to specify a list of applicable branch nodes
to use when computing the P2MP path.
14. It MUST be possible for a PCC to discover P2MP path computation
capability.
15. The PCC MUST be able to request diverse paths when requesting a
P2MP path.
3. Protocol Procedures and Extensions
The following section describes the protocol extensions required to
satisfy the requirements specified in Section 2 ("PCC-PCE
Communication Requirements") of this document.
Zhao, et al. Standards Track PAGE 6
RFC 8306 Extensions to PCEP for P2MP TE LSPs November 2017
3.1. P2MP Capability Advertisement
3.1.1. IGP Extensions for P2MP Capability Advertisement
[RFC 5088] defines a PCE Discovery (PCED) TLV carried in an OSPF
Router Information Link State Advertisement (LSA) as defined in
[RFC 7770] to facilitate PCE discovery using OSPF. [RFC 5088]
specifies that no new sub-TLVs may be added to the PCED TLV. This
document defines a flag in the OSPF PCE Capability Flags to indicate
the capability of P2MP computation.
Similarly, [RFC 5089] defines the PCED sub-TLV for use in PCE
discovery using IS-IS. This document will use the same flag for the
OSPF PCE Capability Flags sub-TLV to allow IS-IS to indicate the
capability of P2MP computation.
The IANA assignment for a shared OSPF and IS-IS P2MP Capability Flag
is documented in Section 6.9 ("OSPF PCE Capability Flag") of this
document.
PCEs wishing to advertise that they support P2MP path computation
would set the bit (10) accordingly. PCCs that do not understand this
bit will ignore it (per [RFC 5088] and [RFC 5089]). PCEs that do not
support P2MP will leave the bit clear (per the default behavior
defined in [RFC 5088] and [RFC 5089]).
PCEs that set the bit to indicate support of P2MP path computation
MUST follow the procedures in Section 3.3.2 ("The P2MP END-POINTS
Object") to further qualify the level of support.
3.1.2. Open Message Extension
Based on the Capabilities Exchange requirement described in
[RFC 5862], if a PCE does not advertise its P2MP capability during
discovery, PCEP should be used to allow a PCC to discover, during the
Open Message Exchange, which PCEs are capable of supporting P2MP path
computation.
To satisfy this requirement, we extend the PCEP OPEN object by
defining an optional TLV to indicate the PCE's capability to perform
P2MP path computations.
IANA has allocated value 6 from the "PCEP TLV Type Indicators"
subregistry, as documented in Section 6.1 ("PCEP TLV Type
Indicators"). The description is "P2MP capable", and the length
value is 2 bytes. The value field is set to default value 0.
Zhao, et al. Standards Track PAGE 7
RFC 8306 Extensions to PCEP for P2MP TE LSPs November 2017
The inclusion of this TLV in an OPEN object indicates that the sender
can perform P2MP path computations.
The capability TLV is meaningful only for a PCE, so it will typically
appear only in one of the two Open messages during PCE session
establishment. However, in the case of PCE cooperation (e.g.,
inter-domain), when a PCE behaving as a PCC initiates a PCE session
it SHOULD also indicate its path computation capabilities.
3.2. Efficient Presentation of P2MP LSPs
When specifying additional leaves or when optimizing existing P2MP TE
LSPs as specified in [RFC 5862], it may be necessary to pass existing
P2MP LSP route information between the PCC and PCE in the request and
reply messages. In each of these scenarios, we need path objects for
efficiently passing the existing P2MP LSP between the PCE and PCC.
We specify the use of the Resource Reservation Protocol Traffic
Engineering (RSVP-TE) extensions Explicit Route Object (ERO) to
encode the explicit route of a TE LSP through the network. PCEP ERO
sub-object types correspond to RSVP-TE ERO sub-object types. The
format and content of the ERO are defined in [RFC 3209] and [RFC 3473].
The Secondary Explicit Route Object (SERO) is used to specify the
explicit route of an S2L sub-LSP. The path of each subsequent S2L
sub-LSP is encoded in a P2MP_SECONDARY_EXPLICIT_ROUTE object SERO.
The format of the SERO is the same as the format of an ERO as defined
in [RFC 3209] and [RFC 3473].
The Secondary Record Route Object (SRRO) is used to record the
explicit route of the S2L sub-LSP. The class of the P2MP SRRO is the
same as the class of the SRRO as defined in [RFC 4873].
The SERO and SRRO are used to report the route of an existing TE LSP
for which a reoptimization is desired. The format and content of the
SERO and SRRO are defined in [RFC 4875].
Zhao, et al. Standards Track PAGE 8
RFC 8306 Extensions to PCEP for P2MP TE LSPs November 2017
PCEP Object-Class and Object-Type values for the SERO and SRRO have
been assigned:
Object-Class Value 29
Name SERO
Object-Type 0: Reserved
1: SERO
2-15: Unassigned
Reference RFC 8306
Object-Class Value 30
Name SRRO
Object-Type 0: Reserved
1: SRRO
2-15: Unassigned
Reference RFC 8306
The IANA assignments are documented in Section 6.5 ("PCEP Objects").
Since the explicit path is available for immediate signaling by the
MPLS or GMPLS control plane, the meanings of all of the sub-objects
and fields in this object are identical to those defined for the ERO.
3.3. P2MP Path Computation Request/Reply Message Extensions
This document extends the existing P2P RP (Request Parameters) object
so that a PCC can signal a P2MP path computation request to the PCE
receiving the PCEP request. The END-POINTS object is also extended
to improve the efficiency of the message exchange between the PCC and
PCE in the case of P2MP path computation.
3.3.1. The Extension of the RP Object
The PCE path computation request and reply messages will need the
following additional parameters to indicate to the receiving PCE
(1) that the request and reply messages have been fragmented across
multiple messages, (2) that they have been requested for a P2MP path,
and (3) whether the route is represented in the compressed or
uncompressed format.
Zhao, et al. Standards Track PAGE 9
RFC 8306 Extensions to PCEP for P2MP TE LSPs November 2017
This document adds the following flags to the RP object:
The F-bit is added to the flag bits of the RP object to indicate to
the receiver that the request is part of a fragmented request or
is not a fragmented request.
o F (RP fragmentation bit - 1 bit):
0: This indicates that the RP is not fragmented or it is the last
piece of the fragmented RP.
1: This indicates that the RP is fragmented and this is not the
last piece of the fragmented RP. The receiver needs to wait
for additional fragments until it receives an RP with the same
RP-ID and with the F-bit set to 0.
The N-bit is added in the flag bits field of the RP object to signal
the receiver of the message that the request/reply is for P2MP or
is not for P2MP.
o N (P2MP bit - 1 bit):
0: This indicates that this is not a Path Computation Request
(PCReq) or Path Computation Reply (PCRep) message for P2MP.
1: This indicates that this is a PCReq or PCRep message for P2MP.
The E-bit is added in the flag bits field of the RP object to signal
the receiver of the message that the route is in the compressed
format or is not in the compressed format. By default, the path
returned by the PCE SHOULD use the compressed format.
o E (ERO-compression bit - 1 bit):
0: This indicates that the route is not in the compressed format.
1: This indicates that the route is in the compressed format.
The IANA assignments are documented in Section 6.2 ("Request
Parameter Bit Flags") of this document.
Zhao, et al. Standards Track PAGE 10
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3.3.2. The P2MP END-POINTS Object
The END-POINTS object is used in a PCReq message to specify the
source IP address and the destination IP address of the path for
which a path computation is requested. To represent the end points
for a P2MP path efficiently, we define two types of END-POINTS
objects for the P2MP path:
o Old leaves whose path can be modified/reoptimized.
o Old leaves whose path must be left unchanged.
With the P2MP END-POINTS object, the PCE Path Computation Request
message is expanded in a way that allows a single request message to
list multiple destinations.
In total, there are now four possible types of leaves in a
P2MP request:
o New leaves to add (leaf type = 1)
o Old leaves to remove (leaf type = 2)
o Old leaves whose path can be modified/reoptimized (leaf type = 3)
o Old leaves whose path must be left unchanged (leaf type = 4)
A given END-POINTS object gathers the leaves of a given type. The
type of leaf in a given END-POINTS object is identified by the
END-POINTS object leaf type field.
Using the P2MP END-POINTS object, the END-POINTS portion of a request
message for the multiple destinations can be reduced by up to 50% for
a P2MP path where a single source address has a very large number of
destinations.
Note that a P2MP path computation request can mix the different types
of leaves by including several END-POINTS objects per RP object as
shown in the PCReq Routing Backus-Naur Form (RBNF) [RFC 5511] format
in Section 3.4 ("Request Message Format").
Zhao, et al. Standards Track PAGE 11
RFC 8306 Extensions to PCEP for P2MP TE LSPs November 2017
The format of the P2MP END-POINTS object body for IPv4
(Object-Type 3) is as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Leaf type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source IPv4 address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination IPv4 address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ... ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination IPv4 address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: The P2MP END-POINTS Object Body Format for IPv4
The format of the END-POINTS object body for IPv6 (Object-Type 4) is
as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Leaf type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Source IPv6 address (16 bytes) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Destination IPv6 address (16 bytes) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ... ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Destination IPv6 address (16 bytes) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: The P2MP END-POINTS Object Body Format for IPv6
Zhao, et al. Standards Track PAGE 12
RFC 8306 Extensions to PCEP for P2MP TE LSPs November 2017
The END-POINTS object body has a variable length. These are
o multiples of 4 bytes for IPv4
o multiples of 16 bytes, plus 4 bytes, for IPv6
3.4. Request Message Format
As per [RFC 5440], a Path Computation Request message (also referred
to as a PCReq message) is a PCEP message sent by a PCC to a PCE to
request a path computation. A PCReq message may carry more than one
path computation request.
As per [RFC 5541], the OF object MAY be carried within a PCReq
message. If an objective function is to be applied to a set of
synchronized path computation requests, the OF object MUST be carried
just after the corresponding SVEC (Synchronization Vector) object and
MUST NOT be repeated for each elementary request.
The PCReq message is encoded as follows using RBNF as defined in
[RFC 5511].
Zhao, et al. Standards Track PAGE 13
RFC 8306 Extensions to PCEP for P2MP TE LSPs November 2017
Below is the message format for the request message:
<PCReq Message> ::= <Common Header>
[<svec-list>]
<request-list>
where:
<svec-list> ::= <SVEC>
[<OF>]
[<metric-list>]
[<svec-list>]
<request-list> ::= <request>[<request-list>]
<request> ::= <RP>
<end-point-rro-pair-list>
[<OF>]
[<LSPA>]
[<BANDWIDTH>]
[<metric-list>]
[<IRO>|<BNC>]
[<LOAD-BALANCING>]
where:
<end-point-rro-pair-list> ::=
<END-POINTS>[<RRO-List>[<BANDWIDTH>]]
[<end-point-rro-pair-list>]
<RRO-List> ::= (<RRO>|<SRRO>)[<RRO-List>]
<metric-list> ::= <METRIC>[<metric-list>]
Figure 3: The Message Format for the Request Message
Note that we preserve compatibility with the definition of <request>
provided in [RFC 5440]. At least one instance of <END-POINTS> MUST be
present in this message.
We have documented the IANA assignment of additional END-POINTS
Object-Type values in Section 6.5 ("PCEP Objects") of this document.
Zhao, et al. Standards Track PAGE 14
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3.5. Reply Message Format
The PCEP Path Computation Reply message (also referred to as a
PCRep message) is a PCEP message sent by a PCE to a requesting PCC in
response to a previously received PCReq message. PCEP supports the
bundling of multiple replies to a set of path computation requests
within a single PCRep message.
The PCRep message is encoded as follows using RBNF as defined in
[RFC 5511].
Below is the message format for the reply message:
<PCRep Message> ::= <Common Header>
<response-list>
where:
<response-list> ::= <response>[<response-list>]
<response> ::= <RP>
[<end-point-path-pair-list>]
[<NO-PATH>]
[<UNREACH-DESTINATION>]
[<attribute-list>]
<end-point-path-pair-list> ::=
[<END-POINTS>]<path>
[<end-point-path-pair-list>]
<path> ::= (<ERO>|<SERO>) [<path>]
where:
<attribute-list> ::= [<OF>]
[<LSPA>]
[<BANDWIDTH>]
[<metric-list>]
[<IRO>]
Figure 4: The Message Format for the Reply Message
The optional END-POINTS object in the reply message is used to
specify which paths are removed, changed, not changed, or added for
the request. The path is only needed for the end points that are
added or changed.
Zhao, et al. Standards Track PAGE 15
RFC 8306 Extensions to PCEP for P2MP TE LSPs November 2017
If the E-bit (ERO-Compress bit) was set to 1 in the request, then the
path will be formed by an ERO followed by a list of SEROs.
Note that we preserve compatibility with the definition of <response>
provided in [RFC 5440] and with the optional
<end-point-path-pair-list> and <path>.
3.6. P2MP Objective Functions and Metric Types
3.6.1. Objective Functions
Six objective functions have been defined in [RFC 5541] for P2P path
computation.
This document defines two additional objective functions -- namely,
SPT (Shortest-Path Tree) and MCT (Minimum-Cost Tree) -- that apply to
P2MP path computation. Hence, two objective function codes are
defined as follows:
Objective Function Code: 7
Name: Shortest-Path Tree (SPT)
Description: Minimize the maximum source-to-leaf cost with respect
to a specific metric or to the TE metric used as the default
metric when the metric is not specified (e.g., TE or IGP metric).
Objective Function Code: 8
Name: Minimum-Cost Tree (MCT)
Description: Minimize the total cost of the tree (i.e., the sum of
the costs of tree links) with respect to a specific metric or to
the TE metric used as the default metric when the metric is not
specified.
Processing these two objective functions is subject to the rules
defined in [RFC 5541].
Zhao, et al. Standards Track PAGE 16
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3.6.2. METRIC Object-Type Values
There are three types defined for the METRIC object in [RFC 5440] --
namely, the IGP metric, the TE metric, and Hop Counts. This document
defines three additional types for the METRIC object: the P2MP IGP
metric, the P2MP TE metric, and the P2MP hop count metric. They
encode the sum of the metrics of all links of the tree. The
following values for these metric types have been assigned; see
Section 6.4.
o P2MP IGP metric: T=8
o P2MP TE metric: T=9
o P2MP hop count metric: T=10
3.7. Non-Support of P2MP Path Computation
o If a PCE receives a P2MP path computation request and it
understands the P2MP flag in the RP object, but the PCE is not
capable of P2MP computation, the PCE MUST send a PCErr message
with a PCEP-ERROR object and corresponding Error-value. The
request MUST then be cancelled at the PCC. The Error-Types and
Error-values have been assigned; see Section 6 ("IANA
Considerations") of this document.
o If the PCE does not understand the P2MP flag in the RP object,
then the PCE would send a PCErr message with Error-Type=2
(Capability not supported) as per [RFC 5440].
3.8. Non-Support by Back-Level PCE Implementations
If a PCE receives a P2MP request and the PCE does not understand the
P2MP flag in the RP object, and therefore the PCEP P2MP extensions,
then the PCE SHOULD reject the request.
3.9. P2MP TE Path Reoptimization Request
A reoptimization request for a P2MP TE path is specified by the use
of the R-bit within the RP object as defined in [RFC 5440] and is
similar to the reoptimization request for a P2P TE path. The only
difference is that the PCC MUST insert the list of Record Route
Objects (RROs) and SRROs after each instance of the END-POINTS object
in the PCReq message, as described in Section 3.4 ("Request Message
Format") of this document.
Zhao, et al. Standards Track PAGE 17
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An example of a reoptimization request and subsequent PCReq message
is described below:
Common Header
RP with P2MP flag/R-bit set
END-POINTS for leaf type 3
RRO list
OF (optional)
Figure 5: PCReq Message Example 1 for Optimization
In this example, we request reoptimization of the path to all leaves
without adding or pruning leaves. The reoptimization request would
use an END-POINTS object with leaf type 3. The RRO list would
represent the P2MP LSP before the optimization, and the modifiable
path leaves would be indicated in the END-POINTS object.
It is also possible to specify distinct leaves whose path cannot be
modified. An example of the PCReq message in this scenario would be:
Common Header
RP with P2MP flag/R-bit set
END-POINTS for leaf type 3
RRO list
END-POINTS for leaf type 4
RRO list
OF (optional)
Figure 6: PCReq Message Example 2 for Optimization
3.10. Adding and Pruning Leaves to/from the P2MP Tree
When adding new leaves to or removing old leaves from the existing
P2MP tree, by supplying a list of existing leaves, it is possible to
optimize the existing P2MP tree. This section explains the methods
for adding new leaves to or removing old leaves from the existing
P2MP tree.
To add new leaves, the PCC MUST build a P2MP request using END-POINTS
with leaf type 1.
To remove old leaves, the PCC MUST build a P2MP request using
END-POINTS with leaf type 2. If no type-2 END-POINTS exist, then the
PCE MUST send Error-Type 17, Error-value 1: the PCE cannot satisfy
the request due to no END-POINTS with leaf type 2.
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When adding new leaves to or removing old leaves from the existing
P2MP tree, the PCC MUST also provide the list of old leaves, if any,
including END-POINTS with leaf type 3, leaf type 4, or both.
Specific PCEP-ERROR objects and types are used when certain
conditions are not satisfied (i.e., when there are no END-POINTS with
leaf type 3 or 4, or in the presence of END-POINTS with leaf type 1
or 2). A generic "Inconsistent END-POINTS" error will be used if a
PCC receives a request that has an inconsistent END-POINTS setting
(i.e., if a leaf specified as type 1 already exists). These IANA
assignments are documented in Section 6.6 ("PCEP-ERROR Objects and
Types") of this document.
For old leaves, the PCC MUST provide the old path as a list of RROs
that immediately follows each END-POINTS object. This document
specifies Error-values when specific conditions are not satisfied.
The following examples demonstrate full and partial reoptimization of
existing P2MP LSPs:
Case 1: Adding leaves with full reoptimization of existing paths
Common Header
RP with P2MP flag/R-bit set
END-POINTS for leaf type 1
RRO list
END-POINTS for leaf type 3
RRO list
OF (optional)
Case 2: Adding leaves with partial reoptimization of existing paths
Common Header
RP with P2MP flag/R-bit set
END-POINTS for leaf type 1
END-POINTS for leaf type 3
RRO list
END-POINTS for leaf type 4
RRO list
OF (optional)
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Case 3: Adding leaves without reoptimization of existing paths
Common Header
RP with P2MP flag/R-bit set
END-POINTS for leaf type 1
RRO list
END-POINTS for leaf type 4
RRO list
OF (optional)
Case 4: Pruning leaves with full reoptimization of existing paths
Common Header
RP with P2MP flag/R-bit set
END-POINTS for leaf type 2
RRO list
END-POINTS for leaf type 3
RRO list
OF (optional)
Case 5: Pruning leaves with partial reoptimization of existing paths
Common Header
RP with P2MP flag/R-bit set
END-POINTS for leaf type 2
RRO list
END-POINTS for leaf type 3
RRO list
END-POINTS for leaf type 4
RRO list
OF (optional)
Case 6: Pruning leaves without reoptimization of existing paths
Common Header
RP with P2MP flag/R-bit set
END-POINTS for leaf type 2
RRO list
END-POINTS for leaf type 4
RRO list
OF (optional)
Zhao, et al. Standards Track PAGE 20
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Case 7: Adding and pruning leaves with full reoptimization of
existing paths
Common Header
RP with P2MP flag/R-bit set
END-POINTS for leaf type 1
END-POINTS for leaf type 2
RRO list
END-POINTS for leaf type 3
RRO list
OF (optional)
Case 8: Adding and pruning leaves with partial reoptimization of
existing paths
Common Header
RP with P2MP flag/R-bit set
END-POINTS for leaf type 1
END-POINTS for leaf type 2
RRO list
END-POINTS for leaf type 3
RRO list
END-POINTS for leaf type 4
RRO list
OF (optional)
Case 9: Adding and pruning leaves without reoptimization of existing
paths
Common Header
RP with P2MP flag/R-bit set
END-POINTS for leaf type 1
END-POINTS for leaf type 2
RRO list
END-POINTS for leaf type 4
RRO list
OF (optional)
Zhao, et al. Standards Track PAGE 21
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3.11. Discovering Branch Nodes
Before computing the P2MP path, a PCE may need to be provided means
to know which nodes in the network are capable of acting as branch
LSRs. A PCE can discover such capabilities by using the mechanisms
defined in [RFC 5073].
3.11.1. Branch Node Object
The PCC can specify a list of nodes that can be used as branch nodes
or a list of nodes that cannot be used as branch nodes by using the
Branch Node Capability (BNC) object. The BNC object has the same
format as the Include Route Object (IRO) as defined in [RFC 5440],
except that it only supports IPv4 and IPv6 prefix sub-objects. Two
Object-Type parameters are also defined:
o Branch node list: List of nodes that can be used as branch nodes.
o Non-branch node list: List of nodes that cannot be used as branch
nodes.
The object can only be carried in a PCReq message. A path
computation request may carry at most one Branch Node object.
The Object-Class and Object-Type values have been allocated by IANA.
The IANA assignments are documented in Section 6.5 ("PCEP Objects").
3.12. Synchronization of P2MP TE Path Computation Requests
There are cases when multiple P2MP LSPs' computations need to be
synchronized. For example, one P2MP LSP is the designated backup of
another P2MP LSP. In this case, path diversity for these dependent
LSPs may need to be considered during the path computation.
The synchronization can be done by using the existing SVEC
functionality as defined in [RFC 5440].
Zhao, et al. Standards Track PAGE 22
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An example of synchronizing two P2MP LSPs, each having two leaves for
Path Computation Request messages, is illustrated below:
Common Header
SVEC for sync of LSP1 and LSP2
OF (optional)
RP for LSP1
END-POINTS1 for LSP1
RRO1 list
RP for LSP2
END-POINTS2 for LSP2
RRO2 list
Figure 7: PCReq Message Example for Synchronization
This specification also defines two flags for the SVEC Object Flag
Field for P2MP path-dependent computation requests. The first flag
allows the PCC to request that the PCE should compute a secondary
P2MP path tree with partial path diversity for specific leaves or a
specific S2L sub-path to the primary P2MP path tree. The second flag
allows the PCC to request that partial paths should be
link direction diverse.
The following flags are added to the SVEC object body in this
document:
o P (Partial Path Diverse bit - 1 bit):
When set, this would indicate a request for path diversity for a
specific leaf, a set of leaves, or all leaves.
o D (Link Direction Diverse bit - 1 bit):
When set, this would indicate a request that a partial path or
paths should be link direction diverse.
The IANA assignments are referenced in Section 6.8 of this document.
3.13. Request and Response Fragmentation
The total PCEP message length, including the common header, is
16 bytes. In certain scenarios, the P2MP computation request may not
fit into a single request or response message. For example, if a
tree has many hundreds or thousands of leaves, then the request or
response may need to be fragmented into multiple messages.
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The F-bit is outlined in Section 3.3.1 ("The Extension of the RP
Object") of this document. The F-bit is used in the RP object to
signal that the initial request or response was too large to fit into
a single message and will be fragmented into multiple messages. In
order to identify the single request or response, each message will
use the same request ID.
3.13.1. Request Fragmentation Procedure
If the initial request is too large to fit into a single request
message, the PCC will split the request over multiple messages. Each
message sent to the PCE, except the last one, will have the F-bit set
in the RP object to signify that the request has been fragmented into
multiple messages. In order to identify that a series of request
messages represents a single request, each message will use the same
request ID.
The assumption is that request messages are reliably delivered and in
sequence, since PCEP relies on TCP.
3.13.2. Response Fragmentation Procedure
Once the PCE computes a path based on the initial request, a response
is sent back to the PCC. If the response is too large to fit into a
single response message, the PCE will split the response over
multiple messages. Each message sent by the PCE, except the last
one, will have the F-bit set in the RP object to signify that the
response has been fragmented into multiple messages. In order to
identify that a series of response messages represents a single
response, each message will use the same response ID.
Again, the assumption is that response messages are reliably
delivered and in sequence, since PCEP relies on TCP.
3.13.3. Fragmentation Example
The following example illustrates the PCC sending a request message
with Req-ID1 to the PCE, in order to add one leaf to an existing tree
with 1200 leaves. The assumption used for this example is that one
request message can hold up to 800 leaves. In this scenario, the
original single message needs to be fragmented and sent using two
smaller messages, which have Req-ID1 specified in the RP object, and
with the F-bit set on the first message and the F-bit cleared on the
second message.
Zhao, et al. Standards Track PAGE 24
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Common Header
RP1 with Req-ID1 and P2MP=1 and F-bit=1
OF (optional)
END-POINTS1 for P2MP
RRO1 list
Common Header
RP2 with Req-ID1 and P2MP=1 and F-bit=0
OF (optional)
END-POINTS1 for P2MP
RRO1 list
Figure 8: PCReq Message Fragmentation Example
To handle a scenario where the last fragmented message piece is lost,
the receiver side of the fragmented message may start a timer once it
receives the first piece of the fragmented message. If the timer
expires and it still has not received the last piece of the
fragmented message, it should send an error message to the sender to
signal that it has received an incomplete message. The relevant
error message is documented in Section 3.15 ("P2MP PCEP-ERROR Objects
and Types").
3.14. UNREACH-DESTINATION Object
The PCE path computation request may fail because all or a subset of
the destinations are unreachable.
In such a case, the UNREACH-DESTINATION object allows the PCE to
optionally specify the list of unreachable destinations.
This object can be present in PCRep messages. There can be up to one
such object per RP.
Zhao, et al. Standards Track PAGE 25
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The following UNREACH-DESTINATION objects (for IPv4 and IPv6) are
defined:
UNREACH-DESTINATION Object-Class is 28.
UNREACH-DESTINATION Object-Type for IPv4 is 1.
UNREACH-DESTINATION Object-Type for IPv6 is 2.
The format of the UNREACH-DESTINATION object body for IPv4
(Object-Type=1) is as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination IPv4 address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ... ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination IPv4 address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9: UNREACH-DESTINATION Object Body for IPv4
The format of the UNREACH-DESTINATION object body for IPv6
(Object-Type=2) is as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Destination IPv6 address (16 bytes) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ... ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Destination IPv6 address (16 bytes) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 10: UNREACH-DESTINATION Object Body for IPv6
Zhao, et al. Standards Track PAGE 26
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3.15. P2MP PCEP-ERROR Objects and Types
To indicate an error associated with a policy violation, the
Error-value "P2MP Path computation is not allowed" has been added to
the existing error code for Error-Type 5 ("Policy violation") as
defined in [RFC 5440] (see also Section 6.6 of this document):
Error-Type=5; Error-value=7: if a PCE receives a P2MP path
computation request that is not compliant with administrative
privileges (i.e., "The PCE policy does not support P2MP path
computation"), the PCE MUST send a PCErr message with a PCEP-ERROR
object (Error-Type=5) and an Error-value of 7. The corresponding
P2MP path computation request MUST also be cancelled.
To indicate capability errors associated with the P2MP path
computation request, Error-Type (16) and subsequent Error-values are
defined as follows for inclusion in the PCEP-ERROR object:
Error-Type=16; Error-value=1: if a PCE receives a P2MP path
computation request and the PCE is not capable of satisfying the
request due to insufficient memory, the PCE MUST send a PCErr
message with a PCEP-ERROR object (Error-Type=16) and an
Error-value of 1. The corresponding P2MP path computation request
MUST also be cancelled.
Error-Type=16; Error-value=2: if a PCE receives a P2MP path
computation request and the PCE is not capable of P2MP
computation, the PCE MUST send a PCErr message with a PCEP-ERROR
object (Error-Type=16) and an Error-value of 2. The corresponding
P2MP path computation request MUST also be cancelled.
To indicate P2MP message fragmentation errors associated with a P2MP
path computation request, Error-Type (18) and subsequent Error-values
are defined as follows for inclusion in the PCEP-ERROR object:
Error-Type=18; Error-value=1: if a PCE has not received the last
piece of the fragmented message, it should send an error message
to the sender to signal that it has received an incomplete message
(i.e., "Fragmented request failure"). The PCE MUST send a PCErr
message with a PCEP-ERROR object (Error-Type=18) and an
Error-value of 1.
Zhao, et al. Standards Track PAGE 27
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3.16. PCEP NO-PATH Indicator
To communicate the reasons for not being able to find a P2MP path
computation, the NO-PATH object can be used in the PCRep message.
One bit is defined in the NO-PATH-VECTOR TLV carried in the NO-PATH
object:
bit 24: when set, the PCE indicates that there is a reachability
problem with all or a subset of the P2MP destinations.
Optionally, the PCE can specify the destination or list of
destinations that are not reachable using the UNREACH-DESTINATION
object defined in Section 3.14.
4. Manageability Considerations
[RFC 5862] describes various manageability requirements in support of
P2MP path computation when applying PCEP. This section describes how
manageability requirements mentioned in [RFC 5862] are supported in
the context of PCEP extensions specified in this document.
Note that [RFC 5440] describes various manageability considerations
for PCEP, and most of the manageability requirements mentioned in
[RFC 5862] are already covered there.
4.1. Control of Function and Policy
In addition to PCE configuration parameters listed in [RFC 5440], the
following additional parameters might be required:
o The PCE may be configured to enable or disable P2MP path
computations.
o The PCE may be configured to enable or disable the advertisement
of its P2MP path computation capability. A PCE can advertise its
P2MP capability via the IGP discovery mechanism discussed in
Section 3.1.1 ("IGP Extensions for P2MP Capability Advertisement")
or during the Open Message Exchange discussed in Section 3.1.2
("Open Message Extension").
4.2. Information and Data Models
A number of MIB objects have been defined in [RFC 7420] for general
PCEP control and monitoring of P2P computations. [RFC 5862] specifies
that MIB objects will be required to support the control and
monitoring of the protocol extensions defined in this document. A
new document will be required to define MIB objects for PCEP control
and monitoring of P2MP computations.
Zhao, et al. Standards Track PAGE 28
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The "ietf-pcep" PCEP YANG module is specified in [PCEP-YANG]. The
P2MP capability of a PCEP entity or a configured peer can be set
using this YANG module. Also, support for P2MP path computation can
be learned using this module. The statistics are maintained in the
"ietf-pcep-stats" YANG module as specified in [PCEP-YANG]. This YANG
module will be required to be augmented to also include the
P2MP-related statistics.
4.3. Liveness Detection and Monitoring
There are no additional considerations beyond those expressed in
[RFC 5440], since [RFC 5862] does not address any additional
requirements.
4.4. Verifying Correct Operation
There are no additional requirements beyond those expressed in
[RFC 4657] for verifying the correct operation of the PCEP sessions.
It is expected that future MIB objects will facilitate verification
of correct operation and reporting of P2MP PCEP requests, responses,
and errors.
4.5. Requirements for Other Protocols and Functional Components
The method for the PCE to obtain information about a PCE capable of
P2MP path computations via OSPF and IS-IS is discussed in
Section 3.1.1 ("IGP Extensions for P2MP Capability Advertisement") of
this document.
The relevant IANA assignment is documented in Section 6.9 ("OSPF PCE
Capability Flag") of this document.
4.6. Impact on Network Operation
It is expected that the use of PCEP extensions specified in this
document will not significantly increase the level of operational
traffic. However, computing a P2MP tree may require more PCE state
compared to a P2P computation. In the event of a major network
failure and multiple recovery P2MP tree computation requests being
sent to the PCE, the load on the PCE may also be significantly
increased.
Zhao, et al. Standards Track PAGE 29
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5. Security Considerations
As described in [RFC 5862], P2MP path computation requests are more
CPU-intensive and also utilize more link bandwidth. In the event of
an unauthorized P2MP path computation request or a denial-of-service
attack, the subsequent PCEP requests and processing may be disruptive
to the network. Consequently, it is important that implementations
conform to the relevant security requirements that specifically help
to minimize or negate unauthorized P2MP path computation requests and
denial-of-service attacks. These mechanisms include the following:
o Securing the PCEP session requests and responses is RECOMMENDED
using TCP security techniques such as the TCP Authentication
Option (TCP-AO) [RFC 5925] or using Transport Layer Security (TLS)
[RFC 8253], as per the recommendations and best current practices
in [RFC 7525].
o Authenticating the PCEP requests and responses to ensure that the
message is intact and sent from an authorized node using the
TCP-AO or TLS is RECOMMENDED.
o Policy control could be provided by explicitly defining which PCCs
are allowed to send P2MP path computation requests to the PCE via
IP access lists.
PCEP operates over TCP, so it is also important to secure the PCE and
PCC against TCP denial-of-service attacks.
As stated in [RFC 6952], PCEP implementations SHOULD support the
TCP-AO [RFC 5925] and not use TCP MD5 because of TCP MD5's known
vulnerabilities and weakness.
Zhao, et al. Standards Track PAGE 30
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6. IANA Considerations
IANA maintains a registry of PCEP parameters. A number of IANA
considerations have been highlighted in previous sections of this
document. IANA made the allocations as per [RFC 6006].
6.1. PCEP TLV Type Indicators
As described in Section 3.1.2, the P2MP capability TLV allows the PCE
to advertise its P2MP path computation capability.
IANA had previously made an allocation from the "PCEP TLV Type
Indicators" subregistry, where RFC 6006 was the reference. IANA has
updated the reference as follows to point to this document.
Value Description Reference
6 P2MP capable RFC 8306
6.2. Request Parameter Bit Flags
As described in Section 3.3.1, three RP Object Flags have been
defined.
IANA had previously made allocations from the PCEP "RP Object Flag
Field" subregistry, where RFC 6006 was the reference. IANA has
updated the reference as follows to point to this document.
Bit Description Reference
18 Fragmentation (F-bit) RFC 8306
19 P2MP (N-bit) RFC 8306
20 ERO-compression (E-bit) RFC 8306
6.3. Objective Functions
As described in Section 3.6.1, this document defines two objective
functions.
IANA had previously made allocations from the PCEP "Objective
Function" subregistry, where RFC 6006 was the reference. IANA has
updated the reference as follows to point to this document.
Code Point Name Reference
7 SPT RFC 8306
8 MCT RFC 8306
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6.4. METRIC Object-Type Values
As described in Section 3.6.2, three METRIC object T fields have been
defined.
IANA had previously made allocations from the PCEP "METRIC Object
T Field" subregistry, where RFC 6006 was the reference. IANA has
updated the reference as follows to point to this document.
Value Description Reference
8 P2MP IGP metric RFC 8306
9 P2MP TE metric RFC 8306
10 P2MP hop count metric RFC 8306
6.5. PCEP Objects
As discussed in Section 3.3.2, two END-POINTS Object-Type values are
defined.
IANA had previously made the Object-Type allocations from the "PCEP
Objects" subregistry, where RFC 6006 was the reference. IANA has
updated the reference as follows to point to this document.
Object-Class Value 4
Name END-POINTS
Object-Type 3: IPv4
4: IPv6
5-15: Unassigned
Reference RFC 8306
As described in Sections 3.2, 3.11.1, and 3.14, four PCEP
Object-Class values and six PCEP Object-Type values have been
defined.
IANA had previously made allocations from the "PCEP Objects"
subregistry, where RFC 6006 was the reference. IANA has updated the
reference to point to this document.
Zhao, et al. Standards Track PAGE 32
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Also, for the following four PCEP objects, codepoint 0 for the
Object-Type field is marked "Reserved", as per Erratum ID 4956 for
RFC 5440. IANA has updated the reference to point to this document.
Object-Class Value 28
Name UNREACH-DESTINATION
Object-Type 0: Reserved
1: IPv4
2: IPv6
3-15: Unassigned
Reference RFC 8306
Object-Class Value 29
Name SERO
Object-Type 0: Reserved
1: SERO
2-15: Unassigned
Reference RFC 8306
Object-Class Value 30
Name SRRO
Object-Type 0: Reserved
1: SRRO
2-15: Unassigned
Reference RFC 8306
Object-Class Value 31
Name BNC
Object-Type 0: Reserved
1: Branch node list
2: Non-branch node list
3-15: Unassigned
Reference RFC 8306
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6.6. PCEP-ERROR Objects and Types
As described in Section 3.15, a number of PCEP-ERROR Object
Error-Types and Error-values have been defined.
IANA had previously made allocations from the PCEP "PCEP-ERROR Object
Error Types and Values" subregistry, where RFC 6006 was the
reference. IANA has updated the reference as follows to point to
this document.
Error
Type Meaning Reference
5 Policy violation
Error-value=7: RFC 8306
P2MP Path computation is not allowed
16 P2MP Capability Error
Error-value=0: Unassigned RFC 8306
Error-value=1: RFC 8306
The PCE cannot satisfy the request
due to insufficient memory
Error-value=2: RFC 8306
The PCE is not capable of P2MP computation
17 P2MP END-POINTS Error
Error-value=0: Unassigned RFC 8306
Error-value=1: RFC 8306
The PCE cannot satisfy the request
due to no END-POINTS with leaf type 2
Error-value=2: RFC 8306
The PCE cannot satisfy the request
due to no END-POINTS with leaf type 3
Error-value=3: RFC 8306
The PCE cannot satisfy the request
due to no END-POINTS with leaf type 4
Error-value=4: RFC 8306
The PCE cannot satisfy the request
due to inconsistent END-POINTS
18 P2MP Fragmentation Error
Error-value=0: Unassigned RFC 8306
Error-value=1: RFC 8306
Fragmented request failure
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6.7. PCEP NO-PATH Indicator
As discussed in Section 3.16, the NO-PATH-VECTOR TLV Flag Field has
been defined.
IANA had previously made an allocation from the PCEP "NO-PATH-VECTOR
TLV Flag Field" subregistry, where RFC 6006 was the reference. IANA
has updated the reference as follows to point to this document.
Bit Description Reference
24 P2MP Reachability Problem RFC 8306
6.8. SVEC Object Flag
As discussed in Section 3.12, two SVEC Object Flags are defined.
IANA had previously made allocations from the PCEP "SVEC Object Flag
Field" subregistry, where RFC 6006 was the reference. IANA has
updated the reference as follows to point to this document.
Bit Description Reference
19 Partial Path Diverse RFC 8306
20 Link Direction Diverse RFC 8306
6.9. OSPF PCE Capability Flag
As discussed in Section 3.1.1, the OSPF Capability Flag is defined to
indicate P2MP path computation capability.
IANA had previously made an assignment from the OSPF Parameters "Path
Computation Element (PCE) Capability Flags" registry, where RFC 6006
was the reference. IANA has updated the reference as follows to
point to this document.
Bit Description Reference
10 P2MP path computation RFC 8306
Zhao, et al. Standards Track PAGE 35
RFC 8306 Extensions to PCEP for P2MP TE LSPs November 2017
7. References
7.1. Normative References
[RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC 2119, March 1997,
<https://www.rfc-editor.org/info/RFC 2119>.
[RFC 3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, DOI 10.17487/RFC 3209, December 2001,
<https://www.rfc-editor.org/info/RFC 3209>.
[RFC 3473] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Resource ReserVation
Protocol-Traffic Engineering (RSVP-TE) Extensions",
RFC 3473, DOI 10.17487/RFC 3473, January 2003,
<https://www.rfc-editor.org/info/RFC 3473>.
[RFC 4873] Berger, L., Bryskin, I., Papadimitriou, D., and A. Farrel,
"GMPLS Segment Recovery", RFC 4873, DOI 10.17487/RFC 4873,
May 2007, <https://www.rfc-editor.org/info/RFC 4873>.
[RFC 4875] Aggarwal, R., Ed., Papadimitriou, D., Ed., and S.
Yasukawa, Ed., "Extensions to Resource Reservation
Protocol - Traffic Engineering (RSVP-TE) for
Point-to-Multipoint TE Label Switched Paths (LSPs)",
RFC 4875, DOI 10.17487/RFC 4875, May 2007,
<https://www.rfc-editor.org/info/RFC 4875>.
[RFC 5073] Vasseur, J., Ed., and J. Le Roux, Ed., "IGP Routing
Protocol Extensions for Discovery of Traffic Engineering
Node Capabilities", RFC 5073, DOI 10.17487/RFC 5073,
December 2007, <https://www.rfc-editor.org/info/RFC 5073>.
[RFC 5088] Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R.
Zhang, "OSPF Protocol Extensions for Path Computation
Element (PCE) Discovery", RFC 5088, DOI 10.17487/RFC 5088,
January 2008, <https://www.rfc-editor.org/info/RFC 5088>.
[RFC 5089] Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R.
Zhang, "IS-IS Protocol Extensions for Path Computation
Element (PCE) Discovery", RFC 5089, DOI 10.17487/RFC 5089,
January 2008, <https://www.rfc-editor.org/info/RFC 5089>.
Zhao, et al. Standards Track PAGE 36
RFC 8306 Extensions to PCEP for P2MP TE LSPs November 2017
[RFC 5440] Vasseur, JP., Ed., and JL. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol (PCEP)", RFC 5440,
DOI 10.17487/RFC 5440, March 2009,
<https://www.rfc-editor.org/info/RFC 5440>.
[RFC 5511] Farrel, A., "Routing Backus-Naur Form (RBNF): A Syntax
Used to Form Encoding Rules in Various Routing Protocol
Specifications", RFC 5511, DOI 10.17487/RFC 5511,
April 2009, <https://www.rfc-editor.org/info/RFC 5511>.
[RFC 5541] Le Roux, JL., Vasseur, JP., and Y. Lee, "Encoding of
Objective Functions in the Path Computation Element
Communication Protocol (PCEP)", RFC 5541,
DOI 10.17487/RFC 5541, June 2009,
<https://www.rfc-editor.org/info/RFC 5541>.
[RFC 7770] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and
S. Shaffer, "Extensions to OSPF for Advertising Optional
Router Capabilities", RFC 7770, DOI 10.17487/RFC 7770,
February 2016, <https://www.rfc-editor.org/info/RFC 7770>.
[RFC 8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in
RFC 2119 Key Words", BCP 14, RFC 8174,
DOI 10.17487/RFC 8174, May 2017,
<https://www.rfc-editor.org/info/RFC 8174>.
7.2. Informative References
[PCEP-YANG]
Dhody, D., Ed., Hardwick, J., Beeram, V., and J. Tantsura,
"A YANG Data Model for Path Computation Element
Communications Protocol (PCEP)", Work in Progress,
draft-ietf-pce-pcep-yang-05, July 2017.
[RFC 4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
Computation Element (PCE)-Based Architecture", RFC 4655,
DOI 10.17487/RFC 4655, August 2006,
<https://www.rfc-editor.org/info/RFC 4655>.
[RFC 4657] Ash, J., Ed., and J. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol Generic
Requirements", RFC 4657, DOI 10.17487/RFC 4657,
September 2006, <https://www.rfc-editor.org/info/RFC 4657>.
Zhao, et al. Standards Track PAGE 37
RFC 8306 Extensions to PCEP for P2MP TE LSPs November 2017
[RFC 5671] Yasukawa, S. and A. Farrel, Ed., "Applicability of the
Path Computation Element (PCE) to Point-to-Multipoint
(P2MP) MPLS and GMPLS Traffic Engineering (TE)", RFC 5671,
DOI 10.17487/RFC 5671, October 2009,
<https://www.rfc-editor.org/info/RFC 5671>.
[RFC 5862] Yasukawa, S. and A. Farrel, "Path Computation Clients
(PCC) - Path Computation Element (PCE) Requirements for
Point-to-Multipoint MPLS-TE", RFC 5862,
DOI 10.17487/RFC 5862, June 2010,
<https://www.rfc-editor.org/info/RFC 5862>.
[RFC 5925] Touch, J., Mankin, A., and R. Bonica, "The TCP
Authentication Option", RFC 5925, DOI 10.17487/RFC 5925,
June 2010, <https://www.rfc-editor.org/info/RFC 5925>.
[RFC 6006] Zhao, Q., Ed., King, D., Ed., Verhaeghe, F., Takeda, T.,
Ali, Z., and J. Meuric, "Extensions to the Path
Computation Element Communication Protocol (PCEP) for
Point-to-Multipoint Traffic Engineering Label Switched
Paths", RFC 6006, DOI 10.17487/RFC 6006, September 2010,
<https://www.rfc-editor.org/info/RFC 6006>.
[RFC 6952] Jethanandani, M., Patel, K., and L. Zheng, "Analysis of
BGP, LDP, PCEP, and MSDP Issues According to the Keying
and Authentication for Routing Protocols (KARP) Design
Guide", RFC 6952, DOI 10.17487/RFC 6952, May 2013,
<https://www.rfc-editor.org/info/RFC 6952>.
[RFC 7420] Koushik, A., Stephan, E., Zhao, Q., King, D., and J.
Hardwick, "Path Computation Element Communication Protocol
(PCEP) Management Information Base (MIB) Module",
RFC 7420, DOI 10.17487/RFC 7420, December 2014,
<https://www.rfc-editor.org/info/RFC 7420>.
[RFC 7525] Sheffer, Y., Holz, R., and P. Saint-Andre,
"Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security
(DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC 7525,
May 2015, <https://www.rfc-editor.org/info/RFC 7525>.
[RFC 8253] Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody,
"PCEPS: Usage of TLS to Provide a Secure Transport for the
Path Computation Element Communication Protocol (PCEP)",
RFC 8253, DOI 10.17487/RFC 8253, October 2017,
<https://www.rfc-editor.org/info/RFC 8253>.
Zhao, et al. Standards Track PAGE 38
RFC 8306 Extensions to PCEP for P2MP TE LSPs November 2017
Appendix A. Summary of Changes from RFC 6006
o Updated the text to use the term "PCC" instead of "user" while
describing the encoding rules in Section 3.10.
o Updated the example in Figure 7 to explicitly include the
RP object.
o Corrected the description of the F-bit in the RP object in
Section 3.13, as per Erratum ID 3836.
o Corrected the description of the fragmentation procedure for the
response in Section 3.13.2, as per Erratum ID 3819.
o Corrected the Error-Type for fragmentation in Section 3.15, as per
Erratum ID 3830.
o Updated the references for the OSPF Router Information Link State
Advertisement (LSA) [RFC 7770] and the PCEP MIB [RFC 7420].
o Added current information and references for PCEP YANG [PCEP-YANG]
and PCEPS [RFC 8253].
o Updated the Security Considerations section to include the TCP-AO
and TLS.
o Updated the IANA Considerations section (Section 6.5) to mark
codepoint 0 as "Reserved" for the Object-Type defined in this
document, as per Erratum ID 4956 for [RFC 5440]. IANA references
have also been updated to point to this document.
Appendix A.1. RBNF Changes from RFC 6006
o Updates to the RBNF for the request message format, per
Erratum ID 4867:
* Updated the request message to allow for the bundling of
multiple path computation requests within a single PCReq
message.
* Added <svec-list> in PCReq messages. This object was missed in
[RFC 6006].
* Added the BNC object in PCReq messages. This object is
required to support P2MP. The BNC object shares the same
format as the IRO, but it only supports IPv4 and IPv6 prefix
sub-objects.
Zhao, et al. Standards Track PAGE 39
RFC 8306 Extensions to PCEP for P2MP TE LSPs November 2017
* Updated the <RRO-List> format to also allow the SRRO. This
object was missed in [RFC 6006].
* Removed the BANDWIDTH object followed by the RRO from
<RRO-List>. The BANDWIDTH object was included twice in
RFC 6006 -- once as part of <end-point-path-pair-list> and also
as part of <RRO-List>. The latter has been removed, and the
RBNF is backward compatible with [RFC 5440].
* Updated the <end-point-rro-pair-list> to allow an optional
BANDWIDTH object only if <RRO-List> is included.
o Updates to the RBNF for the reply message format, per
Erratum ID 4868:
* Updated the reply message to allow for bundling of multiple
path computation replies within a single PCRep message.
* Added the UNREACH-DESTINATION object in PCRep messages. This
object was missed in [RFC 6006].
Zhao, et al. Standards Track PAGE 40
RFC 8306 Extensions to PCEP for P2MP TE LSPs November 2017
Acknowledgements
The authors would like to thank Adrian Farrel, Young Lee, Dan Tappan,
Autumn Liu, Huaimo Chen, Eiji Oki, Nic Neate, Suresh Babu K, Gaurav
Agrawal, Vishwas Manral, Dan Romascanu, Tim Polk, Stewart Bryant,
David Harrington, and Sean Turner for their valuable comments and
input on this document.
Thanks to Deborah Brungard for handling related errata for RFC 6006.
The authors would like to thank Jonathan Hardwick and Adrian Farrel
for providing review comments with suggested text for this document.
Thanks to Jonathan Hardwick for being the document shepherd and for
providing comments and guidance.
Thanks to Ben Niven-Jenkins for RTGDIR reviews.
Thanks to Roni Even for GENART reviews.
Thanks to Fred Baker for the OPSDIR review.
Thanks to Deborah Brungard for being the responsible AD and guiding
the authors.
Thanks to Mirja Kuehlewind, Alvaro Retana, Ben Campbell, Adam Roach,
Benoit Claise, Suresh Krishnan, and Eric Rescorla for their IESG
review and comments.
Zhao, et al. Standards Track PAGE 41
RFC 8306 Extensions to PCEP for P2MP TE LSPs November 2017
Contributors
Fabien Verhaeghe
Thales Communication France
160 boulevard Valmy
92700 Colombes
France
Email: fabien.verhaeghe@gmail.com
Tomonori Takeda
NTT Corporation
3-9-11, Midori-Cho
Musashino-Shi, Tokyo 180-8585
Japan
Email: tomonori.takeda@ntt.com
Zafar Ali
Cisco Systems, Inc.
2000 Innovation Drive
Kanata, Ontario K2K 3E8
Canada
Email: zali@cisco.com
Julien Meuric
Orange
2, Avenue Pierre Marzin
22307 Lannion Cedex
France
Email: julien.meuric@orange.com
Jean-Louis Le Roux
Orange
2, Avenue Pierre Marzin
22307 Lannion Cedex
France
Email: jeanlouis.leroux@orange.com
Mohamad Chaitou
France
Email: mohamad.chaitou@gmail.com
Udayasree Palle
Huawei Technologies
Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560066
India
Email: udayasreereddy@gmail.com
Zhao, et al. Standards Track PAGE 42
RFC 8306 Extensions to PCEP for P2MP TE LSPs November 2017
Authors' Addresses
Quintin Zhao
Huawei Technologies
125 Nagog Technology Park
Acton, MA 01719
United States of America
Email: quintin.zhao@huawei.com
Dhruv Dhody (editor)
Huawei Technologies
Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560066
India
Email: dhruv.ietf@gmail.com
Ramanjaneya Reddy Palleti
Huawei Technologies
Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560066
India
Email: ramanjaneya.palleti@huawei.com
Daniel King
Old Dog Consulting
United Kingdom
Email: daniel@olddog.co.uk
Zhao, et al. Standards Track PAGE 43
RFC TOTAL SIZE: 81269 bytes
PUBLICATION DATE: Friday, December 1st, 2017
LEGAL RIGHTS: The IETF Trust (see BCP 78)
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