wdiff rfc8306.original rfc8306.txt

PCE Working Group
Internet Engineering Task Force (IETF) Q. Zhao
Internet-Draft
Request for Comments: 8306 D. Dhody, Ed.
Intended status: Standards Track R. Palleti
Obsoletes: 6006 (if approved) R. Palleti
Category: Standards Track Huawei Technology
Expires: March 30, 2018 Technologies
ISSN: 2070-1721 D. King
Old Dog Consulting
September 26,
November 2017

Extensions to
the Path Computation Element Communication Protocol (PCEP)
for Point-to-Multipoint Traffic Engineering Label Switched Paths

draft-ietf-pce-rfc6006bis-04

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 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 Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents an Internet Standards Track document.

This document is a product of the Internet Engineering Task Force
(IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list It represents the consensus of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.

Internet-Drafts are draft documents valid the IETF community. It has
received public review and has been approved for a maximum publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of six months RFC 7841.

Information about the current status of this document, any errata,
and how to provide feedback on it may be updated, replaced, or obsoleted by other documents obtained at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."

This Internet-Draft will expire on March 30, 2018.
https://www.rfc-editor.org/info/rfc8306.

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 ....................................................4
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 ................................................5
1.2. Requirements Language . . . . . . . . . . . . . . . . . . 5 ......................................5
2. PCC-PCE Communication Requirements . . . . . . . . . . . . . . 5 ..............................5
3. Protocol Procedures and Extensions . . . . . . . . . . . . . . 6 ..............................6
3.1. P2MP Capability Advertisement . . . . . . . . . . . . . . 6 ..............................7
3.1.1. IGP Extensions for P2MP Computation TLV in the Existing PCE Discovery
Protocol . . . . . . . . . . . . . . . . . . . . . . . 6 Capability Advertisement ....7
3.1.2. Open Message Extension . . . . . . . . . . . . . . . . 8 ..............................7
3.2. Efficient Presentation of P2MP LSPs . . . . . . . . . . . 8 ........................8
3.3. P2MP Path Computation Request/Reply Message Extensions . . 9 .....9
3.3.1. The Extension of the RP Object . . . . . . . . . . . . 9 ......................9
3.3.2. The New P2MP END-POINTS Object . . . . . . . . . . . . 10 .........................11
3.4. Request Message Format . . . . . . . . . . . . . . . . . . 13 ....................................13
3.5. Reply Message Format . . . . . . . . . . . . . . . . . . . 14 ......................................15
3.6. P2MP Objective Functions and Metric Types . . . . . . . . 15 .................16
3.6.1. New Objective Functions . . . . . . . . . . . . . . . 15 ................................16
3.6.2. New Metric Object Types . . . . . . . . . . . . . . . 16 METRIC Object-Type Values ..........................17
3.7. Non-Support of P2MP Path Computation . . . . . . . . . . . 16 ......................17
3.8. Non-Support by Back-Level PCE Implementations . . . . . . 18 .............17
3.9. P2MP TE Path Reoptimization Request . . . . . . . . . . . 18 .......................17
3.10. Adding and Pruning Leaves to/from the P2MP Tree . . . . . 19 ..........18
3.11. Discovering Branch Nodes . . . . . . . . . . . . . . . . 22 .................................22
3.11.1. Branch Node Object . . . . . . . . . . . . . . . . . 22 ................................22
3.12. Synchronization of P2MP TE Path Computation Requests . . 22 .....22
3.13. Request and Response Fragmentation . . . . . . . . . . . 23 .......................23
3.13.1. Request Fragmentation Procedure . . . . . . . . . . . 24 ...................24
3.13.2. Response Fragmentation Procedure . . . . . . . . . . 24 ..................24
3.13.3. Fragmentation Examples . . . . . . . . . . . . . . . 24 Example .............................24
3.14. UNREACH-DESTINATION Object . . . . . . . . . . . . . . . 25 ...............................25
3.15. P2MP PCEP-ERROR Objects and Types . . . . . . . . . . . . 26 ........................27
3.16. PCEP NO-PATH Indicator . . . . . . . . . . . . . . . . . 27 ...................................28
4. Manageability Considerations . . . . . . . . . . . . . . . . . 28 ...................................28
4.1. Control of Function and Policy . . . . . . . . . . . . . . 28 ............................28
4.2. Information and Data Models . . . . . . . . . . . . . . . 28 ...............................28
4.3. Liveness Detection and Monitoring . . . . . . . . . . . . 28 .........................29
4.4. Verifying Correct Operation . . . . . . . . . . . . . . . 29 ...............................29
4.5. Requirements for Other Protocols and Functional
Components . . . . . . . . . . . . . . . . . . . . . . . . 30 ................................................29
4.6. Impact on Network Operation . . . . . . . . . . . . . . . 30 ...............................29
5. Security Considerations . . . . . . . . . . . . . . . . . . . 30 ........................................30
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 31 ............................................31
6.1. PCEP TLV Type Indicators . . . . . . . . . . . . . . . . . 31 ..................................31
6.2. Request Parameter Bit Flags . . . . . . . . . . . . . . . 31 ...............................31
6.3. Objective Functions . . . . . . . . . . . . . . . . . . . 31 .......................................31
6.4. Metric Object Types . . . . . . . . . . . . . . . . . . . 32 METRIC Object-Type Values .................................32
6.5. PCEP Objects . . . . . . . . . . . . . . . . . . . . . . . 32 ..............................................32
6.6. PCEP-ERROR Objects and Types . . . . . . . . . . . . . . . 33 ..............................34
6.7. PCEP NO-PATH Indicator . . . . . . . . . . . . . . . . . . 34 ....................................35
6.8. SVEC Object Flag . . . . . . . . . . . . . . . . . . . . . 34 ..........................................35
6.9. OSPF PCE Capability Flag . . . . . . . . . . . . . . . . . 35 ..................................35
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 35
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 37
8.1. .....................................................36
7.1. Normative References . . . . . . . . . . . . . . . . . . . 37
8.2. ......................................36
7.2. Informative References . . . . . . . . . . . . . . . . . . 38 ....................................37
Appendix A. Summary of the all Changes from RFC 6006 . . . . . . . 40 ......................39
Appendix A.1 A.1. RBNF Changes from RFC 6006 . . . . . . . . . . . . . 40 ..........................39
Acknowledgements ..................................................41
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 ......................................................42
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 43 ................................................43

1. Introduction

The Path Computation Element (PCE) as defined in [RFC4655] is an
entity that is capable of computing a network path or route based on
a network graph, graph and applying computational constraints. A Path
Computation Client (PCC) may make requests to a PCE for paths to be
computed.

[RFC4875] 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 [RFC5671].

The PCE communication Communication Protocol (PCEP) is designed as a communication
protocol between PCCs and PCEs for point-to-point (P2P) path
computations and is defined in [RFC5440]. 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 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 sub-set subset of the S2L sub-LSPs. In the
extreme case, the PCC may request the S2L sub-LSPs to be computed
individually with it being
individually; the PCC's responsibility to decide 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 Hence, the PCC may use one path
computation request Path Computation
Request message or may split the request across multiple path
computation messages.

This document obsoletes [RFC6006] and incorporates all outstanding
Errata: the following
errata:

o Erratum with IDs: IDs 3819, 3830, 3836, 4867, 4868 and 4956. 4868 for [RFC6006]

o Erratum ID 4956 for [RFC5440]

All changes from [RFC6006] are listed in Appendix A.

1.1. Terminology

Terminology used in this document:

TE LSP: Traffic Engineering Label Switched Path.

LSR: Label Switching Router.

OF: Objective Function: Function. A set of one or more optimization criteria
used for the computation of a single path (e.g., path cost
minimization),
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 [RFC4655],
[RFC4875], and [RFC5440].

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 [RFC2119] [RFC8174] 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 described in [RFC5862].
LSPs. The numbering system in the list below corresponds to the
requirement numbers (e.g., R1, R2) used in [RFC5862].

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.

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.

3.1. P2MP Capability Advertisement

3.1.1. IGP Extensions for P2MP Computation TLV in the Existing PCE Discovery Protocol Capability Advertisement

[RFC5088] defines a PCE Discovery (PCED) TLV carried in an OSPF
Router Information Link State Advertisement (LSA) as defined in
[RFC7770] to facilitate PCE discovery using OSPF. [RFC5088]
specifies that no new sub-TLVs may be added to the PCED TLV. This
document defines a new flag in the OSPF PCE Capability Flags to indicate
the capability of P2MP computation.

Similarly, [RFC5089] defines the PCED sub-TLV for use in PCE
Discovery
discovery using IS-IS. This document will use the same flag
requested 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 [RFC5088] and [RFC5089]). PCEs that do not
support P2MP will leave the bit clear (per the default behavior
defined in [RFC5088] and [RFC5089]).

PCEs that set the bit to indicate support of P2MP path computation
MUST follow the procedures in Section 3.3.2 ("The New 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
[RFC5862], 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 a new 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" sub-
registry,
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.

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, leaves or when optimizing existing P2MP TE
LSPs as specified in [RFC5862], 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 new 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 object are defined in [RFC3209] and [RFC3473].

The Secondary Explicit Route Object (SERO) is used to specify the
explicit route of a 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 [RFC3209] and [RFC3473].

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 [RFC4873].

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 [RFC4875].

A new

PCEP object class Object-Class and type are requested Object-Type values for the SERO and SRRO. SRRO have
been assigned:

Object-Class Value 29
Name SERO
Object-Type 0: Reserved
1: SERO
2-15: Unassigned
Reference [This I-D] RFC 8306

Object-Class Value 30
Name SRRO
Object-Type 0: Reserved
1: SRRO
2-15: Unassigned
Reference [This I-D] RFC 8306

The IANA assignment is 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.

This document adds the following flags to the RP Object: 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, 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 PCReq Path Computation Request
(PCReq) or PCRep 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 assignment is assignments are documented in Section 6.2 ("Request
Parameter Bit Flags") of this document.

3.3.2. The New 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 new types of END-POINTS
objects for the P2MP path:

o Old leaves whose path can be modified/reoptimized; modified/reoptimized.

o Old leaves whose path must be left unchanged.

With the new P2MP END-POINTS object, the PCE path computation request Path Computation Request
message is expanded in a way that allows a single request message to
list multiple destinations.

In total, there are now 4 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
END-POINTS object leaf type field.

Using the new 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) [RFC5511] format
in Section 3.4 ("Request Message Format").

The format of the new 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. 1: The New 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. 2: The New P2MP END-POINTS Object Body Format for IPv6
The END-POINTS object body has a variable length. These are

o multiples of 4 bytes for IPv4, and IPv4

o multiples of 16 bytes, plus 4 bytes, for IPv6. IPv6

3.4. Request Message Format

As per [RFC5440], 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 [RFC5541], 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) Vector) object and
MUST NOT be repeated for each elementary request.

The PCReq message is encoded as follows using RBNF as defined in
[RFC5511].

Below is the message format for the request message:

<PCReq Message>::= Message> ::= <Common Header>
[<svec-list>]
<request-list>

where:

<svec-list>::=<SVEC>

<svec-list> ::= <SVEC>
[<OF>]
[<metric-list>]
[<svec-list>]

<request-list>::=<request>[<request-list>]

<request>::=

<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-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>]

<RRO-List> ::= (<RRO>|<SRRO>)[<RRO-List>]
<metric-list> ::= <METRIC>[<metric-list>]

Figure 3. 3: The Message Format for the Request Message

Note that we preserve compatibility with the [RFC5440] definition of
<request>. <request>
provided in [RFC5440]. At least one instance of <endpoints> <END-POINTS> MUST be
present in this message.

We have documented the IANA assignment of additional END-POINTS
Object-Types
Object-Type values in Section 6.5 ("PCEP Objects") of this document.

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
[RFC5511].

Below is the message format for the reply message:

<PCRep Message>::= Message> ::= <Common Header>
<response-list>

where:

<response-list>::=<response>[<response-list>]

<response-list> ::= <response>[<response-list>]

<response> ::= <RP>
[<end-point-path-pair-list>]
[<NO-PATH>]
[<UNREACH-DESTINATION>]
[<attribute-list>]

<end-point-path-pair-list>::=

<end-point-path-pair-list> ::=
[<END-POINTS>]<path>
[<end-point-path-pair-list>]

<path> ::= (<ERO>|<SERO>) [<path>]

where:

<attribute-list>::=[<OF>]

<attribute-list> ::= [<OF>]
[<LSPA>]
[<BANDWIDTH>]
[<metric-list>]
[<IRO>]

Figure 4. 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.

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 [RFC5440] definition of <response>
provided in [RFC5440] and with the optional
<end-point-path-pair-list> and <path>.

3.6. P2MP Objective Functions and Metric Types

3.6.1. New Objective Functions

Six objective functions have been defined in [RFC5541] for P2P path
computation.

This document defines two additional objective functions -- namely,
SPT (Shortest Path (Shortest-Path Tree) and MCT (Minimum Cost (Minimum-Cost Tree) -- that apply to
P2MP path computation. Hence Hence, two new objective function codes have
to be defined.

The description of the two new objective functions is are
defined as follows. follows:

Objective Function Code: 7

Name: Shortest Path 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 Minimum-Cost Tree (MCT)

Description: Minimize the total cost of the tree, that is tree (i.e., the sum of
the costs of tree links, 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 new objective functions is subject to the rules
defined in [RFC5541].

3.6.2. New Metric Object Types METRIC Object-Type Values

There are three types defined for the <METRIC> METRIC object in [RFC5440] --
namely, the IGP metric, the TE metric, and the hop count metric. Hop Counts. This document
defines three additional types for the <METRIC> 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. We
propose the The
following values for these new metric types: 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. Error-value. The
request MUST then be cancelled at the PCC. New The Error-Types and Error-Values are
requested in
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 MUST would send a PCErr message with Error-value=2
(capability Error-Type=2
(Capability not supported). supported) as per [RFC5440].

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 [RFC5440] and is
similar to the reoptimization request for a P2P TE path. The only
difference is that the PCC MUST insert the list of RROs Record Route
Objects (RROs) and SRROs after each type instance of the END-POINTS object
in the PCReq message, as described in
the "Request Section 3.4 ("Request Message Format" section (Section 3.4)
Format") of this document.

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. 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-POINT 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. 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 END-POINTS
with leaf type 1.

To remove old leaves, the PCC MUST build a P2MP request using END-
POINTS
END-POINTS with leaf type 2. If no type-2 END-POINTS exist, then the
PCE MUST send an error type Error-Type 17, value=1: The Error-value 1: the PCE is not capable of
satisfying cannot satisfy
the request due to no END-POINTS with leaf type 2.

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. New
Specific PCEP-ERROR objects and types are necessary for reporting 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-POINT" END-POINTS" error will be used if a
PCC receives a request that has an inconsistent END-POINT 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 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)
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 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)
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)

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 [RFC5073].

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. object. The BNC Object object has the same
format as the Include Route Object (IRO) as defined in [RFC5440],
except that it only supports IPv4 and IPv6 prefix sub-objects. Two Object-
types
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 Request path
computation request may carry at most one Branch Node Object. object.

The Object-Class and Object-types Object-Type values have been allocated by IANA.
The IANA assignment is 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 Synchronization
VECtor (SVEC) SVEC
functionality as defined in [RFC5440].

An example of synchronizing two P2MP LSPs, each having two leaves for
Path Computation Request Messages, 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. 7: PCReq Message Example for Synchronization

This specification also defines two new flags to for the SVEC Object Flag
Field for P2MP path dependent path-dependent computation requests. The first new flag is to allow
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, would allow 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 assignment is 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 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.

The F-bit has been is outlined in "The Section 3.3.1 ("The Extension of the RP Object"
(Section 3.3.1)
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 Examples 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 the Req-ID1 specified in the RP object, and
with the F-bit set on the first message, message and the F-bit cleared on the
second message.

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. 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. When 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.

The following UNREACH-DESTINATION objects will be required: (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)
(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. 9: UNREACH-DESTINATION Object Body for IPv4

The format of the UNREACH-DESTINATION object body for IPv6 (Object-
Type=2)
(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. 10: UNREACH-DESTINATION Object Body for IPv6

3.15. P2MP PCEP-ERROR Objects and Types

To indicate an error associated with a policy violation, a new error
value the
Error-value "P2MP Path computation is not allowed" should be has been added to
the existing error code for policy violation (Error-Type=5) Error-Type 5 ("Policy violation") as
defined in
[RFC5440]: [RFC5440] (see also Section 6.6 of this document):

Error-Type=5; Error-Value=7: 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 (Error-Value=7). 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,
a new Error-Type (16) and subsequent error-values Error-values are
defined as follows for inclusion in the PCEP-ERROR object:

Error-Type=16; Error-Value=1: 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 PCEP-ERROR object (Error-Type=16) and an Error-Value (Error-Value=1).
Error-value of 1. The corresponding P2MP path computation request
MUST also be cancelled.

Error-Type=16; Error-Value=2: 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 (Error-Value=2). 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, a new Error-Type (18) and subsequent error-values Error-values
are defined as follows for inclusion in the PCEP-ERROR object:

Error-Type=18; Error-Value=1: 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
(Error-Value=1).
Error-value of 1.

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 new bit is defined in the NO-PATH-VECTOR TLV carried in the NO-PATH Object:
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 new UNREACH-DESTINATION
object defined in Section 3.14.

4. Manageability Considerations

[RFC5862] describes various manageability requirements in support of
P2MP path computation when applying PCEP. This section describes how
manageability requirements mentioned in [RFC5862] are supported in
the context of PCEP extensions specified in this document.

Note that [RFC5440] describes various manageability considerations in
for PCEP, and most of the manageability requirements mentioned in
[RFC5862] are already covered there.

4.1. Control of Function and Policy

In addition to PCE configuration parameters listed in [RFC5440], the
following additional parameters might be required:

o The ability PCE may be configured to enable or disable P2MP path computations on the
PCE.
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 ("P2MP Computation TLV in the Existing PCE Discovery
Protocol"), ("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 [RFC7420] for general
PCEP control and monitoring of P2P computations in [RFC7420]. computations. [RFC5862] 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.

The "ietf-pcep" PCEP YANG model "ietf-pcep" module is specified in [I-D.ietf-pce-pcep-
yang]. [PCEP-YANG]. The
P2MP capability of a PCEP entity or a configured peer, peer can be set
using this YANG model. Also the module. Also, support for P2MP path computation can
be learned using this model. module. The statistics are maintained in the model
"ietf-pcep-stats" YANG module as specified in [I-D.ietf-
pce-pcep-yang]. [PCEP-YANG]. This YANG model
module will be required to be augmented to also include the P2MP related
P2MP-related statistics.

4.3. Liveness Detection and Monitoring

There are no additional considerations beyond those expressed in
[RFC5440], since [RFC5862] does not address any additional
requirements.

4.4. Verifying Correct Operation

There are no additional requirements beyond those expressed in
[RFC4657] 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 ("P2MP Computation TLV in the Existing PCE Discovery
Protocol") ("IGP Extensions for P2MP Capability Advertisement") of
this document.

The subsequent relevant IANA assignments are 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.

5. Security Considerations

As described in [RFC5862], P2MP path computation requests are more
CPU-intensive and also utilize more link bandwidth. In the event of
an unauthorized P2MP path computation request, request or a denial of service 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
denial-of-service attacks. These mechanisms include: 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) [RFC5925] or using Transport Layer Security (TLS) [I-
D.ietf-pce-pceps],
[RFC8253], as per the recommendations and best current practices
in [RFC7525].

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 Providing policy Policy control could be provided by explicitly defining which PCCs, via IP
access-lists, PCCs
are allowed to send P2MP path computation requests to the PCE. 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 denial-of-service attacks.

As stated in [RFC6952], PCEP implementations SHOULD support the
TCP-AO [RFC5925] and not use TCP-MD5 TCP MD5 because of the TCP MD5's known
vulnerabilities and weakness.

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 [RFC6006].

6.1. PCEP TLV Type Indicators

As described in Section 3.1.2., 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 is requested to
update has
updated the reference as follows to point to this document.

Value Description Reference

6 P2MP capable [This I-D] RFC 8306

6.2. Request Parameter Bit Flags

As described in Section 3.3.1, three RP Object Flags have been
defined.

IANA has had previously made an allocations from the PCEP "RP Object Flag
Field"
sub-registry, subregistry, where RFC 6006 was the reference. IANA is requested to
update has
updated the reference as follows to point to this document.

Bit Description Reference

18 Fragmentation (F-bit) [This I-D] RFC 8306
19 P2MP (N-bit) [This I-D] RFC 8306
20 ERO-compression (E-bit) [This I-D] RFC 8306

6.3. Objective Functions

As described in Section 3.6.1, this document defines two Objective Functions have been
defined. objective
functions.

IANA has had previously made an allocations from the PCEP "Objective
Function" sub-
registry, subregistry, where RFC 6006 was the reference.IANA is requested to
update reference. IANA has
updated the reference as follows to point to this document.

Code Point Name Reference

7 SPT [This I-D] RFC 8306
8 MCT [This I-D] RFC 8306

6.4. Metric Object Types METRIC Object-Type Values

As described in Section 3.6.2, three metric METRIC object T fields have been
defined.

IANA has had previously made an allocations from the PCEP "METRIC Object
T Field"
sub-registry, subregistry, where RFC 6006 was the reference. IANA is requested to
update has
updated the reference as follows to point to this document.

Value Description Reference

8 P2MP IGP metric [This I-D] RFC 8306
9 P2MP TE metric [This I-D] RFC 8306
10 P2MP hop count metric [This I-D] RFC 8306

6.5. PCEP Objects

As discussed in Section 3.3.2, two END-POINTS Object-Types Object-Type values are
defined.

IANA has had previously made the Object-Type allocations from the "PCEP
Objects"
sub-registry, subregistry, where RFC 6006 was the reference. IANA is requested to
update 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 [This I-D] RFC 8306

As described in Section Sections 3.2, Section 3.11.1, and Section 3.14, four PCEP Object-Classes
Object-Class values and six PCEP Object-Types Object-Type values have been
defined.

IANA has made an had previously made allocations from the "PCEP Objects" sub-registry,
subregistry, where RFC 6006 was the reference. IANA is requested to update has updated the
reference as follows to point to this document.

Also, for the following four PCEP objects, the code-point codepoint 0 for the
Object-Type field are is marked "Reserved" with reference to Errata "Reserved", as per Erratum ID
4956. 4956 for
RFC 5440. IANA is requested to update 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 [This I-D] RFC 8306

Object-Class Value 29
Name SERO
Object-Type 0: Reserved
1: SERO
2-15: Unassigned
Reference [This I-D] RFC 8306

Object-Class Value 30
Name SRRO
Object-Type 0: Reserved
1: SRRO
2-15: Unassigned
Reference [This I-D] RFC 8306

Object-Class Value 31
Name Branch Node Capability Object BNC
Object-Type 0: Reserved
1: Branch node list
2: Non-branch node list
3-15: Unassigned
Reference [This I-D] RFC 8306

6.6. PCEP-ERROR Objects and Types

As described in Section 3.15, a number of PCEP-ERROR Object Error Types
Error-Types and Values Error-values have been defined.

IANA has had previously made an allocations from the PCEP "PCEP-ERROR Object
Error Types and Values" sub-registry, subregistry, where RFC 6006 was the
reference. IANA is requested to update has updated the reference as follows to point to
this document.

Error
Type Meaning Reference

5 Policy violation
Error-value=7: [This I-D] RFC 8306
P2MP Path computation is not allowed

16 P2MP Capability Error
Error-Value=0:
Error-value=0: Unassigned [This I-D]
Error-Value=1: [This I-D] RFC 8306
Error-value=1: RFC 8306
The PCE is not capable to cannot satisfy the request
due to insufficient memory
Error-Value=2: [This I-D]
Error-value=2: RFC 8306
The PCE is not capable of P2MP computation

17 P2MP END-POINTS Error
Error-Value=0:
Error-value=0: Unassigned [This I-D]
Error-Value=1: [This I-D] RFC 8306
Error-value=1: RFC 8306
The PCE is not capable to cannot satisfy the request
due to no END-POINTS with leaf type 2
Error-Value=2: [This I-D]
Error-value=2: RFC 8306
The PCE is not capable to cannot satisfy the request
due to no END-POINTS with leaf type 3
Error-Value=3: [This I-D]
Error-value=3: RFC 8306
The PCE is not capable to cannot satisfy the request
due to no END-POINTS with leaf type 4
Error-Value=4: [This I-D]
Error-value=4: RFC 8306
The PCE is not capable to cannot satisfy the request
due to inconsistent END-POINTS

18 P2MP Fragmentation Error
Error-Value=0:
Error-value=0: Unassigned [This I-D]
Error-Value=1: [This I-D] RFC 8306
Error-value=1: RFC 8306
Fragmented request failure

6.7. PCEP NO-PATH Indicator

As discussed in Section 3.16, the NO-PATH-VECTOR TLV Flag Field has
been defined.

IANA has had previously made an allocation from the PCEP "NO-PATH-VECTOR
TLV Flag Field" sub-registry, subregistry, where RFC 6006 was the reference. IANA is
requested to update
has updated the reference as follows to point to this document.

Bit Description Reference

24 P2MP Reachability Problem [This I-D] RFC 8306

6.8. SVEC Object Flag

As discussed in Section 3.12, two SVEC Object Flags are defined.

IANA has had previously made an allocation allocations from the PCEP "SVEC Object Flag
Field"
sub-registry, subregistry, where RFC 6006 was the reference. IANA is requested to
update has
updated the reference as follows to point to this document.

Bit Description Reference

19 Partial Path Diverse [This I-D] RFC 8306
20 Link Direction Diverse [This I-D] 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 has had previously made an assignment from the OSPF Parameters "Path
Computation Element (PCE) Capability Flags" registry, where RFC 6006
was the reference. IANA is requested to update has updated the reference as follows to
point to this document.

Bit Description Reference

10 P2MP path computation [This I-D] RFC 8306

7. Acknowledgements

The authors would like to thank Adrian Farrel, Young Lee, Dan Tappan,
Autumn Liu, Huaimo Chen, Eiji Okim, Nick Neate, Suresh Babu K, Dhruv
Dhody, Udayasree Palle, Gaurav Agrawal, Vishwas Manral, Dan
Romascanu, Tim Polk, Stewart Bryant, David Harrington, and Sean
Turner References

7.1. Normative References

[RFC2119] Bradner, S., "Key words for their valuable comments and input on the RFC 6006.

Thanks use in RFCs to Deborah Brungard for handling of related errata on the Indicate
Requirement Levels", BCP 14, RFC
6006.

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
provide comments 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.

[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and guidance.

Thanks G. Swallow, "RSVP-TE: Extensions to Ben Niven-Jenkins for RTGDIR reviews.

Thanks to Roni Even for GENART reviews.

Thanks to Fred Baker for OPSDIR review.

Thanks to Deborah Brungard for being the responsible AD and guiding
the authors.

Thanks to Mirja Kuhlewind, Alvaro Retana, Ben Campbell, Adam Roach,
Benoit Claise, Suresh Krishnan and Eric Rescorla for the IESG review
and comments.

8. References

8.1. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.

[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP RSVP for LSP
Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001. 2001,
<https://www.rfc-editor.org/info/rfc3209>.

[RFC3473] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Resource ReserVation
Protocol-Traffic Engineering (RSVP-TE) Extensions",
RFC 3473, DOI 10.17487/RFC3473, January 2003. 2003,
<https://www.rfc-editor.org/info/rfc3473>.

[RFC4873] Berger, L., Bryskin, I., Papadimitriou, D., and A. Farrel,
"GMPLS Segment Recovery", RFC 4873, DOI 10.17487/RFC4873,
May 2007. 2007, <https://www.rfc-editor.org/info/rfc4873>.

[RFC4875] Aggarwal, R., Ed., Papadimitriou, D., Ed., and S.
Yasukawa, Ed., "Extensions to Resource Reservation
Protocol - Traffic Engineering (RSVP-TE) for Point-to-
Multipoint
Point-to-Multipoint TE Label Switched Paths (LSPs)",
RFC 4875, DOI 10.17487/RFC4875, May
2007. 2007,
<https://www.rfc-editor.org/info/rfc4875>.

[RFC5073] Vasseur, J., Ed., and J. Le Roux, Ed., "IGP Routing
Protocol Extensions for Discovery of Traffic Engineering
Node Capabilities", RFC 5073, DOI 10.17487/RFC5073,
December 2007. 2007, <https://www.rfc-editor.org/info/rfc5073>.

[RFC5088] 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/RFC5088,
January 2008. 2008, <https://www.rfc-editor.org/info/rfc5088>.

[RFC5089] 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/RFC5089,
January 2008. 2008, <https://www.rfc-editor.org/info/rfc5089>.

[RFC5440] Vasseur, JP., Ed., and JL. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol (PCEP)", RFC 5440,
DOI 10.17487/RFC5440, March 2009,
<https://www.rfc-editor.org/info/rfc5440>.

[RFC5511] Farrel, A., "Routing Backus-Naur Form (RBNF): A Syntax
Used to Form Encoding Rules in Various Routing Protocol
Specifications", RFC 5511, DOI 10.17487/RFC5511,
April 2009.

[RFC5440] Vasseur, JP., Ed., and JL. Le Roux, Ed., "Path
Computation Element (PCE) Communication Protocol (PCEP)",
RFC 5440, March 2009. 2009, <https://www.rfc-editor.org/info/rfc5511>.

[RFC5541] 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/RFC5541, June 2009. 2009,
<https://www.rfc-editor.org/info/rfc5541>.

[RFC7770] 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/RFC7770,
February 2016.

8.2. 2016, <https://www.rfc-editor.org/info/rfc7770>.

[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in
RFC 2119 Key Words", BCP 14, RFC 8174,
DOI 10.17487/RFC8174, May 2017,
<https://www.rfc-editor.org/info/rfc8174>.

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.

[RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
Computation Element (PCE)-Based Architecture", RFC 4655,
DOI 10.17487/RFC4655, August 2006. 2006,
<https://www.rfc-editor.org/info/rfc4655>.

[RFC4657] Ash, J., Ed., and J. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol Generic
Requirements", RFC 4657, DOI 10.17487/RFC4657,
September 2006. 2006, <https://www.rfc-editor.org/info/rfc4657>.

[RFC5671] 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/RFC5671, October 2009. 2009,
<https://www.rfc-editor.org/info/rfc5671>.

[RFC5862] 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/RFC5862, June 2010. 2010,
<https://www.rfc-editor.org/info/rfc5862>.

[RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP
Authentication Option", RFC 5925, DOI 10.17487/RFC5925,
June 2010. 2010, <https://www.rfc-editor.org/info/rfc5925>.

[RFC6006] 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/RFC6006, September 2010. 2010,
<https://www.rfc-editor.org/info/rfc6006>.

[RFC6952] 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/RFC6952, May 2013. 2013,
<https://www.rfc-editor.org/info/rfc6952>.

[RFC7420] Koushik, K., A., Stephan, E., Zhao, Q., King King, D., and J.
Hardwick "PCE communication protocol
Hardwick, "Path Computation Element Communication Protocol
(PCEP) Management Information Base (MIB) Module",
RFC 7420, DOI 10.17487/RFC7420, December 2014. 2014,
<https://www.rfc-editor.org/info/rfc7420>.

[RFC7525] 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 May 2015.

[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, 7525, DOI 10.17487/RFC7525,
May 2017.

[I-D.ietf-pce-pcep-yang]
Dhody, D., Hardwick, J., Beeram, V., and J. Tantsura, "A
YANG Data Model for Path Computation Element
Communications Protocol (PCEP)", draft-ietf-pce-pcep-yang
(work in progress), June 2017.

[I-D.ietf-pce-pceps] 2015, <https://www.rfc-editor.org/info/rfc7525>.

[RFC8253] Lopez, D., Gonzalez de Dios, O., Wu, W., Q., and D. Dhody, "Secure
"PCEPS: Usage of TLS to Provide a Secure Transport for PCEP", draft-ietf-pce-pceps (work in
progress), August 2017. the
Path Computation Element Communication Protocol (PCEP)",
RFC 8253, DOI 10.17487/RFC8253, October 2017,
<https://www.rfc-editor.org/info/rfc8253>.

Appendix A. Summary of the all Changes from RFC 6006

o Updated the text to use the term "PCC" instead of "user" while
describing the encoding rules in section Section 3.10.

o Updated the example in figure Figure 7 to explicitly include the
RP object.

o Corrected the description of the F-bit in the RP object in section
Section 3.13, as per the errata Erratum ID 3836.

o Corrected the description of the fragmentation procedure for the
response in section Section 3.13.2, as per the errata Erratum ID 3819.

o Corrected the Error-Type in section 3.15 for fragmentation, fragmentation in Section 3.15, as per
the errata
Erratum ID 3830.

o Updated the references for the OSPF Router Information Link State
Advertisement (LSA) [RFC7770] and PCEP-MIB the PCEP MIB [RFC7420].

o Add updated Added current information and references for PCEP YANG [I-D.ietf-pce-
pcep-yang] [PCEP-YANG]
and PCEPS [I-D.ietf-pce-pceps]. [RFC8253].

o Updated security considerations the Security Considerations section to include the TCP-AO
and TLS.

o Updated the IANA considerations Considerations section (Section 6.5) to mark code-point
codepoint 0 as reserved "Reserved" for the object type Object-Type defined in this
document, as per the errata Erratum ID 4956. 4956 for [RFC5440]. IANA references are
have also been updated to point to this document.

Appendix A.1 A.1. RBNF Changes from RFC 6006

o Update Updates to the RBNF for Request the request message format: format, per
Erratum ID 4867:

* Update to Updated the request message to allow for the bundling of
multiple path computation requests within a single Path
Computation Request (PCReq) PCReq
message.

* Addition of Added <svec-list> in PCReq message. messages. This object was missed in
[RFC6006].

* Addition of Added the BNC object in PCReq message. messages. This object is
required to support P2MP. It The BNC object shares the same
format as Include Route Object
(IRO) the IRO, but it is a different object. only supports IPv4 and IPv6 prefix
sub-objects.

* Update to Updated the <RRO-List> format, format to also allow Secondary Record
Route object (SRRO). the SRRO. This
object was missed in [RFC6006].

* Removed the BANDWIDTH Object object followed by Record Route Object
(RRO) the RRO from
<RRO-List>. As The BANDWIDTH object doesn't need to follow
for each RRO was included twice in the <RRO-List>, there already exist BANDWIDTH
object follow <RRO-List>
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 [RFC5440].

* Update to Updated the <end-point-rro-pair-list>, <end-point-rro-pair-list> to allow an optional
BANDWIDTH object only if <RRO-List> is included.

* Errata ID: 4867

o Update Updates to the RBNF for Reply the reply message format: format, per
Erratum ID 4868:

* Update to Updated the reply message to allow for bundling of multiple
path computation replies within a single Path Computation Reply
(PCRep) PCRep message.

* Addition of Added the UNREACH-DESTINATION object in PCRep message. messages. This
object was missed in [RFC6006].

* Errata ID: 4868

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 Kuhlewind, Alvaro Retana, Ben Campbell, Adam Roach,
Benoit Claise, Suresh Krishnan, and Eric Rescorla for their IESG
review and comments.

Contributors

Fabien Verhaeghe
Thales Communication France
160 Bd boulevard Valmy
92700 Colombes
France
EMail:
Email: fabien.verhaeghe@gmail.com

Tomonori Takeda
NTT Corporation
3-9-11, Midori-Cho
Musashino-Shi, Tokyo 180-8585
Japan
EMail:
Email: tomonori.takeda@ntt.com

Zafar Ali
Cisco Systems, Inc.
2000 Innovation Drive
Kanata, Ontario K2K 3E8
Canada
EMail:
Email: zali@cisco.com

Julien Meuric
Orange
2, Avenue Pierre-Marzin Pierre Marzin
22307 Lannion Cedex
France
EMail:
Email: julien.meuric@orange.com

Jean-Louis Le Roux
Orange
2, Avenue Pierre-Marzin Pierre Marzin
22307 Lannion Cedex
France
EMail:
Email: jeanlouis.leroux@orange.com

Mohamad Chaitou
France
EMail:
Email: mohamad.chaitou@gmail.com

Udayasree Palle
Huawei Technologies
Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560066
India
EMail:
Email: udayasreereddy@gmail.com

Authors' Addresses

Quintin Zhao
Huawei Technology Technologies
125 Nagog Technology Park
Acton, MA 01719
US
EMail:
United States of America

Email: quintin.zhao@huawei.com

Dhruv Dhody (editor)
Huawei Technology Technologies
Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560066
India
EMail:

Email: dhruv.ietf@gmail.com

Ramanjaneya Reddy Palleti
Huawei Technology Technologies
Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560066
India
EMail:

Email: ramanjaneya.palleti@huawei.com

Daniel King
Old Dog Consulting
UK
EMail:
United Kingdom

Email: daniel@olddog.co.uk