Internet DRAFT - draft-chen-pce-pcep-extension-pce-controller-bier
draft-chen-pce-pcep-extension-pce-controller-bier
PCE R. Chen
Internet-Draft ch. Zhu
Intended status: Standards Track B. Xu
Expires: 22 April 2024 ZTE Corporation
H. Chen
Futurewei
A. Wang
China Telecom
20 October 2023
PCEP Procedures and Protocol Extensions for Using PCE as a Central
Controller (PCECC) of BIER
draft-chen-pce-pcep-extension-pce-controller-bier-05
Abstract
This draft specify a new mechanism where PCE allocates the BIER
information centrally and uses PCEP to distribute them to all nodes,
then PCC generate a "Bit Index Forwarding Table"(BIFT).
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. PCECC BIER Requirements . . . . . . . . . . . . . . . . . . . 3
3. Procedures for Using the PCE as the Central Controller (PCECC)
in BIER . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. PCECC Capability Advertisement . . . . . . . . . . . . . 4
3.2. New BIER Path Setup . . . . . . . . . . . . . . . . . . . 4
3.3. PCECC BIER information allocation and Generation of
BFIT . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.4. Redundant PCEs . . . . . . . . . . . . . . . . . . . . . 5
3.5. Re Delegation and Cleanup . . . . . . . . . . . . . . . . 5
3.6. Synchronization of BIER information Allocations . . . . . 5
4. PCEP extension . . . . . . . . . . . . . . . . . . . . . . . 5
4.1. The OPEN Object . . . . . . . . . . . . . . . . . . . . . 5
4.1.1. PCECC Capability sub-TLV . . . . . . . . . . . . . . 5
4.2. PATH-SETUP-TYPE TLV . . . . . . . . . . . . . . . . . . . 6
4.3. CCI object . . . . . . . . . . . . . . . . . . . . . . . 6
4.3.1. BIER Encapsulation Sub TLV . . . . . . . . . . . . . 7
4.3.2. Address TLVs . . . . . . . . . . . . . . . . . . . . 8
4.4. FEC Object . . . . . . . . . . . . . . . . . . . . . . . 8
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
7. Security Considerations . . . . . . . . . . . . . . . . . . . 8
8. Normative References . . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
[RFC8283]introduces the architecture for PCE as a central controller
as an extension of the architecture described in [RFC4655] and
assumes the continued use of PCEP as the protocol used between PCE
and PCC. [RFC8283]further examines the motivations and applicability
for PCEP as a Southbound Interface (SBI), and introduces the
implications for the protocol.
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[RFC9050] specify the procedures and PCEP protocol extensions for
using the PCE as the central controller for static LSPs, where LSPs
can be provisioned as explicit label instructions at each hop on the
end-to-end path. Each router along the path must be told what label-
forwarding instructions to program and what resources to reserve.
The PCE-based controller keeps a view of the network and determines
the paths of the end-to-end LSPs, and the controller uses PCEP to
communicate with each router along the path of the end-to-end LSP.
[RFC8279] defines a Bit Index Explicit Replication (BIER)
architecture where all intended multicast receivers are encoded as a
bitmask in the multicast packet header within different
encapsulations such as described in [RFC8296]. A router that
receives such a packet will forward the packet based on the bit
position in the packet header towards the receiver(s) following a
precomputed tree for each of the bits in the packet. Each receiver
is represented by a unique bit in the bitmask.
In order to reduce the transmission of redundant information, the
PCE-based controllers do not allocate the BFIT directly. Instead,
the PCC generates the BFIT based on the received bier informations or
the node calculates the nexthop by itself. This document specifies
the procedures and PCEP protocol extensions when a PCE-based
controller is responsible for configuring the BIER informations.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
2. PCECC BIER Requirements
Following key requirements for PCECC-BIER should be considered
when`designing the PCECC based solution:
* PCEP speaker supporting this draft needs to have the capability to
advertise its PCECC-BIER capability to its peers.
* PCEP speaker not supporting this draft needs to be able to reject
PCECC-BIER related message with a reason code that indicates no
support for PCECC.
* PCEP procedures needs to provide a means to update (or cleanup)
the BIER related informations (BIER subdomain-id, BFR-id and BSL
etc) to the PCC.
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* PCEP procedures needs to provide a means to update (or cleanup)
the "Bit Index Forwarding Table"(BIFT) to the PCC.
* PCEP procedures needs to provide a means to synchronize the BIER
related informations (BIER subdomain-id, BFR-id and BSL etc)
between PCE to PCC in the PCEP messages.
3. Procedures for Using the PCE as the Central Controller (PCECC) in
BIER
Active stateful PCE is described in [RFC8231]. PCE as a central
controller (PCECC) reuses existing Active stateful PCE mechanism as
much as possible to control the LSP.
This document uses the same PCEP messages and its extensions which
are described in [RFC9050] for PCECC-BIER as well.
PCEP messages PCRpt, PCInitiate, PCUpd are also used to send LSP
Reports, LSP setup and LSP update respectively. The extended
PCInitiate message described in [RFC9050] is used to download or
cleanup central controller's instructions (CCIs) (BIER related
informations and "Bit Index Forwarding Table"(BIFT) in scope of this
document). The extended PCRpt message described in [RFC9050] is also
used to report the CCIs (BIER related informations) from PCC to PCE.
[RFC9050] specify an object called CCI for the encoding of central
controller's instructions. This document extends the CCI by defining
another object-type for BIER.
3.1. PCECC Capability Advertisement
During PCEP Initialization Phase, PCEP Speakers (PCE or PCC)
advertise their support of PCECC extensions. A PCEP Speaker includes
the "PCECC Capability" sub-TLV, described in [RFC9050].
This document adds B-bit in PCECC-CAPABILITY sub-TLV for BIER.
3.2. New BIER Path Setup
The PCEP messages pertaining to PCECC-BIER MUST include PATH-SETUP-
TYPE TLV [RFC8408] with PST=TBD in the SRP object to clearly identify
the PCECC-BIER is intended.
3.3. PCECC BIER information allocation and Generation of BFIT
There are two ways to generate a "Bit Index Forwarding Table"(BIFT):
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* The PCECC allocate parameters(BIER subdomain-id, BFR-id, BAR and
IPA) carried by CCI object, parameters(BFR prefix, BSL,
Encapsulation Type, BIFT ID, and Max SI) carried by BIER
Encapsulation TLV and parameters (BFR prefix)carried by OFEC
Object to the PCC. On receiving the BIER informations allocation,
each node (PCC) uses IGP protocol to distribute BIER related
information to other nodes. The node calculate the nexthop. In
this case, Each node (PCC) only needs to be allocated its own BIER
informations by the PCECC.
* In scenarios where the IGP protocol is not used/available,Each
node (PCC) is allocated its own and neighbor BIER informations by
the PCECC, then PCC generates a BIFT based on the informations it
receives. The BIER informations include BIER subdomain-id and
BFR-id carried by CCI object, BFR prefix, BSL, Encapsulation Type,
BIFT ID, and Max SI carried by BIER Encapsulation TLV , BFR-NBR
carried by Address TLV and BFR prefix carried by OFEC Object. The
BIFT mainly includes BFR ID, F-BM and BFR nexthop.
3.4. Redundant PCEs
[I-D.ietf-pce-state-sync] describes synchronization mechanism between
the stateful PCEs. The BIER informations allocated by a PCE MUST
also be synchronized among PCEs for PCECC BIER state synchronization.
3.5. Re Delegation and Cleanup
[RFC9050] describes the action needed for CCIs for the Basic PCECC
LSP on this terminated session. Similarly actions should be applied
for the BIER information as well.
3.6. Synchronization of BIER information Allocations
[RFC9050] describes the synchronization of Central Controller's
Instructions (CCI) via LSP state synchronization as described in
[RFC8231] and [RFC8232].Same procedures should be applied for BIER
informations as well.
4. PCEP extension
4.1. The OPEN Object
4.1.1. PCECC Capability sub-TLV
[RFC9050] defined the PCECC-CAPABILITY TLV. A new B-bit is defined
in PCECC-CAPABILITY sub-TLV for PCECC-BIER:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=TBD | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags |B|I|S|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1
where:
B (PCECC-BIER-CAPABILITY - 1 bit): If set to 1 by a PCEP speaker, it
indicates that the PCEP speaker is capable for PCECC-BIER capability
and PCE would allocate BIER information on this session.
4.2. PATH-SETUP-TYPE TLV
The PATH-SETUP-TYPE TLV is defined in [RFC8408]. PST = TBD is used
when Path is setup via PCECC BIER mode.On a PCRpt/PCUpd/PCInitiate
message, the PST=TBD indicates that this path was setup via a PCECC-
BIER based mechanism where either the BIER informations and BIER
forwarding entries were allocated/instructed by PCE via PCECC
mechanism.
4.3. CCI object
The Central Control Instructions (CCI) Object is used by the PCE to
specify the forwarding instructions is defined in [RFC9050]. This
document defines another object-type for BIER purpose.
CCI Object-Type is TBD for BIER as below
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CC-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| subdomain-ID | BAR | IPA | Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BFR-ID | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// Optional TLV //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Figure 2
where:
The field CC-ID is as described in [RFC9050].
BIER subdomain-ID: Unique value identifying the BIER subdomain. (as
defined in [RFC8401].
BAR:BIER Algorithm, as documented in [RFC8401]. Specifies a BIER-
specific algorithm used to calculate underlay paths to reach BFERs.
Values are allocated from the "BIER Algorithms" registry.
IPA:IGP Algorithm, as documented in [RFC8401]. Specifies an IGP
Algorithm to either modify, enhance, or replace the calculation of
underlay paths to reach BFERs as defined by the BAR value. Values
are from the IGP Algorithm registry. 1 octet.
Flags (16 bit): A field used to carry any additional information
pertaining to the CCI.
BFR-ID: A 2-octet field encoding the BFR-id, as documented in
[RFC8279].
Optional TLV: There are two optional TLV are defined/reused in this
draft.
4.3.1. BIER Encapsulation Sub TLV
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | ET| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Max SI |BS Len | BIFT-id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3
where:
The code point for the TLV type is to be defined by IANA.
Length:4
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ET-Flag:ET(Encapsulation type) Flag,There are two Encapsulation
Types:
* 0b00-MPLS encapsulation.
* 0b01-Non-MPLS encapsulation.
Max SI: A 1 octet field encoding the Maximum Set Identifier(Section 1
of [RFC8279] ) used in the encapsulation for this BIER subdomain for
this BitString length.
Local BitString Length (BS Len): Encoded BitString length as per
[RFC8296].
BIFT-id: A 20 bit field encoding the first BIFT-id of the BIFT-id
range.
4.3.2. Address TLVs
Address TLVs described in [RFC9050] are used to associate the next-
hop information, so we Reuse ADDRESS TLV to carry the BFR out-
interface and nexthop informations.
4.4. FEC Object
BIER information is always associated with a host prefix, so we reuse
FEC Object 1'IPv4 Node ID' and FEC Object-Type 2 'IPv6 Node ID'
defined in [RFC8664] to carry the BFR prefix.
5. Acknowledgements
We would like to thank Dhruv Dhody for their useful comments and
suggestions.
6. IANA Considerations
TBD.
7. Security Considerations
The PCECC extension are based on the existing PCEP messages and thus
the security considerations described in
The PCECC extension are based on the existing PCEP messages and thus
the security considerations described in [RFC5440] ,[RFC8231]
,[RFC8281], and [RFC9050] apply to this draft.
8. Normative References
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[I-D.ietf-pce-state-sync]
Litkowski, S., Sivabalan, S., Li, C., and H. Zheng, "Inter
Stateful Path Computation Element (PCE) Communication
Procedures.", Work in Progress, Internet-Draft, draft-
ietf-pce-state-sync-05, 9 July 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-pce-
state-sync-05>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
Computation Element (PCE)-Based Architecture", RFC 4655,
DOI 10.17487/RFC4655, August 2006,
<https://www.rfc-editor.org/info/rfc4655>.
[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>.
[RFC8231] Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path
Computation Element Communication Protocol (PCEP)
Extensions for Stateful PCE", RFC 8231,
DOI 10.17487/RFC8231, September 2017,
<https://www.rfc-editor.org/info/rfc8231>.
[RFC8232] Crabbe, E., Minei, I., Medved, J., Varga, R., Zhang, X.,
and D. Dhody, "Optimizations of Label Switched Path State
Synchronization Procedures for a Stateful PCE", RFC 8232,
DOI 10.17487/RFC8232, September 2017,
<https://www.rfc-editor.org/info/rfc8232>.
[RFC8279] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
Przygienda, T., and S. Aldrin, "Multicast Using Bit Index
Explicit Replication (BIER)", RFC 8279,
DOI 10.17487/RFC8279, November 2017,
<https://www.rfc-editor.org/info/rfc8279>.
[RFC8281] Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path
Computation Element Communication Protocol (PCEP)
Extensions for PCE-Initiated LSP Setup in a Stateful PCE
Model", RFC 8281, DOI 10.17487/RFC8281, December 2017,
<https://www.rfc-editor.org/info/rfc8281>.
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[RFC8283] Farrel, A., Ed., Zhao, Q., Ed., Li, Z., and C. Zhou, "An
Architecture for Use of PCE and the PCE Communication
Protocol (PCEP) in a Network with Central Control",
RFC 8283, DOI 10.17487/RFC8283, December 2017,
<https://www.rfc-editor.org/info/rfc8283>.
[RFC8296] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation
for Bit Index Explicit Replication (BIER) in MPLS and Non-
MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January
2018, <https://www.rfc-editor.org/info/rfc8296>.
[RFC8401] Ginsberg, L., Ed., Przygienda, T., Aldrin, S., and Z.
Zhang, "Bit Index Explicit Replication (BIER) Support via
IS-IS", RFC 8401, DOI 10.17487/RFC8401, June 2018,
<https://www.rfc-editor.org/info/rfc8401>.
[RFC8408] Sivabalan, S., Tantsura, J., Minei, I., Varga, R., and J.
Hardwick, "Conveying Path Setup Type in PCE Communication
Protocol (PCEP) Messages", RFC 8408, DOI 10.17487/RFC8408,
July 2018, <https://www.rfc-editor.org/info/rfc8408>.
[RFC8664] Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W.,
and J. Hardwick, "Path Computation Element Communication
Protocol (PCEP) Extensions for Segment Routing", RFC 8664,
DOI 10.17487/RFC8664, December 2019,
<https://www.rfc-editor.org/info/rfc8664>.
[RFC9050] Li, Z., Peng, S., Negi, M., Zhao, Q., and C. Zhou, "Path
Computation Element Communication Protocol (PCEP)
Procedures and Extensions for Using the PCE as a Central
Controller (PCECC) of LSPs", RFC 9050,
DOI 10.17487/RFC9050, July 2021,
<https://www.rfc-editor.org/info/rfc9050>.
Authors' Addresses
Ran Chen
ZTE Corporation
Nanjing
China
Email: chen.ran@zte.com.cn
Chun Zhu
ZTE Corporation
Nanjing
China
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Email: zhu.chun@zte.com.cn
BenChong Xu
ZTE Corporation
Nanjing
China
Email: xu.benchong@zte.com.cn
Huaimo Chen
Futurewei
Nanjing,
United States of America
Email: Huaimo.chen@futurewei.com
Aijun Wang
China Telecom
Nanjing
China
Email: wangaj3@chinatelecom.cn
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