PCE WG R. Chen
Internet-Draft ch. Zhu
Intended status: Standards Track B. Xu
Expires: March 29, 2021 ZTE Corporation
September 25, 2020
PCEP Procedures and Protocol Extensions for Using PCE as a Central
Controller (PCECC) of BIER
draft-chen-pce-pcep-extension-pce-controller-bier-00
Abstract
This draft specify the procedures and PCEP protocol extensions for
using the PCE as the central controller for BIER.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 3
3. PCECC BIER Requirements . . . . . . . . . . . . . . . . . . . 3
4. Procedures for Using the PCE as the Central Controller
(PCECC) in BIER . . . . . . . . . . . . . . . . . . . . . . . 3
4.1. Stateful PCE Model . . . . . . . . . . . . . . . . . . . 3
4.2. New Functions . . . . . . . . . . . . . . . . . . . . . . 4
4.3. PCECC Capability Advertisement . . . . . . . . . . . . . 4
4.4. BIER Path Operations . . . . . . . . . . . . . . . . . . 4
4.4.1. PCECC Bit Index Explicit Replication (BIER) . . . . . 4
4.4.1.1. PCECC BIER information allocation . . . . . . . . 5
4.4.1.2. Redundant PCEs . . . . . . . . . . . . . . . . . 5
4.4.1.3. Re Delegation and Cleanup . . . . . . . . . . . . 5
4.4.1.4. Synchronization of BIER information Allocations . 5
4.5. PCEP messages . . . . . . . . . . . . . . . . . . . . . . 5
4.5.1. The OPEN Object . . . . . . . . . . . . . . . . . . . 5
4.5.1.1. PCECC Capability sub-TLV . . . . . . . . . . . . 5
4.5.2. PATH-SETUP-TYPE TLV . . . . . . . . . . . . . . . . . 6
4.5.3. CCI object . . . . . . . . . . . . . . . . . . . . . 6
4.5.3.1. BIER Encapsulation Sub TLV . . . . . . . . . . . 7
4.5.4. FEC Object . . . . . . . . . . . . . . . . . . . . . 8
5. Security Considerations . . . . . . . . . . . . . . . . . . . 8
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 8
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
9. 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.
[I-D.ietf-pce-pcep-extension-for-pce-controller]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.
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[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.
This document specifies the procedures and PCEP protocol extensions
when a PCE-based controller is also responsible for configuring the
forwarding actions on the routers (BIER information distribution in
this case).
2. Conventions used in this document
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 RFC2119.
3. PCECC BIER Requirements
Following key requirements for PCECC-BIER should be considered
when`designing the PCECC based solution:
o PCEP speaker supporting this draft needs to have the capability to
advertise its PCECC-BIER capability to its peers.
o 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.
o 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.
o 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.
4. Procedures for Using the PCE as the Central Controller (PCECC) in
BIER
4.1. Stateful PCE Model
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.
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4.2. New Functions
This document uses the same PCEP messages and its extensions which
are described in [I-D.ietf-pce-pcep-extension-for-pce-controller]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
[I-D.ietf-pce-pcep-extension-for-pce-controller] is used to download
or cleanup central controller's instructions (CCIs) (BIER related
informations in scope of this document). The extended PCRpt message
described in [I-D.ietf-pce-pcep-extension-for-pce-controller] is also
used to report the CCIs (BIER related informations) from PCC to PCE.
[I-D.ietf-pce-pcep-extension-for-pce-controller]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.
4.3. 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
[I-D.ietf-pce-pcep-extension-for-pce-controller].
This document adds B-bit in PCECC-CAPABILITY sub-TLV for BIER.
4.4. BIER Path Operations
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 LSP is intended.
4.4.1. PCECC Bit Index Explicit Replication (BIER)
BIER as described in [RFC8402] defines an architecture where all
intended multicast receivers are encoded as a bitmask in the
multicast packet header within different encapsulations such as
described in [RFC8296].
[RFC8401] defines IS-IS extensions to distribute the BIER
information(BIER subdomain-id, BFR-id and BSL etc).This document
proposes a new mechanism where PCE allocates centrally and uses PCEP
to advertise the BIER information(BIER subdomain-id, BFR-id and BSL
etc). In some deployments PCE (and PCEP) are better suited than IGP
because of centralized nature of PCE and direct TCP based PCEP
session to the node.
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4.4.1.1. PCECC BIER information allocation
Each node (PCC) is allocated BIER information by the PCECC.The BIER
information mainly includes BIER subdomain-id, BFR-id, BSL, BFR
prefix, BSL, Encapsulation Type, BIFT ID,Max SI and BFR nexthop.
The PCECC allocate the BIER subdomain-id, BFR-id , BFR prefix, BSL,
Encapsulation Type, BIFT ID, and Max SI to the PCC, On receiving the
BIER information allocation, each node (PCC) uses IGP protocol to
distribute BIER related information to other nodes. The node
calculate the nexthop.
4.4.1.2. Redundant PCEs
[I-D.litkowski-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.
4.4.1.3. Re Delegation and Cleanup
[I-D.ietf-pce-pcep-extension-for-pce-controller] 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.
4.4.1.4. Synchronization of BIER information Allocations
[I-D.ietf-pce-pcep-extension-for-pce-controller]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 information as well.
4.5. PCEP messages
4.5.1. The OPEN Object
4.5.1.1. PCECC Capability sub-TLV
[I-D.ietf-pce-pcep-extension-for-pce-controller] defined the
PCECCCAPABILITY 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
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.
4.5.2. 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 were
allocated/instructed by PCE via PCECC mechanism.
4.5.3. CCI object
The Central Control Instructions (CCI) Object is used by the PCE to
specify the forwarding instructions is defined in
[I-D.ietf-pce-pcep-extension-for-pce-controller]. 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 | Algorithm | Flags |C|O|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BFR-ID | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// Optional TLV //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2
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The field CC-ID is as described in
[I-D.ietf-pce-pcep-extension-for-pce-controller].
BIER subdomain-ID: Unique value identifying the BIER subdomain. (as
defined in [RFC8401].
The 0 and C bit was defined in
[I-D.ietf-pce-pcep-extension-for-pce-controller].
BFR-ID: A 2-octet field encoding the BFR-id, as documented in
[RFC8279].
Optional TLV: There are two optional TLV are defined in this draft.
4.5.3.1. 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flage | ET| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Max SI |BS Len | BIFT-id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3
The code point for the TLV type is to be defined by IANA.
Length:4
ET-Flag:ET(Encapsulation type) Flag,There are two Encapsulation
Types:
o 0b00-MPLS encapsulation.
o 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].
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BIFT-id: A 20 bit field encoding the first BIFT-id of the BIFT-id
range.
4.5.4. 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 [I-D.zhao-pce-pcep-extension-pce-controller-sr] to carry
the BFR prefix.
5. Security Considerations
TBD.
6. IANA Considerations
TBD.
7. Contributors
The following author contributed significantly to this document:
Dhruv Dhody
Huawei
rdhruv.ietf@gmail.com
8. Acknowledgements
TBD.
9. Normative References
[I-D.ietf-pce-pcep-extension-for-pce-controller]
Li, Z., Peng, S., Negi, M., Zhao, Q., and C. Zhou, "PCEP
Procedures and Protocol Extensions for Using PCE as a
Central Controller (PCECC) of LSPs", draft-ietf-pce-pcep-
extension-for-pce-controller-07 (work in progress),
September 2020.
[I-D.litkowski-pce-state-sync]
Litkowski, S., Sivabalan, S., Li, C., and H. Zheng, "Inter
Stateful Path Computation Element (PCE) Communication
Procedures.", draft-litkowski-pce-state-sync-08 (work in
progress), July 2020.
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[I-D.zhao-pce-pcep-extension-pce-controller-sr]
Li, Z., Peng, S., Negi, M., Zhao, Q., and C. Zhou, "PCEP
Procedures and Protocol Extensions for Using PCE as a
Central Controller (PCECC) of SR-LSPs", draft-zhao-pce-
pcep-extension-pce-controller-sr-07 (work in progress),
July 2020.
[RFC4655] Farrel, A., Vasseur, J., 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>.
[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>.
[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>.
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[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>.
Authors' Addresses
Ran Chen
ZTE Corporation
Email: chen.ran@zte.com.cn
Chun Zhu
ZTE Corporation
Email: zhu.chun@zte.com.cn
BenChong Xu
ZTE Corporation
Email: xu.benchong@zte.com.cn
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