PCE WG R. Chen
Internet-Draft B. Xu
Intended status: Standards Track ch. Zhu
Expires: March 28, 2021 ZTE Corporation
September 24, 2020
PCEP Procedures and Protocol Extensions for Using PCE as a Central
Controller (PCECC) of BIER-TE
draft-chen-pce-controller-bier-te-00
Abstract
This document specifies extensions to PCEP protocol when a PCE-based
controller is also responsible for configuring the forwarding actions
on the routers, in addition to computing the paths for packet flows
in a BIER-TE network and telling the edge routers what instructions
to attach to packets as they enter the network.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 3
3. PCECC BIER-TE Requirements . . . . . . . . . . . . . . . . . 3
4. Procedures for Using the PCE as the Central Controller
(PCECC) in BIER . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. Stateful PCE Model . . . . . . . . . . . . . . . . . . . 4
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)-TE . . . 5
4.4.1.1. PCECC BIER-TE 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 . . . . . . . . . . . . . . . . . . . 6
4.5.1.1. PCECC Capability sub-TLV . . . . . . . . . . . . 6
4.5.2. PATH-SETUP-TYPE TLV . . . . . . . . . . . . . . . . . 6
4.5.3. CCI object . . . . . . . . . . . . . . . . . . . . . 6
4.5.3.1. BIER Encapsulation Sub-TLV . . . . . . . . . . . 8
4.5.3.2. Address TLVs . . . . . . . . . . . . . . . . . . 8
4.5.3.3. ROUTE-DISTINGUISHER TLV . . . . . . . . . . . . . 9
4.5.3.4. FEC object . . . . . . . . . . . . . . . . . . . 9
5. Security Considerations . . . . . . . . . . . . . . . . . . . 9
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 9
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
9. Normative References . . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
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
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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.
Bit Index Explicit Replication (BIER)-TE shares architecture and
packet formats with BIER as described in [RFC8279]. BIER-TE forwards
and replicates packets based on a BitString in the packet header, but
every BitPosition of the BitString of a BIER-TE packet indicates one
or more adjacencies as described in [I-D.ietf-bier-te-arch].
This document extends
[I-D.ietf-pce-pcep-extension-for-pce-controller] to specify the
procedures and PCEP protocol extensions for using the PCE as the
central controller for BIER-TE.
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-TE Requirements
Following key requirements for PCECC BIER-TE 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-TE capability to its peers.
o PCEP speaker not supporting this draft needs to be able to reject
PCECC BIER-TE 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-TE related informations (BIER subdomain-id, adjacencies
BitPosition(s), and Adjacency Types etc) to the PCC.
o PCEP procedures needs to provide a means to synchronize the BIER-
TE related informations(BIER subdomain-id, adjacencies
BitPosition(s), and Adjacency Types etc) between PCE to PCC in the
PCEP messages.
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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.
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-TE 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-TE 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-TE 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-TE.
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 T-bit in PCECC-CAPABILITY sub-TLV for BIER-TE.
4.4. BIER Path Operations
The PCEP messages pertaining to PCECC BIER-TE MUST include PATH-
SETUP-TYPE TLV [RFC8408] with PST=TBD in the SRP object to clearly
identify the PCECC BIER-TE LSP is intended.
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4.4.1. PCECC Bit Index Explicit Replication (BIER)-TE
Bit Index Explicit Replication (BIER)-TE shares architecture and
packet formats with BIER as described in [RFC8279]. BIER-TE forwards
and replicates packets based on a BitString in the packet header, but
every BitPosition of the BitString of a BIER-TE packet indicates one
or more adjacencies as described in [I-D.ietf-bier-te-arch].
This document proposes a new mechanism where PCE allocates centrally
and uses PCEP to advertise the BIER-TE information(BIER subdomain-id,
adjacencies BitPosition(s), and Adjacency Types etc).
4.4.1.1. PCECC BIER-TE information allocation
Each node (PCC) is allocated a node BIER-TE information by the PCECC.
The PCECC sends PCInitiate message to update the BIFT table of each
node.The BIER-TE information mainly includes BIER subdomain-id,
adjacencies BitPosition(s), and Adjacency Types etc. On receiving
the BIER-TE information allocation, each node (PCC) download the
forwarding instructions accordingly.
4.4.1.2. Redundant PCEs
[I-D.litkowski-pce-state-sync] describes synchronization mechanism
between the stateful PCEs. The BIER-TE informations allocated by a
PCE MUST also be synchronized among PCEs for PCECC BIER-TE 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-TE
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-TE information as well.
4.5. PCEP messages
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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 T-bit is defined in PCECC-CAPABILITY sub-
TLV for PCECC BIER-TE:
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 |T|I|S|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1
T (PCECC BIER-TE CAPABILITY - 1 bit): If set to 1 by a PCEP speaker,
it indicates that the PCEP speaker is capable for PCECC BIER-TE
capability and PCE would allocate BIER-TE 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-TE mode.On a PCRpt/PCUpd/PCInitiate
message, the PST=TBD indicates that this path was setup via a PCECC
BIER-TE based mechanism where either the BIER-TE 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-TE purpose.
CCI Object-Type is TBD for BIER-TE as below
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CC-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| subdomain-ID | BSL | Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SI |adj-t| BitPosition | Reserved|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// Optional TLV //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2
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].
BSL: A 1 octet field encodes the length in bits of the BitString as
per [RFC8296], the maximum length of the BitString is 5,it indicates
the length of BitString is 1024.It is used to refer to the number of
bits in the BitString.
SI: Set Identifier (Section 1 of [RFC8279] used in the encapsulation
for this BIER subdomain for this BitString length, 1 octet.
BitPositions: BitPositions indicate adjacencies,16bit.
The "Reserved" (1 octets) fields are currently unused, and MUST be
set to zero on transmission and ignored on reception.
Adjacency Types:There are three types in this document.
o 0b000:Forward Connected
o 0b001:Forward Routed
o 0b010: Local Decap
o ECMP will discuss in next version.
Optional TLV: There are three optional TLV are defined/reused in this
draft.
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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].
BIFT-id: A 20 bit field encoding the first BIFT-id of the BIFT-id
range.
4.5.3.2. Address TLVs
When the adjacency type is 0b000:Forward Connected, the BFR address
information (BFR out-interface and nexthop informations) should be
carried in the CCI Object.
Address TLVs defined in
[I-D.ietf-pce-pcep-extension-for-pce-controller] are used to
associate the next-hop information, so we Reuse ADDRESS TLV to carry
the BFR out-interface and nexthop informations.
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4.5.3.3. ROUTE-DISTINGUISHER TLV
When the adjacency type is 0b001: Forward Routed, a VRF and the next-
hop informations should be carried in the CCI Object, so we reuse the
ROUTE-DISTINGUISHER TLV defined in [I-D.ietf-pce-pcep-flowspec] and
Address TLVs defined in
[I-D.ietf-pce-pcep-extension-for-pce-controller] to carry the next
hop is associated with a specific VPN identified by the RD.
When the adjacency type is 0b010: Local Decap, only a VRF should be
carried in the CCI Object. Reuse the ROUTE-DISTINGUISHER TLV which
is defined in [I-D.ietf-pce-pcep-flowspec] carries an RD value, used
to identify a VRF.
4.5.3.4. FEC object
BIER-TE information is always associated with adjacency, 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 clearly
identify the adjacency for which a SI: BitPosition is being
allocated.
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.
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9. Normative References
[I-D.ietf-bier-te-arch]
Eckert, T., Cauchie, G., and M. Menth, "Tree Engineering
for Bit Index Explicit Replication (BIER-TE)", draft-ietf-
bier-te-arch-08 (work in progress), July 2020.
[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.ietf-pce-pcep-flowspec]
Dhody, D., Farrel, A., and Z. Li, "PCEP Extension for Flow
Specification", draft-ietf-pce-pcep-flowspec-10 (work in
progress), August 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.
[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>.
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[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>.
[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
BenChong Xu
ZTE Corporation
Email: xu.benchong@zte.com.cn
Chun Zhu
ZTE Corporation
Email: zhu.chun@zte.com.cn
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