draft-ietf-pce-stateful-hpce-08.txt   draft-ietf-pce-stateful-hpce-09.txt 
PCE Working Group D. Dhody PCE Working Group D. Dhody
Internet-Draft Y. Lee Internet-Draft Y. Lee
Intended status: Informational Huawei Technologies Intended status: Informational Huawei Technologies
Expires: December 7, 2019 D. Ceccarelli Expires: December 12, 2019 D. Ceccarelli
Ericsson Ericsson
J. Shin J. Shin
SK Telecom SK Telecom
D. King D. King
Lancaster University Lancaster University
O. Gonzalez de Dios O. Gonzalez de Dios
Telefonica I+D Telefonica I+D
June 6, 2019 June 10, 2019
Hierarchical Stateful Path Computation Element (PCE). Hierarchical Stateful Path Computation Element (PCE).
draft-ietf-pce-stateful-hpce-08 draft-ietf-pce-stateful-hpce-09
Abstract Abstract
A Stateful Path Computation Element (PCE) maintains information on A Stateful Path Computation Element (PCE) maintains information on
the current network state, including: computed Label Switched Path the current network state, including: computed Label Switched Path
(LSPs), reserved resources within the network, and pending path (LSPs), reserved resources within the network, and pending path
computation requests. This information may then be considered when computation requests. This information may then be considered when
computing new traffic engineered LSPs, and for associated computing new traffic engineered LSPs, and for associated and
and dependent LSPs, received from Path Computation Clients (PCCs). dependent LSPs, received from Path Computation Clients (PCCs). The
Initialize the result of path computation from PCE is also helpful Path computation response from a PCE is helpful for the PCC to
for the PCC to gracefully establish the computed LSP. gracefully establish the computed LSP.
The Hierarchical Path Computation Element (H-PCE) architecture, The Hierarchical Path Computation Element (H-PCE) architecture,
provides an architecture to allow the optimum sequence of provides an architecture to allow the optimum sequence of
inter-connected domains to be selected, and network policy to be inter-connected domains to be selected, and network policy to be
applied if applicable, via the use of a hierarchical relationship applied if applicable, via the use of a hierarchical relationship
between PCEs. between PCEs.
Combining the capabilities of Stateful PCE and the Hierarchical PCE Combining the capabilities of Stateful PCE and the Hierarchical PCE
would be advantageous. This document describes general considerations would be advantageous. This document describes general considerations
and use cases for the deployment of Stateful, and not Stateless, PCEs and use cases for the deployment of Stateful, and not Stateless, PCEs
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This Internet-Draft will expire on December 7, 2019. This Internet-Draft will expire on December 12, 2019.
Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . .3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Use-cases and Applicability of Hierarchical Stateful PCE .4 1.1. Use-cases and Applicability of Hierarchical Stateful PCE . 4
1.1.1 Applicability to ACTN . . . . . . . . . . . . . . . . .5 1.1.1 Applicability to ACTN . . . . . . . . . . . . . . . . . 5
1.1.2 End-to-End Contiguous LSP . . . . . . . . . . . . . . .5 1.1.2 End-to-End Contiguous LSP . . . . . . . . . . . . . . . 5
1.1.3 Applicability of a Stateful P-PCE . . . . . . . . . . .6 1.1.3 Applicability of a Stateful P-PCE . . . . . . . . . . . 6
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . .6 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Hierarchical Stateful PCE . . . . . . . . . . . . . . . . . .7 3. Hierarchical Stateful PCE . . . . . . . . . . . . . . . . . . 7
3.1. Passive Operations . . . . . . . . . . . . . . . . . . . .9 3.1. Passive Operations . . . . . . . . . . . . . . . . . . . . 8
3.2. Active Operations . . . . . . . . . . . . . . . . . . . .10 3.2. Active Operations . . . . . . . . . . . . . . . . . . . . 10
3.3. PCE Initiation of LSPs . . . . . . . . . . . . . . . . . .11 3.3. PCE Initiation of LSPs . . . . . . . . . . . . . . . . . . 11
3.3.1. Per Domain Stitched LSP . . . . . . . . . . . . . . .12 3.3.1. Per Domain Stitched LSP . . . . . . . . . . . . . . . 12
4. Security Considerations . . . . . . . . . . . . . . . . . . .14 4. Security Considerations . . . . . . . . . . . . . . . . . . . 14
5. Manageability Considerations . . . . . . . . . . . . . . . . .15 5. Manageability Considerations . . . . . . . . . . . . . . . . . 15
5.1. Control of Function and Policy . . . . . . . . . . . . . .15 5.1. Control of Function and Policy . . . . . . . . . . . . . . 15
5.2. Information and Data Models . . . . . . . . . . . . . . .15 5.2. Information and Data Models . . . . . . . . . . . . . . . 15
5.3. Liveness Detection and Monitoring . . . . . . . . . . . .15 5.3. Liveness Detection and Monitoring . . . . . . . . . . . . 15
5.4. Verify Correct Operations . . . . . . . . . . . . . . . .15 5.4. Verify Correct Operations . . . . . . . . . . . . . . . . 15
5.5. Requirements On Other Protocols . . . . . . . . . . . . .15 5.5. Requirements On Other Protocols . . . . . . . . . . . . . 15
5.6. Impact On Network Operations . . . . . . . . . . . . . . .16 5.6. Impact On Network Operations . . . . . . . . . . . . . . . 15
6. Other Considerations . . . . . . . . . . . . . . . . . . . . .16 5.7. Error Handling between PCEs . . . . . . . . . . . . . . . 16
6.1. Applicability to Inter-Layer Traffic Engineering . . . . .16 6. Other Considerations . . . . . . . . . . . . . . . . . . . . . 16
6.2. Scalability Considerations . . . . . . . . . . . . . . . .17 6.1. Applicability to Inter-Layer Traffic Engineering . . . . . 16
6.3. Confidentiality . . . . . . . . . . . . . . . . . . . . .17 6.2. Scalability Considerations . . . . . . . . . . . . . . . . 17
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . .18 6.3. Confidentiality . . . . . . . . . . . . . . . . . . . . . 17
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .18 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
9. References . . . . . . . . . . . . . . . . . . . . . . . . .18 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 17
9.1. Normative References . . . . . . . . . . . . . . . . . . .18 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
9.2. Informative References . . . . . . . . . . . . . . . . . .19 9.1. Normative References . . . . . . . . . . . . . . . . . . . 17
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . .21 9.2. Informative References . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .21 Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21
1. Introduction 1. Introduction
The Path Computation Element communication Protocol (PCEP) [RFC5440] The Path Computation Element communication Protocol (PCEP) [RFC5440]
provides mechanisms for Path Computation Elements (PCEs) to perform provides mechanisms for Path Computation Elements (PCEs) to perform
path computations in response to Path Computation Clients' (PCCs) path computations in response to Path Computation Clients' (PCCs)
requests. requests.
A stateful PCE is capable of considering, for the purposes of A stateful PCE is capable of considering, for the purposes of path
path computation, not only the network state in terms of links and computation, not only the network state in terms of links and nodes
nodes (referred to as the Traffic Engineering Database or TED) but (referred to as the Traffic Engineering Database or TED) but also the
also the status of active services (previously computed paths, status of active services (previously computed paths, and currently
and currently reserved resources, stored in the Label Switched reserved resources, stored in the Label Switched Paths Database
Paths Database (LSP-DB). (LSP-DB).
[RFC8051] describes general considerations for a stateful PCE [RFC8051] describes general considerations for a stateful PCE
deployment and examines its applicability and benefits, as well as deployment and examines its applicability and benefits, as well as
its challenges and limitations through a number of use cases. its challenges and limitations through a number of use cases.
[RFC8231] describes a set of extensions to PCEP to provide stateful [RFC8231] describes a set of extensions to PCEP to provide stateful
control. A stateful PCE has access to not only the information control. A stateful PCE has access to not only the information
carried by the network's Interior Gateway Protocol (IGP), but also carried by the network's Interior Gateway Protocol (IGP), but also
the set of active paths and their reserved resources for its the set of active paths and their reserved resources for its
computations. The additional state allows the PCE to compute computations. The additional state allows the PCE to compute
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architecture which can be used for computing end-to-end paths for architecture which can be used for computing end-to-end paths for
inter-domain MPLS Traffic Engineering (TE) and GMPLS Label Switched inter-domain MPLS Traffic Engineering (TE) and GMPLS Label Switched
Paths (LSPs). Within the Hierarchical PCE (H-PCE) architecture Paths (LSPs). Within the Hierarchical PCE (H-PCE) architecture
[RFC6805], the Parent PCE (P-PCE) is used to compute a multi-domain [RFC6805], the Parent PCE (P-PCE) is used to compute a multi-domain
path based on the domain connectivity information. A Child PCE path based on the domain connectivity information. A Child PCE
(C-PCE) may be responsible for a single domain or multiple domains, (C-PCE) may be responsible for a single domain or multiple domains,
it is used to compute the intra-domain path based on its domain it is used to compute the intra-domain path based on its domain
topology information. topology information.
This document presents general considerations for stateful PCEs, and This document presents general considerations for stateful PCEs, and
not Stateless, in the hierarchical PCE architecture. In particular, not Stateless PCEs, in the hierarchical PCE architecture. In
the behavior changes and additions to the existing stateful PCE particular, the behavior changes and additions to the existing
mechanisms (including PCE-initiated LSP setup and active PCE usage) stateful PCE mechanisms (including PCE-initiated LSP setup and active
in the context of networks using the H-PCE architecture. PCE usage) in the context of networks using the H-PCE architecture.
In this document, Sections 3.1 and 3.2 focus on end to end (E2E) In this document, Sections 3.1 and 3.2 focus on end to end (E2E)
inter-domain TE LSP. Section 3.3.1 describes the operations for inter-domain TE LSP. Section 3.3.1 describes the operations for
stitching Per Domain LSPs. stitching Per Domain LSPs.
Deployment of stateless H-PCE Architecture
1.1. Use-cases and Applicability of Hierarchical Stateful PCE 1.1. Use-cases and Applicability of Hierarchical Stateful PCE
As per [RFC6805], in the hierarchical PCE architecture, a P-PCE As per [RFC6805], in the hierarchical PCE architecture, a P-PCE
maintains a domain topology map that contains the child domains and maintains a domain topology map that contains the child domains and
their interconnections. Usually, the P-PCE has no information about their interconnections. Usually, the P-PCE has no information about
the content of the child domains. But if the PCE is applied to the the content of the child domains. But if the PCE is applied to the
Abstraction and Control of TE Networks (ACTN) [RFC8453] as described Abstraction and Control of TE Networks (ACTN) [RFC8453] as described
in [I-D.ietf-pce-applicability-actn], the Provisioning Network in [I-D.ietf-pce-applicability-actn], the Provisioning Network
Controller (PNC) can provide an abstract topology to the Multi-Domain Controller (PNC) can provide an abstract topology to the Multi-Domain
Service Coordinator (MDSC). Thus the P-PCE in MDSC could be aware of Service Coordinator (MDSC). Thus the P-PCE in MDSC could be aware of
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[I-D.ietf-pce-applicability-actn] examines the applicability of PCE [I-D.ietf-pce-applicability-actn] examines the applicability of PCE
to the ACTN framework. To support the function of multi domain to the ACTN framework. To support the function of multi domain
coordination via hierarchy, the hierarchy of stateful PCEs play a coordination via hierarchy, the hierarchy of stateful PCEs play a
crucial role. crucial role.
In the ACTN framework, a Customer Network Controller (CNC) can In the ACTN framework, a Customer Network Controller (CNC) can
request the MDSC to check whether there is a possibility to meet request the MDSC to check whether there is a possibility to meet
Virtual Network (VN) requirements before requesting for the VN to be Virtual Network (VN) requirements before requesting for the VN to be
provisioned. The H-PCE architecture as described in [RFC6805] can provisioned. The H-PCE architecture as described in [RFC6805] can
support this function using PCReq and PCRep messages between the support this function using PCReq and PCRep messages between the
P-PCE and C-PCEs. When the CNC requests for VN provisioning, the P-PCE and C-PCEs. When the CNC requests for VN provisioning, the MDSC
MDSC decompose this request into multiple inter-domain LSP decompose this request into multiple inter-domain LSP provisioning
provisioning requests, which might be further decomposed to requests, which might be further decomposed to per-domain path
per-domain path segments. This is described in Section 3.3.1. The segments. This is described in Section 3.3.1. The MDSC uses the LSP
MDSC uses the LSP Initiate Request (PCInitiate) message from the Initiate Request (PCInitiate) message from the P-PCE towards the
P-PCE towards the C-PCE, and the C-PCE reports the state back to the C-PCE, and the C-PCE reports the state back to the P-PCE via a Path
P-PCE via a Path Computation State Report (PCRpt) message. The P-PCE Computation State Report (PCRpt) message. The P-PCE could make
could make changes to the LSP via the use of a Path Computation changes to the LSP via the use of a Path Computation Update Request
Update Request (PCUpd) message. (PCUpd) message.
In this case, the P-PCE (as MDSC) interacts with multiple C-PCEs (as In this case, the P-PCE (as MDSC) interacts with multiple C-PCEs (as
PNCs) along the inter-domain path of the LSP. PNCs) along the inter-domain path of the LSP.
1.1.2 End-to-End Contiguous LSP 1.1.2 End-to-End Contiguous LSP
Different signaling methods for inter-domain RSVP-TE signaling are Different signaling methods for inter-domain RSVP-TE signaling are
identified in [RFC4726]. Contiguous LSPs are achieved using the identified in [RFC4726]. Contiguous LSPs are achieved using the
procedures of [RFC3209] and [RFC3473] to create a single end-to-end procedures of [RFC3209] and [RFC3473] to create a single end-to-end
LSP that spans all domains. [RFC6805] describes the technique to LSP that spans all domains. [RFC6805] describes the technique to
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The C-PCE would delegate control of the inter-domain LSP to the P-PCE The C-PCE would delegate control of the inter-domain LSP to the P-PCE
so that the P-PCE can make changes to it. Note that, if the C-PCE so that the P-PCE can make changes to it. Note that, if the C-PCE
becomes aware of a topology change that is hidden from the P-PCE, it becomes aware of a topology change that is hidden from the P-PCE, it
could take back the delegation from the P-PCE to act on it itself. could take back the delegation from the P-PCE to act on it itself.
Similarly, a P-PCE could also request for delegation if it needs to Similarly, a P-PCE could also request for delegation if it needs to
make a change to the LSP (refer to make a change to the LSP (refer to
[I-D.ietf-pce-lsp-control-request]). [I-D.ietf-pce-lsp-control-request]).
2. Terminology 2. Terminology
The terminology is as per [RFC4655], [RFC5440], [RFC6805], [RFC8231], The terminology is as per [RFC4655], [RFC5440], [RFC6805], [RFC8051],
and [RFC8281]. [RFC8231], and [RFC8281].
3. Hierarchical Stateful PCE 3. Hierarchical Stateful PCE
As described in [RFC6805], in the hierarchical PCE architecture, a As described in [RFC6805], in the hierarchical PCE architecture, a
P-PCE maintains a domain topology map that contains the child domains P-PCE maintains a domain topology map that contains the child domains
(seen as vertices in the topology) and their interconnections (links (seen as vertices in the topology) and their interconnections (links
in the topology). The P-PCE has no information about the content of in the topology). The P-PCE has no information about the content of
the child domains. Each child domain has at least one PCE capable of the child domains. Each child domain has at least one PCE capable of
computing paths across the domain. These PCEs are known as C-PCEs computing paths across the domain. These PCEs are known as C-PCEs
and have a direct relationship with the P-PCE. The P-PCE builds the and have a direct relationship with the P-PCE. The P-PCE builds the
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SPEAKER-IDENTITY-TLV (defined in [RFC8232]) is included in the LSP SPEAKER-IDENTITY-TLV (defined in [RFC8232]) is included in the LSP
object to identify the Ingress (PCC). The PLSP-ID used in the object to identify the Ingress (PCC). The PLSP-ID used in the
forwarded PCRpt by the C-PCE to P-PCE is same as the original one forwarded PCRpt by the C-PCE to P-PCE is same as the original one
used by the PCC. used by the PCC.
3.1. Passive Operations 3.1. Passive Operations
Procedures as described in [RFC6805] are applied and where the Procedures as described in [RFC6805] are applied and where the
ingress C-PCE (Child PCE), triggers a path computation request for ingress C-PCE (Child PCE), triggers a path computation request for
the LER in the domain where the LSP originates, sends a request to the LER in the domain where the LSP originates, sends a request to
the P-PCE. The P-PCE selects a set of candidate domain paths based the P-PCE. The P-PCE selects a set of candidate domain paths based on
on the domain topology and the state of the inter-domain links. It the domain topology and the state of the inter-domain links. It then
then sends computation requests to the C-PCEs responsible for each sends computation requests to the C-PCEs responsible for each of the
of the domains on the candidate domain paths. Each C-PCE computes a domains on the candidate domain paths. Each C-PCE computes a set of
set of candidate path segments across its domain and sends the candidate path segments across its domain and sends the results to
results to the P-PCE. The P-PCE uses this information to select path the P-PCE. The P-PCE uses this information to select path segments
segments and concatenate them to derive the optimal end-to-end and concatenate them to derive the optimal end-to-end inter-domain
inter-domain path. The end-to-end path is then sent to the C-PCE path. The end-to-end path is then sent to the C-PCE that received
that received the initial path request, and this C-PCE passes the the initial path request, and this C-PCE passes the path on to the
path on to the PCC that issued the original request. PCC that issued the original request.
As per [RFC8231], PCC sends an LSP State Report carried on a PCRpt As per [RFC8231], PCC sends an LSP State Report carried on a PCRpt
message to the C-PCE, indicating the LSP's status. The C-PCE may message to the C-PCE, indicating the LSP's status. The C-PCE may
further propagate the State Report to the P-PCE. A local policy at further propagate the State Report to the P-PCE. A local policy at
C-PCE may dictate which LSPs to be reported to the P-PCE. The PCRpt C-PCE may dictate which LSPs to be reported to the P-PCE. The PCRpt
message is sent from C-PCE to P-PCE. message is sent from C-PCE to P-PCE.
State synchronization mechanism as described in [RFC8231] and State synchronization mechanism as described in [RFC8231] and
[RFC8232] are applicable to A PCEP session between C-PCE and P-PCE as [RFC8232] are applicable to a PCEP session between C-PCE and P-PCE as
well. well.
We use the sample hierarchical domain topology example from [RFC6805] We use the sample hierarchical domain topology example from [RFC6805]
as the reference topology for the entirety of this document. It is as the reference topology for the entirety of this document. It is
shown in Figure 1. shown in Figure 1.
----------------------------------------------------------------- -----------------------------------------------------------------
| Domain 5 | | Domain 5 |
| ----- | | ----- |
| |PCE 5| | | |PCE 5| |
| ----- | | ----- |
| | | |
| ---------------- ---------------- ---------------- | | ---------------- ---------------- ---------------- |
| | Domain 1 | | Domain 2 | | Domain 3 | | | | Domain 1 | | Domain 2 | | Domain 3 | |
| | | | | | | | | | | | | | | |
| | ----- | | ----- | | ----- | | | | ----- | | ----- | | ----- | |
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| | | | | | | |
| | ----- | | | | ----- | |
| | |PCE 4| | | | | |PCE 4| | |
| | ----- | | | | ----- | |
| | | | | | | |
| | Domain 4 | | | | Domain 4 | |
| ---------------- | | ---------------- |
| | | |
----------------------------------------------------------------- -----------------------------------------------------------------
Figure 1: Sample Hierarchical Domain Topology Figure 1: Sample Hierarchical Domain Topology
Steps 1 to 11 are exactly as described in section 4.6.2 (Hierarchical Steps 1 to 11 are exactly as described in section 4.6.2 (Hierarchical
PCE End-to-End Path Computation Procedure) of [RFC6805], the PCE End-to-End Path Computation Procedure) of [RFC6805], the
following additional steps are added for stateful PCE: following additional steps are added for stateful PCE:
(A) The Ingress LSR initiates the setup of the LSP as per the path (A) The Ingress LSR initiates the setup of the LSP as per the path
and reports to the PCE1 the LSP status ("GOING-UP"). and reports to the PCE1 the LSP status ("GOING-UP").
(B) The PCE1 further reports the status of the LSP to the P-PCE (B) The PCE1 further reports the status of the LSP to the P-PCE
(PCE5). (PCE5).
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PCE (the Ingress domain PCE), the PCE further propagates the update PCE (the Ingress domain PCE), the PCE further propagates the update
request to the PCC. request to the PCC.
The P-PCE uses the same mechanism described in Section 3.1 to compute The P-PCE uses the same mechanism described in Section 3.1 to compute
the end to end path using PCReq and PCRep messages. the end to end path using PCReq and PCRep messages.
For active operations, the following steps are required when For active operations, the following steps are required when
delegating the LSP, again using the reference architecture described delegating the LSP, again using the reference architecture described
in Figure 1 (Sample Hierarchical Domain Topology). in Figure 1 (Sample Hierarchical Domain Topology).
(1) The Ingress LSR delegates the LSP to the PCE1 via PCRpt message (A) The Ingress LSR delegates the LSP to the PCE1 via PCRpt message
with D flag set. with D flag set.
(2) The PCE1 further delegates the LSP to the P-PCE (PCE5). (B) The PCE1 further delegates the LSP to the P-PCE (PCE5).
Steps 4 to 10 of section 4.6.2 of [RFC6805] are executed to determine (C) Steps 4 to 10 of section 4.6.2 of [RFC6805] are executed to
the end to end path. determine the end to end path.
(3) The P-PCE (PCE5) sends the update request to the C-PCE (D) The P-PCE (PCE5) sends the update request to the C-PCE (PCE1)
(PCE1) via PCUpd message. via PCUpd message.
(4) The PCE1 further updates the LSP to the Ingress LSR (PCC). (E) The PCE1 further updates the LSP to the Ingress LSR (PCC).
(5) The Ingress LSR initiates the setup of the LSP as per the path (F) The Ingress LSR initiates the setup of the LSP as per the path
and reports to the PCE1 the LSP status ("GOING-UP"). and reports to the PCE1 the LSP status ("GOING-UP").
(6) The PCE1 further reports the status of the LSP to the P-PCE (G) The PCE1 further reports the status of the LSP to the P-PCE
(PCE5). (PCE5).
(7) The Ingress LSR notifies the LSP state to PCE1 when the state is (H) The Ingress LSR notifies the LSP state to PCE1 when the state is
"UP". "UP".
(8) The PCE1 further reports the status of the LSP to the P-PCE (I) The PCE1 further reports the status of the LSP to the P-PCE
(PCE5). (PCE5).
3.3. PCE Initiation of LSPs 3.3. PCE Initiation of LSPs
[RFC8281] describes the setup, maintenance and teardown of PCE- [RFC8281] describes the setup, maintenance and teardown of PCE-
initiated LSPs under the stateful PCE model, without the need for initiated LSPs under the stateful PCE model, without the need for
local configuration on the PCC, thus allowing for a dynamic network local configuration on the PCC, thus allowing for a dynamic network
that is centrally controlled and deployed. To instantiate or delete that is centrally controlled and deployed. To instantiate or delete
an LSP, the PCE sends the Path Computation LSP Initiate Request an LSP, the PCE sends the Path Computation LSP Initiate Request
(PCInitiate) message to the PCC. In case of inter-domain LSP in (PCInitiate) message to the PCC. In case of inter-domain LSP in
Hierarchical PCE architecture, the initiation operations can be Hierarchical PCE architecture, the initiation operations can be
carried out at the P-PCE. In which case after P-PCE finishes the E2E carried out at the P-PCE. In which case after P-PCE finishes the E2E
path computation, it can send the PCInitiate message to the C-PCE path computation, it can send the PCInitiate message to the C-PCE
(the Ingress domain PCE), the PCE further propagates the initiate (the Ingress domain PCE), the PCE further propagates the initiate
request to the PCC. request to the PCC.
The following additional steps are also initially performed, for PCE The following steps are performed, for PCE initiated operations,
initiated operations, again using the reference architecture again using the reference architecture described in Figure 1 (Sample
described in Figure 1 (Sample Hierarchical Domain Topology): Hierarchical Domain Topology):
(1) The P-PCE (PCE5) is requested to initiate a LSP.
Steps 4 to 10 of section 4.6.2 of [RFC6805] are executed to determine (A) The P-PCE (PCE5) is requested to initiate a LSP. Steps 4 to 10
the end to end path. of section 4.6.2 of [RFC6805] are executed to determine the end
to end path.
(2) The P-PCE (PCE5) sends the initiate request to the child (B) The P-PCE (PCE5) sends the initiate request to the child PCE
PCE (PCE1) via PCInitiate message. (PCE1) via PCInitiate message.
(3) The PCE1 further propagates the initiate message to the Ingress (C) The PCE1 further propagates the initiate message to the Ingress
LSR (PCC). LSR (PCC).
(4) The Ingress LSR initiates the setup of the LSP as per the path (D) The Ingress LSR initiates the setup of the LSP as per the path
and reports to the PCE1 the LSP status ("GOING-UP"). and reports to the PCE1 the LSP status ("GOING-UP").
(5) The PCE1 further reports the status of the LSP to the P-PCE (E) The PCE1 further reports the status of the LSP to the P-PCE
(PCE5). (PCE5).
(6) The Ingress LSR notifies the LSP state to PCE1 when the state is (F) The Ingress LSR notifies the LSP state to PCE1 when the state is
"UP". "UP".
(7) The PCE1 further reports the status of the LSP to the P-PCE (G) The PCE1 further reports the status of the LSP to the P-PCE
(PCE5). (PCE5).
The Ingress LSR (PCC) generates the PLSP-ID for the LSP and inform The Ingress LSR (PCC) would generate the PLSP-ID for the LSP and
the C-PCE, which is propagated to the P-PCE as described in inform the C-PCE, which is propagated to the P-PCE.
[I-D.litkowski-pce-state-sync]
3.3.1. Per Domain Stitched LSP 3.3.1. Per Domain Stitched LSP
The Hierarchical PCE architecture as per [RFC6805] is primarily used The Hierarchical PCE architecture as per [RFC6805] is primarily used
for E2E LSP. With PCE-Initiated capability, another mode of for E2E LSP. With PCE-Initiated capability, another mode of
operation is possible, where multiple intra-domain LSPs are initiated operation is possible, where multiple intra-domain LSPs are initiated
in each domain which are further stitched to form an E2E LSP. The in each domain which are further stitched to form an E2E LSP. The
P-PCE sends PCInitiate message to each C-PCE separately to initiate P-PCE sends PCInitiate message to each C-PCE separately to initiate
individual LSP segments along the domain path. These individual per individual LSP segments along the domain path. These individual per
domain LSP are stitched together by some mechanism, which is out of domain LSP are stitched together by some mechanism, which is out of
scope of this document (Refer [I-D.dugeon-pce-stateful- scope of this document (Refer [I-D.dugeon-pce-stateful-
interdomain]). interdomain]).
The following additional steps are also initially performed, for the The following steps are performed, for the Per Domain stitched LSP
Per Domain stitched LSP operation, again using the reference operation, again using the reference architecture described in Figure
architecture described in Figure 1 (Sample Hierarchical Domain 1 (Sample Hierarchical Domain Topology):
Topology):
(1) The P-PCE (PCE5) is requested to initiate a LSP.
Steps 4 to 10 of section 4.6.2 of [RFC6805] are executed to determine (A) The P-PCE (PCE5) is requested to initiate a LSP. Steps 4 to 10
the end to end path, which are broken into per-domain LSPs say - of section 4.6.2 of [RFC6805] are executed to determine the end
to end path, which are broken into per-domain LSPs say -
o S-BN41 o S-BN41
o BN41-BN33
o BN33-D o BN41-BN33
o BN33-D
It should be noted that the P-PCE may use other mechanisms to It should be noted that the P-PCE may use other mechanisms to
determine the suitable per-domain LSPs (apart from [RFC6805]). determine the suitable per-domain LSPs (apart from [RFC6805]).
For LSP (BN33-D) For LSP (BN33-D)
(2) The P-PCE (PCE5) sends the initiate request to the child (B) The P-PCE (PCE5) sends the initiate request to the child PCE
PCE (PCE3) via PCInitiate message for LSP (BN33-D). (PCE3) via PCInitiate message for LSP (BN33-D).
(3) The PCE3 further propagates the initiate message to BN33. (C) The PCE3 further propagates the initiate message to BN33.
(4) BN33 initiates the setup of the LSP as per the path and reports (D) BN33 initiates the setup of the LSP as per the path and reports
to the PCE3 the LSP status ("GOING-UP"). to the PCE3 the LSP status ("GOING-UP").
(5) The PCE3 further reports the status of the LSP to the P-PCE (E) The PCE3 further reports the status of the LSP to the P-PCE
(PCE5). (PCE5).
(6) The node BN33 notifies the LSP state to PCE3 when the state is (F) The node BN33 notifies the LSP state to PCE3 when the state is
"UP". "UP".
(7) The PCE3 further reports the status of the LSP to the P-PCE (G) The PCE3 further reports the status of the LSP to the P-PCE
(PCE5). (PCE5).
For LSP (BN41-BN33) For LSP (BN41-BN33)
(8) The P-PCE (PCE5) sends the initiate request to the child PCE (H) The P-PCE (PCE5) sends the initiate request to the child PCE
(PCE4) via PCInitiate message for LSP (BN41-BN33). (PCE4) via PCInitiate message for LSP (BN41-BN33).
(9) The PCE4 further propagates the initiate message to BN41. (I) The PCE4 further propagates the initiate message to BN41.
(10) BN41 initiates the setup of the LSP as per the path and reports (J) BN41 initiates the setup of the LSP as per the path and reports
to the PCE4 the LSP status ("GOING-UP"). to the PCE4 the LSP status ("GOING-UP").
(11) The PCE4 further reports the status of the LSP to the P-PCE (K) The PCE4 further reports the status of the LSP to the P-PCE
(PCE5). (PCE5).
(l2) The node BN41 notifies the LSP state to PCE4 when the state is (L) The node BN41 notifies the LSP state to PCE4 when the state is
"UP". "UP".
(13) The PCE4 further reports the status of the LSP to the P-PCE (M) The PCE4 further reports the status of the LSP to the P-PCE
(PCE5). (PCE5).
For LSP (S-BN41) For LSP (S-BN41)
(14) The P-PCE (PCE5) sends the initiate request to the child (N) The P-PCE (PCE5) sends the initiate request to the child PCE
PCE (PCE1) via PCInitiate message for LSP (S-BN41). (PCE1) via PCInitiate message for LSP (S-BN41).
(15) The PCE1 further propagates the initiate message to node S. (O) The PCE1 further propagates the initiate message to node S.
(16) S initiates the setup of the LSP as per the path and reports to (P) S initiates the setup of the LSP as per the path and reports to
the PCE1 the LSP status ("GOING-UP"). the PCE1 the LSP status ("GOING-UP").
(17) The PCE1 further reports the status of the LSP to the P-PCE (Q) The PCE1 further reports the status of the LSP to the P-PCE
(PCE5). (PCE5).
(18) The node S notifies the LSP state to PCE1 when the state is (R) The node S notifies the LSP state to PCE1 when the state is
"UP". "UP".
(19) The PCE1 further reports the status of the LSP to the P-PCE (S) The PCE1 further reports the status of the LSP to the P-PCE
(PCE5). (PCE5).
Additionally: Additionally:
(20) Once P-PCE receives report of each per-domain LSP, it (T) Once P-PCE receives report of each per-domain LSP, it should use
should use suitable stitching mechanism, which is out of scope suitable stitching mechanism, which is out of scope of this
of this document. In this step, P-PCE (PCE5) could also document. In this step, P-PCE (PCE5) could also initiate an E2E
initiate an E2E LSP (S-D) by sending the PCInitiate message to LSP (S-D) by sending the PCInitiate message to Ingress C-PCE
Ingress C-PCE (PCE1). (PCE1).
It is also possible to stitch the per-domain LSP at the same Note that each per-domain LSP can be setup in parallel. Further, it
time as the per-domain LSPs are initiated. This option is is also possible to stitch the per-domain LSP at the same time as the
defined in [I-D.dugeon-pce-stateful-interdomain]. per-domain LSPs are initiated. This option is defined in
[I-D.dugeon-pce-stateful-interdomain].
4. Security Considerations 4. Security Considerations
The security considerations listed in [RFC8231],[RFC6805] and The security considerations listed in [RFC8231],[RFC6805] and
[RFC5440] apply to this document as well. As per [RFC6805], it is [RFC5440] apply to this document as well. As per [RFC6805], it is
expected that the parent PCE will require all child PCEs to use full expected that the parent PCE will require all child PCEs to use full
security when communicating with the parent. security when communicating with the parent.
Any multi-domain operation necessarily involves the exchange of Any multi-domain operation necessarily involves the exchange of
information across domain boundaries. This is bound to represent a information across domain boundaries. This is bound to represent a
skipping to change at page 15, line 7 skipping to change at page 15, line 6
path information using path-keys [RFC5520], and the hierarchical PCE path information using path-keys [RFC5520], and the hierarchical PCE
architecture is specifically designed to enable as much isolation of architecture is specifically designed to enable as much isolation of
domain topology and capabilities information as is possible. The LSP domain topology and capabilities information as is possible. The LSP
state in the PCRpt message must continue to maintain the internal state in the PCRpt message must continue to maintain the internal
domain confidentiality when required. domain confidentiality when required.
The security consideration for PCE-Initiated LSP as per [RFC8281] is The security consideration for PCE-Initiated LSP as per [RFC8281] is
also applicable from P-PCE to C-PCE. also applicable from P-PCE to C-PCE.
Thus securing the PCEP session (between the P-PCE and the C-PCE) Thus securing the PCEP session (between the P-PCE and the C-PCE)
using the TCP Authentication Option (TCP-AO) [RFC5925] or using the TCP Authentication Option (TCP-AO) [RFC5925] or Transport
Transport Layer Security (TLS) [RFC8253] mechanisms are recommended. Layer Security (TLS) [RFC8253] mechanisms are recommended.
5. Manageability Considerations 5. Manageability Considerations
All manageability requirements and considerations listed in All manageability requirements and considerations listed in
[RFC5440], [RFC6805], [RFC8231], and [RFC8281] apply to Stateful H- [RFC5440], [RFC6805], [RFC8231], and [RFC8281] apply to Stateful H-
PCE defined in this document. In addition, requirements and PCE defined in this document. In addition, requirements and
considerations listed in this section apply. considerations listed in this section apply.
5.1. Control of Function and Policy 5.1. Control of Function and Policy
skipping to change at page 16, line 15 skipping to change at page 16, line 11
5.6. Impact On Network Operations 5.6. Impact On Network Operations
Mechanisms defined in [RFC5440] and [RFC8231] also apply to PCEP Mechanisms defined in [RFC5440] and [RFC8231] also apply to PCEP
extensions defined in this document. extensions defined in this document.
The stateful H-PCE technique brings the applicability of stateful PCE The stateful H-PCE technique brings the applicability of stateful PCE
as described in [RFC8051], for the LSP traversing multiple domains. as described in [RFC8051], for the LSP traversing multiple domains.
5.7. Error Handling between PCEs 5.7. Error Handling between PCEs
Error types and notifications useful for correct PCEP operation Error types and notifications useful for correct PCEP operation may
may be implemented for managing parent and child PCE interaction. be implemented for managing parent and child PCE interaction. PCEP
PCEP Error behavior propagation, notification and error criticality Error behavior propagation, notification and error criticality level,
level, are further defined in [I-D.ietf-pce-enhanced-errors]. are further defined in [I-D.ietf-pce-enhanced-errors].
6. Other Considerations 6. Other Considerations
6.1. Applicability to Inter-Layer Traffic Engineering 6.1. Applicability to Inter-Layer Traffic Engineering
[RFC5623] describes a framework for applying the PCE-based [RFC5623] describes a framework for applying the PCE-based
architecture to inter-layer (G)MPLS traffic engineering. The H-PCE architecture to inter-layer (G)MPLS traffic engineering. The H-PCE
Stateful architecture with stateful P-PCE coordinating with the Stateful architecture with stateful P-PCE coordinating with the
stateful C-PCEs of higher and lower layer is shown in the figure stateful C-PCEs of higher and lower layer is shown in the figure
below. below.
skipping to change at page 21, line 36 skipping to change at page 21, line 36
Dhruv Dhody Dhruv Dhody
Huawei Technologies Huawei Technologies
Divyashree Techno Park, Whitefield Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560066 Bangalore, Karnataka 560066
India India
EMail: dhruv.ietf@gmail.com EMail: dhruv.ietf@gmail.com
Young Lee Young Lee
Huawei Technologies Futurewei
5340 Legacy Drive, Building 3 5340 Legacy Drive, Building 3
Plano, TX 75023 Plano, TX 75023
USA USA
EMail: leeyoung@huawei.com EMail: younglee.tx@gmail.com
Daniele Ceccarelli Daniele Ceccarelli
Ericsson Ericsson
Torshamnsgatan,48 Torshamnsgatan,48
Stockholm Stockholm
Sweden Sweden
EMail: daniele.ceccarelli@ericsson.com EMail: daniele.ceccarelli@ericsson.com
Jongyoon Shin Jongyoon Shin
SK Telecom SK Telecom
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