draft-ietf-pce-stateful-hpce-01.txt   draft-ietf-pce-stateful-hpce-02.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 31, 2017 D. Ceccarelli Expires: May 1, 2018 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 29, 2017 October 28, 2017
Hierarchical Stateful Path Computation Element (PCE). Hierarchical Stateful Path Computation Element (PCE).
draft-ietf-pce-stateful-hpce-01 draft-ietf-pce-stateful-hpce-02
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 dependent LSPs, received from Path Computation Clients (PCCs). and dependent LSPs, received from Path Computation Clients (PCCs).
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Hierarchical PCE architecture. Hierarchical PCE architecture.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
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The Path Computation Element communication Protocol (PCEP) provides The Path Computation Element communication Protocol (PCEP) provides
mechanisms for Path Computation Elements (PCEs) to perform path mechanisms for Path Computation Elements (PCEs) to perform path
computations in response to Path Computation Clients' (PCCs) 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 computation, not only the network state in terms of links and path computation, not only the network state in terms of links and
nodes (referred to as the Traffic Engineering Database or TED) but nodes (referred to as the Traffic Engineering Database or TED) but
also the status of active services (previously computed paths, also the status of active services (previously computed paths,
and currently reserved resources, stored in the Label Switched and currently reserved resources, stored in the Label Switched
Paths Database (LSPDB). Paths Database (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.
[I-D.ietf-pce-stateful-pce] describes a set of extensions to PCEP to [RFC8231] describes a set of extensions to PCEP to provide stateful
provide stateful control. A stateful PCE has access to not only the control. A stateful PCE has access to not only the information
information carried by the network's Interior Gateway Protocol (IGP), carried by the network's Interior Gateway Protocol (IGP), but also
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
constrained paths while considering individual LSPs and their constrained paths while considering individual LSPs and their
interactions. [I-D.ietf-pce-pce-initiated-lsp] describes the setup, interactions. [I-D.ietf-pce-pce-initiated-lsp] describes the setup,
maintenance and teardown of PCE-initiated LSPs under the stateful PCE maintenance and teardown of PCE-initiated LSPs under the stateful PCE
model. model.
[I-D.ietf-pce-stateful-pce] also describes the active stateful PCE. [RFC8231] also describes the active stateful PCE. The active PCE
The active PCE functionality allows a PCE to reroute an existing functionality allows a PCE to reroute an existing LSP or make changes
LSP or make changes to the attributes of an existing LSP, or delegate to the attributes of an existing LSP, or delegate control of specific
control of specific LSPs to a new PCE. LSPs to a new PCE.
The ability to compute shortest constrained TE LSPs in Multiprotocol The ability to compute shortest constrained TE LSPs in Multiprotocol
Label Switching (MPLS) and Generalized MPLS (GMPLS) networks across Label Switching (MPLS) and Generalized MPLS (GMPLS) networks across
multiple domains has been identified as a key motivation for PCE multiple domains has been identified as a key motivation for PCE
development. [RFC6805] describes a Hierarchical PCE (H-PCE) development. [RFC6805] describes a Hierarchical PCE (H-PCE)
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
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1.1. Requirements Language 1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
2. Terminology 2. Terminology
The terminology is as per [RFC4655], [RFC5440], [RFC6805], and The terminology is as per [RFC4655], [RFC5440], [RFC6805], and
[I-D.ietf-pce-stateful-pce]. [RFC8231].
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
domain topology map either via direct configuration (allowing network domain topology map either via direct configuration (allowing network
policy to also be applied) or from learned information received from policy to also be applied) or from learned information received from
each C-PCE. each C-PCE.
[I-D.ietf-pce-stateful-pce] specifies new functions to support a [RFC8231] specifies new functions to support a stateful PCE. It also
stateful PCE. It also specifies that a function can be initiated specifies that a function can be initiated either from a PCC towards
either from a PCC towards a PCE (C-E) or from a PCE towards a PCC a PCE (C-E) or from a PCE towards a PCC (E-C).
(E-C).
This document extends these functions to support H-PCE Architecture This document extends these functions to support H-PCE Architecture
from a C-PCE towards a P-PCE (CE-PE) or from a P-PCE from a C-PCE towards a P-PCE (CE-PE) or from a P-PCE towards a C-PCE
towards a C-PCE (PE-CE). All PCE types herein (i.e., PE or CE) (PE-CE). All PCE types herein (i.e., PE or CE) are assumed to be
are assumed to be 'stateful PCE'. 'stateful PCE'.
A number of interactions are expected in the Hierarchical Stateful A number of interactions are expected in the Hierarchical Stateful
PCE architecture, these include: PCE architecture, these include:
LSP State Report (CE-PE): a child stateful PCE sends an LSP state LSP State Report (CE-PE): a child stateful PCE sends an LSP state
report to a Parent Stateful PCE whenever the state of a LSP report to a Parent Stateful PCE whenever the state of a LSP
changes. changes.
LSP State Synchronization (CE-PE): after the session between the LSP State Synchronization (CE-PE): after the session between the
Child and Parent stateful PCEs is initialized, the P-PCE must Child and Parent stateful PCEs is initialized, the P-PCE must
learn the state of C-PCE's TE LSPs. learn the state of C-PCE's TE LSPs.
LSP Control Delegation (CE-PE,PE-CE): a C-PCE grants to the LSP Control Delegation (CE-PE,PE-CE): a C-PCE grants to the P-PCE
P-PCE the right to update LSP attributes on one or more LSPs; the right to update LSP attributes on one or more LSPs; the C-PCE
the C-PCE may withdraw the delegation or the P-PCE may may withdraw the delegation or the P-PCE may give up the
give up the delegation at any time. delegation at any time.
LSP Update Request (PE-CE): a stateful P-PCE requests LSP Update Request (PE-CE): a stateful P-PCE requests modification
modification of attributes on a C-PCE's TE LSP. of attributes on a C-PCE's TE LSP.
PCE LSP Initiation Request (PE-CE): a stateful P-PCE requests PCE LSP Initiation Request (PE-CE): a stateful P-PCE requests C-PCE
C-PCE to initiate a TE LSP. to initiate a TE LSP.
Note that this hierarchy is recursive and thus a LSR could delegate Note that this hierarchy is recursive and thus a LSR could delegate
the control to a PCE, which may delegate to its parent, which may the control to a PCE, which may delegate to its parent, which may
further delegate it to its parent (if it exist or needed). Similarly further delegate it to its parent (if it exist or needed). Similarly
update operations could also be applied recursively. update operations could also be applied recursively.
[I-D.ietf-pce-hierarchy-extensions] defines the H-PCE capability TLV [I-D.ietf-pce-hierarchy-extensions] defines the H-PCE capability TLV
that should be used in the OPEN message to advertise the H-PCE that should be used in the OPEN message to advertise the H-PCE
capability. [I-D.ietf-pce-stateful-pce] defines the stateful PCE capability. [RFC8231] defines the stateful PCE capability TLV. The
capability TLV. The presence of both TLVs represent the support for presence of both TLVs represent the support for stateful H-PCE
stateful H-PCE operations as described in this document. operations as described in this document.
[I-D.litkowski-pce-state-sync] describes the procedures to allow a [I-D.litkowski-pce-state-sync] describes the procedures to allow a
stateful communication between PCEs for various use-cases. The stateful communication between PCEs for various use-cases. The
procedures and extensions as described in Section 3 of procedures and extensions as described in Section 3 of
[I-D.litkowski-pce-state-sync] are also applicable to Child and [I-D.litkowski-pce-state-sync] are also applicable to Child and
Parent PCE communication. Parent PCE communication.
3.1. Passive Operations 3.1. Passive Operations
Procedures as described in [RFC6805] are applied, where the ingress Procedures as described in [RFC6805] are applied, where the ingress
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the inter-domain links. It then sends computation requests to the C- the inter-domain links. It then sends computation requests to the C-
PCEs responsible for each of the domains on the candidate domain PCEs responsible for each of the domains on the candidate domain
paths. Each C-PCE computes a set of candidate path segments across paths. Each C-PCE computes a set of candidate path segments across
its domain and sends the results to the P-PCE. The P-PCE uses this its domain and sends the results to the P-PCE. The P-PCE uses this
information to select path segments and concatenate them to derive information to select path segments and concatenate them to derive
the optimal end-to-end inter-domain path. The end-to-end path is the optimal end-to-end inter-domain path. The end-to-end path is
then sent to the C-PCE that received the initial path request, and then sent to the C-PCE that received the initial path request, and
this C-PCE passes the path on to the PCC that issued the original this C-PCE passes the path on to the PCC that issued the original
request. request.
As per [I-D.ietf-pce-stateful-pce], PCC sends an LSP State Report As per [RFC8231], PCC sends an LSP State Report carried on a PCRpt
carried on a PCRpt message to the C-PCE, indicating the LSP's status. message to the C-PCE, indicating the LSP's status. The C-PCE MAY
The C-PCE MAY further propagate the State Report to the P-PCE. A further propagate the State Report to the P-PCE. A local policy at
local policy at C-PCE MAY dictate which LSPs to be reported to the P- C-PCE MAY dictate which LSPs to be reported to the P-PCE. The PCRpt
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 State synchronization mechanism as described in [RFC8231] and
[I-D.ietf-pce-stateful-pce] and [RFC8233] are applicable to PCEP session between C-PCE and P-PCE as
[I-D.ietf-pce-stateful-sync-optimizations] are applicable to PCEP well.
session between C-PCE and P-PCE as well.
Taking the sample hierarchical domain topology example from [RFC6805] Taking the sample hierarchical domain topology example from [RFC6805]
as the reference topology for the entirety of this document. as the reference topology for the entirety of this document.
----------------------------------------------------------------- -----------------------------------------------------------------
| Domain 5 | | Domain 5 |
| ----- | | ----- |
| |PCE 5| | | |PCE 5| |
| ----- | | ----- |
| | | |
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(PCE5). (PCE5).
(3) The Ingress LSR notifies the LSP state to PCE1 when the state is (3) The Ingress LSR notifies the LSP state to PCE1 when the state is
"UP". "UP".
(4) The PCE1 further reports the status of the LSP to the P-PCE (4) The PCE1 further reports the status of the LSP to the P-PCE
(PCE5). (PCE5).
3.2. Active Operations 3.2. Active Operations
[I-D.ietf-pce-stateful-pce] describes the case of active stateful [RFC8231] describes the case of active stateful PCE. The active PCE
PCE. The active PCE functionality uses two specific PCEP messages: functionality uses two specific PCEP messages:
o Update Request (PCUpd) o Update Request (PCUpd)
o State Report (PCRpt) o State Report (PCRpt)
The first is sent by the PCE to a Path Computation Client (PCC) for The first is sent by the PCE to a Path Computation Client (PCC) for
modifying LSP attributes. The PCC sends back a PCRpt to acknowledge modifying LSP attributes. The PCC sends back a PCRpt to acknowledge
the requested operation or report any change in LSP's state. the requested operation or report any change in LSP's state.
As per [RFC8051], Delegation is an operation to As per [RFC8051], Delegation is an operation to grant a PCE,
grant a PCE, temporary rights to modify a subset of LSP parameters on temporary rights to modify a subset of LSP parameters on one or more
one or more PCC's LSPs. The C-PCE may further choose to delegate PCC's LSPs. The C-PCE may further choose to delegate to P-PCE based
to P-PCE based on a local policy. The PCRpt message with "D" on a local policy. The PCRpt message with "D" (delegate) flag is
(delegate) flag is sent from C-PCE to P-PCE. sent from C-PCE to P-PCE.
To update an LSP, a PCE send to the PCC, an LSP Update Request using To update an LSP, a PCE send to the PCC, an LSP Update Request using
a PCUpd message. For LSP delegated to the P-PCE via the child a PCUpd message. For LSP delegated to the P-PCE via the child PCE,
PCE, the P-PCE can use the same PCUpd message to request change the P-PCE can use the same PCUpd message to request change to the C-
to the C-PCE (the Ingress domain PCE), the PCE further propagates PCE (the Ingress domain PCE), the PCE further propagates the update
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.
The following additional steps are also initially performed, The following additional steps are also initially performed, for
for active operations, again using the reference architecture active operations, again using the reference architecture described
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 (1) 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). (2) 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 Steps 4 to 10 of section 4.6.2 of [RFC6805] are executed to determine
the end to end path. the end to end path.
(3) The P-PCE (PCE5) sends the update request to the C-PCE (3) The P-PCE (PCE5) sends the update request to the C-PCE
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3.3. PCE Initiation Operation 3.3. PCE Initiation Operation
[I-D.ietf-pce-pce-initiated-lsp] describes the setup, maintenance and [I-D.ietf-pce-pce-initiated-lsp] describes the setup, maintenance and
teardown of PCE-initiated LSPs under the stateful PCE model, without teardown of PCE-initiated LSPs under the stateful PCE model, without
the need for local configuration on the PCC, thus allowing for a the need for local configuration on the PCC, thus allowing for a
dynamic network that is centrally controlled and deployed. To dynamic network that is centrally controlled and deployed. To
instantiate or delete an LSP, the PCE sends the Path Computation LSP instantiate or delete an LSP, the PCE sends the Path Computation LSP
Initiate Request (PCInitiate) message to the PCC. In case of inter- Initiate Request (PCInitiate) message to the PCC. In case of inter-
domain LSP in Hierarchical PCE architecture, the initiation domain LSP in Hierarchical PCE architecture, the initiation
operations can be carried out at the P-PCE. In which case after operations can be carried out at the P-PCE. In which case after
P-PCE finishes the E2E path computation, it can send the P-PCE finishes the E2E path computation, it can send the PCInitiate
PCInitiate message to the C-PCE (the Ingress domain PCE), the PCE message to the C-PCE (the Ingress domain PCE), the PCE further
further propagates the initiate request to the PCC. propagates the initiate request to the PCC.
The following additional steps are also initially performed, The following additional steps are also initially performed, for PCE
for PCE initiated operations, again using the reference initiated operations, again using the reference architecture
architecture described in Figure 1 (Sample Hierarchical Domain described in Figure 1 (Sample Hierarchical Domain Topology):
Topology):
(1) The P-PCE (PCE5) is requested to initiate a LSP. (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 Steps 4 to 10 of section 4.6.2 of [RFC6805] are executed to determine
the end to end path. the end to end path.
(2) The P-PCE (PCE5) sends the initiate request to the child (2) The P-PCE (PCE5) sends the initiate request to the child
PCE (PCE1) via PCInitiate message. PCE (PCE1) via PCInitiate message.
(3) The PCE1 further propagates the initiate message to the Ingress (3) The PCE1 further propagates the initiate message to the Ingress
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(7) The PCE1 further reports the status of the LSP to the P-PCE (7) The PCE1 further reports the status of the LSP to the P-PCE
(PCE5). (PCE5).
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 P-PCE sends PCInitiate message to each C-PCE separately to initiate
initiate individual LSP segments along the domain path. These individual LSP segments along the domain path. These individual per
individual per domain LSP are stitched together by some mechanism, domain LSP are stitched together by some mechanism, which is out of
which is out of scope of this document. The P-PCE may also send scope of this document. The P-PCE may also send the PCInitiate
the PCInitiate message to the ingress C-PCE to initiate the E2E message to the ingress C-PCE to initiate the E2E LSP separately.
LSP separately.
The following additional steps are also initially performed, The following additional steps are also initially performed, for the
for the Per Domain stiched LSP operation, again using the reference Per Domain stiched LSP operation, again using the reference
architecture described in Figure 1 (Sample Hierarchical Domain architecture described in Figure 1 (Sample Hierarchical Domain
Topology): Topology):
(1) The P-PCE (PCE5) is requested to initiate a LSP. (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 Steps 4 to 10 of section 4.6.2 of [RFC6805] are executed to determine
the end to end path, which are broken into per-domain LSPs say - the end to end path, which are broken into per-domain LSPs say -
o S-BN41 o S-BN41
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+ L1 + + L2 + + L1 + + L2 +
+---+ +---+ +---+ +---+
Figure 2: Sample Inter-Layer Topology Figure 2: Sample Inter-Layer Topology
All procedures described in Section 3 are applicable to inter-layer All procedures described in Section 3 are applicable to inter-layer
path setup as well. path setup as well.
4.2. Applicability to ACTN 4.2. Applicability to ACTN
[I-D.ietf-teas-actn-framework] describes framework for [I-D.ietf-teas-actn-framework] describes framework for Abstraction
Abstraction and Control of TE Networks (ACTN), where each Physical and Control of TE Networks (ACTN), where each Provisioning Network
Network Controller (PNC) is equivalent to C-PCE and P-PCE is Controller (PNC) is equivalent to C-PCE and P-PCE is the Multi-Domain
the Multi-Domain Service Coordinator (MDSC). The Per domain stitched Service Coordinator (MDSC). The Per domain stitched LSP as per the
LSP as per the Hierarchical PCE architecture described in Hierarchical PCE architecture described in Section 3.3.1 and Section
Section 3.3.1 and Section 4.1 is well suited for ACTN. 4.1 is well suited for ACTN.
[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 stateful hierarchy of PCEs plays a coordination via hierarchy, the stateful hierarchy of PCEs plays a
crucial role. crucial role.
In ACTN framework, Customer Network Controller (CNC) can request the In ACTN framework, Customer Network Controller (CNC) can request the
MDSC to check if there is a possibility to meet Virtual Network (VN) MDSC to check if there is a possibility to meet Virtual Network (VN)
requirements (before requesting for VN provision). The H-PCE requirements (before requesting for VN provision). The H-PCE
architecture as described in [RFC6805] can supports via the use of architecture as described in [RFC6805] can supports via the use of
PCReq and PCRep messages between the P-PCE and C-PCEs. PCReq and PCRep messages between the P-PCE and C-PCEs.
5. Scalability Considerations 5. Scalability Considerations
It should be noted that if all the C-PCEs would report all the LSPs It should be noted that if all the C-PCEs would report all the LSPs
in their domain, it could lead to scalability issues for the P-PCE. in their domain, it could lead to scalability issues for the P-PCE.
Thus it is recommended to only report the LSPs which are involved in Thus it is recommended to only report the LSPs which are involved in
H-PCE, i.e. the LSPs which are either delegated to the P-PCE or H-PCE, i.e. the LSPs which are either delegated to the P-PCE or
initiated by the P-PCE. Scalability considerations for PCEP as per initiated by the P-PCE. Scalability considerations for PCEP as per
[I-D.ietf-pce-stateful-pce] continue to apply for the PCEP session [RFC8231] continue to apply for the PCEP session between child and
between child and parent PCE. parent PCE.
6. Security Considerations 6. Security Considerations
The security considerations listed in [I-D.ietf-pce-stateful- The security considerations listed in [RFC8231],[RFC6805] and
pce],[RFC6805] and [RFC5440] apply to this document as well. As per [RFC5440] apply to this document as well. As per [RFC6805], it is
[RFC6805], it is expected that the parent PCE will require all child expected that the parent PCE will require all child PCEs to use full
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
significant security and confidentiality risk especially when the significant security and confidentiality risk especially when the
child domains are controlled by different commercial concerns. PCEP child domains are controlled by different commercial concerns. PCEP
allows individual PCEs to maintain confidentiality of their domain allows individual PCEs to maintain confidentiality of their domain
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 SHOULD continue to use this. state in the PCRpt message SHOULD continue to use this.
The security consideration for PCE-Initiated LSP as per The security consideration for PCE-Initiated LSP as per
[I-D.ietf-pce-pce-initiated-lsp] is also applicable from P-PCE to C- [I-D.ietf-pce-pce-initiated-lsp] is also applicable from P-PCE to C-
PCE. 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 mechanism like TCP Authentication Option (TCP-AO) [RFC5925] or using mechanism like TCP Authentication Option (TCP-AO) [RFC5925] or
Transport Layer Security (TLS) [I-D.ietf-pce-pceps] is RECOMMENDED. Transport Layer Security (TLS) [RFC8253] is RECOMMENDED.
7. Manageability Considerations 7. Manageability Considerations
All manageability requirements and considerations listed in All manageability requirements and considerations listed in
[RFC5440], [RFC6805], [I-D.ietf-pce-stateful-pce], and [RFC5440], [RFC6805], [RFC8231], and [I-D.ietf-pce-pce-initiated-lsp]
[I-D.ietf-pce-pce-initiated-lsp] apply to Stateful H-PCE defined in apply to Stateful H-PCE defined in this document. In addition,
this document. In addition, requirements and considerations listed requirements and considerations listed in this section apply.
in this section apply.
7.1. Control of Function and Policy 7.1. Control of Function and Policy
Support of the hierarchical procedure will be controlled by the Support of the hierarchical procedure will be controlled by the
management organization responsible for each child PCE. The parent management organization responsible for each child PCE. The parent
PCE must only accept path computation requests from authorized child PCE must only accept path computation requests from authorized child
PCEs. If a parent PCE receives report from an unauthorized child PCEs. If a parent PCE receives report from an unauthorized child
PCE, the report should be dropped. All mechanism as described in [I- PCE, the report should be dropped. All mechanism as described in
D.ietf-pce-stateful-pce] and [I-D.ietf-pce-pce-initiated-lsp] [RFC8231] and [I-D.ietf-pce-pce-initiated-lsp] continue to apply.
continue to apply.
7.2. Information and Data Models 7.2. Information and Data Models
An implementation SHOULD allow the operator to view the stateful and An implementation SHOULD allow the operator to view the stateful and
H-PCE capabilities advertised by each peer. The PCEP YANG module [I- H-PCE capabilities advertised by each peer. The PCEP YANG module [I-
D.ietf-pce-pcep-yang] can be extended to include details stateful H- D.ietf-pce-pcep-yang] can be extended to include details stateful H-
PCE. PCE.
7.3. Liveness Detection and Monitoring 7.3. Liveness Detection and Monitoring
Mechanisms defined in this document do not imply any new liveness Mechanisms defined in this document do not imply any new liveness
detection and monitoring requirements in addition to those already detection and monitoring requirements in addition to those already
listed in [RFC5440]. listed in [RFC5440].
7.4. Verify Correct Operations 7.4. Verify Correct Operations
Mechanisms defined in this document do not imply any new operation Mechanisms defined in this document do not imply any new operation
verification requirements in addition to those already listed in verification requirements in addition to those already listed in
[RFC5440] and [I-D.ietf-pce-stateful-pce]. [RFC5440] and [RFC8231].
7.5. Requirements On Other Protocols 7.5. Requirements On Other Protocols
Mechanisms defined in this document do not imply any new requirements Mechanisms defined in this document do not imply any new requirements
on other protocols. on other protocols.
7.6. Impact On Network Operations 7.6. Impact On Network Operations
Mechanisms defined in [RFC5440] and [I-D.ietf-pce-stateful-pce] also Mechanisms defined in [RFC5440] and [RFC8231] also apply to PCEP
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.
8. IANA Considerations 8. IANA Considerations
There are no IANA considerations. There are no IANA considerations.
9. Acknowledgments 9. Acknowledgments
skipping to change at page 16, line 8 skipping to change at page 15, line 50
Element (PCE) Communication Protocol (PCEP)", RFC 5440, Element (PCE) Communication Protocol (PCEP)", RFC 5440,
DOI 10.17487/RFC5440, March 2009, DOI 10.17487/RFC5440, March 2009,
<http://www.rfc-editor.org/info/rfc5440>. <http://www.rfc-editor.org/info/rfc5440>.
[RFC6805] King, D., Ed. and A. Farrel, Ed., "The Application of the [RFC6805] King, D., Ed. and A. Farrel, Ed., "The Application of the
Path Computation Element Architecture to the Determination Path Computation Element Architecture to the Determination
of a Sequence of Domains in MPLS and GMPLS", RFC 6805, DOI of a Sequence of Domains in MPLS and GMPLS", RFC 6805, DOI
10.17487/RFC6805, November 2012, 10.17487/RFC6805, November 2012,
<http://www.rfc-editor.org/info/rfc6805>. <http://www.rfc-editor.org/info/rfc6805>.
[I-D.ietf-pce-stateful-pce] [RFC8231] Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path
Crabbe, E., Minei, I., Medved, J., and R. Varga, "PCEP Computation Element Communication Protocol (PCEP)
Extensions for Stateful PCE", draft-ietf-pce-stateful- Extensions for Stateful PCE", RFC 8231,
pce-21 (work in progress), June 2017. DOI 10.17487/RFC8231, September 2017,
<https://www.rfc-editor.org/info/rfc8231>.
[I-D.ietf-pce-pce-initiated-lsp] [I-D.ietf-pce-pce-initiated-lsp]
Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "PCEP Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "PCEP
Extensions for PCE-initiated LSP Setup in a Stateful PCE Extensions for PCE-initiated LSP Setup in a Stateful PCE
Model", draft-ietf-pce-pce-initiated-lsp-10 (work in Model", draft-ietf-pce-pce-initiated-lsp-11 (work in
progress), June 2017. progress), October 2017.
10.2. Informative References 10.2. Informative References
[RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
Element (PCE)-Based Architecture", RFC 4655, Element (PCE)-Based Architecture", RFC 4655,
DOI 10.17487/RFC4655, August 2006, DOI 10.17487/RFC4655, August 2006,
<http://www.rfc-editor.org/info/rfc4655>. <http://www.rfc-editor.org/info/rfc4655>.
[RFC5520] Bradford, R., Ed., Vasseur, JP., and A. Farrel, [RFC5520] Bradford, R., Ed., Vasseur, JP., and A. Farrel,
"Preserving Topology Confidentiality in Inter-Domain Path "Preserving Topology Confidentiality in Inter-Domain Path
skipping to change at page 16, line 46 skipping to change at page 16, line 42
[RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP [RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP
Authentication Option", RFC 5925, DOI 10.17487/RFC5925, Authentication Option", RFC 5925, DOI 10.17487/RFC5925,
June 2010, <http://www.rfc-editor.org/info/rfc5925>. June 2010, <http://www.rfc-editor.org/info/rfc5925>.
[RFC8051] Zhang, X., Ed. and I. Minei, Ed., "Applicability of a [RFC8051] Zhang, X., Ed. and I. Minei, Ed., "Applicability of a
Stateful Path Computation Element (PCE)", RFC 8051, Stateful Path Computation Element (PCE)", RFC 8051,
DOI 10.17487/RFC8051, January 2017, DOI 10.17487/RFC8051, January 2017,
<http://www.rfc-editor.org/info/rfc8051>. <http://www.rfc-editor.org/info/rfc8051>.
[I-D.ietf-pce-stateful-sync-optimizations] [RFC8233] Dhody, D., Wu, Q., Manral, V., Ali, Z., and K. Kumaki,
Crabbe, E., Minei, I., Medved, J., Varga, R., Zhang, X., "Extensions to the Path Computation Element Communication
and D. Dhody, "Optimizations of Label Switched Path State Protocol (PCEP) to Compute Service-Aware Label Switched
Synchronization Procedures for a Stateful PCE", draft- Paths (LSPs)", RFC 8233, DOI 10.17487/RFC8233, September
ietf-pce-stateful-sync-optimizations-10 (work in 2017, <https://www.rfc-editor.org/info/rfc8233>.
progress), March 2017.
[RFC8253] Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody,
"PCEPS: Usage of TLS to Provide a Secure Transport for the
Path Computation Element Communication Protocol (PCEP)",
RFC 8253, DOI 10.17487/RFC8253, October 2017,
<https://www.rfc-editor.org/info/rfc8253>.
[I-D.ietf-teas-actn-framework] [I-D.ietf-teas-actn-framework]
Ceccarelli D. and Y. Lee, "Framework for Abstraction and Ceccarelli D. and Y. Lee, "Framework for Abstraction and
Control of Transport Networks", draft-ietf-teas- Control of Transport Networks", draft-ietf-teas-
actn-framework-06 (work in progress), June 2017. actn-framework-11 (work in progress), October 2017.
[I-D.ietf-pce-applicability-actn] [I-D.ietf-pce-applicability-actn]
Dhody, D., Lee, Y., and D. Ceccarelli, "Applicability of Dhody, D., Lee, Y., and D. Ceccarelli, "Applicability of
Path Computation Element (PCE) for Abstraction and Path Computation Element (PCE) for Abstraction and
Control of TE Networks (ACTN)", draft-ietf-pce- Control of TE Networks (ACTN)", draft-ietf-pce-
applicability-actn-00 (work in progress), June 2017. applicability-actn-02 (work in progress), October 2017.
[I-D.litkowski-pce-state-sync] [I-D.litkowski-pce-state-sync]
Litkowski, S., Sivabalan, S., and D. Dhody, "Inter Litkowski, S., Sivabalan, S., and D. Dhody, "Inter
Stateful Path Computation Element communication Stateful Path Computation Element communication
procedures", draft-litkowski-pce-state-sync-01 (work in procedures", draft-litkowski-pce-state-sync-02 (work in
progress), February 2017. progress), August 2017.
[I-D.ietf-pce-hierarchy-extensions] [I-D.ietf-pce-hierarchy-extensions]
Zhang, F., Zhao, Q., Dios, O., Casellas, R., and D. King, Zhang, F., Zhao, Q., Dios, O., Casellas, R., and D. King,
"Extensions to Path Computation Element Communication "Extensions to Path Computation Element Communication
Protocol (PCEP) for Hierarchical Path Computation Elements Protocol (PCEP) for Hierarchical Path Computation Elements
(PCE)", draft-ietf-pce-hierarchy-extensions-03 (work in (PCE)", draft-ietf-pce-hierarchy-extensions-03 (work in
progress), July 2016. progress), July 2016.
[I-D.ietf-pce-pceps] [I-D.ietf-pce-pcep-yang]
Lopez, D., Dios, O., Wu, W., and D. Dhody, "Secure Dhody, D., Hardwick, J., Beeram, V., and j.
Transport for PCEP", draft-ietf-pce-pceps-14 (work in jefftant@gmail.com, "A YANG Data Model for Path
progress), May 2017. Computation Element Communications Protocol (PCEP)",
draft-ietf-pce-pcep-yang-05 (work in progress), June 2017.
Appendix A. Contributor Addresses Appendix A. Contributor Addresses
Avantika Avantika
Huawei Technologies Huawei Technologies
Divyashree Techno Park, Whitefield Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560066 Bangalore, Karnataka 560066
India India
EMail: s.avantika.avantika@gmail.com EMail: s.avantika.avantika@gmail.com
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