draft-ietf-teas-pce-central-control-01.txt   draft-ietf-teas-pce-central-control-02.txt 
TEAS Working Group A. Farrel, Ed. TEAS Working Group A. Farrel, Ed.
Internet-Draft Juniper Networks Internet-Draft Juniper Networks
Intended status: Informational Q. Zhao, Ed. Intended status: Informational Q. Zhao, Ed.
Expires: June 8, 2017 R. Li Expires: November 15, 2017 R. Li
Huawei Technologies Huawei Technologies
C. Zhou C. Zhou
Cisco Systems Cisco Systems
December 5, 2016 May 14, 2017
An Architecture for Use of PCE and PCEP in a Network with Central An Architecture for Use of PCE and PCEP in a Network with Central
Control Control
draft-ietf-teas-pce-central-control-01 draft-ietf-teas-pce-central-control-02
Abstract Abstract
The Path Computation Element (PCE) has become established as a core The Path Computation Element (PCE) has become established as a core
component of Software Defined Networking (SDN) systems. It can component of Software Defined Networking (SDN) systems. It can
compute optimal paths for traffic across a network for any definition compute optimal paths for traffic across a network for any definition
of "optimal" and can also monitor changes in resource availability of "optimal" and can also monitor changes in resource availability
and traffic demands to update the paths. and traffic demands to update the paths.
Conventionally, the PCE has been used to derive paths for MPLS Label Conventionally, the PCE has been used to derive paths for MPLS Label
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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 http://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."
This Internet-Draft will expire on June 8, 2017. This Internet-Draft will expire on November 15, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2016 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
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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
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3.1.1. Applicability to Control Plane Operated Networks . . 12 3.1.1. Applicability to Control Plane Operated Networks . . 12
3.1.2. Static LSPs in MPLS . . . . . . . . . . . . . . . . . 12 3.1.2. Static LSPs in MPLS . . . . . . . . . . . . . . . . . 12
3.1.3. MPLS Multicast . . . . . . . . . . . . . . . . . . . 13 3.1.3. MPLS Multicast . . . . . . . . . . . . . . . . . . . 13
3.1.4. Transport SDN . . . . . . . . . . . . . . . . . . . . 13 3.1.4. Transport SDN . . . . . . . . . . . . . . . . . . . . 13
3.1.5. Segment Routing . . . . . . . . . . . . . . . . . . . 13 3.1.5. Segment Routing . . . . . . . . . . . . . . . . . . . 13
3.1.6. Service Function Chaining . . . . . . . . . . . . . . 14 3.1.6. Service Function Chaining . . . . . . . . . . . . . . 14
3.2. High-Level Applicability . . . . . . . . . . . . . . . . 14 3.2. High-Level Applicability . . . . . . . . . . . . . . . . 14
3.2.1. Traffic Engineering . . . . . . . . . . . . . . . . . 14 3.2.1. Traffic Engineering . . . . . . . . . . . . . . . . . 14
3.2.2. Traffic Classification . . . . . . . . . . . . . . . 15 3.2.2. Traffic Classification . . . . . . . . . . . . . . . 15
3.2.3. Service Delivery . . . . . . . . . . . . . . . . . . 15 3.2.3. Service Delivery . . . . . . . . . . . . . . . . . . 15
4. Protocol Implications . . . . . . . . . . . . . . . . . . . . 16 4. Protocol Implications / Guidance for Solution Developers . . 16
5. Security Considerations . . . . . . . . . . . . . . . . . . . 16 5. Security Considerations . . . . . . . . . . . . . . . . . . . 16
6. Manageability Considerations . . . . . . . . . . . . . . . . 17 6. Manageability Considerations . . . . . . . . . . . . . . . . 17
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 17 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 17
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 18 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 18
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 18 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 18
10.1. Normative References . . . . . . . . . . . . . . . . . . 18 10.1. Normative References . . . . . . . . . . . . . . . . . . 18
10.2. Informative References . . . . . . . . . . . . . . . . . 18 10.2. Informative References . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21
1. Introduction 1. Introduction
The Path Computation Element (PCE) [RFC4655] was developed to offload The Path Computation Element (PCE) [RFC4655] was developed to offload
path computation function from routers in an MPLS traffic engineered path computation function from routers in an MPLS traffic engineered
network. Since then, the role and function of the PCE has grown to network. Since then, the role and function of the PCE has grown to
cover a number of other uses (such as GMPLS [RFC7025]) and to allow cover a number of other uses (such as GMPLS [RFC7025]) and to allow
delegated control [I-D.ietf-pce-stateful-pce] and PCE-initiated use delegated control [I-D.ietf-pce-stateful-pce] and PCE-initiated use
of network resources [I-D.ietf-pce-pce-initiated-lsp]. of network resources [I-D.ietf-pce-pce-initiated-lsp].
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components and is flexible to a number of deployment models and use components and is flexible to a number of deployment models and use
cases. In this hybrid approach (shown in Figure 3) the network cases. In this hybrid approach (shown in Figure 3) the network
controller is PCE-enabled and can also speak PCEP as the SBI (i.e., controller is PCE-enabled and can also speak PCEP as the SBI (i.e.,
it can communicate with each node along the path using PCEP). That it can communicate with each node along the path using PCEP). That
means that the controller can communicate with a conventional control means that the controller can communicate with a conventional control
plane-enabled NE using PCEP and can also use the same protocol to plane-enabled NE using PCEP and can also use the same protocol to
program individual NEs. In this way the PCE-based controller can program individual NEs. In this way the PCE-based controller can
control a wider range of networks and deliver many different control a wider range of networks and deliver many different
functions as described in Section 3. functions as described in Section 3.
There will be a trade-off in different application scenarios. In
some cases the use of a control plane will simplify deployment (for
example, by distributing recovery actions), and in other cases a
control plane may add operational complexity.
PCEP is essentially already capable of acting as an SBI and only PCEP is essentially already capable of acting as an SBI and only
small, use case- specific modifications to the protocol are needed to small, use case- specific modifications to the protocol are needed to
support this architecture. The implications for the protocol are support this architecture. The implications for the protocol are
discussed further in Section 4. discussed further in Section 4.
-------------------------------------------- --------------------------------------------
| Orchestrator / Service Manager / OSS / NMS | | Orchestrator / Service Manager / OSS / NMS |
-------------------------------------------- --------------------------------------------
^ ^
| |
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transport networks. In this respect a transport network is a network transport networks. In this respect a transport network is a network
built from any technology below the IP layer and designed to carry built from any technology below the IP layer and designed to carry
traffic transparently in a connection-oriented way. Thus, an MPLS traffic transparently in a connection-oriented way. Thus, an MPLS
traffic engineering network is a transport network although it is traffic engineering network is a transport network although it is
more common to consider technologies such as Time Division more common to consider technologies such as Time Division
Multiplexing (TDM) and Optical Transport Networks (OTN). Multiplexing (TDM) and Optical Transport Networks (OTN).
Transport networks may be operated with or without a control plane Transport networks may be operated with or without a control plane
and may have point-to-point or point-to-multipoint connections. and may have point-to-point or point-to-multipoint connections.
Thus, all of the considerations in Section 3.1.1, Section 3.1.2, and Thus, all of the considerations in Section 3.1.1, Section 3.1.2, and
Section 3.1.3 apply. It may be the case that additional technology- Section 3.1.3 apply so that the normal PCEP message allow a PCE-based
specific parameters are needed to configure the NEs and these central controller to provision a transport network. It is usually
parameters will need to be carried in the PCEP messages. the case that additional technology-specific parameters are needed to
configure the NEs or LSPs in transport networks: parameters such as
optical characteristic. Such parameters will need to be carried in
the PCEP messages: new protocol extensions may be needed, and some
are already being worked on in [I-D.ietf-pce-wson-rwa-ext].
3.1.5. Segment Routing 3.1.5. Segment Routing
Segment routing is described in [I-D.ietf-spring-segment-routing]. Segment routing is described in [I-D.ietf-spring-segment-routing].
It relies on a series of forwarding instructions being placed in the It relies on a series of forwarding instructions being placed in the
header or a packet. At each hop in the network a router looks at the header or a packet. At each hop in the network a router looks at the
first instruction and may: continue to forward the packet unchanged; first instruction and may: continue to forward the packet unchanged;
strip the top instruction and forward the packet; or strip the top strip the top instruction and forward the packet; or strip the top
instruction, insert some additional instructions, and forward the instruction, insert some additional instructions, and forward the
packet. packet.
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or Ethernet VPNs [RFC7432]), or Pseudowires [RFC3985]. or Ethernet VPNs [RFC7432]), or Pseudowires [RFC3985].
Delivering services over a network in an optimal way requires Delivering services over a network in an optimal way requires
coordination in the way that network resources are allocated to coordination in the way that network resources are allocated to
support the services. A PCE-based central controller can consider support the services. A PCE-based central controller can consider
the whole network and all components of a service at once when the whole network and all components of a service at once when
planning how to deliver the service. It can then use PCEP to manage planning how to deliver the service. It can then use PCEP to manage
the network resources and to install the necessary associations the network resources and to install the necessary associations
between those resources. between those resources.
4. Protocol Implications 4. Protocol Implications / Guidance for Solution Developers
PCEP is a push-pull protocol that is designed to move requests and PCEP is a push-pull protocol that is designed to move requests and
responses between a server (the PCE) and clients (the PCCs, i.e., the responses between a server (the PCE) and clients (the PCCs, i.e., the
network elements). In particular, it has a message (PCInitiate network elements). In particular, it has a message (PCInitiate
[I-D.ietf-pce-pce-initiated-lsp]) that can be sent by the PCE to [I-D.ietf-pce-pce-initiated-lsp]) that can be sent by the PCE to
install state or cause actions at the PCC, and a response message install state or cause actions at the PCC, and a response message
(PCRpt) that is used to confirm the request. (PCRpt) that is used to confirm the request.
As such, there is an expectation that only relatively minor changes As such, there is an expectation that only relatively minor changes
to PCEP are required to support the concept of a PCE-based to PCEP are required to support the concept of a PCE-based
controller. The only work expected to be needed is small extensions controller. The only work expected to be needed is extensions to
to carry additional or specific information elements for the existing PCEP messages to carry additional or specific information
individual use cases. Where possible, consistent with the general elements for the individual use cases, which maintain backward
principles of how protocols are extended, any additions to the compatibility and do not impact existing PCEP deployments. Where
protocol should be made in a generic way such that they are open to possible, consistent with the general principles of how protocols are
use in a range of applications. extended, any additions to the protocol should be made in a generic
way such that they are open to use in a range of applications.
It is anticipated that new documents will be produced for each use It is anticipated that new documents will be produced for each use
case dependent on support and demand. Such documents will explain case dependent on support and demand. Such documents will explain
the use case and define the necessary protocol extensions. the use case and define the necessary protocol extensions.
Protocol extensions could have impact on existing PCEP deployments
and the interoperability between different implementations. It is
anticipated that changes of the PCEP protocol or addition of
information elements could require additional testing to ensure
interoperability between different PCEP implementations.
It is reasonable to expect that implementations are able to select a
subset or profile of the protocol extensions and PCEP features that
are relevant for the application scenario in which they will be
deployed. Identification of these profiles should form part of the
protocol itself so that interoperability can be easily determined and
so that testing can be limited to the specific profiles.
5. Security Considerations 5. Security Considerations
Security considerations for a PCE-based controller are little Security considerations for a PCE-based controller are little
different from those for any other PCE system. That is, the different from those for any other PCE system. That is, the
operation relies heavily on the use and security of PCEP and so operation relies heavily on the use and security of PCEP and so
consideration should be given to the security features discussed in consideration should be given to the security features discussed in
[RFC5440] and the additional mechanisms described in [RFC5440] and the additional mechanisms described in
[I-D.ietf-pce-pceps]. [I-D.ietf-pce-pceps].
It should be observed that the trust model of a network that operates It should be observed that the trust model of a network that operates
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each individual NE. This model may be considerably easier to manage each individual NE. This model may be considerably easier to manage
and so is more likely to be operated with a high level of security. and so is more likely to be operated with a high level of security.
However, debate will rage over overall system security and the However, debate will rage over overall system security and the
opportunity for attacks in an architecture with a central controller opportunity for attacks in an architecture with a central controller
since the network can be vulnerable to denial of service attacks on since the network can be vulnerable to denial of service attacks on
the controller, and the forwarding system may be harmed by attacks on the controller, and the forwarding system may be harmed by attacks on
the messages sent to individual NEs. In short, while the the messages sent to individual NEs. In short, while the
interactions with a PCE-based controller are not substantially interactions with a PCE-based controller are not substantially
different from those in any other SDN architecture, the security different from those in any other SDN architecture, the security
implications of SDN are still open for discussion. The IRTF's SDN implications of SDN are still open for discussion. The IRTF's SDN
Research Group (SDNRG) continues to discuss this topic. Research Group (SDNRG) discussed this topic.
It is expected that each new document that is produced for a specific It is expected that each new document that is produced for a specific
use case will also include considerations of the security impacts of use case will also include considerations of the security impacts of
the use of a PCE-based central controller on the network type and the use of a PCE-based central controller on the network type and
services being managed. services being managed.
6. Manageability Considerations 6. Manageability Considerations
The architecture described in this document is a management The architecture described in this document is a management
architecture: the PCE-based controller is a management component that architecture: the PCE-based controller is a management component that
controls the network through a southbound management protocol (PCEP). controls the network through a southbound management protocol (PCEP).
The use of different PCEP options and protocol extensions may have an
impact on interoperability, which is a management issue. As noted in
Section 4, protocol extensions should be done in a way that makes it
possible to identify profiles of PCEP to aid interoperability and
this will aid deployment and manageability.
RFC 5440 [RFC5440] contains a substantive manageability RFC 5440 [RFC5440] contains a substantive manageability
considerations section that examines how a PCE-based system and a considerations section that examines how a PCE-based system and a
PCE-enabled system may be managed. A MIB module for PCEP was PCE-enabled system may be managed. A MIB module for PCEP was
published as RFC 7420 [RFC7420] and a YANG module for PCEP has also published as RFC 7420 [RFC7420] and a YANG module for PCEP has also
been proposed [I-D.pkd-pce-pcep-yang]. been proposed [I-D.pkd-pce-pcep-yang].
7. IANA Considerations 7. IANA Considerations
This document makes no requests for IANA action. This document makes no requests for IANA action.
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[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>.
10.2. Informative References 10.2. Informative References
[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-07 (work in Model", draft-ietf-pce-pce-initiated-lsp-09 (work in
progress), July 2016. progress), March 2017.
[I-D.ietf-pce-pceps] [I-D.ietf-pce-pceps]
Lopez, D., Dios, O., Wu, W., and D. Dhody, "Secure Lopez, D., Dios, O., Wu, Q., and D. Dhody, "Secure
Transport for PCEP", draft-ietf-pce-pceps-10 (work in Transport for PCEP", draft-ietf-pce-pceps-12 (work in
progress), July 2016. progress), April 2017.
[I-D.ietf-pce-stateful-pce] [I-D.ietf-pce-stateful-pce]
Crabbe, E., Minei, I., Medved, J., and R. Varga, "PCEP Crabbe, E., Minei, I., Medved, J., and R. Varga, "PCEP
Extensions for Stateful PCE", draft-ietf-pce-stateful- Extensions for Stateful PCE", draft-ietf-pce-stateful-
pce-18 (work in progress), December 2016. pce-18 (work in progress), December 2016.
[I-D.ietf-pce-wson-rwa-ext]
Lee, Y. and R. Casellas, "PCEP Extension for WSON Routing
and Wavelength Assignment", draft-ietf-pce-wson-rwa-ext-06
(work in progress), December 2016.
[I-D.ietf-spring-segment-routing] [I-D.ietf-spring-segment-routing]
Filsfils, C., Previdi, S., Decraene, B., Litkowski, S., Filsfils, C., Previdi, S., Decraene, B., Litkowski, S.,
and R. Shakir, "Segment Routing Architecture", draft-ietf- and R. Shakir, "Segment Routing Architecture", draft-ietf-
spring-segment-routing-10 (work in progress), November spring-segment-routing-11 (work in progress), February
2016. 2017.
[I-D.pkd-pce-pcep-yang] [I-D.pkd-pce-pcep-yang]
Dhody, D., Hardwick, J., Beeram, V., and j. Dhody, D., Hardwick, J., Beeram, V., and j.
jefftant@gmail.com, "A YANG Data Model for Path jefftant@gmail.com, "A YANG Data Model for Path
Computation Element Communications Protocol (PCEP)", Computation Element Communications Protocol (PCEP)",
draft-pkd-pce-pcep-yang-06 (work in progress), July 2016. draft-pkd-pce-pcep-yang-06 (work in progress), July 2016.
[I-D.zhao-pce-pcep-extension-for-pce-controller] [I-D.zhao-pce-pcep-extension-for-pce-controller]
Zhao, Q., Li, Z., Dhody, D., and C. Zhou, "PCEP Procedures Zhao, Q., Li, Z., Dhody, D., and C. Zhou, "PCEP Procedures
and Protocol Extensions for Using PCE as a Central and Protocol Extensions for Using PCE as a Central
Controller (PCECC) of LSPs", draft-zhao-pce-pcep- Controller (PCECC) of LSPs", draft-zhao-pce-pcep-
extension-for-pce-controller-03 (work in progress), March extension-for-pce-controller-04 (work in progress),
2016. January 2017.
[I-D.zhao-teas-pcecc-use-cases] [I-D.zhao-teas-pcecc-use-cases]
Zhao, Q., Li, Z., Khasanov, B., Ke, Z., Fang, L., Zhou, Zhao, Q., Li, Z., Khasanov, B., Ke, Z., Fang, L., Zhou,
C., Communications, T., Rachitskiy, A., and A. Gulida, C., Communications, T., Rachitskiy, A., and A. Gulida,
"The Use Cases for Using PCE as the Central "The Use Cases for Using PCE as the Central
Controller(PCECC) of LSPs", draft-zhao-teas-pcecc-use- Controller(PCECC) of LSPs", draft-zhao-teas-pcecc-use-
cases-02 (work in progress), October 2016. cases-02 (work in progress), October 2016.
[RFC2702] Awduche, D., Malcolm, J., Agogbua, J., O'Dell, M., and J. [RFC2702] Awduche, D., Malcolm, J., Agogbua, J., O'Dell, M., and J.
McManus, "Requirements for Traffic Engineering Over MPLS", McManus, "Requirements for Traffic Engineering Over MPLS",
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