Internet DRAFT - draft-ietf-pce-gmpls-aps-req
draft-ietf-pce-gmpls-aps-req
Network Working Group T. Otani
Internet-Draft K. Ogaki
Intended status: Informational KDDI
Expires: January 22, 2014 D. Caviglia
Ericsson
F. Zhang
Huawei Technologies
C. Margaria
Coriant R&D GmbH
July 21, 2013
Requirements for GMPLS applications of PCE
draft-ietf-pce-gmpls-aps-req-09.txt
Abstract
The initial effort of the PCE (Path computation element) WG was
mainly focused on MPLS. As a next step, this draft describes
functional requirements for GMPLS application of PCE.
Status of This Memo
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This Internet-Draft will expire on January 22, 2014.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. GMPLS applications of PCE . . . . . . . . . . . . . . . . . . 3
2.1. Path computation in GMPLS network . . . . . . . . . . . . 3
2.2. Unnumbered Interface . . . . . . . . . . . . . . . . . . 5
2.3. Asymmetric Bandwidth Path Computation . . . . . . . . . . 5
3. Requirements for GMPLS application of PCE . . . . . . . . . . 5
3.1. Requirements on Path Computation Request . . . . . . . . 5
3.2. Requirements on Path Computation Reply . . . . . . . . . 6
3.3. GMPLS PCE Management . . . . . . . . . . . . . . . . . . 8
4. Security Considerations . . . . . . . . . . . . . . . . . . . 8
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
6. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 8
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
7.1. Normative References . . . . . . . . . . . . . . . . . . 8
7.2. Informative References . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
The initial effort of the PCE (Path computation element) WG was
mainly focused on solving the path computation problem within a
domain or over different domains in MPLS networks. As the same case
with MPLS, service providers (SPs) have also come up with
requirements for path computation in GMPLS-controlled networks
[RFC3945] such as wavelength, TDM-based or Ethernet-based networks as
well.
[RFC4655] and [RFC4657] discuss the framework and requirements for
PCE on both packet MPLS networks and GMPLS-controlled networks. This
document complements these RFCs by providing some considerations of
GMPLS applications in the intra-domain and inter-domain networking
environments and indicating a set of requirements for the extended
definition of PCE-related protocols.
Note that the requirements for inter-layer and inter-area traffic
engineering described in [RFC6457] and [RFC4927] are outside of the
scope of this document.
Constraint-based shortest path first (CSPF) computation within a
domain or over domains for signaling GMPLS Label Switched Paths
(LSPs) is usually more stringent than that of MPLS TE LSPs [RFC4216],
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because the additional constraints, e.g., interface switching
capability, link encoding, link protection capability, SRLG (Shared
risk link group) [RFC4202] and so forth need to be considered to
establish GMPLS LSPs. GMPLS signaling protocol [RFC3473] is designed
taking into account bi-directionality, switching type, encoding type
and protection attributes of the TE links spanned by the path, as
well as LSP encoding and switching type of the end points,
appropriately.
This document provides requirements for GMPLS applications of PCE in
support of GMPLS path computation, included are requirements for both
intra-domain and inter-domain environments.
2. GMPLS applications of PCE
2.1. Path computation in GMPLS network
Figure 1 depicts a model GMPLS network, consisting of an ingress
link, a transit link as well as an egress link. We will use this
model to investigate consistent guidelines for GMPLS path
computation. Each link at each interface has its own switching
capability, encoding type and bandwidth.
Ingress Transit Egress
+-----+ link1-2 +-----+ link2-3 +-----+ link3-4 +-----+
|Node1|------------>|Node2|------------>|Node3|------------>|Node4|
| |<------------| |<------------| |<------------| |
+-----+ link2-1 +-----+ link3-2 +-----+ link4-3 +-----+
Figure 1: Path computation in GMPLS networks
For the simplicity in consideration, the below basic assumptions are
made when the LSP is created.
(1) Switching capabilities of outgoing links from the ingress and
egress nodes (link1-2 and link4-3 in Figure 1) are consistent with
each other.
(2) Switching capabilities of all transit links including incoming
links to the ingress and egress nodes (link2-1 and link3-4) are
consistent with switching type of a LSP to be created.
(3) Encoding-types of all transit links are consistent with encoding
type of a LSP to be created.
GMPLS-controlled networks (e.g., GMPLS-based TDM networks) are
usually responsible for transmitting data for the client layer.
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These GMPLS-controlled networks can provide different types of
connections for customer services based on different service
bandwidth requests.
The applications and the corresponding additional requirements for
applying PCE to, for example, GMPLS-based TDM networks, are described
in Figure 2. In order to simplify the description, this document
just discusses the scenario in SDH networks as an example. The
scenarios in SONET or OTN are similar to this scenario.
N1 N2
+-----+ +------+ +------+
| |-------| |--------------| | +-------+
+-----+ | |---| | | | |
A1 +------+ | +------+ | |
| | | +-------+
| | | PCE
| | |
| +------+ |
| | | |
| | |-----| |
| +------+ | |
| N5 | |
| | |
+------+ +------+
| | | | +-----+
| |--------------| |--------| |
+------+ +------+ +-----+
N3 N4 A2
Figure 2: A simple TDM (SDH) network
Figure 2 shows a simple TDM (SDH) network topology, where N1, N2, N3,
N4 and N5 are all SDH switches. Assume that one Ethernet service
with 100M bandwidth is required from A1 to A2 over this network. The
client Ethernet service could be provided by a VC4 container from N1
to N4, and it could also be provided by three concatenated VC3
containers (Contiguous or Virtual concatenation) from N1 to N4.
In this scenario, when the ingress node (e.g., N1) receives a client
service transmitting request, the type of containers (one VC4 or
three concatenated VC3) could be determined by PCC (Path computation
client) (e.g., N1 or NMS), but could also be determined by PCE
automatically based on policy [RFC5394]. If it is determined by PCC,
PCC should be capable of specifying the ingress node and egress node,
signal type, the type of the concatenation and the number of the
concatenation in a PCReq (Path computation request) message. PCE
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should consider those parameters during path computation. The route
information (co-route or separated-route) should be specified in a
PCRep (Path computation reply) message if path computation is
performed successfully.
As described above, PCC should be capable of specifying TE attributes
defined in the next section and PCE should compute a path
accordingly.
Where a GMPLS network is consisting of inter-domain (e.g., inter-AS
or inter-area) GMPLS-controlled networks, requirements on the path
computation follows [RFC5376] and [RFC4726].
2.2. Unnumbered Interface
GMPLS supports unnumbered interface ID that is defined in [RFC3477],
which means that the endpoints of the path may be unnumbered. It
should also be possible to request a path consisting of the mixture
of numbered links and unnumbered links, or a P2MP (Point-to-
multipoint) path with different types of endpoints. Therefore, the
PCC should be capable of indicating the unnumbered interface ID of
the endpoints in the PCReq message.
2.3. Asymmetric Bandwidth Path Computation
As per [RFC6387], GMPLS signaling can be used for setting up an
asymmetric bandwidth bidirectional LSP. If a PCE is responsible for
the path computation, the PCE should be capable of computing a path
for the bidirectional LSP with asymmetric bandwidth. It means that
the PCC should be able to indicate the asymmetric bandwidth
requirements in forward and reverse directions in the PCReq message.
3. Requirements for GMPLS application of PCE
3.1. Requirements on Path Computation Request
As for path computation in GMPLS-controlled networks as discussed in
section 2, the PCE should appropriately consider the GMPLS TE
attributes listed below once a PCC or another PCE requests a path
computation. The path calculation request message from the PCC or
the PCE must contain the information specifying appropriate
attributes. According to [RFC5440], [PCE-WSON-REQ] and to RSVP
procedures like explicit label control(ELC),the additional attributes
introduced are as follows:
(1) Switching capability/type: as defined in [RFC3471], [RFC4203]
and, all current and future values.
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(2) Encoding type: as defined in [RFC3471], [RFC4203] and, all
current and future values.
(3) Signal Type: as defined in [RFC4606] and, all current and future
values.
(4) Concatenation Type: In SDH/SONET and OTN, two kinds of
concatenation modes are defined: contiguous concatenation which
requires co-route for each member signal and requires all the
interfaces along the path to support this capability, and virtual
concatenation which allows diverse routes for the member signals and
only requires the ingress and egress interfaces to support this
capability. Note that for the virtual concatenation, it also may
specify co-routed or separated-routed. See [RFC4606] and [RFC4328]
about concatenation information.
(5) Concatenation Number: Indicates the number of signals that are
requested to be contiguously or virtually concatenated. Also see
[RFC4606] and [RFC4328].
(6) Technology-specific label(s) such as defined in [RFC4606],
[RFC6060], [RFC6002] or [RFC6205].
(7) e2e Path protection type: as defined in [RFC4872], e.g., 1+1
protection, 1:1 protection, (pre-planned) rerouting, etc.
(8) Administrative group: as defined in [RFC3630]
(9) Link Protection type: as defined in [RFC4203]
(10)Support for unnumbered interfaces: as defined in [RFC3477]
(11)Support for asymmetric bandwidth request: as defined in [RFC6387]
(12)Support for explicit label control during the path computation.
(13)Support of label restrictions in the requests/responses,
similarly to RSVP-TE ERO (Explicit route object) and XRO (Exclude
route object) as defined in [RFC3473] and [RFC4874].
3.2. Requirements on Path Computation Reply
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As described above, a PCE should compute the path that satisfies the
constraints which are specified in the PCReq message. Then the PCE
should send a PCRep message including the computation result to the
PCC. For Path Computation Reply message (PCRep) in GMPLS networks,
there are some additional requirements. The PCEP (PCE communication
protocol) PCRep message must be extended to meet the following
requirements.
(1) Path computation with concatenation
In the case of path computation involving concatenation, when a PCE
receives the PCReq message specifying the concatenation constraints
described in section 3.1, the PCE should compute a path accordingly.
For path computation involving contiguous concatenation, a single
route is required and all the interfaces along the route should
support contiguous concatenation capability. Therefore, the PCE
should compute a path based on the contiguous concatenation
capability of each interface and only one ERO which should carry the
route information for the response.
For path computation involving virtual concatenation, only the
ingress/egress interfaces need to support virtual concatenation
capability and there may be diverse routes for the different member
signals. Therefore, multiple EROs may be needed for the response.
Each ERO may represent the route of one or multiple member signals.
In the case where one ERO represents several member signals among the
total member signals, the number of member signals along the route of
the ERO must be specified.
(2) Label constraint
In the case that a PCC does not specify the exact label(s) when
requesting a label-restricted path and the PCE is capable of
performing the route computation and label assignment computation
procedure, the PCE needs to be able to specify the label of the path
in a PCRep message.
Wavelength restriction is a typical case of label restriction. More
generally in GMPLS-controlled networks label switching and selection
constraints may apply and a PCC may request a PCE to take label
constraint into account and return an ERO containing the label or set
of label that fulfil the PCC request.
(3) Roles of the routes
When a PCC specifies the protection type of an LSP, the PCE should
compute the working route and the corresponding protection route(s).
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Therefore, the PCRep should allow to distinguish the working
(nominal) and the protection routes. According to these routes,
RSVP-TE procedure appropriately creates both the working and the
protection LSPs for example with ASSOCIATION object [RFC6689].
3.3. GMPLS PCE Management
This document does not change any of the management or operational
details for networks that utilise PCE. Please refer to [RFC4655] for
an overview of this scenery. However, this document proposes the
introduction of several PCEP objects and data for the better
integration of PCE with GMPLS networks. Those protocol elements will
need to be visible in any management tools that apply to the PCE,
PCC, and PCEP. That includes, but is not limited to, adding
appropriate objects to existing PCE MIB modules that are used for
modelling and monitoring PCEP deployments [PCEP-MIB]. Ideas for what
objects are needed may be guided by the relevant GMPLS extensions in
GMPLS-TE-STD-MIB [RFC4802]."
4. Security Considerations
PCEP extensions to support GMPLS should be considered under the same
security as current PCE work and this extension will not change the
underlying security issues. Sec. 10 of [RFC5440] describes the list
of security considerations in PCEP. At the time [RFC5440] was
published, TCP Authentication Option (TCP-AO) had not been fully
specified for securing the TCP connections that underlie PCEP
sessions. TCP-AO [RFC5925] has now been published and PCEP
implementations should fully support TCP-AO according to [RFC6952].
5. IANA Considerations
This document has no actions for IANA.
6. Acknowledgement
The author would like to express the thanks to Ramon Casellas, Julien
Meuric, Adrian Farrel, Yaron Sheffer and Shuichi Okamoto for their
comments.
7. References
7.1. Normative References
[RFC3471] Berger, L., "Generalized Multi-Protocol Label Switching
(GMPLS) Signaling Functional Description", RFC 3471,
January 2003.
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[RFC3473] Berger, L., "Generalized Multi-Protocol Label Switching
(GMPLS) Signaling Resource ReserVation Protocol-Traffic
Engineering (RSVP-TE) Extensions", RFC 3473, January 2003.
[RFC3477] Kompella, K. and Y. Rekhter, "Signalling Unnumbered Links
in Resource ReSerVation Protocol - Traffic Engineering
(RSVP-TE)", RFC 3477, January 2003.
[RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630, September
2003.
[RFC3945] Mannie, E., "Generalized Multi-Protocol Label Switching
(GMPLS) Architecture", RFC 3945, October 2004.
[RFC4202] Kompella, K. and Y. Rekhter, "Routing Extensions in
Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 4202, October 2005.
[RFC4203] Kompella, K. and Y. Rekhter, "OSPF Extensions in Support
of Generalized Multi-Protocol Label Switching (GMPLS)",
RFC 4203, October 2005.
[RFC4328] Papadimitriou, D., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Extensions for G.709 Optical
Transport Networks Control", RFC 4328, January 2006.
[RFC4606] Mannie, E. and D. Papadimitriou, "Generalized Multi-
Protocol Label Switching (GMPLS) Extensions for
Synchronous Optical Network (SONET) and Synchronous
Digital Hierarchy (SDH) Control", RFC 4606, August 2006.
[RFC4802] Nadeau, T. and A. Farrel, "Generalized Multiprotocol Label
Switching (GMPLS) Traffic Engineering Management
Information Base", RFC 4802, February 2007.
[RFC4872] Lang, J., Rekhter, Y., and D. Papadimitriou, "RSVP-TE
Extensions in Support of End-to-End Generalized Multi-
Protocol Label Switching (GMPLS) Recovery", RFC 4872, May
2007.
[RFC4927] Le Roux, J., "Path Computation Element Communication
Protocol (PCECP) Specific Requirements for Inter-Area MPLS
and GMPLS Traffic Engineering", RFC 4927, June 2007.
[RFC5376] Bitar, N., Zhang, R., and K. Kumaki, "Inter-AS
Requirements for the Path Computation Element
Communication Protocol (PCECP)", RFC 5376, November 2008.
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[RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation Element
(PCE) Communication Protocol (PCEP)", RFC 5440, March
2009.
[RFC6002] Berger, L. and D. Fedyk, "Generalized MPLS (GMPLS) Data
Channel Switching Capable (DCSC) and Channel Set Label
Extensions", RFC 6002, October 2010.
[RFC6060] Fedyk, D., Shah, H., Bitar, N., and A. Takacs,
"Generalized Multiprotocol Label Switching (GMPLS) Control
of Ethernet Provider Backbone Traffic Engineering (PBB-
TE)", RFC 6060, March 2011.
[RFC6205] Otani, T. and D. Li, "Generalized Labels for Lambda-
Switch-Capable (LSC) Label Switching Routers", RFC 6205,
March 2011.
[RFC6387] Takacs, A., Berger, L., Caviglia, D., Fedyk, D., and J.
Meuric, "GMPLS Asymmetric Bandwidth Bidirectional Label
Switched Paths (LSPs)", RFC 6387, September 2011.
[RFC6689] Berger, L., "Usage of the RSVP ASSOCIATION Object", RFC
6689, July 2012.
7.2. Informative References
[PCE-WSON-REQ]
Lee, Y., Bernstein, G., Martensson, J., Takeda, T.,
Tsuritani, T., and O. de Dios, "PCEP Requirements for WSON
Routing and Wavelength Assignment", draft-ietf-pce-wson-
routing-wavelength-09 (work in progress), June 2013.
[PCEP-MIB]
Koushik, A., Emile, S., Zhao, Q., King, D., and J.
Hardwick, "PCE communication protocol (PCEP) Management
Information Base", draft-ietf-pce-pcep-mib-05 (work in
progress), July 2013.
[RFC4216] Zhang, R. and J. Vasseur, "MPLS Inter-Autonomous System
(AS) Traffic Engineering (TE) Requirements", RFC 4216,
November 2005.
[RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
Element (PCE)-Based Architecture", RFC 4655, August 2006.
[RFC4657] Ash, J. and J. Le Roux, "Path Computation Element (PCE)
Communication Protocol Generic Requirements", RFC 4657,
September 2006.
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[RFC4726] Farrel, A., Vasseur, J., and A. Ayyangar, "A Framework for
Inter-Domain Multiprotocol Label Switching Traffic
Engineering", RFC 4726, November 2006.
[RFC4874] Lee, CY., Farrel, A., and S. De Cnodder, "Exclude Routes -
Extension to Resource ReserVation Protocol-Traffic
Engineering (RSVP-TE)", RFC 4874, April 2007.
[RFC5394] Bryskin, I., Papadimitriou, D., Berger, L., and J. Ash,
"Policy-Enabled Path Computation Framework", RFC 5394,
December 2008.
[RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP
Authentication Option", RFC 5925, June 2010.
[RFC6457] Takeda, T. and A. Farrel, "PCC-PCE Communication and PCE
Discovery Requirements for Inter-Layer Traffic
Engineering", RFC 6457, December 2011.
[RFC6952] Jethanandani, M., Patel, K., and L. Zheng, "Analysis of
BGP, LDP, PCEP, and MSDP Issues According to the Keying
and Authentication for Routing Protocols (KARP) Design
Guide", RFC 6952, May 2013.
Authors' Addresses
Tomohiro Otani
KDDI Corporation
2-3-2 Nishi-shinjuku
Shinjuku-ku, Tokyo
Japan
Phone: +81-(3) 3347-6006
Email: tm-otani@kddi.com
Kenichi Ogaki
KDDI Corporation
3-10-10 Iidabashi
Chiyoda-ku, Tokyo
Japan
Phone: +81-(3) 6678-0284
Email: ke-oogaki@kddi.com
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Diego Caviglia
Ericsson
16153 Genova Cornigliano
Italy
Phone: +390106003736
Email: diego.caviglia@ericsson.com
Fatai Zhang
Huawei Technologies Co., Ltd.
F3-5-B R&D Center, Huawei Base
Bantian, Longgang District, Shenzhen 518129
P.R.China
Phone: +86-755-28972912
Email: zhangfatai@huawei.com
Cyril Margaria
Coriant R&D GmbH
St Martin Strasse 76
Munich, 81541
Germany
Phone: +49 89 5159 16934
Email: cyril.margaria@coriant.com
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