Network Working Group Tomohiro Otani
Internet-Draft KDDI
Intended status: Informational Kenichi Ogaki
KDDI R&D Labs
Diego Caviglia
Ericsson
Fatai Zhang
Huawei
Expires: December 27, 2012 June 27, 2012
Requirements for GMPLS applications of PCE
Document: draft-ietf-pce-gmpls-aps-req-06.txt
Status of this Memo
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This Internet-Draft will expire on December 27, 2012.
Abstract
The initial effort of PCE WG is specifically focused on MPLS (Multi-
protocol label switching). As a next step, this draft describes
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functional requirements for GMPLS (Generalized MPLS) application of
PCE (Path computation element).
Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC-2119 [RFC2119].
Table of Contents
1. Introduction ................................................. 2
2. Terminology .................................................. 3
3. GMPLS applications of PCE .................................... 3
3.1. GMPLS network model ..................................... 3
3.2. Path computation in GMPLS network ....................... 4
3.3. Unnumbered Interfaces ................................... 6
3.4. Asymmetric Bandwidth Path Computation ................... 6
4. Requirements for GMPLS application of PCE .................... 6
4.1. Requirements of Path Computation Request ................ 6
4.2. Requirements of Path Computation Reply .................. 8
4.3. GMPLS PCE Management .................................... 9
5. Security consideration ....................................... 9
6. IANA Considerations .......................................... 9
7. Acknowledgement .............................................. 9
8. References ................................................... 9
8.1. Normative References..................................... 9
8.2. Informative References................................... 11
9. Authors' Addresses ........................................... 13
1. Introduction
The initial effort of PCE WG is 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
networks 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 (non-packet switch capable)
GMPLS networks. This document complements these documents 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 series of PCE related
protocols.
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Note that the requirements for inter-layer traffic engineering
described in [RFC6457] 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 more stringent than that of MPLS TE LSPs [RFC4216],
because the additional constraints, e.g., interface switching
capability, link encoding, link protection capability and so forth
need to be considered to establish GMPLS LSPs [CSPF]. GMPLS
signaling protocol [RFC3471, RFC3473] is designed taking into
account bi-directionality, switching type, encoding type, SRLG, and
protection attributes of the TE links spanned by the path, as well
as LSP encoding and switching type for the end points, appropriately.
This document provides the investigated results of GMPLS
applications of PCE for the support of GMPLS path computation. This
document also provides requirements for GMPLS applications of PCE in
GMPLS intra-domain and inter-domain environments.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
3. GMPLS applications of PCE
3.1. GMPLS network model
Figure 1 depicts a typical network, consisting of several GMPLS
domains, assumed in this document. D1, D2, D3 and D4 have multiple
inter-domain links, while D5 has only one inter-domain link. These
domains follow the definition in [RFC4726].
+---------+
+---------|GMPLS D2|----------+
| +----+----+ |
+----+----+ | +----+----+ +---------+
|GMPLS D1| | |GMPLS D4|---|GMPLS D5|
+----+----+ | +----+----+ +---------+
| +----+----+ |
+---------|GMPLS D3|----------+
+---------+
Figure 1: GMPLS Inter-domain network model.
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Each domain is configured using various switching and link
technologies defined in [RFC3945] and an end-to-end route needs to
respect TE link attributes like switching capability, encoding type,
etc., making the problem a bit different from the case of classical
(packet) MPLS. In order to route from one GMPLS domain to another
GMPLS domain appropriately, each domain manages traffic engineering
database (TED) by PCE, and exchanges or provides route information
of paths, while concealing its internal topology information.
3.2. Path computation in GMPLS network
[CSPF] describes consideration of GMPLS TE attributes during path
computation. Figure 2 depicts a typical GMPLS network, consisting of
an ingress link, a transit link as well as an egress link, to
investigate a consistent guideline 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 2: 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 2) must be 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) should
be consistent with switching type of a LSP to be created.
(3) Encoding-types of all transit links should be consistent with
encoding type of a LSP to be created.
[CSPF] indicates the possible tables of switching capability,
encoding type and bandwidth at the ingress link, transiting links
and the egress link which need to be satisfied with GMPLS path
computation of the created LSP.
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The non-packet GMPLS networks (e.g., GMPLS-based TDM networks) are
usually responsible for transmitting data for the client layer.
These GMPLS 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 non-packet networks, for example, GMPLS-based TDM
networks, are described in Figure 3. In order to simplify the
description, this document just discusses the scenario in SDH
networks as an example. The scenarios in SONET or G.709 ODUk layer
networks are similar to this scenario.
N1 N2
+-----+ +------+ +------+
| |-------| |--------------| | +-------+
+-----+ | |---| | | | |
A1 +------+ | +------+ | |
| | | +-------+
| | | PCE
| | |
| +------+ |
| | | |
| | |-----| |
| +------+ | |
| N5 | |
| | |
+------+ +------+
| | | | +-----+
| |--------------| |--------| |
+------+ +------+ +-----+
N3 N4 A2
Figure 3: A simple TDM(SDH) network
Figure 3 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 connection from
N1 to N4, and it could also be provided by three concatenated VC3
connections (Contiguous or Virtual concatenation) from N1 to N4.
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In this scenario, when the ingress node (e.g., N1) receives a client
service transmitting request, the type of connections (one VC4 or
three concatenated VC3) could be determined by PCC (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
message. PCE should consider those parameters during path
computation. The route information (co-route or separated-route)
should be specified in a PCRep message if path computation is
performed successfully.
3.3. Unnumbered Interfaces
GMPLS supports unnumbered interface ID that is defined in [RFC 3477],
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 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.
3.4. 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.
4. Requirements for GMPLS application of PCE
In this section, we describe requirements for GMPLS applications of
PCE in order to establish GMPLS LSP.
4.1. Requirements of Path Computation Request
As for path computation in GMPLS networks as discussed in section 3,
the PCE should consider the GMPLS TE attributes appropriately
according to tables in [CSPF] once a PCC or another PCE requests a
path computation. Indeed, the path calculation request message from
the PCC or the PCE must contain the information specifying
appropriate attributes. According to [RFC5440],[PCEP-EXT],[ PCE-
WSON-REQ] and to RSVP procedures like explicit label
control(ELC),the additional attributes introduced are as follows:
[RFC5440]
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(1) Switching capability: PSC1-4, L2SC, DCSC [RFC6002], 802_1 PBB-TE
[RFC6060], TDM, LSC, FSC
(2) Encoding type: as defined in [RFC4202], [RFC4203], e.g.,
Ethernet, SONET/SDH, Lambda, etc.
(3) Signal Type: Indicates the type of elementary signal that
constitutes the requested LSP. A lot of signal types with different
granularity have been defined in SONET/SDH and G.709 ODUk, such as
VC11, VC12, VC2, VC3 and VC4 in SDH, and ODU1, ODU2 and ODU3 in
G.709 ODUk. See[RFC4606] , [RFC4328]and [OSPF-G709] or [RSVP-TE-
G709].
(4) Concatenation Type: In SDH/SONET and G.709 ODUk networks, 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 wavelength label as defined
in [RFC6205], or labels defined in [RFC4606], [RFC6060] or [RFC6002].
(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) The PCC/PCE should be able to provide label restrictions
similar to RSVP on the requests/responses
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4.2. Requirements of Path Computation Reply
As described above, a PCC must support to initiate a PCReq message
specifying above mentioned attributes. The 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 PCRep message must be extended to meet the following
requirements.
(1) Concatenation path computation
In the case of concatenation path computation, when a PCE receives
the PCReq message specifying the concatenation constraints described
in section 4.1, the PCE should compute the path which satisfies the
specified concatenation constraints.
For contiguous concatenation path computation, the routes of each
member signal must be co-routed 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 virtual concatenation path computation, only the ingress/egress
interfaces need to support virtual concatenation capability and
maybe there are 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 that 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 doesn't specify the label when requesting a
label-resctricted path and the PCE is capable of performing the
route 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 but is
only one instance of it. More generally in GMPLS networks label
switching and selection constraint may apply and a PCC may request a
PCE to take label constraint into account and return an ERO
containing the labels or set of label that fulfill the PCC request.
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The PCReq aspects are covered in section 4.1 in the requirements 6,
12 and 13.
(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).
Therefore, the PCRep should be capable of indicating which one is
working or protection route.
4.3. GMPLS PCE Management
PCE related Management Information Bases must consider extensions to
be satisfied with requirements for GMPLS applications. For
extensions, [RFC4802] are defined to manage TE database and may be
referred to accommodate GMPLS TE attributes in the PCE.
5. Security consideration
PCE extensions to support GMPLS should be considered under the same
security as current PCE work. This extension will not change the
underlying security issues.
6. IANA Considerations
This document has no actions for IANA.
7. Acknowledgement
The author would like to express the thanks to Shuichi Okamoto for
their comments.
8. References
8.1. Normative References
[RFC2119] S. Bradner, "Key words for use in RFCs to indicate
requirements levels", RFC 2119, March 1997.
[RFC3471] Berger, L., "Generalized Multi-Protocol Label Switching
(MPLS) Signaling Functional Description", RFC 3471,
January 2003.
[RFC3473] Berger, L., "Generalized Multi-Protocol Label Switching
(MPLS) Signaling - Resource ReserVation Protocol Traffic
Engineering (RSVP-TE) Extensions", RFC 3473, January 2003.
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[RFC3477] K.Kompella,et al,"Signalling Unnumbered Links in Resource
ReSerVation Protocol-Traffic Engineering(RSVP-TE)",January
2003.
[RFC3630] D. Katz et al., "Traffic Engineering (TE) Extensions to
OSPF Version 2", RFC3630, September 2003.
[RFC3945] E. Mannie, et al, "Generalized Multi-Protocol Label
Switching Architecture", RFC3945, October, 2004.
[RFC4202] K. Kompella, and Y. Rekhter, "Routing Extensions in
Support of Generalized Multi-Protocol Label Switching",
RFC4202, Oct. 2005.
[RFC4203] K. Kompella, and Y. Rekhter, "OSPF Extensions in Support
of Generalized Multi-Protocol Label Switching", RFC4203,
Oct. 2005.
[RFC4328] D. Papadimitriou, Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Extensions for G.709 Optical
Transport Networks Control", RFC4328, January 2006.
[RFC6387] Takacs, A., Berger, L., Caviglia, D., Fedyk, D., and J.
Meuric, "GMPLS Asymmetric Bandwidth Bidirectional Label
Switched Paths (LSPs)", RFC 6387, September 2011.
[RFC4606] E. Mannie and D. Papadimitriou, "Generalized Multi-
Protocol Label Switching (GMPLS) Extensions for
Synchronous Optical Network (SONET) and Synchronous
Digital Hierarchy (SDH) Control", RFC4606, August 2006.
[RFC4802] T. Nadeau and A. Farrel, Ed., "Generalized Multiprotocol
Label Switching (GMPLS) Traffic Engineering Management
Information Base", RFC4802, Feb. 2007.
[RFC4872] J.P. Lang, Ed., "RSVP-TE Extensions in Support of End-to-
End Generalized Multi-Protocol Label Switching (GMPLS)
Recovery", RFC4872, May 2007.
[RFC5440] J.P. Vasseur, et al, "Path Computation Element (PCE)
Communication Protocol (PCEP)", RFC5440, March 2009.
[RFC6002] Lou Berger, et al.,"Generalized MPLS (GMPLS) Data Channel
Switching Capable (DCSC) and Channel Set Label Extensions",
RFC6002, October 2010.
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[RFC6060] Don Fedyk, et al., "Generalized Multiprotocol Label
Switching (GMPLS) control of Ethernet PBB-TE", RFC6060,
March 2011.
[RFC6205] T. Otani, Ed., "Generalized Labels for G.694 Lambda-
Switching Capable Label Switching Routers", RFC6205, March
2011
[RFC6387] Takacs, et. al., "GMPLS Asymmetric Bandwidth Bidirectional
Label Switched Paths (LSPs)", RFC6387, September 2011
8.2. Informative References
[RFC4216] R. Zhan, et al, "MPLS Inter-Autonomous System (AS) Traffic
Engineering (TE) Requirements", RFC4216, November 2005.
[RFC4655] A. Farrel, et al, "A Path Computation Element (PCE)-Based
Architecture", RFC4655, Aug., 2006.
[RFC4657] J. Ash, et al, "Path computation element (PCE)
communication protocol generic requirements", RFC4657,
Sept., 2007.
[RFC4726] A. Farrel, et al, "A framework for inter-domain MPLS
traffic engineering", RFC4726, November 2006.
[RFC5394] I. Bryskin et al., "Policy-Enabled Path Computation
Framework", RFC5394, December 2008.
[RFC6457] T.Takeda,et al,"PCC-PCE Communication and PCE
Discovery Requirements for Inter-Layer
Engineering",RFC6457,December 2011.
[CSPF] T. Otani, et al, "Considering Generalized Multiprotocol
Label Switching Traffic Engineering Attributes During Path
Computation", draft-otani-ccamp-gmpls-cspf-constraints-
07.txt, Feb., 2008.
[PCEP-EXT] C.Margaria,et al, "PCEP extensions for GMPLS",draft-ietf-
pce-gmpls-PCEP-EXTs, in progress.
[PCE-WSON-REQ] Y.Lee, et al,"PCEP Requirements for WSON Routing and
Wavelength Assignment",draft-ietf-pce-wson-routing-
wavelength, in progress.
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[OSPF-G709] D.Ceccarelli,et al,"Traffic Engineering Extensions to
OSPF for Generalized MPLS(GMPLS) Control of Evolving G.709
OTN Networks", in progress.
[RSVP-TE-G709] Fatai Zhang,et al,"Generalized Multi-Protocol Label
Switching(GMPLS) Signaling Extensions for the evolving
G.709 Optical Transport Network Control", in progress.
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9. Authors' Addresses
Tomohiro Otani
KDDI Corporation
2-3-2 Nishi-shinjuku Shinjuku-ku, Tokyo 163-8003 Japan
Phone: +81-3-3347-6006
Email: tm-otani@kddi.com
Kenichi Ogaki
KDDI R&D Laboratories, Inc.
2-1-15 Ohara Fujimino-shi, Saitama 356-8502 Japan
Phone: +81-49-278-7897
Email: ogaki@kddilabs.jp
Diego Caviglia
Ericsson
16153 Genova Cornigliano, ITALY
Phone: +390106003736
Email: diego.caviglia@ericsson.com
Fatai Zhang
Huawei Technologies
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
Nokia Siemens Networks
St Martin Strasse 76
Munich, 81541
Germany
Phone: +49 89 5159 16934
Email: cyril.margaria@nsn.com
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