Network Working Group Tomohiro Otani
Internet Draft KDDI
Intended status: Informational Kenichi Ogaki
KDDI R&D Labs
Diego Caviglia
Ericsson
Fatai Zhang
Huawei
Expires: January 2011 July 6, 2010
Requirements for GMPLS applications of PCE
Document: draft-ietf-pce-gmpls-aps-req-02.txt
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Abstract
The initial effort of PCE WG is specifically focused on MPLS (Multi-
protocol label switching). As a next step, this draft describes
functional requirements for GMPLS (Generalized MPLS) application of
PCE (Path computation element).
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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 [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.......................3
3.3. Unnumbered Interface....................................5
3.4. Asymmetric Bandwidth Path Computation...................6
4. Requirement for GMPLS application of PCE.....................6
4.1. PCE requirements........................................6
4.2. PCC requirements........................................7
4.3. GMPLS PCE Management....................................7
5. Security consideration.......................................7
6. IANA Considerations..........................................7
7. Acknowledgement..............................................7
8. References...................................................7
9. Authors' Addresses...........................................9
1. Introduction
The initial effort of PCE WG is focused on solving the path
computation problem 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 photonics,
TDM-based or Ethernet-based networks as well.
[PCE-ARCH] and [PCECP-REQ] 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 consideration 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.
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 LSPs [MPLS-AS], 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
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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 the 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
GMPLS inter-domain connections, and D5 has only one GMPLS inter-
domain connection. These domains follow the definition in [RFC4726].
+---------+
+---------|GMPLS D2|----------+
| +----+----+ |
+----+----+ | +----+----+ +---------+
|GMPLS D1| | |GMPLS D4|---|GMPLS D5|
+----+----+ | +----+----+ +---------+
| +----+----+ |
+---------|GMPLS D3|----------+
+---------+
Figure 1: GMPLS Inter-domain network model.
Each domain is configured using various switching and link
technologies defined in [Arch] 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.
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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 table of switching capability, encoding
type and bandwidth at the ingress link, transiting links and the
egress link which need to be satisfied with the created LSP.
The non-packet GMPLS networks (e.g., 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 in 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.
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N1 N2
+-----+ +------+ +------+
| |-------| |--------------| | +-------+
+-----+ | |---| | | | |
A1 +------+ | +------+ | |
| | | +-------+
| | | PCE
| | |
| +------+ |
| | | |
| | |-----| |
| +------+ | |
| N5 | |
| | |
+------+ +------+
| | | | +-----+
| |--------------| |--------| |
+------+ +------+ +-----+
N3 N4 A2
Figure 3: A simple SDH network
Figure 3 shows a simple 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.
The type of connection(s) (one VC4 or three concatenated VC3) that is
required needs to be specified by PCC (e.g., N1 or NMS), but could
also be determined by PCE automatically based on policy [RFC5394].
Therefore, the signal type, the type of the concatenation and the
number of the concatenation should also be considered during path
computation for PCE.
3.3. Unnumbered Interface
GMPLS support 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 between a numbered link and
an unnumbered link, or a P2MP path between different types of
endpoints. Therefore, the PCC should be capable of indicating the
unnumbered interface ID of the endpoints in the PCReq message.
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3.4. Asymmetric Bandwidth Path Computation
As per [RFC 5467], 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. Requirement for GMPLS application of PCE
In this section, we describe requirements for GMPLS applications of
PCE in order to establish GMPLS LSP.
4.1. PCE requirements
As for path computation in GMPLS networks as discussed in section 3,
the PCE needs to 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 needs to contain the information specifying
appropriate attributes. Additional attributes to those already
defined in [PCECP] are as follows.
(1) Switching capability: PSC1-4, L2SC, DCSC [DCSC-Ext], 802_1 PBB-TE
[GMPLS-PBB-TE], 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] and [RFC4328].
(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].
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(6) Wavelength Label: as defined in [Lambda-label].
(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 [RFC 5467].
4.2. PCC requirements
As described above, a PCC needs to support to initiate path
computation request specifying abovementioned attributes. Afterwards,
GMPLS signaling will be invoked according to the responded messages
from the PCE.
4.3. GMPLS PCE Management
PCE related Management Information Bases need to consider extensions
to be satisfied with requirements for GMPLS applications. For
extensions, [GMPLS-TEMIB] 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 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
his comments.
8. References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
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[PCE-ARCH] A. Farrel, et al, "A Path Computation Element (PCE)-Based
Architecture", RFC4655, Aug., 2006.
[PCECP-REQ] J. Ash, et al, "Path computation element (PCE) communication
protocol generic requirements", RFC4657, Sept., 2007.
[MPLS-AS] R. Zhan, et al, "MPLS Inter-Autonomous System (AS) Traffic
Engineering (TE) Requirements", RFC4216, November 2005.
[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.
[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.
[RFC4726] A. Farrel, et al, "A framework for inter-domain MPLS traffic
engineering", RFC4726, November 2006.
[Arch] E. Mannie, et al, "Generalized Multi-Protocol Label
Switching Architecture", RFC3945, October, 2004.
[PCECP] J.P. Vasseur, et al, "Path Computation Element (PCE)
Communication Protocol (PCEP)", RFC5440, March 2009.
[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.
[RFC4872] J.P. Lang, Ed., "RSVP-TE Extensions in Support of End-to-End
Generalized Multi-Protocol Label Switching (GMPLS)
Recovery", RFC4872, May 2007.
[GMPLS-TEMIB] T. Nadeau and A. Farrel, Ed., "Generalized
Multiprotocol Label Switching (GMPLS) Traffic Engineering
Management Information Base", RFC4802, Feb. 2007.
[RFC3630] D. Katz et al., "Traffic Engineering (TE) Extensions to OSPF
Version 2", RFC3630, September 2003.
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[Lambda-label] T. Otani, Ed., "Generalized Labels for G.694 Lambda-
Switching Capable Label Switching Routers", draft-ietf-
ccamp-gmpls-g-694-lambda-labels, in progress.
[RFC5394] I. Bryskin et al., " Policy-Enabled Path Computation
Framework", RFC5394, December 2008.
[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.
[RFC4328] D. Papadimitriou, Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Extensions for G.709 Optical
Transport Networks Control", RFC4328, January 2006.
[DCSC-Ext] Lou Berger, et al.,"Generalized MPLS (GMPLS) Data Channel
Switching Capable (DCSC) and Channel Set Label Extensions",
in progress.
[GMPLS-PBB-TE] Don Fedyk, et al., "Generalized Multiprotocol Label
Switching (GMPLS) control of Ethernet PBB-TE", in progress.
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 Co., Ltd.
F3-5-B R&D Center, Huawei Base,
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Bantian, Longgang District
Shenzhen 518129 P.R.China
Phone: +86-755-28972912
Email: zhangfatai@huawei.com
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