Network Working Group Tomohiro Otani
Internet-Draft KDDI
Intended status: Informational Kenichi Ogaki
Expires: January, 2010 KDDI R&D Labs
Diego Caviglia
Ericsson
Fatai Zhang
Huawei
July 8, 2009
Requirements for GMPLS applications of PCE
Document: draft-ietf-pce-gmpls-aps-req-01.txt
Status of this Memo
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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).
Table of Contents
Status of this Memo..............................................1
Abstract.........................................................1
1. Introduction..................................................3
2. Conventions used in this document.............................3
3. GMPLS applications of PCE.....................................3
4. Requirement for GMPLS application of PCE......................5
5. Security consideration........................................6
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6. IANA Considerations...........................................7
7. Acknowledgement...............................................7
8. Intellectual Property.........................................7
9. Informative references........................................8
Author's Addresses...............................................9
Full Copyright statement.........................................9
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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
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. 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].
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].
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+---------+
+---------|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.
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
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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.
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.
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
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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, 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].
(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]
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
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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. Intellectual Property
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the result of an attempt made to obtain a general license or
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9. Informative references
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[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.
[Lambda-label] T. Otani, Ed., "Generalized Labels for G.694 Lambda-
Switching Capable Label Switching Routers", draft-
ietf-ccamp-gmpls-g-694-lambda-labels-04.txt, Mar.
2009.
[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
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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.
Author's 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
Bantian, Longgang District
Shenzhen 518129 P.R.China
Phone: +86-755-28972912
Email: zhangfatai@huawei.com
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