Network Working Group
Internet Draft Kenji Kumaki, Ed
Proposed Category: Informational KDDI Corporation
Expires: June, 2007 Tomohiro Otani
KDDI R&D Labs
Shuichi Okamoto
NICT
Kazuhiro Fujihara
Yuichi Ikejiri
NTT
Communications
December, 2006
Interworking Requirements to Support operation of MPLS-TE over GMPLS
networks
draft-ietf-ccamp-mpls-gmpls-interwork-reqts-00.txt
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Copyright (C) The Internet Society (2006).
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Abstract
This document describes a framework and Service Provider requirements
for operating Multiprotocol Label Switching (MPLS) traffic
engineering (TE) networks over Generalized MPLS (GMPLS) networks.
Operation of an MPLS-TE network as a client network to a GMPLS
network has enhanced operational capabilities than provided by a co-
existent protocol model (ships in the night).
The GMPLS network may be a packet or a non-packet network, and may
itself be a multi-layer network supporting both packet and non-packet
technologies. A MPLS-TE Label Switched Path (LSP) originates and
terminates on an MPLS Label Switching Router (LSR). The GMPLS network
provides transparent transport for the end-to-end MPLS-TE LSP.
Specification of solutions is out of scope for this document.
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...................................................3
2. Reference model................................................4
3. Detailed Requirements..........................................5
3.1 End-to-End Signaling.......................................5
3.2 Triggered Establishment of GMPLS LSPs......................5
3.3 Diverse Paths for End-to-End MPLS-TE LSPs..................5
3.4 Advertisement of MPLS-TE Information via the GMPLS Network.5
3.5 Selective Advertisement of MPLS-TE Information via a Border
Node...........................................................6
3.6 Interworking of MPLS-TE and GMPLS protection...............6
3.7 Independent Failure Recovery and Reoptimization............6
3.8 Complexity and Risks.......................................6
3.9 Scalability consideration..................................6
3.10 Performance Consideration.................................7
3.11 Management Considerations.................................7
4. Security Considerations........................................7
5. Recommended Solution Architecture..............................7
5.1 Use of Contiguous, Hierarchical, and Stitched LSPs.........8
5.2 MPLS-TE Control Plane Connectivity.........................8
5.3 Fast Reroute Protection....................................8
6. IANA Considerations............................................9
7. Normative References...........................................9
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8. Informative References........................................10
9. Acknowledgments...............................................10
10.Author's Addresses............................................10
1. Introduction
Multiprotocol Label Switching traffic engineering (MPLS-TE) networks
are often deployed over transport networks such that the transport
networks provide connectivity between the Label Switching Routers
(LSRs) in the MPLS-TE network. Increasingly, these transport networks
are operated using a Generalized Multiprotocol Label Switching
(GMPLS) control plane and label Switched Paths (LSPs) in the GMPLS
network provide connectivity in the MPLS-TE network.
Generalized Multiprotocol Label Switching (GMPLS) protocols were
developed as extensions to Multiprotocol Label Switching traffic
engineering (MPLS-TE) protocols. MPLS-TE is limited to the control of
packet switching networks, but GMPLS can also control sub-packet
technologies at layers one and two.
The GMPLS network may be managed by an operator as a separate network
(as it was when it was under management plane control before the use
of GMPLS as a control plane), but optimizations of management and
operation may be achieved by coordinating the use of the MPLS-TE and
GMPLS networks and operating the two networks with a close
client/server relationship.
GMPLS LSP setup may triggered by the signaling of MPLS-TE LSPs in the
MPLS-TE network so that the GMPLS network is reactive to the needs of
the MPLS-TE network. The triggering process can be under the control
of operator policies without needing direct intervention by an
operator.
The client/server configuration just described can also apply in
migration scenarios for MPLS-TE packet switching networks that are
being migrated to be under GMPLS control. [MIGRATE] describes a
migration scenario called the Island Model. In this scenario, groups
of nodes (islands) are migrated from the MPLS-TE protocols to the
GMPLS protocols and operate entirely surrounded by MPLS-TE nodes (the
sea). This scenario can be effectively managed as a client/server
network relationship using the framework described in this document.
In order to correctly manage the dynamic interaction between the MPLS
and GMPLS networks, it is necessary to understand the operational
requirements and the control that the operator can impose. Although
this problem is very similar to the multi-layer networks described in
[MLN], it must be noted that those networks operate GMPLS protocols
in both the client and server networks which facilitates smoother
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interworking. Where the client network uses MPLS-TE protocols over
the GMPLS server network there is a need to study the interworking of
the two protocol sets.
This document examines the protocol requirements for protocol
interworking to operate an MPLS-TE network as a client network over a
GMPLS server network, and provides a framework for such operations.
2. Reference model
The reference model used in this document is shown in Figure 1. It
can easily be seen that the interworking between MPLS-TE and GMPLS
protocols must occur on a node and not on a link. Nodes on the
interface between the MPLS-TE and GMPLS networks must be responsible
for handling both protocol sets and for providing any protocol
interworking that is required. We call these nodes Border Routers.
-------------- ------------------------- --------------
| MPLS Client | | GMPLS Server Network | | MPLS Client |
| Network | | | | Network |
| | | | | |
| ---- --+--+-- ----- ----- --+--+-- ---- |
| | | | | | | | | | | | | |
| |MPLS|_| Border |__|GMPLS|_|GMPLS|__| Border |_|MPLS| |
| |LSR | | Router | | LSR | | LSR | | Router | |LSR | |
| | | | | | | | | | | | | |
| ---- --+--+-- ----- ----- --+--+-- ---- |
| | | | | |
| | | | | |
-------------- ------------------------- --------------
| | GMPLS LSP | |
| |<------------------------->| |
| |
|<--------------------------------------------->|
End-to-End MPLS-TE LSP
Figure 1. Reference model of MPLS-TE/GMPLS interworking
MPLS-TE network connectivity is provided through a GMPLS LSP which is
created between Border Routers. End-to-end connectivity between MPLS
LSRs in the client MPLS-TE networks is provided by an MPLS-TE LSP
that is carried across the MPLS-TE network by the GMPLS LSP using
hierarchical LSP techniques [RFC4206], LSP stitching segments
[STITCH] or a contiguous LSP. LSP stitching segments and contiguous
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LSPs are only available where the GMPLS network is a packet switching
network.
3. Detailed Requirements
This section describes detailed requirements for MPLS-TE/GMPLS
interworking in support of the reference model shown in figure 1.
3.1 End-to-End Signaling
The solution MUST be able to preserve MPLS signaling information
signaled within the MPLS-TE client network at the start of the MPLS-
TE LSP, and deliver it on the other side of the GMPLS server network
for use within the MPLS-TE client network at the end of the MPLS-TE
LSP. This may require protocol mapping (and re-mapping), protocol
tunneling, or the use of remote protocol adjacencies.
3.2 Triggered Establishment of GMPLS LSPs
The solution MUST provide the ability to establish end-to-end MPLS-
TE LSPs over a GMPLS server network. It SHOULD be possible for GMPLS
LSPs across the core network to be set up between Border Routers
triggered by the signaling of MPLS-TE LSPs in the client network.
GMPLS LSPs MAY also be pre-established as the result of management
plane control.
3.3 Diverse Paths for End-to-End MPLS-TE LSPs
The solution SHOULD provide the ability to establish end-to-end
MPLS-TE LSPs having diverse paths for protection of the LSP traffic.
This means that MPLS-TE LSPs SHOULD be kept diverse both within the
client MPLS-TE network and as they cross the server GMPLS network.
This means that there SHOULD be a mechanism to request the provision
of diverse GMPLS LSPs between a pair of Border Routers to provide
protection of the GMPLS span, but also that there SHOULD be a way to
keep GMPLS LSPs between different Border Routers disjoint.
3.4 Advertisement of MPLS-TE Information via the GMPLS Network
The solution SHOULD provide the ability to advertise of TE
information from MPLS-TE client networks across the GMPLS server
network.
The advertisement of TE information from within an MPLS-TE client
network to all LSRs in the client network enables a head end LSR to
compute an optimal path for an LSP to a tail end LSR that is reached
over the GMPLS server network.
Where there is more than one client MPLS-TE network, the TE
information from separate MPLS-TE networks MUST be kept private,
confidential and secure.
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3.5 Selective Advertisement of MPLS-TE Information via a Border Node
The solution SHOULD provide the ability to distribute TE reachability
information from the GMPLS server network to MPLS-TE networks
selectively. This information is useful for the LSRs in the MPLS-TE
networks to compute paths that cross the GMPLS server network and to
select the correct Border Routers to provide connectivity.
The solution MUST NOT distribute TE information from within a non-PSC
GMPLS server network to any client MPLS-TE network as that
information may cause confusion and selection of inappropriate paths.
3.6 Interworking of MPLS-TE and GMPLS protection
If an MPLS-TE LSPs is protected using MPLS Fast Reroute (FRR)
[RFC4090], then similar PROTECTION MUST be provided over the GMPLS
island. Operator and policy controls SHOULD be made available at the
Border Router to determine how suitable protection is provided in the
GMPLS island.
3.7 Independent Failure Recovery and Reoptimization
The solution SHOULD provide failure recovery and reoptimization in
the GMPLS server network without impacting MPLS-TE client network and
vice versa. That is, it SHOULD be possible to recover from a fault
within the GMPLS island or to reoptimize the path across the GMPLS
island without requiring signaling activity within the MPLS-TE client
network. Similarly, it SHOULD be possible to perform recovery or
reoptimization within the MPLS-TE client network without requiring
signaling activity within the GMPLS server networks.
In case that failure in the GMPLS server network can not be repaired
transparently, some kind of notification of the failure SHOULD be
transmitted to MPLS-TE network.
3.8 Complexity and Risks
The solution SHOULD NOT introduce unnecessary complexity to the
current operating network to such a degree that it would affect the
stability and diminish the benefits of deploying such a solution in
service provider networks.
3.9 Scalability consideration
The solution MUST scale well with consideration to at least the
following considerations.
- The number of GMPLS-capable nodes (i.e., the size of the GMPLS
server network).
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- The number of MPLS-TE-capable nodes (i.e., the size of the MPLS-TE
client network).
- The number of MPLS-TE client networks.
- The number of GMPLS LSPs.
- The number of MPLS-TE LSPs.
3.10 Performance Consideration
The solution SHOULD be evaluated with regard to the following
criteria.
- Failure and restoration time.
- Impact and scalability of the control plane due to added
overheads.
- Impact and scalability of the data/forwarding plane due to added
overheads.
3.11 Management Considerations
Manageability of deployment of an MPLS-TE client network over GMPLS
server network MUST addresses the following considerations.
- Need for coordination of MIB modules used for control plane
management and monitoring in the client and server networks.
- Need for diagnostic tools that can discover and isolate faults
across the border between the MPLS-TE client and GMPLS server
networks.
4. Security Considerations
We will write security considerations in next version.
5. Recommended Solution Architecture
The recommended solution architecture to meet the requirements set
out in the previous sections is known as the Border Peer Model. This
architecture is a variant of the Augmented Model described in
[RFC3945]. The remainder of this document presents an overview of
this architecture. Details of protocol solutions are described in
[BORDER-PEER].
In the Augmented Model, routing information from the lower layer
(server) network is filtered at the interface to the higher layer
(client) network and is distributed within the higher layer network.
In the Border Peer Model, the interface between the client and server
networks is the Border Router. This router has visibility of the
routing information in the server network yet also participates as a
peer in the client network. However, the Border Router does not
distribute server routing information into the client network.
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The Border Peer Model may also be contrasted with the Overlay Model
[RFC3945]. In this model there is a protocol request/response
interface (the user network interface - UNI) between the client and
server networks. [RFC4208] shows how this interface may be supported
by GMPLS protocols operated between client edge and server edge
routers while retaining the routing information within the server
network. The Border Peer Model can be viewed as placing the UNI
within the Border Router thus giving the Border Router peer
capabilities in both the client and server network.
5.1 Use of Contiguous, Hierarchical, and Stitched LSPs
All three LSP types MAY be supported in the Border Peer Model, but
contiguous LSPs are the hardest to support because they require
protocol mapping between the MPLS-TE client network and the GMPLS
server network. Such protocol mapping can currently be achieved since
MPLS-TE signaling protocols are a subset of GMPLS, but this mechanism
is not future-proofed.
Contiguous and stitched LSPs can only be supported where the GMPLS
server network has the same switching type (that is, packet
switching) as the MPLS-TE network. Requirements for independent
failure recovery within the GMPLS island require the use of loose
path reoptimization techniques [LOOSE-REOPT] and end-to-end make-
before-break [RFC3209] which will not provide rapid recovery.
For these reasons, the use of hierarchical LSPs across the server
network is RECOMMENDED for the Border Peer Model, but see the
discussion of Fast Reroute protection in section 5.3.
5.2 MPLS-TE Control Plane Connectivity
Control plane connectivity between MPLS-TE LSRs connected by a GMPLS
island in the Border Peer Model MAY be provided by the control
channels of the GMPLS network. If this is done, a tunneling mechanism
(such as GRE [RFC2784]) SHOULD be used to ensure that MPLS-TE
information is not consumed by the GMPLS LSRs. But care is required
to avoid swamping the control plane of the GMPLS network with MPLS-TE
control plane (particularly routing) messages.
In order to ensure scalability, control plane messages for the MPLS-
TE client network MAY be carried between Border Routers in a single
hop MPLS-TE LSP routed through the data plane of the GMPLS server
network.
5.3 Fast Reroute Protection
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If the GMPLS network is packet switching, Fast Reroute protection can
be offered on all hops of a contiguous LSP. If the GMPLS network is
packet switching then all hops of a hierarchical GMPLS LSP or GMPLS
stitching segment can be protected using Fast Reroute. If the end-to-
end MPLS-TE LSP requests Fast Reroute protection, the GMPLS packet
switching network SHOULD provide such protection.
However, note that it is not possible to provide FRR node protection
of the upstream Border Router without careful consideration of
available paths, and protection of the downstream Border Router is
not possible where hierarchical LSPs or stitching segments are used.
Note further that Fast Reroute is not available in non-packet
technologies. However, other protection techniques are supported by
GMPLS for non-packet networks and are likely to provide similar
levels of protection.
The limitations of FRR need careful consideration by the operator and
may lead to the decision to provide end-to-end protection for the
MPLS-TE LSP.
6. IANA Considerations
This requirement document makes no requests for IANA action.
7. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, December 2001.
[RFC3945] Mannie, E., "Generalized Multi-Protocol Label Switching
(GMPLS) Architecture", RFC3945, October 2004.
[RFC4090] Pan, P., Swallow, G. and A. Atlas, "Fast Reroute
Extensions to RSVP-TE for LSP Tunnels", RFC 4090, May 2005.
[RFC4206] Kompella, K., and Rekhter, Y., "Label Switched Paths (LSP)
Hierarchy with Generalized Multi-Protocol Label Switching
(GMPLS) Traffic Engineering (TE)", RFC 4206, October 2005.
[RFC4208] Swallow, G., et al., "Generalized Multiprotocol Label
Switching (GMPLS) User-Network Interface (UNI): Resource
ReserVation Protocol-Traffic Engineering (RSVP-TE) Support
for the Overlay Model", RFC 4208, October 2005.
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[STITCH] Ayyangar, A., Vasseur, JP. "Label Switched Path Stitching
with Generalized MPLS Traffic Engineering", draft-ietf-
ccamp-lsp-stitching, work in progress.
8. Informative References
[RFC2784] Farinacci, D., et al., "Generic Routing Encapsulation
(GRE)", RFC 2784, March 2000.
[BORDER-PEER] Kumaki, K. et al. "Operational, Deployment and
Interworking Considerations for GMPLS", draft-kumaki-
ccamp-mpls-gmpls-interworking, work in progress.
[LOOSE-REOPT] Vasseur, JP., Ikejiri, Y., and Zhang, R.,
"Reoptimization of Multiprotocol Label Switching
(MPLS) Traffic Engineering (TE) loosely routed Label
Switch Path (LSP)", draft-ietf-ccamp-loose-path-reopt,
work in progress.
[MIGRATE] Shiomoto, K., et al., "Framework for MPLS-TE to GMPLS
migration", draft-ietf-ccamp-mpls-gmpls-interwork-fmwk,
work in progress.
[MLN] Shiomoto, K., Papadimitriou, D., Le Roux, J.L., Vigoureux, M.,
Brungard, D., "Requirements for GMPLS-based multi-region and
multi-layer networks (MRN/MLN)", draft-ietf-ccamp-gmpls-mln-
reqs, work in progress.
9. Acknowledgments
The author would like to express the thanks to Raymond Zhang, Adrian
Farrel, and Deborah Brungard for their helpful and useful comments
and feedback.
10.Author's Addresses
Kenji Kumaki (Editor)
KDDI Corporation
Garden Air Tower
Iidabashi, Chiyoda-ku,
Tokyo 102-8460, JAPAN
Email: ke-kumaki@kddi.com
Tomohiro Otani
KDDI R&D Laboratories, Inc.
2-1-15 Ohara Kamifukuoka Phone: +81-49-278-7357
Saitama, 356-8502. Japan Email: otani@kddilabs.jp
Shuichi Okamoto
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NICT JGN II Tsukuba Reserach Center
1-8-1, Otemachi Chiyoda-ku, Phone : +81-3-5200-2117
Tokyo, 100-0004, Japan E-mail :okamoto-s@nict.go.jp
Kazuhiro Fujihara
NTT Communications Corporation
Tokyo Opera City Tower 3-20-2 Nishi Shinjuku, Shinjuku-ku
Tokyo 163-1421, Japan
EMail: kazuhiro.fujihara@ntt.com
Yuichi Ikejiri
NTT Communications Corporation
Tokyo Opera City Tower 3-20-2 Nishi Shinjuku, Shinjuku-ku
Tokyo 163-1421, Japan
EMail: y.ikejiri@ntt.com
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