Network Working Group N. Sprecher
Internet-Draft Y. Weingarten
Intended status: Informational Nokia Siemens Networks
Expires: July 8, 2011 K. Hong
L. Fang
Cisco Systems, Inc.
January 4, 2011
Migration Considerations and Techniques for Multiprotocol Label
Switching Transport Profile based Networks and Services
draft-sprecher-mpls-tp-migration-03.txt
Abstract
MPLS-TP defines a packet-based network architecture and a
comprehensive set of tools that allow service providers to reliably
deliver next generation services and applications, in a simple,
scalable, and cost-effective way. Such services are BW-hungry based
and require strict guaranteed SLA. Delivering next generation
services over an MPLS-TP based network in an economic way, enables
service providers to remain competitive while increasing their
revenues.
This document presents the motivations for migrating from different
legacy transport networks and services to MPLS-TP, and discusses the
considerations and strategies for the migration.
The document also proposes specific activities and techniques needed
to ensure a smooth migration path from the different transport
networks and services to MPLS-TP.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on July 8, 2011.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Overview of MPLS-TP . . . . . . . . . . . . . . . . . . . 4
1.2. Motivations for Upgrading Networks . . . . . . . . . . . . 5
2. Terminology and References . . . . . . . . . . . . . . . . . . 6
2.1. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. General Migration Strategies . . . . . . . . . . . . . . . . . 7
3.1. Island model . . . . . . . . . . . . . . . . . . . . . . . 8
3.2. Phased model . . . . . . . . . . . . . . . . . . . . . . . 9
3.3. Integrated model . . . . . . . . . . . . . . . . . . . . . 10
4. Migrating from TDM . . . . . . . . . . . . . . . . . . . . . . 11
4.1. Main motivation . . . . . . . . . . . . . . . . . . . . . 11
4.2. Migration Activities and Techniques . . . . . . . . . . . 11
5. Migrating from ATM . . . . . . . . . . . . . . . . . . . . . . 11
5.1. Main motivation . . . . . . . . . . . . . . . . . . . . . 11
5.2. Migration activities and Techniques . . . . . . . . . . . 11
6. Migrating from Ethernet . . . . . . . . . . . . . . . . . . . 11
6.1. Main motivation . . . . . . . . . . . . . . . . . . . . . 11
6.2. Migration activities and Techniques . . . . . . . . . . . 11
7. Migrating from MPLS . . . . . . . . . . . . . . . . . . . . . 11
7.1. MPLS-TE . . . . . . . . . . . . . . . . . . . . . . . . . 11
7.1.1. Main motivation . . . . . . . . . . . . . . . . . . . 11
7.1.2. Migration activities and Techniques . . . . . . . . . 11
7.2. IP/MPLS . . . . . . . . . . . . . . . . . . . . . . . . . 11
7.2.1. Main motivation . . . . . . . . . . . . . . . . . . . 11
7.2.2. Migration activities and Techniques . . . . . . . . . 11
8. Migrating from pre-standard MPLS-TP (T-MPLS) . . . . . . . . . 11
8.1. Main motivation . . . . . . . . . . . . . . . . . . . . . 11
8.2. Migration activities and Techniques . . . . . . . . . . . 11
9. Manageability Considerations . . . . . . . . . . . . . . . . . 12
10. Security Considerations . . . . . . . . . . . . . . . . . . . 12
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12
13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
13.1. Normative References . . . . . . . . . . . . . . . . . . . 12
13.2. Informative References . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13
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Editors' Note:
This Informational Internet-Draft is aimed at achieving IETF
Consensus before publication as an RFC and will be subject to an IETF
Last Call.
[RFC Editor, please remove this note before publication as an RFC and
insert the correct Streams Boilerplate to indicate that the published
RFC has IETF Consensus.]
1. Introduction
1.1. Overview of MPLS-TP
The Transport Profile for MPLS (MPLS-TP) is being specified in the
IETF as part of a joint effort with the ITU-T to develop a definition
of the MPLS network that will fulfill the strict requirements for
transport networks that are accepted by the ITU-T. This profile will
be based on the definitions of the MPLS, MPLS Traffic Engineering,
and Multi-Segment Pseudo-Wire architectures defined in [RFC3031],
[RFC3985], and [RFC5659].
The requirements for MPLS-TP are detailed in [RFC5654]. These
requirements were developed in full cooperation between the IETF and
ITU-T, and reflect the needs to adhere to the architecture of MPLS
while including the enhanced level of service transparency, and
Operations, Administration, and Maintenance (OAM) functionality
required for stable transport networks. The requirements for the OAM
functionality are further developed and defined in [MPLS-TP-OAM],
providing the list of OAM procedures to be supported by MPLS-TP.
The architecture for MPLS-TP is defined in [RFC5921] and builds upon
the experience of the MPLS architecture. The architecture is
designed to allow MPLS-TP networks to operate whether the
configuration was implemented by use of control-plane signaling or a
management application. In addition, the MPLS-TP architecture is
designed to support networks that may not be using IP forwarding and
addressing. The framework defines the different service structures
supported by MPLS-TP and the interworking between these service
structures and existing MPLS services. Also defined are the
characteristics of the profile that defines MPLS-TP. This synergy of
architectures guarantees the service provider the ability to provide
services with guaranteed and strict Service Level Agreements in a
highly scalable robust network while reducing operational costs.
A main focus of MPLS-TP is the definition of OAM functionality for
MPLS data paths that support the transport services. MPLS-TP
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provides a comprehensive set of OAM tools for fault management and
performance monitoring, supporting the network and the services at
different nested levels (i.e. at the end-to-end level, a segment of a
path, and link level). The OAM tools may be used to monitor the
network infrastructure, to enhance the general behavior, and
performance level of the network. The tools may also be used to
monitor the service level offered to the end customer, allowing
verification of the SLA parameters, and enabling rapid response in
the event of a failure or service degradation. The OAM tools help
reduce OPEX, minimizing the overhead of trouble shooting, and
enhancing customer satisfaction which, in turn, helps to enable the
delivery of high-margin premium services.
The architectural constructs and the methodology of the OAM
functionality is defined by [MPLS-TP-OAM-Fwk]. This includes the
definition of the transport entities that are monitored by the OAM
procedures and detailed description of how the OAM procedures are
applied to these transport entities. A central issue in MPLS-TP OAM
is the independence of the OAM from the existence of an operational
control plane in the network. This feature is supported by the
creation of an in-band control channel that is used to transmit the
OAM procedures across the transport paths. A cornerstone of the
definition of the OAM procedures is to use existing IETF OAM tools as
the basis of the MPLS-TP OAM procedures wherever possible, this
principle is used as the underlying foundation for the definition of
the OAM tools defined for MPLS-TP.
Protection mechanisms for the MPLS-TP transport paths are described
in [MPLS-TP-Surviv] and are conformed with different topological
configurations of the network.
1.2. Motivations for Upgrading Networks
The growth of packet traffic has significantly increased, driven by
the high demand and penetration of new packet-based services and
multimedia applications, across the access, aggregation and core
networks and is expected to continue to increase. With the movement
toward packet-based services, the transport network has to evolve to
encompass the provision of packet-aware capabilities while enabling
carriers to leverage their installed, as well as planned, transport
infrastructure investments.
Carriers are in need of technologies capable of efficiently
supporting packet-based services and applications on their transport
networks with guaranteed Service Level Agreements (SLAs). The need
to increase their revenue while remaining competitive forces
operators to look for the lowest network Total Cost of Ownership
(TCO), and as such requires investment in equipment and facilities
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(Capital Expenditure (CAPEX)) and Operational Expenditure (OPEX) be
minimized.
There are a number of technology options for carriers to meet the
challenge of increased service sophistication and transport
efficiency, with increasing usage of hybrid packet-transport and
circuit-transport technology solutions. To address this challenge,
it is essential that packet-transport technology be available that
can provide reliability, operational simplicity - preserving the look
and feel to which service providers have accustomed, multi-layer
operations, resiliency, control, and multi-technology management.
Transport carriers require control and deterministic usage of network
resources. They need end-to-end control to engineer network paths
and to efficiently utilize network resources. They require
capabilities to support static (management-plane-based) or dynamic
(control-plane-based) provisioning of deterministic, protected, and
secured services and their associated resources. For transport
carriers, it is also important to ensure smooth interworking of the
packet transport network with other existing/legacy packet networks,
and provide mappings to enable packet transport carriage over a
variety of transport network infrastructures.
MPLS is a maturing packet technology and it is already playing an
important role in transport networks and services. The development
of MPLS-TP has proposed a set of compatible technology enhancements
to existing MPLS standards to extent the definition of MPLS toward
supporting traditional transport operational models. These
enhancements inherit all the supporting QoS, recovery, control and
data plane mechanisms already defined within standards. MPLS-TP will
enable the deployment of packet-based transport networks that will
efficiently scale to support packet services in a simple and cost-
effective way.
2. Terminology and References
2.1. Acronyms
This draft uses the following acronyms:
MPLS-TP Multiprotocol Label Switching - Transport Protocol
OAM Operations, Administration, and Maintenance
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3. General Migration Strategies
A migration strategy is necessary for service providers to maintain
their installed base and minimize the investment in new equipment.
The migration should be a smooth and seamless transfer of technology
while continuing to support the services that generate the revenues.
This means that the migration strategy should address the following
considerations:
o Cost-effective - Minimize the number of migration steps, stay
within budget for both operating (OPEX) and capital (CAPEX)
expenses.
o Service continuity - perform the switchover without a service
break to existing customers and their services.
o Provide a reliable fall-back - don't burn your bridges until the
new connections are secure and robust enough to maintain the
service-level agreements.
o Minimum switchover time - when everything is in place need to
minimize the side-effects by minimizing the time needed to have
the new service platform performing.
o Aspects of data-plane, OAM and recovery mechanisms, control plane
and management-plane
Different migration models have been discussed in the literature.
The most basic model, forklifting the new technology, in our case
MPLS-TP, onto the network involves simultaneously upgrading the
entire network to work with the new technology. This type of
migration is very risky if the new technology does not work as
expected in the live network after disabling the legacy technology.
In order to minimize the risk, it could be possible to install an
entire parallel network based on MPLS-TP and then switch over from
the legacy network to the MPLS-TP network. However, this would be
very costly, i.e. purchasing equipment for two parallel networks, and
again could not guarantee that the new technology network would work
as planned. This, in turn, would cause a major disruption of
services. Therefore, in the following descriptions we concentrate on
the following models:
o Island model - introducing the MPLS-TP in separate sub-domains of
the network. The transport paths may cross the different
technology domains that are connected by gateways. See section
3.1 for more details.
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o Phased model - where the existing equipment is slowly upgraded
with new MPLS-TP capabilities as needed. For more details see
section 3.2.
o Integrated model - network nodes are either legacy nodes or dual-
mode nodes supporting both legacy and MPLS-TP capabilities. See
section 3.3 for more details.
It should be noted that not all of these models are relevant to
migration from specific legacy technologies. The relevance for each
technology of the particular migration model will be discussed in the
sections below that discuss the specific technologies.
3.1. Island model
In this migration model presented previously in [RFC5145] the service
provider introduces clusters of MPLS-TP nodes that are interconnected
with the legacy clusters through border nodes. The border nodes act
as gateways, that are responsible for the mapping or adaptation of
protocol elements that may be transmitted between legacy and MPLS-TP
nodes.
End-to-end services may traverse between the islands. The
configuration of the transport paths may be "balanced" or
"unbalanced". In a balanced path configuration both endpoints of the
path are nodes of the same technology, but the path may have crossed
islands of the other technology in the middle of the path, see
Figure 1. An unbalanced path configuration would be if the path
starts at a node of one technology and ends at a node supporting the
second technology, see Figure 1.
+----+ +--+ +----+ +--+ +----+ +--+ +----+
|Lgcy| |LN| |Brdr| |TP| |Brdr| |LN| |Lgcy|
| |==========| |==========| |=========| |
..|........Service...Transport...Path.................|...
| |==========| |==========| |=========| |
|Conn| | | |Gtwy| | | |Gtwy| | | |Conn|
+----+ +--+ +----+ +--+ +----+ +--+ +----+
. . . . . .
| Legacy | | MPLS-TP | | Legacy |
|<----Island---->| |<---Island--->| |<---Island--->|
LN - one or more Legacy Nodes
TP - one or more MPLS-TP LSR
Brdr Gtwy - Border node that acts as gateway
Lgcy Conn - Legacy node that where service connects
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Figure 1: Balanced island path
+----+ +--+ +----+ +--+ +----+
|Lgcy| |LN| |Brdr| |TP| | TP |
| |==========| |==========| |
....|...Service...Transport...Path.......|...
| |==========| |==========| |
|Conn| | | |Gtwy| | | |Conn|
+----+ +--+ +----+ +--+ +----+
. . . .
| Legacy | | MPLS-TP |
|<----Island---->| |<---Island--->|
LN - one or more Legacy Nodes
TP - one or more MPLS-TP LSR
Brdr Gtwy - Border node that acts as gateway
Lgcy Conn - Legacy node that where service connects
TP Conn - MPLS-TP LER
Figure 2: Unbalanced island path
The tools that may be used at the border, gateway, nodes may be based
on either layered networks - only when using balanced islands, or on
an interworking or mapping function between protocols. An MPLS-TP
island would provide the layered network solution through the use of
an LSP between TE-links to carry legacy traffic, when possible.
This model is very useful when upgrading the network in stages, where
new MPLS-TP equipment is upgraded in clusters that form an island.
These islands can be slowly expanded and merged until they create a
single MPLS-TP network. Whenever the islands are expanded or merged
make-before-break procedures should be employed in order to keep
services running.
3.2. Phased model
In this model the existing equipment is upgraded with the features
and functionality of the new technology. The new functionality is
introduced as needed, while ensuring interoperability with the legacy
technology. This is highly dependent upon the equipment to support
the new functionality and the support of all the vendors to implement
the same functionality.
The advantage of this model is that it allows the service provider to
quickly support enhanced capabilities on his existing equipment.
However, this model is not applicable to all legacy technologies.
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For this to work the new capabilities need to be backward compatible
with the legacy technology, and all of the vendors, involved in the
migration, need to implement the new capabilities specified by the
service provider.
3.3. Integrated model
This model allows the operator to run services over two clouds of the
network simultaneously. One cloud would continue to support the
legacy technology, while the second cloud would support the new
MPLS-TP services. The services would be routed to the proper cloud
by new "dual-mode" nodes that would support an integrated MPLS-TP and
legacy functionality, see Figure 3. These dual-mode nodes would
route the different services to the paths in the different technology
clouds. This avoids the need for interworking that is required in
the island model described in section 3.1.
______________________________________
_/ Service Provider's Network \
/ ____ ___ ____ \___
_/ _/ \___/ \ _/ \__ \
/ / \__/ ... \_ \___
/ / ....... ... \ \
| +--------| ...Legacy Logical Network .. |---+ |
| |.........\.. .. .. ../....| |
| |. \ ___.... ___ __ _/ .| |
| +----+ \_/ \____/ \___/ \____/ +----+ |
....|Dual| |Dual|...
| | | | | |
****|Mode| ____ ___ ____ |Mode|***
| +----+ _/ \___/ \ _/ \__ +----+ |
\ | * / \__/ \_ *| |
\ | ******* /*** **\****| /
\ +--------| ***MPLS-TP Logical Ntwrk*** |---+ /
\____ \ *** ***** ***** / |
\ \ ___ ****___ ***__ _/ /
\ \_/ \____/ \___/ \____/ ___/
\____________________________________/
.... - Legacy service path
**** - MPLS-TP service path
Figure 3: Integrated model network
Gradual migration is supported by this model. The dual-mode nodes
are either legacy nodes that are upgraded to support MPLS-TP
functionality. Services can be switched gradually from the legacy
transport paths to the MPLS-TP paths as they become available, using
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make-before-break procedures. Eventually, as all the service paths
are transferred to MPLS-TP the legacy technology cloud can be taken
off-line.
4. Migrating from TDM
4.1. Main motivation
4.2. Migration Activities and Techniques
5. Migrating from ATM
5.1. Main motivation
5.2. Migration activities and Techniques
6. Migrating from Ethernet
6.1. Main motivation
6.2. Migration activities and Techniques
7. Migrating from MPLS
7.1. MPLS-TE
7.1.1. Main motivation
7.1.2. Migration activities and Techniques
7.2. IP/MPLS
7.2.1. Main motivation
7.2.2. Migration activities and Techniques
8. Migrating from pre-standard MPLS-TP (T-MPLS)
8.1. Main motivation
8.2. Migration activities and Techniques
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9. Manageability Considerations
10. Security Considerations
11. IANA Considerations
This informational document makes no requests for IANA action.
12. Acknowledgments
13. References
13.1. Normative References
[RFC5654] Niven-Jenkins, B., Ed., Brungard, D., Ed., Betts, M., Ed.,
Sprecher, N., and S. Ueno, "Requirements of an MPLS
Transport Profile", RFC 5317, February 2009.
[MPLS-TP-OAM]
Busi, I., Ed. and B. Niven-Jenkins, Ed., "Requirements for
OAM in MPLS Transport Networks",
draft-ietf-mpls-tp-oam-requirements, Work in Progress.
[MPLS-TP-OAM-Fwk]
Busi, I., Ed. and B. Niven-Jenkins, Ed., "A Framework for
MPLS in Transport Networks",
draft-ietf-mpls-tp-oam-framework, Work in Progress.
[MPLS-TP-Surviv]
Sprecher, N. and A. Farrel, "Multiprotocol Label Switching
Transport Profile Survivability Framework",
draft-ietf-mpls-tp-survive-fwk, Work in Progress.
13.2. Informative References
[RFC3985] Bryant, S. and P. Pate, "Pseudo Wire Emulation Edge-to-
Edge (PWE3) Architecture", RFC 3985, March 2005.
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031, January 2001.
[RFC5659] Bocci, M. and S. Bryant, "An Architecture for Multi-
Segment Pseudo Wire Emulation Edge-to-Edge", RFC 5659,
October 2009.
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[RFC5145] Shiomoto, K., "Framework for MPLS-TE to GMPLS Migration",
RFC 5145, March 2008.
[RFC5921] Bocci, M., Ed., Bryant, S., Ed., Frost, D., Ed., Levrau,
L., Ed., and L. Berger, Ed., "A Framework for MPLS in
Transport Networks", RFC 5921.
[RFC5920] Levrau, L., Ed., "A Framework for MPLS in Transport
Networks", RFC 5920.
Authors' Addresses
Nurit Sprecher
Nokia Siemens Networks
3 Hanagar St. Neve Ne'eman B
Hod Hasharon, 45241
Israel
Email: nurit.sprecher@nsn.com
Yaacov Weingarten
Nokia Siemens Networks
3 Hanagar St. Neve Ne'eman B
Hod Hasharon, 45241
Israel
Email: yaacov.weingarten@nsn.com
Kyung-Yeop Hong
Cisco Systems, Inc.
300 Beaver Brook Road
Boxborough, Massachusetts 01719
USA
Email: hongk@cisco.com
Luyuan Fang
Cisco Systems, Inc.
300 Beaver Brook Road
Boxborough, MA 01719
USA
Email: lufang@cisco.com
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