draft-caviglia-ccamp-pc-and-sc-reqs-04.txt September 2006
Network Working Group
Internet Draft Diego Caviglia
Intended Status: Informational Dino Bramanti
Ericsson
Dan Li
Document: Huawei
draft-caviglia-ccamp-pc-and-sc-reqs-04.txt
Expires: March 2007
Requirements for the Conversion Between Permanent Connections and
Switched Connections in a Generalized Multiprotocol Label Switching
(GMPLS) Network
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Abstract
From a Carrier perspective, the possibility of turning a Permanent
Connection (PC) into a Soft Permanent Connection (SPC) and vice
versa, without actually affecting Data Plane traffic being carried
over it, is a valuable option. In other terms, such operation can be
seen as a way of transferring the ownership and control of an
existing and in-use Data Plane connection between the Management
Plane and the Control Plane, leaving its Data Plane state untouched.
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This memo sets out the requirements for such procedures within a
Generalized Multiprotocol Label Switching (GMPLS) network.
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 [1].
Table of Contents
1 Introduction...................................................3
1.1 Motivation..................................................3
1.2 Label Switched Path Terminology.............................3
1.3 LSP within GMPLS Control Plane..............................4
1.4 Resource Ownership..........................................4
1.5 Setting Up a GMPLS Controlled Network.......................5
2 Typical Use Cases..............................................5
2.1 PC to SC/SPC Conversion.....................................5
2.2 SC to PC Conversion.........................................6
3 Requirements...................................................6
3.1 Data Plane LSP Consistency..................................6
3.2 No Disruption of User Traffic...............................6
3.3 Transfer from Management Plane to Control Plane.............6
3.4 Transfer from Control Plane to Management Plane.............6
3.5 Synchronization of state among nodes during conversion......7
3.6 Support of Soft Permanent Connections.......................7
3.7 Failure of Transfer.........................................7
4 Security Considerations........................................7
5 IANA Consideration.............................................7
6 References.....................................................8
6.1 Normative References........................................8
6.2 Informative References......................................8
7 Acknowledgments................................................8
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1 Introduction
In a typical, traditional transport network scenario, Data Plane
connections between two endpoints are controlled by means of a
Network Management System (NMS) operating within the Management
Plane (MP). The NMS/MP is the owner of such transport connections,
being responsible of their setup, teardown, and maintenance.
Provisioned connections of this kind, initiated and managed by the
Management Plane, are known as Permanent Connections (PCs).
When the setup, teardown, and maintenance of connections is achieved
by means of a signaling protocol owned by the Control Plane such
connections are known as Switched Connections (SCs).
In many deployments a hybrid connection type will be used. A Soft
Permanent Connection (SPC) is a combination of a permanent
connection segment at the source user-to-network side, a permanent
connection segment at the destination user-to-network side, and a
switched connection segment within the core network. The permanent
parts of the SPC are owned by the Management Plane, and the switched
parts are owned by the Control Plane.
1.1 Motivation
The main motivation for this work is the LSP conversion from
Management Plane to Control Plane. The objective is to be able to
introduce a control plane into an existing network without
disrupting user traffic.
Conversion from the Management Plane to Control Plane is proposed as
a mandatory requirement while the conversion from the Control Plane
to Management is seen as a nice to have feature. The requirement for
LSP conversion from Control Plane to Management Plane should be
scoped as a back-out procedure.
1.2 Label Switched Path Terminology
A Label Switched Path (LSP) has different semantics depending on the
plane in which it the term is used.
In the Data Plane, an LSP indicates the Data Plane forwarding path.
It defines the forwarding or switching operations at each network
entity. It is the sequence of data plane resources (links, labels,
cross-connects) that achieves end-to-end data transport.
In the Management Plane, an LSP is the management state information
(such as the connection attributes and path information)associated
with and necessary for the creation and maintenance of a Data Plane
connection.
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In the Control Plane, an LSP is the control plane state information
(such as Path and Resv state)associated with and necessary for the
creation and maintenance of a Data Plane connection.
A permanent connection has an LSP presence in the Data Plane and the
Management Plane. A switched connection has an LSP presence in the
Data Plane and the Control Plane. An SPC has LSP presence in the
Data Plane for its entire length, but has Management Plane presence
for part of its length and Control Plane presence for part of its
length.
In this document, when we talk about the LSP conversion between
Control plane and Management plane, we mainly focus on the
conversion of control plane state information and management state
information.
1.3 LSP within GMPLS Control Plane
Generalized Multiprotocol Label Switching (GMPLS)[2], [3] defines a
powerful Control Plane architecture for transport networks. This
includes both routing and signaling protocols for the creation and
maintenance of Label Switched Paths (LSPs) in networks whose Data
Plane is based on different technologies such as optical TDM
transport ad WDM.
1.4 Resource Ownership
A resource used by an LSP is said to be 'owned' by the plane that
was used to set up the LSP through that part of the network. Thus,
all the resources used by a permanent connection are owned by the
Management Plane, and all the resources used by a switched
connection are owned by the Control Plane. The resources used by an
SPC are divided between the Management Plane (for the resources used
by the permanent connection segments at the edge of the network) and
the Control Plane (for the resources used by the switched segment in
the middle of the network).
The division of resources available for ownership by the Management
and Control Planes is an architectural issue. A carrier may decide
to pre-partition the resources at a network entity so that LSPs
under Management Plane control use one set of resources and LSPs
under Control Plane control use another set of resources. Other
carriers may choose to make this distinction resource-by-resource as
LSPs are established.
It should be noted, however, that even when a resource is owned by
the Control Plane it will usually be the case that the Management
Plane has a controlling interest in the resource. Consider, for
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example, that in the event of a Control Plane failure, the
Management Plane needs to be able to de-provision resources. Also
consider the basic safety requirements that imply that management
commands must be available to set laser out of service.
1.5 Setting Up a GMPLS Controlled Network
The implementation of a new network using a Generalized
Multiprotocol Label Switching (GMPLS) Control Plane may be
considered as a green field deployment. But in many cases it is
desirable to introduce a GMPLS Control Plane into an existing
transport network that is already populated with permanent
connections under Management Plane control.
In a mixed scenario, permanent connections owned by the Management
Plane and switched connections owned by the Control Plane have to
coexist within the network.
It is also desirable to transfer the control of connections from the
Management Plane to the Control Plane so that connections that were
originally under the control of an NMS are now under the control of
the GMPLS protocols. In case such connections are in service, such
conversion must be performed in a way that does not affect traffic.
Since attempts to move a LSP under GMPLS control might fail due to a
number of reasons outside the scope of this draft, it is also
advisable to have a mechanism to convert the control of an LSP back
to the Management Plane, in fact undoing the whole process.
Note that a permanent connection may be converted to a switched
connection or to an SPC, and an SPC may be converted to a switched
connection as well(PC to SC, PC to SPC, and SPC to SC). So the
reverse mappings may be also needed (SC to PC, SC to SPC, and SPC to
PC).
2 Typical Use Cases
2.1 PC to SC/SPC Conversion
A typical scenario where a PC to SC (or SPC) procedure can be a
useful option is at the initial stage of Control Plane deployment in
an existing network. In such a case all the network connections,
possibly carrying traffic, are already set up as PCs and are owned
by the Management Plane.
Next step in such conversion process presents a similar scenario
where the network is partially controlled by the Management Plane
and partially controlled by the Control Plane (PCs and SCs/SPCs
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coexist). In this case a network upgrade by a Control Plane coverage
extension may be required.
In both cases the point is that a connection, set up and owned by
the Management Plane, may need to be transferred to Control Plane
control. If a connection is carrying traffic, its transfer has to be
done without any disruption to the Data Plane traffic.
2.2 SC to PC Conversion
The main reason making a SC to PC conversion interesting is to give
an operator the chance of undoing somehow the action represented by
the above introduced PC to SC conversion.
In other words the SC to PC conversion is a back-out procedure and
as such is not considered mandatory in this document, still being a
useful functional resource.
Again it is worth stressing the requirement that such `SPC to PC`
conversion is achieved without any effect on the associated Data
Plane state so that the connection continues to be operational and
to carry traffic during the transition.
3 Requirements
This section sets out the basic requirements for procedures and
processes that are used to perform the functions this document is
about.
3.1 Data Plane LSP Consistency
The Data Plane LSP, staying in place throughout the whole transfer
process, MUST follow the same path through the network and MUST use
the same network resources.
3.2 No Disruption of User Traffic
The transfer process MUST NOT cause any disruption of user traffic
flowing over the LSP whose control is being transferred or any other
LSP in the network.
3.3 Transfer from Management Plane to Control Plane
It MUST be possible to transfer the ownership of an LSP from the
Management Plane to the Control Plane
3.4 Transfer from Control Plane to Management Plane
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It SHOULD be possible to transfer the ownership of an LSP from the
Control Plane to the Management Plane.
3.5 Synchronization of state among nodes during conversion
It MUST be assured that the state of the LSP is synchronized among
all nodes traversed by it before proceeding to the conversion.
3.6 Support of Soft Permanent Connections
It MUST be possible to segment an LSP such that it is converted to
or from an SPC.
3.7 Failure of Transfer
It MUST be possible for a transfer from one plane to the other to
fail in a non-destructive way leaving the ownership unchanged and
without impacting traffic.
If during the transfer procedure some issues arise causing an
unsuccessful or incomplete, unexpected result it MUST be assured
that at the end:
1) Traffic over Data Plane is not affected
2) The LSP status is consistent in all the TNEs involved in the
procedure
Point 2 above assures that, even in case of some failure during the
transfer, the state of the affected LSP is brought back to the
initial one and it is fully under control of the owning entity.
4 Security Considerations
Allowing control of an LSP to be taken away from a plane introduces
another way in which services may be disrupted by malicious
intervention.
It is expected that any solution to the requirements in this
document will utilize the security mechanisms inherent in the
Management Plane and Control Plane protocols, and no new security
mechanisms are needed if these tools are correctly used.
Note also that implementations may enable policy components to help
determine whether individual LSPs may be transferred between planes.
5 IANA Considerations
This requirement document makes no requests for IANA action.
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6 References
6.1 Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997
6.2 Informative References
[2] L. Berger (Ed.) "Generalized Multi-Protocol Label Switching
(GMPLS) Signaling Functional Description", RFC 3471, January 2003
[3] L. Berger (Ed.) "Generalized Multi-Protocol Label Switching
(GMPLS) Signaling Resource ReserVation Protocol-Traffic Engineering
(RSVP-TE) Extensions", RFC 3473, January 2003
7 Acknowledgments
We whish to thank the following people (listed randomly) Adrian
Farrel for his editorial assistance to prepare this draft for
publication, Dean Cheng and Julien Meuric, Dimitri Papadimitriou,
Deborah Brungard, Igor Bryskin, Lou Berger, Don Fedyk, John Drake
and Vijay Pandian for their suggestions and comments on the CCAMP
list.
8 Authors' Addresses
Diego Caviglia
Marconi
Via A. Negrone 1/A
Genova-Sestri Ponente, Italy
Phone: +390106003738
Email: diego.caviglia@marconi.com
Dino Bramanti
Marconi
Via Moruzzi 1
C/O Area Ricerca CNR
Pisa, Italy
Email: dino.bramanti@marconi.com
Nicola Ciulli
NextWorks
Corso Italia 116
56125 Pisa, Italy
Email: n.ciulli@nextworks.it
Dan Li
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Huawei Technologies Co., LTD.
Huawei Base, Bantian, Longgang,
Shenzhen 518129 P.R.China
danli@huawei.com
Tel: +86-755-28972910
Han Li
China Mobile Communications Co.
53A Xibianmennei Ave. Xuanwu District
Beijing 100053 P.R. China
lihan@chinamobile.com
Tel: +86-10-66006688 ext. 3092
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