Network work group Diego Caviglia
Internet Draft Dino Bramanti
Ericsson
Dan Li
Huawei
Dave McDysan
Verizon
Intended Status: Informational
Expires: February 2008 August 3, 2007
Requirements for the Conversion Between Permanent Connections and
Switched Connections in a Generalized Multiprotocol Label Switching
(GMPLS) Network
draft-ietf-ccamp-pc-and-sc-reqs-01.txt
Status of this Memo
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Abstract
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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.
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 [RFC 2119].
Table of Contents
1. Introduction.................................................3
2. Motivation...................................................3
3. Label Switched Path Terminology..............................4
4. LSP within GMPLS Control Plane...............................4
4.1. Resource Ownership......................................4
4.2. Setting Up a GMPLS Controlled Network...................5
5. Typical Use Cases............................................6
5.1. PC to SC/SPC Conversion.................................6
5.2. SC to PC Conversion.....................................7
6. Requirements.................................................7
6.1. Data Plane LSP Consistency..............................7
6.2. No Disruption of User Traffic...........................7
6.3. Transfer from Management Plane to Control Plane.........8
6.4. Transfer from Control Plane to Management Plane.........8
6.5. Synchronization of state among nodes during conversion..8
6.6. Support of Soft Permanent Connections...................8
6.7. Failure of Transfer.....................................8
7. Security Considerations......................................8
8. IANA Considerations..........................................9
9. References...................................................9
9.1. Normative References....................................9
9.2. Informative References..................................9
10. Acknowledgments.............................................9
11. Authors' Addresses.........................................10
12. Full Copyright Statement...................................11
13. Intellectual Property Statement............................11
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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) [G.8081].
When the setup, teardown, and maintenance of connections are achieved
by means of a signaling protocol owned by the Control Plane such
connections are known as Switched Connections (SCs) [G.8081].
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 [G.8081].
At least some control plane initiated aspects of a connection must be
capable of being queried by the management plane. These aspects
should be independent of how the connection was established.
2. Motivation
The main motivation for this work is the LSP conversion from
Management Plane PC to Control Plane SC. The objective is to be able
to introduce a control plane into an existing network without
disrupting user traffic. An example of this is an operator
establishing PCs before the SC technology is mature, or SC
interoperation is achieved between multiple implementations.
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, or desirable, feature. The
requirement for LSP conversion from Control Plane to Management Plane
should be scoped as a back-out procedure.
A significant benefit of GMPLS in networks is discovering and
validating the current state of the network. For example, an operator
could invoke an SC, determine that the automatically discovered path
is good and then "pin" a connection to this specific path using the
SC to PC conversion procedures. This is attractive to network
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operators who prefer the static nature of the path for a PC as
compared with the potentially dynamic path of an SC.
3. 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.
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
Management Plane and Control Plane, we mainly focus on the conversion
of Control Plane state information and Management Plane state
information.
4. LSP within GMPLS Control Plane
Generalized Multiprotocol Label Switching (GMPLS) [RFC 3471], [RFC
3473] 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 TDM
(SDH/SONET G.709 at ODUk level) transport and WDM (G.709 OCh level).
4.1. 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
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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). Note that the management plane assigns
resources to the control plane.
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 e.g. the
basic safety requirements that imply that management commands must be
available to set laser out of service.
4.2. 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 highly
desirable to have a mechanism to convert the control of an LSP back
to the Management Plane, in fact undoing the whole process for
reasons summarized in the motivation section.
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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).
Conversion to/from control/management will occur in many MIBs or
network management data structures where the owner of the hop level
information (e.g., cross-connect, label assignment, label stacking,
etc.) is identified as either a specific control protocol, or manual
(i.e., NMS). When converting, this hop-level owner information needs
to be completed for all hops. If conversion cannot be done for all
hops, then the conversion must be done for no hops and the state of
the hop level information restored to that before the conversion was
attempted, and an error condition reported to the management system.
In either case of conversion, the Management Plane shall initiate the
change. When converting from a PC to an SC, the management system
must somehow indicate to each hop that a control protocol is now to
be used, and then configure the data needed by control protocol at
the connection endpoints. When converting from an SC to a PC, the
management plane must change the owner of each hop. Somehow, then the
instance in the control plane must be removed without affecting the
data plane. This may best be done via a make before break operation.
The case where the CP and/or MP fail at one or more nodes during the
conversion procedure must be handled in the solution. If the network
is viewed as the database of record (including data, control and
management plane elements), then a solution that has procedures
similar to those of a two-phase database commit process may be needed
to ensure integrity and support the need to revert to the state prior
to the conversion attempt if there is a CP and/or MP failure during
the attempted conversion.
5. Typical Use Cases
5.1. 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 coexist).
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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.
5.2. 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 specified as mandatory in this document, but is still a
highly desirable function.
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.
6. Requirements
This section sets out the basic requirements for procedures and
processes that are used to perform the functions this document is
about.
6.1. 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.
6.2. 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.
SC to PC conversion and vice-versa shall occur without generating
management plane alarms toward the end users at neither the UNI
endpoints nor the NMS.
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6.3. 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
6.4. Transfer from Control Plane to Management Plane
It SHOULD be possible to transfer the ownership of an LSP from the
Control Plane to the Management Plane.
6.5. 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.
6.6. Support of Soft Permanent Connections
It MUST be possible to segment an LSP such that it is converted to or
from an SPC.
6.7. 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 Transport Network Elements
(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.
7. 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
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and Control Plane protocols, and no new security mechanisms are
needed if these tools are correctly used.
If SNMP MIBs are used for configuration, then the management plane
should support at least authentication for PC<>SC configuration
changes as specified in [RFC 3414].
Note also that implementations may enable policy components to help
determine whether individual LSPs may be transferred between planes.
8. IANA Considerations
This requirement document makes no requests for IANA action.
9. References
9.1. Normative References
[RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997
[G.8081] ITU-T, "Terms and definitions for Automatically Switched
Optical Networks (ASON)," Recommendation G.8081/Y.1353,
June 2004
[RFC 3414] U. Blumenthal, B. Wijnen, "User-based Security Model(USM)
for version 3 of the Simple Network Management Protocol
(SNMPv3)," RFC 3414, December 2002
9.2. Informative References
[RFC 3471] L. Berger (Ed.) "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Functional Description", RFC
3471, January 2003
[RFC 3473] L. Berger (Ed.) "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Resource ReserVation
Protocol-Traffic Engineering (RSVP-TE) Extensions", RFC
3473, January 2003
10. 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.
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11. Authors' Addresses
Diego Caviglia
Ericsson
Via A. Negrone 1/A
Genova-Sestri Ponente, Italy
Phone: +390106003738
Email: diego.caviglia@marconi.com
Dino Bramanti
Ericsson
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
Huawei Technologies Co., LTD.
Huawei Base, Bantian, Longgang,
Shenzhen 518129 P.R.Chin
Phone: +86-755-28972910
Email: danli@huawei.com
Han Li
China Mobile Communications Co.
53A Xibianmennei Ave. Xuanwu District
Beijing 100053 P.R. China
Phone: +86-10-66006688 ext.3092
Email: lihan@chinamobile.com
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Dave McDysan
Verizon
Ashburn, VA, USA
Email: dave.mcdysan@verizon.com
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