draft-caviglia-ccamp-pc-and-sc-reqs-02.txt     June 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-02.txt 
                                                                        
   Expires:                                               December 2006 
    
    
     Requirements for the Conversion Between Permanent Connections and 
    Switched Connections in a Generalized Multiprotocol Label Switching 
                              (GMPLS) Network 
    
Status of this Memo 
    
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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  Label Switched Path Terminology.............................3 
   1.2  LSP within GMPLS Control Plane..............................4 
   1.3  Resource Ownership..........................................4 
   1.4  Migration to GMPLS Control..................................4 
   2  Typical Use Cases..............................................5 
   2.1  PC to SC Conversion.........................................5 
   2.2  SC to PC Conversion.........................................5 
   3  Problem Explanation............................................6 
   4  Requirements...................................................7 
   4.1  Data Plane LSP Consistency..................................7 
   4.2  No Disruption of User Traffic...............................7 
   4.3  Transfer from Management Plane to Control Plane.............7 
   4.4  Transfer from Control Plane to Management Plane.............7 
   4.5  Synchronization of state among nodes during migration.......7 
   4.6  Support of Soft Permanent Connections.......................7 
   4.7  Failure of Transfer.........................................7 
   4.8  Backward Compatibility......................................8 
   4.9  Re-Use of Protocol Mechanisms...............................8 
   5  Security Considerations........................................8 
   6  IANA Consideration.............................................8 
   7  References.....................................................8 
   7.1  Normative References........................................8 
   7.2  Informative References......................................8 
   8  Acknowledgments................................................9 
    










 
 
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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  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. 
 
 
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   In this document, when we talk about the LSP migration between 
   Control plane and Management plane, we mainly focus on the migration 
   of control plane state information and management state information. 
    
    
1.2  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.  
    
1.3  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 as a controlling interest in the resource. Consider, for 
   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. 
    
1.4  Migration to GMPLS Control 
    
   The deployment 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 

 
 
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   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 migrate 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. Where such connections are in service, such 
   migration must be performed in a way that does not affect traffic. 
    
   Since attempts to migrate to GMPLS control might fail it is also 
   advisable to have a mechanism to convert the control of an LSP back 
   to the Management Plane. 
    
   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 (PC to SC, PC to SPC, and SPC to SC). So the reverse 
   mappings are also needed (SC to PC, SC to SPC, and SPC to PC). 
    
2    Typical Use Cases 
    
2.1  PC to SC Conversion 
    
   A typical scenario where a "PC to 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 are 
   already set up as PCs and are owned by the Management Plane. 
    
   As part of a migration strategy another similar scenario will arise 
   when a network is partially controlled by the Management Plane and 
   partially controlled by the Control Plane (PCs and SCs coexist), and 
   an upgrade or coverage extension of the Control Plane is required.  
    
   In both cases, a connection, set up and owned by the Management 
   Plane, may need to be transferred to Control Plane control. Where 
   the connection is carrying traffic, this transfer has to be done 
   without any disruption to the Data Plane traffic.  
    
2.2  SC to PC Conversion 
    
   An example of a scenario where the "SPC to PC" procedure may be used 
   is when a Control Plane failure happens in a certain area of the 
   network, and the ability of the Control Plane to control the 
   connections is partially lost. In such a case, according to the 
   configured policy at each node, the Data Plane connections which are 
   owned by the Control Plane could be smoothly switched over to 
 
 
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   Management Plane. Again there is a requirement that this is achieved 
   without any interference to the associated Data Plane state so that 
   the connection continues to be operational and to carry traffic 
   during the transition.  
    
3    Problem Explanation 
    
   Having the ownership of an LSP means having ownership of the 
   resources used by the LSP as defined in section 1.2. 
    
   In general when the Management Plane has ownership of an LSP the 
   Control Plane cannot see the LSP and cannot exert control over the 
   resources used by the LSP. Depending on implementation, any attempt 
   by the Control Plane to exert control over the resources will fail. 
   For example, an attempt to set up a new LSP within the Control Plane 
   that uses a resource owned by the Management Plane will fail. 
    
   In general, when the Control Plane has ownership of an LSP the 
   Management Plane has restricted control over the resources used by 
   the LSP. The Management Plane may be able to see the Control Plane 
   LSP (in fact, this is one of the objectives of a Management Plane), 
   but the Management Plane cannot provision a new LSP that uses the 
   resources in use for the Control Plane LSP. As described in section 
   1.2, the Management Plane may have some direct control over the 
   resources in use for Control Plane controlled LSPs (for example, for 
   safety reasons), but this does not alter the basic ownership 
   property of those resources. 
    
   It is always the case that the Management and Control Planes cannot 
   directly change each other`s LSP state. 
    
   Therefore, in order to transfer the ownership of an LSP from one 
   plane to another, it is not simply enough to initiate the normal 
   procedures for setting up an LSP in the plane that is taking over. 
   For example, if an attempt is made for the Control Plane to take 
   over a Management Plane LSP by the use of normal signaling messages 
   then there are two possibilities. 
    
   - If the signaling messages do not specify the precise Data Plane 
   resources to be used, a new LSP will be established in the Data 
   Plane using different resources from those in use by the Management 
   Plane LSP. This is not the objective since such a procedure would 
   require the data to be switched to the new LSP which might involve 
   interruption to the traffic. Further, the network may be 
   sufficiently resource constrained that such a process is impossible. 
    
   - If the signaling messages specify the precise resources to use in 
   order to ensure that the new Control Plane LSP will use the same 
   resources as the Management Plane LSP, then the Control Plane LSP 
 
 
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   will fail to set up because the resources are already in use and 
   owned by the Management Plane. 
    
   Clearly some new procedures and protocol extensions are needed to 
   enable this simple function. 
4    Requirements 
    
   This section sets out the basic requirements for procedures and 
   processes that are used to perform the functions described in this 
   document. 
    
4.1  Data Plane LSP Consistency 
    
   The Data Plane LSP in place before and after the transfer process 
   MUST follow the same path through the network and MUST use the same 
   network resources. 
    
4.2  No Disruption of User Traffic 
    
   The transfer process MUST NOT cause any disruption of user traffic 
   on the LSP being transferred or any other LSP in the network. 
    
4.3  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 
    
4.4  Transfer from Control Plane to Management Plane 
    
   It MUST be possible to transfer the ownership of an LSP from the 
   Control Plane to the Management Plane. 
    
4.5  Synchronization of state among nodes during migration 
    
   It MUST be assured that the state of the LSP is synchronized among 
   all nodes traversed by it before proceeding to the migration.  
    
4.6  Support of Soft Permanent Connections 
    
   It MUST be possible to segment an LSP such that it is converted to 
   or from an SPC. 
    
4.7  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. 
    

 
 
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4.8  Backward Compatibility 
    
   Any new procedures and protocol extensions MUST be fully backward 
   compatible. This means that should any LSR on the path of an LSP be 
   unable to handle the new procedures or protocol extensions the 
   design of the procedures and specification of the extensions MUST be 
   such that a transfer failure automatically occurs and the ownership 
   remains unchanged. 
    
4.9  Re-Use of Protocol Mechanisms 
    
   Any new procedures or protocol extensions SHOULD make use of 
   existing procedures and protocol objects where possible. 
    
5    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. 
    
6    IANA Consideration  
    
   This requirement document makes no requests for IANA action. 
    
7    References 
    
7.1  Normative References 
    
    [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement 
   Levels", BCP 14, RFC 2119, March 1997  
        
7.2   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  
    

 
 
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8    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 and 
   Vijay Pandian for their suggestions and comments on the CCAMP list.  
    
9  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  
      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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