NETCONF B. Lengyel Internet-Draft Ericsson Hungary Intended status: Standards Track M. Bjorklund Expires: August 28, 2008 Tail-f Systems February 25, 2008 Partial Lock RPC for NETCONF draft-ietf-netconf-partial-lock-01 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on August 28, 2008. Copyright Notice Copyright (C) The IETF Trust (2008). Abstract The NETCONF protocol defines the lock and unlock RPCs that lock entire configuration datastores. In some situations, a way to lock only parts of a configuration datastore is required. This document defines a capability-based extension to the NETCONF protocol for locking portions of a configuration datastore. Lengyel & Bjorklund Expires August 28, 2008 [Page 1] Internet-Draft Partial Lock RPC for NETCONF February 2008 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Definition of Terms . . . . . . . . . . . . . . . . . . . 3 2. Partial Locking Capability . . . . . . . . . . . . . . . . . . 3 2.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.2. Dependencies . . . . . . . . . . . . . . . . . . . . . . . 4 2.3. Capability Identifier . . . . . . . . . . . . . . . . . . 4 2.4. New Operations . . . . . . . . . . . . . . . . . . . . . . 4 2.4.1. . . . . . . . . . . . . . . . . . . . . 4 2.4.2. . . . . . . . . . . . . . . . . . . . 7 2.5. Modifications to Existing Operations . . . . . . . . . . . 8 2.6. Interactions with Other Capabilities . . . . . . . . . . . 8 2.6.1. Writable-Running Capability . . . . . . . . . . . . . 8 2.6.2. Candidate Configuration Capability . . . . . . . . . . 8 2.6.3. Distinct Startup Capability . . . . . . . . . . . . . 8 3. Security Considerations . . . . . . . . . . . . . . . . . . . 8 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 5. Appendix A - Change Log . . . . . . . . . . . . . . . . . . 10 5.1. Open Issues . . . . . . . . . . . . . . . . . . . . . . . 10 5.2. -00 . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 5.3. 00-01 . . . . . . . . . . . . . . . . . . . . . . . . . . 10 6. Appendix B - YANG Module for Partial Locking (non-normative) . . . . . . . . . . . . . . . . . . . . . . . 11 7. Appendix C - XML Schema for Partial Locking (non-normative) . . . . . . . . . . . . . . . . . . . . . . . 13 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15 9. Normative References . . . . . . . . . . . . . . . . . . . . . 16 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17 Intellectual Property and Copyright Statements . . . . . . . . . . 18 Lengyel & Bjorklund Expires August 28, 2008 [Page 2] Internet-Draft Partial Lock RPC for NETCONF February 2008 1. Introduction The NETCONF protocol [RFC4741] describes the lock and unlock RPCs that operate on entire configuration datastores. Often, multiple management sessions need to be able to modify the configuration of a managed device in parallel. In these cases, locking only parts of a configuration datastore is needed. This document defines an extension to the NETCONF protocol to allow this. The mechanism for partial locking is based on the existing XPath filtering mechanisms. Partial locking is defined as a capability to NETCONF. 1.1. Definition of Terms The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14, [RFC2119]. 2. Partial Locking Capability 2.1. Overview The :partial-lock capability indicates that the device supports the locking of its configuration with a scope smaller then a complete configuration datastore. The scope to be locked is specified by using restricted or full XPath expressions. Partial locking covers configuration data, but not state data. The system ensures that configuration resources covered by the lock are not be modified by other NETCONF or non-NETCONF management operations such as SNMP and the CLI. The duration of the partial lock is defined as beginning when the partial lock is granted and lasting until either the corresponding operation succeeds or the NETCONF session terminates. A NETCONF session MAY have multiple parts of one or more datastores locked using partial lock operations. The operation returns a lock-id to identify each successfully acquired lock. Lengyel & Bjorklund Expires August 28, 2008 [Page 3] Internet-Draft Partial Lock RPC for NETCONF February 2008 2.2. Dependencies Partial locking uses only restricted XPath expressions to describe the lock's scope, as described in Section 2.4.1 for the select element. However if optionally the :xpath capability is also supported, partial locking can utilize any Xpath 1.0 expression. 2.3. Capability Identifier urn:ietf:params:netconf:capability:partial-lock:1.0 2.4. New Operations 2.4.1. The operation allows the client to lock a portion of a data store. The portion to lock is specified by using XPath expressions in the select elements of the operation. Each XPath expression MUST return a node set. The select XPath expressions are evaluated only once at lock time, thereafter the scope of the lock is maintained as a set of nodes. If the configuration data is later altered in a way that would make the original select XPath expressions evaluate to a different set of nodes, this does not affect the scope of the partial lock. XPath is only used for the creation of the partial lock. Conceptually the scope of the lock is defined by the returned nodeset and not by the XPath expression. A operation MUST be handled atomically by the NETCONF server. The server either locks all requested parts of the data store or none. If a node is locked by a session, only that same session is able to modify that node or any node in the subtree underneath it. If a top level node of a locked subtree is deleted, any other session can recreate it, as it is not covered by the lock anymore. A partial lock MUST fail if: o Any NETCONF session (including the current session) owns the global lock on the datastore. o Any part of the scope to be locked is already locked by another management session/protocol, including other NETCONF sessions using the or any other non-NETCONF management Lengyel & Bjorklund Expires August 28, 2008 [Page 4] Internet-Draft Partial Lock RPC for NETCONF February 2008 method. o The NETCONF server implements access control and the locking user does not have at least some basic access rights, e.g., read rights, to all of the datastore section to be locked. The exact handling of access rights is outside the scope of this document, but it is assumed that there is an access control system that MAY deny or allow the partial lock operation. As with most locking systems, there is a possibility that two users trying to lock different parts of the configuration become dead- locked. To avoid this situation, clients SHOULD lock everything they need in one operation. If that operation still fails, the client SHOULD back down, release any already acquired locks, and retry the procedure after some time interval. The length of the interval should preferably be random to avoid repeated dead-locks when both (or all) clients back down and then repeat locking. It is the intention to keep partial-locking simple, so when a partial lock is executed you get what you asked for: a set of nodes that are locked for writing. There are some other issues that are intentionally not addressed for the sake of simplicity. o Locking does not effect read operations. o If a part of a datastore is locked, this has no effect on any unlocked parts of the datastore. If this is a problem e.g. the operator's changes depend on data values in the unlocked part of the datastore, the operator should include these values in the scope of the lock. o An operator is allowed to edit the configuration both inside and outside the scope of a lock. It is the operator's responsibility to lock all parts of the datastore that are crucial for a specific management action. Note: The operation does not modify the global operation defined in the base NETCONF Protocol [RFC4741]. If part of a datastore is already locked by , then a global lock for that datastore fails even if the global lock is attempted by the same NETCONF session which owns the partial-lock. Parameters: Lengyel & Bjorklund Expires August 28, 2008 [Page 5] Internet-Draft Partial Lock RPC for NETCONF February 2008 target: Name of the configuration datastore of which a part shall be locked. URLs are not accepted. select: One or more 'select' elements each containing an XPath expression. The XPath expression is evaluated in a context where the context node is the root of the server's conceptual data model, and the set of namespace declarations are those in scope on the select element. The select expressions MUST return a node set. If the device supports the :xpath capability as well any valid XPath 1.0 expression can be used, if not, the XPath expression MUST be limited to an Instance Identifier expression [Editor's Note: add text or reference]. An Instance Identifier is an absolute path expression in abbreviated syntax, where predicates are used only to specify values for nodes defined as keys to distinguish multiple instances.] Example: Lock virtual router 1 and interface eth1 xmlns:if="http://example.com/ns/interface"> nc:message-id="135"> xmlns:if="http://example.com/ns/interface"> nc:message-id="135"> 127 Positive Response: Lengyel & Bjorklund Expires August 28, 2008 [Page 6] Internet-Draft Partial Lock RPC for NETCONF February 2008 If the device was able to satisfy the request, an is sent with a element (lock identifier) in the element. Negative Response: If a lock is already held on any node within the subtrees to be locked, the element shall be 'lock-denied' and the element shall include the of the lock owner. If the lock is held by a non-NETCONF entity, a of 0 (zero) is included. If the select expressions return an empty node set, the shall be 'operation-failed', and the shall be 'no- matches'. If any select expression returns anything but a node set, the shall be 'invalid-value'. If the :xpath capability is not supported and the XPath expression is not an Instance Identifier, the shall be 'invalid-value'. If access control denies the partial lock, the shall be 'access-denied'. 2.4.2. The operation unlocks a part of a datastore that was previously locked using during the same session. Parameters: lock-id: Lock identifier to unlock; taken from a reply to a previous operation. Example: Unlock 127 Positive Response: Lengyel & Bjorklund Expires August 28, 2008 [Page 7] Internet-Draft Partial Lock RPC for NETCONF February 2008 If the device was able to satisfy the request, an is sent that contains an element. A positive response MUST be sent even if all of the locked part of the datastore has already been deleted. Negative Response: If the parameter does not identify a lock which is owned by the session, an 'invalid-value' error is returned. 2.5. Modifications to Existing Operations None. 2.6. Interactions with Other Capabilities 2.6.1. Writable-Running Capability Partial locking of the running datastore can only be done if the :writable-running capability is supported by the device. 2.6.2. Candidate Configuration Capability Partial locking of the candidate datastore can only be done if the :candidate capability is supported by the device. The partial locking of the candidate datastore does not depend on whether the datastore was modified or not. 2.6.3. Distinct Startup Capability Partial locking of the startup datastore can only be done if the :startup capability is supported by the device. 3. Security Considerations The same considerations as for the base NETCONF Protocol [RFC4741] are valid. It is assumed that the and RPCs are only allowed for an authenticated user after passing some access control mechanism. Lengyel & Bjorklund Expires August 28, 2008 [Page 8] Internet-Draft Partial Lock RPC for NETCONF February 2008 4. IANA Considerations This document registers a URN for the the following NETCONF capability in the netconf registry (RFC4741], sect 10.3): +---------------+---------------------------------------------------+ | Index | Capability Identifier | +---------------+---------------------------------------------------+ | :partial-lock | urn:ietf:params:netconf:capability:partial-lock:1 | | | .0 | +---------------+---------------------------------------------------+ Lengyel & Bjorklund Expires August 28, 2008 [Page 9] Internet-Draft Partial Lock RPC for NETCONF February 2008 5. Appendix A - Change Log 5.1. Open Issues Shall we allow the locking of non-existent nodes? The operator might want to reserve an object or rather its key/name even if he will create the object later. Should we include more detailed information in error results to help debug lock conflicts, e.g. the userId of the conflicting session, the XPath expression of the conflicting session, the instanceId of the first object where the lock conflict was found? Should we allow users to lock parts of multiple datastores (e.g. /top/routing both in the candidate and the running datastore) in one operation? This would decrease the probability of a dead- lock, but currently the (global) operation doesn't support this. 5.2. -00 Created from draft-lengyel-ngo-partial-lock-01.txt 5.3. 00-01 Added YANG module. Lengyel & Bjorklund Expires August 28, 2008 [Page 10] Internet-Draft Partial Lock RPC for NETCONF February 2008 6. Appendix B - YANG Module for Partial Locking (non-normative) The following Yang modul defines the and operations. This and the following Appendix are non-normative as the method to define NETCONF operations is not yet agreed. Either the YANG or the XSD or some other model will later probably become normative. module netconf-partial-lock { namespace urn:ietf:params:xml:ns:netconf:partial-lock:1.0; prefix pl; organization "IETF NETCONF Working Group"; contact "Balazs Lengyel Ericsson Hungary, Inc. balazs.lengyel@ericsson.com"; description "This YANG module defines the and operations."; revision 2008-01-07 { description "Inital version."; } grouping configName { description "A choice to list the datastore names for NETCONF. This could be moved to a netconf.yang module."; choice configNameType { leaf running { type empty; } leaf candidate { type empty; } leaf startup { type empty; } } } rpc partial-lock { input { uses configName; leaf-list select { type string; min-elements 1; } } output { Lengyel & Bjorklund Expires August 28, 2008 [Page 11] Internet-Draft Partial Lock RPC for NETCONF February 2008 leaf lockId { type uint32; } } } rpc partial-unlock { input { leaf lockId { type uint32; } } } } Lengyel & Bjorklund Expires August 28, 2008 [Page 12] Internet-Draft Partial Lock RPC for NETCONF February 2008 7. Appendix C - XML Schema for Partial Locking (non-normative) The following XML Schema defines the and operations: Schema defining the partial-lock and unlock operations. Lengyel & Bjorklund Expires August 28, 2008 [Page 13] Internet-Draft Partial Lock RPC for NETCONF February 2008 Lengyel & Bjorklund Expires August 28, 2008 [Page 14] Internet-Draft Partial Lock RPC for NETCONF February 2008 8. Acknowledgements Thanks to Andy Bierman, Sharon Chisholm, Phil Shafer and many other members of the NETCONF WG for providing important input to this document. Lengyel & Bjorklund Expires August 28, 2008 [Page 15] Internet-Draft Partial Lock RPC for NETCONF February 2008 9. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC4741] "NETCONF Configuration Protocol", RFC 4741, December 2006. Lengyel & Bjorklund Expires August 28, 2008 [Page 16] Internet-Draft Partial Lock RPC for NETCONF February 2008 Authors' Addresses Balazs Lengyel Ericsson Hungary Email: balazs.lengyel@ericsson.com Martin Bjorklund Tail-f Systems Email: mbj@tail-f.com Lengyel & Bjorklund Expires August 28, 2008 [Page 17] Internet-Draft Partial Lock RPC for NETCONF February 2008 Full Copyright Statement Copyright (C) The IETF Trust (2008). 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