Re: [Netconf] AD review for draft-ietf-netconf-partial-lock-08.txt

From: Bert Wijnen (IETF) [mailto:bertietf at bwijnen.net]
Sent: Wednesday, July 01, 2009 5:08 PM
To: Balazs Lengyel; Romascanu, Dan (Dan); Martin Bjorklund
Cc: netconf mailing list
Subject: Re: [Netconf] AD review for draft-ietf-netconf-partial-lock-08.txt

Dan, is there any new text that Balazs should include in the next (hopefully final)

draft-ietf-netconf-partial-lock-08.txt

draft-ietf-netconf-partial-lock-09.txt

NETCONF B. Lengyel

Internet-Draft Ericsson

Intended status: Standards Track M. Bjorklund

Expires: December 5, 2009 Tail-f Systems

Expires: December 13, 2009 Tail-f Systems

June 03, 2009

June 11, 2009

Partial Lock RPC for NETCONF

draft-ietf-netconf-partial-lock-08

draft-ietf-netconf-partial-lock-09

Status of this Memo

This Internet-Draft is submitted to IETF in full conformance with the

provisions of BCP 78 and BCP 79.

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Abstract

The NETCONF protocol defines the lock and unlock RPCs, used to 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.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4

1.1. Definition of Terms . . . . . . . . . . . . . . . . . . . 3

1.1. Definition of Terms . . . . . . . . . . . . . . . . . . . 4

2. Partial Locking Capability . . . . . . . . . . . . . . . . . . 3

2. Partial Locking Capability . . . . . . . . . . . . . . . . . . 4

2.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 4

2.1.1. Usage Scenarios . . . . . . . . . . . . . . . . . . . 4

2.1.1. Usage Scenarios . . . . . . . . . . . . . . . . . . . 5

2.2. Dependencies . . . . . . . . . . . . . . . . . . . . . . . 6

2.2. Dependencies . . . . . . . . . . . . . . . . . . . . . . . 7

2.3. Capability Identifier . . . . . . . . . . . . . . . . . . 6

2.3. Capability Identifier . . . . . . . . . . . . . . . . . . 7

2.4. New Operations . . . . . . . . . . . . . . . . . . . . . . 6

2.4. New Operations . . . . . . . . . . . . . . . . . . . . . . 7

2.4.1. <partial-lock> . . . . . . . . . . . . . . . . . . . . 6

2.4.1. <partial-lock> . . . . . . . . . . . . . . . . . . . . 7

2.4.2. <partial-unlock> . . . . . . . . . . . . . . . . . . . 11

2.4.2. <partial-unlock> . . . . . . . . . . . . . . . . . . . 12

2.5. Modifications to Existing Operations . . . . . . . . . . . 11

2.5. Modifications to Existing Operations . . . . . . . . . . . 13

2.6. Interactions with Other Capabilities . . . . . . . . . . . 12

2.6. Interactions with Other Capabilities . . . . . . . . . . . 14

2.6.1. Candidate Configuration Capability . . . . . . . . . . 12

2.6.1. Candidate Configuration Capability . . . . . . . . . . 14

2.6.2. Confirmed Commit Capability . . . . . . . . . . . . . 12

2.6.2. Confirmed Commit Capability . . . . . . . . . . . . . 14

2.6.3. Distinct Startup Capability . . . . . . . . . . . . . 12

2.6.3. Distinct Startup Capability . . . . . . . . . . . . . 14

3. Security Considerations . . . . . . . . . . . . . . . . . . . 12

3. Security Considerations . . . . . . . . . . . . . . . . . . . 14

4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13

4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15

5. Appendix A - XML Schema for Partial Locking (normative) . . 15

5. Appendix A - XML Schema for Partial Locking (normative) . . 16

6. Appendix B - YANG Module for Partial Locking

(non-normative) . . . . . . . . . . . . . . . . . . . . . . . 19

(non-normative) . . . . . . . . . . . . . . . . . . . . . . . 20

7. Appendix C - Usage Example - Reserving nodes for future

editing (non-normative) . . . . . . . . . . . . . . . . . . . 22

editing (non-normative) . . . . . . . . . . . . . . . . . . . 23

8. Appendix D - Change Log . . . . . . . . . . . . . . . . . . 27

8. Appendix D - Change Log . . . . . . . . . . . . . . . . . . 28

8.1. 07-08 . . . . . . . . . . . . . . . . . . . . . . . . . . 27

8.1. 08-09 . . . . . . . . . . . . . . . . . . . . . . . . . . 28

8.2. 06-07 . . . . . . . . . . . . . . . . . . . . . . . . . . 27

8.2. 07-08 . . . . . . . . . . . . . . . . . . . . . . . . . . 28

8.3. 05-06 . . . . . . . . . . . . . . . . . . . . . . . . . . 27

8.3. 06-07 . . . . . . . . . . . . . . . . . . . . . . . . . . 28

8.4. 04-05 . . . . . . . . . . . . . . . . . . . . . . . . . . 27

8.4. 05-06 . . . . . . . . . . . . . . . . . . . . . . . . . . 28

8.5. 03-04 . . . . . . . . . . . . . . . . . . . . . . . . . . 27

8.5. 04-05 . . . . . . . . . . . . . . . . . . . . . . . . . . 28

8.6. 02-03 . . . . . . . . . . . . . . . . . . . . . . . . . . 28

8.6. 03-04 . . . . . . . . . . . . . . . . . . . . . . . . . . 28

8.7. 01-02 . . . . . . . . . . . . . . . . . . . . . . . . . . 28

8.7. 02-03 . . . . . . . . . . . . . . . . . . . . . . . . . . 29

8.8. 00-01 . . . . . . . . . . . . . . . . . . . . . . . . . . 28

8.8. 01-02 . . . . . . . . . . . . . . . . . . . . . . . . . . 29

8.9. -00 . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

8.9. 00-01 . . . . . . . . . . . . . . . . . . . . . . . . . . 29

9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 29

8.10. -00 . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 30

9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 30

10.1. Normative References . . . . . . . . . . . . . . . . . . . 30

10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 31

10.2. Informative References . . . . . . . . . . . . . . . . . . 30

10.1. Normative References . . . . . . . . . . . . . . . . . . . 31

Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 31

10.2. Informative References . . . . . . . . . . . . . . . . . . 31

Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 32

1. Introduction

The [NETCONF] protocol describes the lock and unlock operations 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 a

capability based extension to the NETCONF protocol to support partial

locking of NETCONF datastores using a mechanism based on the existing

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node in the conceptual XML datastore. It contains an absolute

path _expression_ in abbreviated syntax, where predicates are used

only to specify values for nodes defined as keys to distinguish

multiple instances.

o Scope of the lock: initially the set of nodes returned by the

XPath expressions in a successful partial-lock operation. The set

might be modified if some of the nodes are deleted.

o Protected area: the set of nodes that are protected from

modification by the lock. This consist of nodes in the scope of

modification by the lock. This set consists of nodes in the scope

the lock and nodes in subtrees under them.

of the lock and nodes in subtrees under them.

2. Partial Locking Capability

2.1. Overview

The :partial-lock capability indicates that the device supports the

locking of its configuration with a more limited scope than a

complete configuration datastore. The scope to be locked is

specified by using restricted or full XPath expressions. Partial

locking only affects configuration data.

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2.1.1. Usage Scenarios

In the following we describe a few scenarios for partial locking.

Partial locking is primarily useful towards the running

configuration. However it can be used to lock a candidate datastore

as well. While scenarios using the running datastore are seen as the

most important, as an example a scenario involving the candidate

datastore is also presented. Besides the three described here, there

are many other usage scenarios possible.

2.1.1.1. Multiple managers handling the writable running datastore

2.1.1.1. Multiple managers handling the writable running datastore with

overlapping sections

Multiple managers are handling the same NETCONF agent simultaneously.

The agent is handled via the writable running datastore. Each

manager has his or her own task, which might involve the modification

of overlapping sections of the datastore.

After collecting and analyzing input and preparing the NETCONF

operations off-line, the manager locks the areas that are important

for his task using one single <partial-lock> operation. The manager

executes a number of <edit-config> operations to modify the

configuration, then releases the partial-lock. The lock should be

held for only a short time (seconds rather then minutes). The

held for the shortest possible time (e.g. seconds rather then

manager should collect all human input before locking anything. As

minutes). The manager should collect all human input before locking

each manager locks only a part of the data model, usually multiple

anything. As each manager locks only a part of the data model,

operators can execute the <edit-config> operations simultaneously.

usually multiple operators can execute the <edit-config> operations

simultaneously.

2.1.1.2. Multiple managers handling the writable running datastore,

distinct management areas

Multiple managers are handling the same NETCONF agent simultaneously.

The agent is handled via the writable running datastore. The agent's

data model contains a number of well defined separate areas that can

be configured without impacting other areas. An example can be a

server with multiple applications running on it, or a number of a

network elements with a common NETCONF agent for management.

Each manager has his or her own task, which does not involve the

modification of overlapping sections of the datastore.

The manager locks his area with a <partial-lock> operation, uses a

number of <edit-config> commands to modify it, later releases the

lock. As each manager has his functional area assigned to him, and

he locks only that area, multiple managers can edit the configuration

simultaneously. Locks can be held for extended periods (minutes,

simultaneously. Locks can be held for extended periods (e.g.

hours), as this will not hinder other managers.

minutes, hours), as this will not hinder other managers.

This scenario assumes, that the global lock operation from [NETCONF]

is not used.

2.1.1.3. Multiple managers handling the candidate datastore in a semi-

coordinated work mode

Multiple managers are handling the same NETCONF agent simultaneously.

The agent is handled via the candidate datastore. Each manager has

his or her own task which might involve the modification of

overlapping sections of the datastore.

After collecting and analyzing input and preparing the NETCONF

operations off-line, the manager locks the areas that are important

for his task using one single <partial-lock> operation in both the

candidate and the running datastore. He executes a number of <edit-

config> operations to modify the configuration, then releases the

partial-lock. The lock should be held for only a short time (seconds

partial-lock. The lock should only be held for the shortest possible

rather then minutes).

time (e.g. seconds rather then minutes).

Operators coordinate with each other. When all of them finish their

tasks one of them orders commit. If any of the operators are still

working, and holds a lock, the commit will fail, and will need to be

repeated after all managers finish.

Warning: When multiple managers use the candidate configuration in

parallel, there is a risk that the interaction of access control

(which is still implementation specific at the time of this writing)

and the commit operation might result in a dead-lock, as illustrated

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The <partial-lock> operation is designed for simplicity, so when a

partial lock is executed you get what you asked for: a set of nodes

that are locked for writing. As a consequence users must observe the

following:

o Locking does not affect read operations.

o If part of a datastore is locked, this has no effect on any

unlocked parts of the datastore. If this is a problem (e.g.,

changes depend on data values or nodes outside the protected part

of the datastore), these nodes should be included in the protected

of the datastore), these nodes SHOULD be included in the protected

area of the lock.

o Configuration data can be edited both inside and outside the

protected area of a lock. It is the responsibility of the NETCONF

client application to lock all relevant parts of a datastore that

are crucial for a specific management action.

Note: The <partial-lock> operation does not modify the global <lock>

operation defined in the base NETCONF Protocol [NETCONF]. If part of

a datastore is already locked by <partial-lock>, then a global lock

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not an Instance Identifier, the <error-tag> is 'invalid-value', the

<error-app-tag> is 'invalid-lock-specification'.

If access control denies the partial lock, the <error-tag> is

'access-denied'.

2.4.1.2. Deadlock Avoidance

As with most locking systems, it is possible that two management

sessions trying to lock different parts of the configuration could

become dead-locked. To avoid this situation, clients should lock

become dead-locked. To avoid this situation, clients SHOULD lock

everything they need in one operation. If locking fails, the client

should back-off, release any previously acquired locks, and retry the

MUST back-off, release any previously acquired locks, and SHOULD

procedure after waiting some randomized time interval.

retry the procedure after waiting some randomized time interval.

2.4.2. <partial-unlock>

The operation unlocks the parts of the datastores that were

previously locked using <partial-lock> during the same session.

Parameters:

lock-id: Identity of the lock to be unlocked. This lock-id MUST

have been received as a response to a lock request by the manager

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users's sessions.

The NETCONF server may log partial lock requests in an audit

trail.

A lock that is hung for some reason (e.g., a broken TCP connection

that the server has not yet recognised) can be released using another

NETCONF session by explicitly killing the session owning that lock

using the <kill-session> operation.

Partial locking is NOT an authorization mechanism; it SHOULD NOT be

Partial locking is not an authorization mechanism; it SHOULD NOT be

used to provide security or access control. Partial locking SHOULD

only be used as a mechanism for providing consistency when multiple

managers are trying to configure the node. It is vital that users

easily understand the exact scope of a lock. This is why the scope

is determined when granting a lock and is not modified thereafter.

4. IANA Considerations

This document registers two URIs for the NETCONF XML namespace in the

IETF XML registry [RFC3688]. Note that the capability URN is

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<nc:rpc xmlns="urn:ietf:params:xml:ns:netconf:partial-lock:1.0"

xmlns:nc="urn:ietf:params:xml:ns:netconf:base:1.0"

message-id="105">

<partial-unlock>

<lock-id>1</lock-id>

</partial-unlock>

</nc:rpc>

8. Appendix D - Change Log

8.1. 07-08

8.1. 08-09

Clarifications

8.2. 06-07

8.2. 07-08

Clarifications

8.3. 06-07

Changed XSD and YANG to allow additional proprietary datastores to be

locked.

8.3. 05-06

8.4. 05-06

Added usage example

Clarified error messages

Clarified interaction with edit-config continue-on-error

Improved YANG: indentation, canonical order, contact info

Added usage example in appendix C

Synchronized YANG and XSD

8.4. 04-05

8.5. 04-05

Language and editorial updates

all app-tags are with dashes without spaces

Added usage scenarios

Changed encoding

Clarified definitions, separated scope of lock and protected area

8.5. 03-04

8.6. 03-04

Minor clarifications

Added list of locked-nodes to the output of partial-lock.

Added <target> wrapper around datastore names.

Allowed atomic/one operation locking of datastore parts in multiple

datastores.

Improved English (hopefully)

Removed the <data> element from rpc-reply following the text of

rfc4741.

8.6. 02-03

8.7. 02-03

Minor clarifications

Same descriptions in XSD and YANG.

8.7. 01-02

8.8. 01-02

Made XSD normative

Clarified that no specific access control is assumed.

Clarified that non-existing nodes are NOT covered by the lock, even

if they where existing and covered by the lock when it was originally

granted.

Some rewording

Added app-tags for two of the error cases.

Made YANG an informative reference

Enhanced security considerations.

8.8. 00-01

8.9. 00-01

Added YANG module.

8.9. -00

8.10. -00

Created from draft-lengyel-ngo-partial-lock-01.txt

9. Acknowledgements

Thanks to Andy Bierman, Sharon Chisholm, Phil Shafer , David

Harrington, Mehmet Ersue, Wes Hardaker, Juergen Schoenwaelder, Washam

Fan and many other members of the NETCONF WG for providing important

input to this document.

End of changes. 25 change blocks.

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82 lines changed or added

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Re: [Netconf] AD review for draft-ietf-netconf-partial-lock-08.txt

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