RFC3139: Requirements for Configuration Management of IP-based Networks

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Network Working Group                                         L. Sanchez
Request for Comments: 3139                                       Megisto
Category: Informational                                    K. McCloghrie
                                                              J. Saperia
                                                          JDS Consultant
                                                               June 2001

     Requirements for Configuration Management of IP-based Networks

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2001).  All Rights Reserved.


   This memo discusses different approaches to configure networks and
   identifies a set of configuration management requirements for IP-
   based networks.

Table of Contents

   1.0  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . 2
       1.1 Motivation, Scope and Goals of this document . . . . . . . 2
       1.2 Requirements Terminology . . . . . . . . . . . . . . . . . 3
       1.3 Audience . . . . . . . . . . . . . . . . . . . . . . . . . 3
       1.4 Definition of Technical Terms. . . . . . . . . . . . . . . 3
   2.0 Statement of the Problem  . . . . . . . . . . . . . . . . . .  4
   3.0 Requirements for an IP-based Configuration Management System . 7
   4.0 Security Considerations . . . . . . . . . . . . . . . . . . .  9
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  9
   References. . . . . . . . . . . . . . . . . . . . . . . . . . . .  9
   Authors' Addresses. . . . . . . . . . . . . . . . . . . . . . . . 10
   Full Copyright Statement. . . . . . . . . . . . . . . . . . . . . 11

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1.0 Introduction

1.1 Motivation, Scope and Goals of this document

   A number of IETF working groups have introduced new technologies
   which offer integrated and differentiated services.  To support these
   new technologies, working group members found that they had new
   requirements for configuration of these technologies. One of these
   new requirements was for the provisioning (configuration) of behavior
   at the network level.

   An example of this type of configuration would be instructing all
   routers in a network to provide 'gold' service to a particular set of
   customers.  Depending on the specific network equipment and
   definition of 'gold' service, this configuration request might
   translate to different configuration parameters on different vendors
   equipment and many individual configuration commands at the router.
   This higher level of configuration management has come to commonly be
   known as policy based management.

   Working groups associated with these new technologies believed that
   the existing SNMP based management framework, while adequate for
   fault, configuration management at the individual instance (e.g.,
   interface) level, performance and other management functions commonly
   associated with it, was not able to meet these new needs.  As a
   result they began working on new solutions and approaches.

   COPS [COPS] for RSVP [RSVP] provides routers with the opportunity to
   ask their Policy Server for an admit/reject decision for a particular
   RSVP session.  This model allows routers to outsource their resource
   allocation decisions to some other entity.  However, this model does
   not work with DiffServ [DSARCH] where there is no signalling
   protocol.  Therefore, the policies that affect resource allocation
   decisions must be provisioned to the routers.  It became evident that
   there was a need for coordinating both RSVP-based and DiffServ-based
   policies to provide end2end QoS.  Working groups began to extend and
   leverage approaches such as COPS for RSVP to support Diffserv
   policies.  This gave birth to COPS-PR [COPS-PR].

   These extensions caused concern that the IETF was about to develop a
   set of fragmented solutions which were locally optimized for specific
   technologies and not well integrated in the existing Internet
   Management Framework.  The concern prompted some of the Area
   Directors associated with the Operations and Management, Transport
   and General areas, and some IAB members to organize a two day meeting
   in mid September 1999.  The primary purpose of the meeting was to
   examine the requirements for configuration management and evaluate
   the COPS/PIB and SNMP/MIB approaches in light of these requirements.

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   At the end of the two day meeting there was no consensus on several
   issues and as a result a number of 'design teams' were created.  This
   document is the output of the design team chartered with the
   identification of a global set of configuration management
   requirements.  This document has benefited from feedback received
   during the Configuration Management BOF that took place on November
   11, 1999 during the 46th IETF in Washington DC, USA.  The document
   has also benefited from comments sent to the confmgt@ops.ietf.org
   mailing list.

1.2 Requirements Terminology

   Keywords "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT" and
   "MAY" that appear in this document are to be interpreted as described
   in RFC 2119 [Bra97].

1.3 Audience

   The target audience for this document includes system designers,
   implementers of network configuration and management technology and
   others interested in gaining a general background understanding of
   the issues related to configuration management in general, and in the
   Internet in particular along with associated requirements.  This
   document assumes that the reader is familiar with the Internet
   Protocol, related networking technology, and general network
   management terms and concepts.

1.4 Definition of Terms

   Device-Local Configuration

   Configuration data that is specific to a particular network device.
   This is the finest level of granularity for configuring network

   Network-Wide Configuration

   Configuration data that is not specific to any particular network
   device and from which multiple device-local configurations can be
   derived.  Network-wide configuration provides a level of abstraction
   above device-local configurations.

   Configuration Data Translator

   A function that transforms Configuration Management Data (high-level
   policies) or Network-wide configuration data (middle-level policies)
   into device local configurations (low-level policies) based on the

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   generic capabilities of network devices.  This function can be
   performed either by devices themselves or by some intermediate

2.0 Statement of the Problem

   Configuring large networks is becoming an increasingly difficult
   task.  The problem intensifies as networks increase their size, not
   only in terms of number of devices, but also with a greater variety
   of devices, with each device having increasing functionality and
   complexity.  That is, networks are getting more complex in multiple
   dimensions simultaneously (number of devices, time scales for
   configuration, etc.)  making the task of configuring these more

   In the past, configuring a network device has been a three step
   process.  The network operator, engineer or entity responsible for
   the network created a model of the network and its expected behavior.
   Next, this (model + expected behavior) was formalized and recorded in
   the form of high-level policies.  Finally, these policies were then
   translated into device-local configurations and provisioned into each
   network device for enforcement.

   Any high-level policy changes (changes in the network topology and/or
   its expected behavior) needed to be translated and provisioned to all
   network devices affected by the change.  Figure 1 depicts this model
   and shows how high-level policies for a network could be translated
   into four device-local configurations.  In this model, network
   operators or engineers functioned as configuration data translators;
   they translated the high-level policies to device-local configuration

   A configuration data translator could take the topology independent
   behavior description such as high-level policies (first input source)
   combine it with topology information (second input source) as well as
   status/performance/monitoring information (third input source) to
   derive device-local configurations.  Note that there could be several
   configuration data translators operating in tandem on a set of
   devices.  However, there could be only one configuration data
   translator operating at a particular device at any given instance.

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                Configuration Management
               Data (High-level Policies)
   Network                 V                Network
   Topology ----->   Configuration    <---- Status/performance
   Information     Data Translator(s)       Information
     |               |               |               |
   Device          Device          Device          Device
   Local           Local           Local           Local
   Conf(1)         Conf(2)         Conf(3)         Conf(4)

   Figure 1. Current model for configuring network devices.

   Historically, network operators and engineers used protocols and
   mechanisms such as SNMP and CLI applications to provision or
   configure network devices.  In their current versions, these
   mechanisms have proven to be difficult to use because of their low-
   level of granularity and their device-specific nature.  This problem
   is worse when provisioning multiple network devices requiring large
   amounts of configuration data.

   It is evident that network administrators and existing configuration
   management software can not keep up with the growth in complexity of
   networks and that an efficient, integrated configuration management
   solution is needed.  Several IETF Working Groups working on this
   problem converged into adding a layer of abstraction to the
   traditional configuration management process described in figure 1.
   Figure 2 depicts this process after the layer of abstraction is
   added.  As in the previous figure, first the network operator,
   engineer or entity responsible for the network creates a model of the
   network and its expected behavior.  This is formalized and recorded
   in the form of high-level policies.

   These policies are combined with topology information as well as
   status/performance information to generate network-wide configuration
   data.  These middle level-policies are simpler to manage and
   represent behaviors shared by multiple network devices.

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                  Configuration Management
                 Data (High-level Policies)
   Network                  V                 Network
   Topology ----->     Network-Wide     <---- Status/performance
   Information        Configuration           Information
                    Data Translator(s)
     |               |               |               |
   Device          Device          Device          Device
   Local           Local           Local           Local
   Conf(1)         Conf(2)         Conf(3)         Conf(4)

   Figure 2. Proposed model for configuring network devices.

   Device local configurations are generated by automated configuration
   data translators and are supplied to each network device for
   enforcement.  Note how this model only describes the function of the
   configuration data translators and it does not dictate its functional
   location.  This is to say that translators may reside outside of the
   devices (as it was the case in figure 1 since they were humans) or
   may be possibly collocated with each device.

   As in the previous model, any high-level policy changes (changes in
   the network topology and/or its expected behavior) needs to be
   propagated to all network devices affected by the change.  However,
   in the configuration model depicted in figure 2 network operators and
   engineers can specify the behavior of the network in a simplified
   manner reducing the amount of device specific knowledge needed.

   One should keep in mind that in some cases per instance device local
   configuration is needed in network devices.  An integrated solution
   MUST allow room for this.  Also, the introduction of automated
   configuration data translators assumes that all information needed to

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   make an error free conversion of network-wide configuration data into
   device-local configuration data is available.  In the event that such
   data is not available the solution MUST detect this and act

3.0 Requirements for an IP-based Configuration Management System

   All IETF WGs active in this area agrees upon the following
   requirements for configuration management.  An integrated
   configuration management solution MUST:

   1)   provide means by which the behavior of the network can be
         specified at a level of abstraction (network-wide
         configuration) higher than a set of configuration information
         specific to individual devices,

   2)    be capable of translating network-wide configurations into
         device-local configuration.  The identification of the relevant
         subset of the network-wide policies to be down-loaded is
         according to the capabilities of each device,

   3)    be able to interpret device-local configuration, status and
         monitoring information within the context of network-wide

   4)    be capable of provisioning (e.g., adding, modifying, deleting,
         dumping, restoring) complete or partial configuration data to
         network devices simultaneously or in a synchronized fashion as

         4a)   be able to provision multiple device-local configurations
               to support fast switch-overs without the need to down-
               load potentially large configuration changes to many

   5)    provide means by which network devices can send feedback
         information (configuration data confirmation, network status
         and monitoring information, specific events, etc.) to the
         management system,

   6)    be capable of provisioning complete or partial configuration
         data to network devices dynamically as a result of network
         specific or network-wide events,

   7)    provide efficient and reliable means compared to current
         versions of today's mechanisms (CLI, SNMP) to provision large
         amounts of configuration data,

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   8)    provide secure means to provision configuration data.  The
         system must provide support for access control, authentication,
         integrity-checking, replay- protection and/or privacy security
         services.  The minimum level of granularity for access control
         and authentication is host based.  The system SHOULD support
         user/role based access control and authentication for users in
         different roles with different access privileges,

   9)    provide expiration time and effective time capabilities to
         configuration data.  It is required that some configuration
         data items be set to expire, and other items be set to never

   10)   provide error detection (including data-specific errors) and
         failure recovery mechanisms (including prevention of
         inappropriately partial configurations when needed) for the
         provisioning of configuration data,

   11)   eliminate the potential for mis-configuration occurring through
         concurrent shared write access to the device's configuration

   12)   provide facilities (with host and user-based authentication
         granularity) to help in tracing back configuration changes,

   13)   allow for the use of redundant components, both network
         elements and configuration application platforms, and for the
         configuration of redundant network elements.

   14)   be flexible and extensible to accommodate future needs.
         Configuration management data models are not fixed for all time
         and are subject to evolution like any other management data
         model.  It is therefore necessary to anticipate that changes
         will be needed, but it is not possible to anticipate what those
         changes might be.  Such changes could be to the configuration
         data model, supporting message types, data types, etc., and to
         provide mechanisms that can deal with these changes effectively
         without causing inter-operability problems or having to
         replace/update large amounts of fielded networking devices,

   15)   leverage knowledge of the existing SNMP management
         infrastructure.  The system MUST leverage knowledge of and
         experience with MIBs and SMI.

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Security Considerations

   This document reflects the current requirements that the IETF
   believes configuration management systems MUST have to properly
   support IP-based networks.  The authors believe that a configuration
   management system MUST provide mechanisms by which one can ascertain
   the integrity and authenticity of the configuration data at all
   times.  In some cases the privacy of the data is important therefore
   configuration management system MUST provide facilities to support
   this services as required not only while the data is stored but also
   during provisioning or reception.  Requirements eight and twelve
   capture the required security services.


   The authors thank Juergen Schoenwaelder for his contributions to this
   document.  The authors also thank Walter Weiss and Andrew Smith for
   providing feedback to early versions of this document.  Finally, the
   authors thank the IESG for motivating and supporting this work.


   [Bra97]     Bradner, S., "Key Words for use in RFCs to indicate
               Requirement Levels", BCP 14, RFC 2119, March 1997.

   [COPS]      Boyle, J., Cohen, R., Durham, D., Herzog, S., Rajan, R.
               and A. Sastry, "The COPS (Common Open Policy Service)
               Protocol", RFC 2748, August 1999.

   [RSVP]      Braden, R., Editor, et al., "Resource ReSerVation
               Protocol (RSVP) Version 1 - Functional Specification",
               RFC 2205, September 1997.

   [COPS-RSVP] Boyle, J., Cohen, R., Durham, D., Herzog, S., Rajan, R.
               and A. Sastry, "COPS usage for RSVP", RFC 2749, June

   [COPS-PROV] Chan, K., Seligson, J., Durham, D., Gai, S., McCloghrie,
               K., Herzog, S., Reichmeyer, F., Yavatkar, R. and A.
               Smith, "COPS Usage for Policy Provisioning (COPS-PR)",
               RFC 3084, March 2001.

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Authors' Addresses

   Keith McCloghrie
   Cisco Systems, Inc.
   170 West Tasman Drive
   San Jose, CA  95134-1706

   Phone: +1 (408) 526-5260
   EMail: kzm@cisco.com

   Luis A. Sanchez
   Megisto Systems
   20251 Century Boulevard
   Germantown, MD  02138

   Phone: +1 (301) 444-1747
   EMail: lsanchez@megisto.com

   Jon Saperia
   JDS Consulting, Inc.
   174 Chapman Street
   Watertown, MA 02472

   Phone: +1 (617) 744-1079
   EMail: saperia@jdscons.com

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Full Copyright Statement

   Copyright (C) The Internet Society (2001).  All Rights Reserved.

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   This document and the information contained herein is provided on an


   Funding for the RFC Editor function is currently provided by the
   Internet Society.

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