Network Working Group L. Sanchez
Request for Comments: 3139 Megisto
Category: Informational K. McCloghrie
Cisco
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.
Abstract
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
devices.
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
entity.
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
complex.
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
data.
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
|
|
|
|
V
Configuration
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
accordingly.
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
configurations,
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
necessary,
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
devices,
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
expire,
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
data,
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.
Acknowledgments
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.
References
[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
1999.
[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
USA
Phone: +1 (408) 526-5260
EMail: kzm@cisco.com
Luis A. Sanchez
Megisto Systems
20251 Century Boulevard
Germantown, MD 02138
USA
Phone: +1 (301) 444-1747
EMail: lsanchez@megisto.com
Jon Saperia
JDS Consulting, Inc.
174 Chapman Street
Watertown, MA 02472
USA
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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Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
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RFC, FYI, BCP