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Internet Engineering Task Force (IETF) A. Farrel
Request for Comments: 6123 Old Dog Consulting
Category: Historic February 2011
ISSN: 2070-1721
Inclusion of Manageability Sections in
Path Computation Element (PCE) Working Group Drafts
Abstract
It has often been the case that manageability considerations have
been retrofitted to protocols after they have been specified,
standardized, implemented, or deployed. This is sub-optimal.
Similarly, new protocols or protocol extensions are frequently
designed without due consideration of manageability requirements.
The Operations Area has developed "Guidelines for Considering
Operations and Management of New Protocols and Protocol Extensions"
(RFC 5706), and those guidelines have been adopted by the Path
Computation Element (PCE) Working Group.
Previously, the PCE Working Group used the recommendations contained
in this document to guide authors of Internet-Drafts on the contents
of "Manageability Considerations" sections in their work. This
document is retained for historic reference.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for the historical record.
This document defines a Historic Document for the Internet community.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6123.
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Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
1. Introduction
This document is produced for historic reference.
When new protocols or protocol extensions are developed, it is often
the case that not enough consideration is given to the manageability
of the protocols or to the way in which they will be operated in the
network. The result is that manageability considerations are only
understood once the protocols have been implemented and sometimes not
until after they have been deployed.
The resultant attempts to retrofit manageability mechanisms are not
always easy or architecturally pleasant. Furthermore, it is possible
that certain protocol designs make manageability particularly hard to
achieve.
Recognizing that manageability is fundamental to the utility and
success of protocols designed within the IETF, and that simply
defining a MIB module does not necessarily provide adequate
manageability, this document was developed to define recommendations
for the inclusion of Manageability Considerations sections in all
Internet-Drafts produced within the PCE Working Group. It was the
intention that meeting these recommendations would ensure that proper
consideration was given to the support of manageability at all stages
of the protocol development process from Requirements and
Architecture through Specification and Applicability.
It is clear that the presence of such a section in an Internet-Draft
does not guarantee that the protocol will be well-designed or
manageable. However, the inclusion of this section will ensure that
the authors have the opportunity to consider the issues, and, by
reading the material in this document, they will gain some guidance.
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This document was developed within the PCE Working Group and was used
to help guide the authors and editors within the working group to
produce Manageability Considerations sections in the Internet-Drafts
and RFCs produced by the working group.
[RFC5706] presents general guidance from the IETF's Operations Area
for considering Operations and Management of new protocols and
protocol extensions. It has been adopted by the PCE Working Group to
provide guidance to editors and authors within the working group, so
this document is no longer required. However, the working group
considers that it will be useful to archive this document as Historic
for future reference.
1.1. Requirements Notation
This document is not a protocol specification. 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 [RFC2119] in order that the contents of a
Manageability Considerations section can be clearly understood.
1.2. What Is Manageability?
In this context, "manageability" is used to refer to the interactions
between a network operator (a human or an application) and the
network components (hosts, routers, switches, applications, and
protocols) performed to ensure the correct operation of the network.
Manageability issues are often referred to under the collective
acronym, FCAPS [X.700], which stands for the following:
- Fault management
- Configuration
- Accounting
- Performance
- Security
Conventionally, Security is already covered an Internet-Draft in its
own Security Considerations section, and this document does not in
any way diminish the need for that section. Indeed, as pointed out
in Section 6, a full consideration of other aspects of manageability
may increase the text that should be supplied in the Security
Considerations section.
The author of a Manageability Considerations section should certainly
consider all aspects of FCAPS. The author should reflect on how the
manageability of a new protocol impacts the manageability and
operation of the entire network. Specific optional subsections (see
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Section 2.3) should be added as necessary to describe features of
FCAPS that are pertinent but are not covered by the recommended
subsections. More discussion of what manageability is and what may
be included in a Manageability Considerations section can be found in
[RFC5706].
As part of documenting the manageability considerations for a new
protocol or for protocol extensions, authors should consider that one
of the objectives of specifying protocols within the IETF is to
ensure interoperability of implementations. This interoperability
extends to the manageability function so that it is an ideal that
there should be implementation independence between management
applications and managed entities. This may be promoted by the use
of standardized management protocols and by the specification of
standard information models.
Note that, in some contexts, reference is made to the term
"management plane". This is used to describe the exchange of
management messages through management protocols (often transported
by IP and by IP transport protocols) between management applications
and the managed entities such as network nodes. The management plane
may use distinct addressing schemes, virtual links or tunnels, or a
physically separate management control network. The management plane
should be seen as separate from, but possibly overlapping with, the
control plane, in which signaling and routing messages are exchanged,
and the forwarding plane (sometimes called the data plane or user
plane), in which user traffic is transported.
2. Presence and Placement of Manageability Considerations Sections
Note that examples of the sections described here can be found in the
documents listed in Appendix A.
2.1. Null Manageability Considerations Sections
In the event that there are no manageability requirements for an
Internet-Draft, the draft SHOULD still contain a Manageability
Considerations section. The presence of this section indicates to
the reader that due consideration has been given to manageability and
that there are no (or no new) requirements.
In this case, the section SHOULD contain a simple statement such as
"There are no new manageability requirements introduced by this
document" and SHOULD briefly explain why that is the case with a
summary of manageability mechanisms that already exist.
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Note that a null Manageability Considerations section may take some
effort to compose. It is important to demonstrate to the reader that
no additional manageability mechanisms are required, and it is often
hard to prove that something is not needed. A null Manageability
Considerations section SHOULD NOT consist only of the simple
statement that there are no new manageability requirements.
If an Internet-Draft genuinely has no manageability impact, it should
be possible to construct a simple null Manageability Considerations
section that explains why this is the case.
2.2. Recommended Subsections
If the Manageability Considerations section is not null, it SHOULD
contain at least the following subsections. Guidance on the content
of these subsections can be found in Section 3 of this document.
- Control of Function through Configuration and Policy
- Information and Data Models, e.g., MIB modules
- Liveness Detection and Monitoring
- Verifying Correct Operation
- Requirements on Other Protocols and Functional Components
- Impact on Network Operation
In the event that one or more of these subsections is not relevant,
it SHOULD still be present and SHOULD contain a simple statement
explaining why the subsection is not relevant. That is, null
subsections are allowed, and each should be formed following the
advice in Section 2.1.
2.3. Optional Subsections
The list of subsections above is not intended to be prescriptively
limiting. Other subsections can and SHOULD be added according to the
requirements of each individual Internet-Draft. If a topic does not
fit comfortably into any of the subsections listed, the authors
should be relaxed about adding new subsections as necessary.
2.4. Placement of Manageability Considerations Sections
The Manageability Considerations section SHOULD be placed immediately
before the Security Considerations section in any Internet-Draft.
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3. Guidance on the Content of Subsections
This section gives guidance on the information to be included in each
of the recommended subsections listed above. Note that, just as
other subsections may be included, so additional information MAY also
be included in these subsections.
3.1. Control of Function through Configuration and Policy
This subsection describes the functional elements that may be
controlled through configuration and/or policy.
For example, many protocol specifications include timers that are
used as part of the operation of the protocol. These timers often
have default values suggested in the protocol specification and do
not need to be configurable. However, it is often the case that the
protocol requires that the timers can be configured by the operator
to ensure specific behavior by the implementation.
Even if all configurable items have been described within the body of
the document, they SHOULD be identified in this subsection, but a
reference to another section of the document is sufficient if there
is a full description elsewhere.
Other protocol elements are amenable to control through the
application of local or network-wide policy. It is not the intention
that this subsection should give details of policy implementation
since that is covered by more general policy framework specifications
such as [RFC3060] and [RFC3460]. Additionally, specific frameworks
for policy as applicable within protocol or functional architectures
are also normally covered in separate documents, for example,
[RFC5394].
However, this section SHOULD identify which protocol elements are
potentially subject to policy and should give guidance on the
application of policy for successful operation of the protocol.
Where this material is already described within the body of the
document, this subsection SHOULD still identify the issues and
reference the other sections of the document.
3.2. Information and Data Models
This subsection SHOULD describe the information and data models
necessary for the protocol or the protocol extensions. This
includes, but is not necessarily limited to, the MIB modules
developed specifically for the protocol functions specified in the
document.
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Where new or extended MIB modules are recommended, it is helpful if
this section can give an overview of the items to be modeled by the
MIB modules. This does not require an object-by-object description
of all of the information that needs to be modeled, but it could
explain the high-level "object groupings" (perhaps to the level of
suggesting the MIB tables) and certainly should explain the major
manageable entities. For example, a protocol specification might
include separate roles for "sender" and "receiver" and might be
broken into a "session" and individual "transactions"; if so, this
section could list these functionalities as separate manageable
entities.
[RFC3444] may be useful in determining what information to include in
this section.
The description in this section can be by reference where other
documents already exist.
It should be noted that the significance of MIB modules may be
decreasing, but there is still a requirement to consider the managed
objects necessary for successful operation of the protocol or
protocol extensions. This means that due consideration should be
given not only to what objects need to be managed but also to what
management model should be used. There are now several options,
including the MIB/SNMP (Simple Network Management Protocol) model and
the Network Configuration Protocol (NETCONF) model, being developed
by the NETCONF Data Modeling Language (NETMOD) Working Group [YANG].
3.3. Liveness Detection and Monitoring
Liveness detection and monitoring apply both to the control plane and
the data plane.
Mechanisms for detecting faults in the control plane or for
monitoring its liveness are usually built into the control plane
protocols or inherited from underlying data plane or forwarding plane
protocols. These mechanisms do not typically require additional
management capabilities but are essential features for the protocol
to be usable and manageable. Therefore, this section SHOULD
highlight the mechanisms in the new protocol or protocol extensions
that are required in order to ensure liveness detection and
monitoring within the protocol.
Further, when a control plane fault is detected, there is often a
requirement to coordinate recovery action through management
applications or at least to record the fact in an event log. This
section SHOULD identify the management actions expected when the
protocol detects a control plane fault.
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Where the protocol is responsible for establishing data or user plane
connectivity, liveness detection and monitoring usually need to be
achieved through other mechanisms. In some cases, these mechanisms
already exist within other protocols responsible for maintaining
lower layer connectivity, but it will often be the case that new
procedures are required so that failures in the data path can be
detected and reported rapidly, allowing remedial action to be taken.
This section SHOULD refer to other mechanisms that are assumed to
provide monitoring of data plane liveness and SHOULD identify
requirements for new mechanisms as appropriate.
This section SHOULD describe the need for liveness and detection
monitoring, SHOULD highlight existing tools, SHOULD identify
requirements and specifications for new tools (as appropriate for the
level of the document being written), and SHOULD describe the
coordination of tools with each other, with management applications,
and with the base protocol being specified.
3.4. Verifying Correct Operation
An important function that Operations and Management (OAM) can
provide is a toolset for verifying the correct operation of a
protocol. To some extent, this may be achieved through access to
information and data models that report the status of the protocol
and the state installed on network devices. However, it may also be
valuable to provide techniques for testing the effect that the
protocol has had on the network by sending data through the network
and observing its behavior.
Thus, this section SHOULD include details of how the correct
operation of the protocols described by the Internet-Draft can be
tested, and, in as far as the Internet-Draft impacts on the operation
of the network, this section SHOULD include a discussion about how
the correct end-to-end operation of the network can be tested and how
the correct data or forwarding plane function of each network element
can be verified.
There may be some overlap between this section and that describing
liveness detection and monitoring since the same tools may be used in
some cases.
3.5. Requirements on Other Protocols and Functional Components
The text in this section SHOULD describe the requirements that the
new protocol puts on other protocols and functional components as
well as requirements from other protocols that have been considered
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in designing the new protocol. This is pertinent to manageability
because those other protocols may already be deployed and operational
and because those other protocols also need to be managed.
It is not appropriate to consider the interaction between the new
protocol and all other protocols in this section, but it is important
to identify the specific interactions that are assumed for the
correct functioning of the new protocol or protocol extensions.
3.6. Impact on Network Operation
The introduction of a new protocol or extensions to an existing
protocol may have an impact on the operation of existing networks.
This section SHOULD outline such impacts (which may be positive),
including scaling concerns and interactions with other protocols.
For example, a new protocol that doubles the number of active,
reachable addresses in use within a network might need to be
considered in the light of the impact on the scalability of the IGPs
operating within the network.
A very important feature that SHOULD be addressed in this section is
backward compatibility. If protocol extensions are being introduced,
what impact will this have on a network that has an earlier version
of the protocol deployed? Will it be necessary to upgrade all nodes
in the network? Can the protocol versions operate side by side? Can
the new version of the protocol be tunneled through the old version?
Can existing services be migrated without causing a traffic hit or is
a "maintenance period" required to perform the upgrade? What are the
configuration implications for the new and old protocol variants?
Where a new protocol is introduced, issues similar to backward
compatibility may exist and SHOULD be described. How is migration
from an old protocol to the new protocol achieved? Do existing
protocols need to be interfaced to the new protocol?
3.7. Other Considerations
Anything that is not covered in one of the recommended subsections
described above but is needed to understand the manageability
situation SHOULD be covered in an additional section. This may be a
catch-all section named "Other Considerations" or may be one or more
additional optional sections as described in Section 2.3.
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4. IANA Considerations
This document does not introduce any new codepoints or name spaces
for registration with IANA. It makes no request to IANA for action.
Internet-Drafts SHOULD NOT introduce new codepoints, name spaces, or
requests for IANA action within the Manageability Considerations
section.
5. Manageability Considerations
This document defines Manageability Considerations sections
recommended for inclusion in all PCE Working Group Internet-Drafts.
As such, the whole document is relevant to manageability.
Note that the impact of the application of this document to Internet-
Drafts produced within the PCE Working Group should be that PCE
protocols and associated protocols are designed and extended with
manageability in mind. This should result in more robust and more
easily deployed protocols.
However, since this document does not describe any specific protocol,
protocol extensions, or protocol usage, no manageability
considerations need to be discussed here.
(This is an example of a null Manageability Considerations section).
6. Security Considerations
This document is Historic and describes the format and content of
Internet-Drafts. As such, it introduces no new security concerns.
However, there is a clear overlap between security, operations, and
management. The manageability aspects of security SHOULD be covered
within the mandatory Security Considerations of each Internet-Draft.
New security considerations introduced by the Manageability
Considerations section MUST be covered in the Security Considerations
section.
Note that fully designing a protocol before it is implemented
(including designing the manageability aspects) is likely to result
in a more robust protocol. That is a benefit to network security.
Retrofitting manageability to a protocol can make the protocol more
vulnerable to security attacks, including attacks through the new
manageability facilities. Therefore, the use of this document is
RECOMMENDED in order to help ensure the security of all protocols to
which it is applied.
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7. Acknowledgements
This document is based on earlier work exploring the need for
Manageability Considerations sections in all Internet-Drafts produced
within the Routing Area of the IETF. That document was produced by
Avri Doria and Loa Andersson working with the current author. Their
input was both sensible and constructive.
Peka Savola provided valuable feedback on an early versions of the
original document. Thanks to Bert Wijnen, Dan Romascanu, David
Harrington, Lou Berger, Spender Dawkins, Tom Petch, Matthew Meyer,
Dimitri Papdimitriou, Stewart Bryant, and Jamal Hadi Salim for their
comments.
Thanks to the PCE Working Group for adopting the ideas contained in
this document and for including Manageability Considerations sections
in their Internet-Drafts and RFCs.
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
8.2. Informative References
[RFC3060] Moore, B., Ellesson, E., Strassner, J., and A. Westerinen,
"Policy Core Information Model -- Version 1 Specification",
RFC 3060, February 2001.
[RFC3460] Moore, B., Ed., "Policy Core Information Model (PCIM)
Extensions", RFC 3460, January 2003.
[RFC3444] Pras, A. and J. Schoenwaelder, "On the Difference between
Information Models and Data Models", RFC 3444, January
2003.
[RFC5394] Bryskin, I., Papadimitriou, D., Berger, L., and J. Ash,
"Policy-Enabled Path Computation Framework", RFC 5394,
December 2008.
[RFC5706] Harrington, D., "Guidelines for Considering Operations and
Management of New Protocols and Protocol Extensions", RFC
5706, November 2009.
[X.700] CCITT Recommendation X.700 (1992), Management framework for
Open Systems Interconnection (OSI) for CCITT applications.
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[YANG] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)", RFC 6020,
October 2010.
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Appendix A. Example Manageability Considerations Sections
Readers are referred to the following documents for example
Manageability Considerations sections that received positive comments
during IESG review:
Farrel, A., Vasseur, J.-P., and J. Ash, "A Path Computation Element
(PCE)-Based Architecture", RFC 4655, August 2006.
Le Roux, J., Ed., "Requirements for Path Computation Element (PCE)
Discovery", RFC 4674, October 2006.
Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R. Zhang,
"OSPF Protocol Extensions for Path Computation Element (PCE)
Discovery", RFC 5088, January 2008.
Vasseur, JP., Ed., and JL. Le Roux, Ed., "Path Computation Element
(PCE) Communication Protocol (PCEP)", RFC 5440, March 2009.
Bradford, R., Ed., Vasseur, JP., and A. Farrel, "Preserving Topology
Confidentiality in Inter-Domain Path Computation Using a Path-Key-
Based Mechanism", RFC 5520, April 2009.
Oki, E., Takeda, T., Le Roux, JL., and A. Farrel, "Framework for PCE-
Based Inter-Layer MPLS and GMPLS Traffic Engineering", RFC 5623,
September 2009.
Author's Address
Adrian Farrel
Old Dog Consulting
EMail: adrian@olddog.co.uk
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