Network Working Group T. Clausen
Internet-Draft LIX, Ecole Polytechnique
Intended status: Informational U. Herberg
Expires: January 5, 2015 Fujitsu Laboratories of America
July 4, 2014
Snapshot of OLSRv2-Routed MANET Management
draft-ietf-manet-olsrv2-management-snapshot-01
Abstract
This document describes how Mobile Ad Hoc Networks (MANETs) are
typically managed, in terms of pre-deployment management, as well as
rationale and means of monitoring and management of MANET routers
running the Optimized Link State Routing protocol version 2 (OLSRv2)
and its constituent MANET NehgiborHood Discovery Protocol (NHDP).
Apart from pre-deployment management for setting up IP addresses and
security related credentials, OLSRv2 only needs routers to agree one
single parameter (called "C"). Other parameters for tweaking network
performance may be determined during operation of the network, and
need not be the same in all routers. This, using MIB modules and
related management protocols such as SNMP (or possibly other, less
"chatty", protocols). In addition, for debugging purposes,
monitoring data and performance related counters, as well as
notifications ("traps") can be sent to the Network Management System
(NMS) via standardized management protocols. This document
Status of this Memo
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This Internet-Draft will expire on January 5, 2015.
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
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document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Statement of Purpose . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Pre-Deployment Management . . . . . . . . . . . . . . . . . . 4
3.1. Lower Layer Alignment . . . . . . . . . . . . . . . . . . 4
3.2. Interface Addresses . . . . . . . . . . . . . . . . . . . 4
3.3. Security Material . . . . . . . . . . . . . . . . . . . . 5
3.4. The Value of C . . . . . . . . . . . . . . . . . . . . . . 5
4. How do we Manage OLSRv2-based MANETs? . . . . . . . . . . . . 5
4.1. Internal Management . . . . . . . . . . . . . . . . . . . 6
4.2. External Management . . . . . . . . . . . . . . . . . . . 6
5. What and Why do we Manage and Monitor? . . . . . . . . . . . . 7
6. Typical Communication Patterns . . . . . . . . . . . . . . . . 8
7. This Document does not Constrain how to Manage and Monitor
MANETs . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 11
9. Informative References . . . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
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1. Introduction
The MANET routing protocol OLSRv2 [RFC7181], as well as its
constituent parts NHDP [RFC6130], [RFC5497], [RFC5148], [RFC5444],
[RFC7182], [RFC7183], is designed to autonomously maintain routes
across a dynamic network topology. OLSRv2 is designed so as to
minimize operator intervention throughout the duration of a network
deployment, and to allow for heterogeneous configuration of routers
within the same network deployment: most configuration values are
either of local significance only (e.g., message jitter parameters)
or, when they are not, are carried in control signals exchanged
between routers (e.g., information validity time).
All the same, a small set of configuration options must be
established in each router prior to deployment, with some requiring
agreement among all the routers within the same deployment.
Furthermore, throughout the duration of a network deployment,
external management and monitoring of a network may be desirable,
e.g., for performance optimization or debugging purposes.
1.1. Statement of Purpose
Deployments of OLSRv2 are diverse, and may include community
networks, constrained environments, tactical networks, etc. Each
such environment may present distinctly different requirements as to
management and monitoring.
This document does therefore explicitly not pretend to provide an
exhaustive description of how all OLSRv2 network deployments should
be managed and monitored - and does, specifically, not prescribe any
management model. This document also does not address management of
MANET routing protocols, other than OLSRv2 (and its constituent
protocols).
What this document does, however, is to present how some OLSRv2
network deployments are managed and monitored, using well-established
management patterns and well-known protocols. In particular, this
document addresses several of the consideration from [RFC5706], in
particular Section 3 ("Management Considerations - How Will the
Protocol Be Managed?").
2. Terminology
This document uses terminology from [RFC7181], [RFC6130], and
[RFC5497].
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3. Pre-Deployment Management
Prior to operation of an OLSRv2 network, or more precisely, prior to
proper operation of OLSRv2 and its constituent parts, certain
parameters need to be configured on each router. The following
sections describe the required pre-deployment management.
3.1. Lower Layer Alignment
Interoperability between routers requires alignment of lower protocol
layers below OLSRv2. In particular, all routers in the same MANET
topology must be pre-configured to use the same IP address family
(IPv4 or IPv6). In a single OLSRv2 topology, it is not possible to
mix IPv4 and IPv6 addresses, notably because [RFC5444] messages can
contain either IPv4 *or* IPv6 addresses, but not both at the same
time. It is, however, possible to run two instances of OLSRv2, one
instance for IPv4 and another one for IPv6, within the same network.
In addition to the IP address family, other lower layer parameters
may also need to be aligned, e.g., radio channel selections. A
single OLSRv2 topology may, of course, span different link layers (or
the same link layer with different configuration settings such as
cryptographic keys) when routers in the topology have OLSRv2
interfaces towards these different link layers.
3.2. Interface Addresses
According to [RFC6130], and as used by [RFC7181], each interface of a
router must be configured with at least one IP address. [RFC6130]
provides guidance as to the characteristics of such IP addresses,
including the (limited) conditions under which an IP address may be
configured on multiple interfaces.
While automatic configuration of IP addresses on router interfaces is
not excluded, currently no address autoconfiguration protocols have
been standardized (in the IETF) to accomplish this. As a
consequence, static configuration, or proprietary (as in: non-
standardized) protocols ensure this.
Note that this required pre-deployment of interface addresses does
not include "external" IP addresses, i.e., IP addresses that are
configured on local non-MANET interfaces or IP addresses from remote
destinations reachable through this router (i.e., addresses for which
this router serves as gateway). These can be added or removed
dynamically during runtime of OLSRv2. Such local non-MANET interface
addresses are managed by way of the Local Interface Set (as defined
in [RFC6130]) and remote addresses by way of the Attached Network Set
(as defined in [RFC7181]).
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3.3. Security Material
Security material (keys, algorithms, etc.) must be available for
generating Integrity Check Values (ICVs) for outgoing control
messages, and to allow validating ICVs in incoming control messages
[RFC7182] [RFC7183].
The appropriate way of making such security material available is
dependent on the deployment type. For example, community networks
(such as "Funkfeuer", http://funkfeuer.at), do currently not use any
security at all. Other deployment types may use a simple manual
shared key distribution mechanism, or may use a proprietary key
distribution protocol. Tactical networks have much more stringent
requirements for distributing key material, e.g., using manual
distribution of the keys on encrypted USB keys, and with defensive
mechanisms (up to and including mechanisms involving depleted
uranium) if the keys are compromised.
In general, Automatic Key Management (AKM) as well as static/manual
or other out-of-band mechanisms, can be viable options for
distributing keys. Currently, no standardized AKM mechanism for
MANETs exist. If the IETF standardizes such mechanisms in the
future, for deployment types where such is appropriate, these can be
used for distributing keys. Until such time, manual key distribution
as well as proprietary mechanisms, prevail.
The important point to make here, however, is that by whichever
method (automatic/manual, dynamic/static, ... ) a key and other
security material is made available, the security mechanisms of
OLSRv2, as defined by [RFC7183], will be able to properly use it for
generating and validating ICVs.
3.4. The Value of C
The only pre-deployment configuration parameter that directly impacts
protocol operation is the value of C. This value is used by each
router for calculating the representation of interval and validity
time, as included in control messages. All routers in a deployment
must agree on the value of C, as described in [RFC5497].
4. How do we Manage OLSRv2-based MANETs?
A deployed OLSRv2 network is, as previously discussed, operating
autonomously, but occasionally with internal or external management
operations being desirable, described in the following two sections.
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4.1. Internal Management
Internal management describes a local process running on a router
that automatically (i.e., without external messaging or human
interaction) modifies the configuration of OLSRv2 based on different
environmental factors. For example, the HELLO interval may be
updated according to the rate of topology changes measured (or,
inferred: after all, the 'M' in MANET is for "Mobility") locally: if
the rate is high, then a more frequent HELLO update assures that
routes are more accurate. At a lower rate of topology changes,
network capacity and energy capacity of the router may be conserved
by increasing the HELLO interval.
Depending on the use case, many different automatic configuration
agents can be envisioned. As parameters in NHDP and OLSRv2 are
either only used locally or, in the case of HELLO_INTERVAL and
REFRESH_INTERVAL, are selected locally and then included in the
messages exchanged between adjacent routers in their HELLO messages,
none of these automatic local configuration methods needs necessarily
to be standardized: different routers doing different things will
interoperate.
4.2. External Management
For the deployments described by this document (but see Section 7),
external management operations are undertaken by a central Network
Management Station (NMS).
The MIB modules developed for OLSRv2 [RFC7184] and for its
constituent protocol NHDP [RFC6779] are verbose, in as much as that
they expose for interrogation the complete protocol and router state,
as well as enable setting all parameters (timer intervals, time-outs,
jitter values etc.). They do explicitly not enable setting the value
of C (as that is required to be constant and uniform across the
network, see Section 3.4), nor distributing security material (see
Section 3.3).
In some deployments, the NMS communicates with individual routers by
way of SNMP - and, more commonly, by way of "proprietary" simpler,
less verbose and (often) less secure protocols, and over UDP. Note
that this does not constitute a recommendation, but rather an
observation that (apparently) SNMP has found less application in
MANETs. The "Writable MIB Module IESG Statement"
(http://www.ietf.org/iesg/statement/writable-mib-module.html)
recommends to use MIB modules for read-only operations only, and to
use YANG/NETCONF for read-write operations instead. While
publication of the MIB modules developed for OLSRv2 and NHDP predates
this statement, it may be possible to translate read-only objects
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from the MIB modules into YANG modules using [RFC6643]. A complete
YANG model representing similar objects as in the MIB modules could
be future work.
The predecessor of OLSRv2, OLSR [RFC3626] did not have an associated
MIB module. Many deployments of OLSR did not support network
management operations per se (i.e., configuration-on-launch was the
way in which routers in these deployments were managed). Those
implementations and deployments of OLSR that did support network
management operations used a similar architecture to the one
described in this document, but with "proprietary" protocols and APIs
for parameters and router states, "proprietary" data-models, etc. It
can be speculated that the "proprietary" protocols used for
communication between the NMS and the MIB modules on each router also
for OLSRv2, in part, exist as inherited from the protocols used for
OLSR. Aligned with the recommendations from [RFC5706], management of
OLSRv2 (in the form of the MIB modules for OLSRv2 and NHDP) has been
developed alongside the standardization process of OLSRv2, rather
than as an afterthought.
Finally, it is uncommon to see an NMS permanently active in a
deployed OLSRv2 network; rather, on an "ad hoc" basis an NMS is
introduced into the network, parameters configured or state
interrogated, following which the NMS disappears. Part of the
rationale for this is that in a MANET, network connectivity from
every MANET router to an NMS cannot be guaranteed at all times due to
the dynamicity of the network topology.
5. What and Why do we Manage and Monitor?
As indicated earlier, OLSRv2 and its constituent protocol NHDP, are
reasonably robust with respect to parameter values: a deployment can
operate with different parameters used in different routers in the
same network. That being said, adapting these parameters according
to circumstances is (often) desired. For example, in a stable
network (such as a wired network), TC messages may be sent
infrequently and with long validity times, whereas in a highly
dynamic network (such as in a vehicular network) TC messages may need
to be sent more frequently and HELLO messages for discovering the
local topology (almost) continuously. In a similar vein, the message
emission intervals and the information validity times should also be
commensurate with the available network capacity: millisecond
intervals between TC messages, for example, will consume all
available network capacity whereas hourly intervals will be
inappropriate even for a static and stable, wired, network (by way of
simply new routers arriving in the network, which will not "learn"
the network topology before undue long delays).
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This adaptation may happen autonomously by a central NMS monitoring
and adopting the parameters globally, autonomously by an NMS in each
router, monitoring its local topology (and its stability) and
adapting parameters locally, or by manual operator intervention.
Given the dynamic and evolutive topology of OLSRv2 networks, a highly
desirable property of an NMS is the ability to display and offer
visibility of the current network status - for example, to display a
graphical map of which routers are currently part of the network. As
a proactive protocol, OLSRv2 maintains, in each router, a topology
map including all destinations and a subset of the links present in
the network (particularly true in a very dense network). A typical
feature of an NMS is to inquire as to the topology map of a single
router. A slightly less typical feature is to inquire all (or, at
least, many) routers in a network, with the purpose of presenting a
complete topology map.
In addition to actively monitoring an OLSRv2 network, erroneous or
unusual conditions on a router can be flagged to management, e.g.,
detection of an unusually high number of 1-hop or 2-hop neighborhood
changes in a short amount of time, indicating potential problems in
that area of the network. [RFC6779] and [RFC7184] facilitate
proactively sending "notifications" (also known as traps) from the
router towards an NMS. The MIB modules defined in [RFC6779] and
[RFC7184] allow for defining both the threshold and the time window
of how many times this erroneous condition may occur in the time
window before the notification is sent to the NMS. Once the NMS
receives a notification, a network operator may investigate if there
is a problem that needs to be resolved, e.g., by changing parameters
via the above-described external management.
6. Typical Communication Patterns
This section describes typical (management) communications patterns
in an operating (post-startup) network. One of the key
characteristics of OLSRv2 is that is enables an efficient flooding
mechanism (denoted "MPR Flooding"). For some management scenarios,
this facilitates better performance by (scope-limited) flooding
management requests to MANET routers, rather than sending multiple
consecutive unicast messages. While the MIB modules developed for
OLSRv2 and NHDP do not support such broadcast operation (due to the
nature of SNMP), some of the proprietary management tools mentioned
in Section 4 take advantage of this for increased performance.
The below list of such communication patterns is not claimed to be
exhaustive, and depending on the deployment, different patterns may
be used. However, these patterns have been observed in many
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deployments of OLSRv2 and its constituent parts, as well as of its
predecessor OLSR.
a) Inquire the state (complete topology graph, link states, and local
links - even those not part of topology graph) of a router. An
NMS would typically initiate that request. OLSRv2 contains a
number of "Information Bases"; basically, tables with rows
representing information about local interfaces, other routers in
the MANET or the topology of the MANET as perceived by the MANET
router. These tables are also reflected as objects in the MIB
modules and can be inquired via, e.g., GETBULK for getting
multiple rows in a single request. Depending on the number of
MANET routers in the network as well as the density of the MANET,
tables for one-hop and two-hop routers, as well as routers in
further distance, these tables can contain a substantial amount of
information, and so inquiring them will return multiple KB or more
of data back to the NMS. Given the dynamic topology and often
bandwidth-constrained wireless links between MANET routers, this
is not a very common operation in many deployments. Moreover,
this would typically only be required in debugging situations, as
during regular operations, OLSRv2 updates the state automatically
and reacts to changes (e.g., by triggering control message
generation). This type of operation can benefit from the
optimized flooding mechanism, by requesting the state from
multiple routers in a region of the MANET in a single request.
b) Inquire the history/statistics of a router. This request,
initiated by an NMS, is typically a small inquiry, such as "how
many local link changes have you seen within the past n minutes/
seconds/hours". This may be very rare, or it may be several times
per minute per router for a while: if the NMS is trying to, e.g.,
"tune" message intervals and timers, by sending this request to a
group of topologically close routers - until, that is, the NMS
decides that the topology has stabilized and will ease up. Again,
this feature of requesting performance related information is
supported by the MIB modules for OLSRv2 and NHDP. While SNMP does
not support sending the inquiry via optimized flooding,
proprietary protocols take advantage of the optimized flooding
mechanism, to reduce the number of unicast requests.
c) Change the configuration of a router. Other than in the above
case in b) (tuning), this really happens only when somehow a
router gets a new uplink to an external network, and either a new
gateway is added into the network, and/or a new prefix needs to be
distributed to the routers. The MIB modules for OLSRv2 and NHDP
allow to set all configuration parameters of each router.
Optimized flooding may significantly reduce the amount of unicast
requests, but are not supported by SNMP.
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d) Visualizing the network as a router sees it. As in a MANET,
routers may move and link quality may vary due to link layer
characteristics, the network topology may change frequently. In a
naive way, this would essentially be the NMS setting up a
connection to the router in question, and getting a copy of all
routing protocol control messages to construct its own topology
graph as would have done that router. Typically, it consists of
the router sending a notification to the NMS when a topological
change happens, i.e., when either of its information bases change.
Even better, it consists of these notifications being "filtered"
to only send for those changes that actually impact the usable
topology. The latter case is supported by the MIB modules for
OLSRv2 and NHDP in the form of notifications (also called "traps")
that are send from the MANET router to the NMS. While these
notifications alone do not allow the NMS to visualize the
topology, they may suffice to inform the NMS of an unusual change
of the topology, and the NMS may inquire the current topology via
the process described in a).
e) Rekeying There is currently no (standard) mechanism for automated
key management. One of the reasons for this may be that it is
difficult to come up with a single such that will satisfy the
requirements for all the different deployments. However, in MANET
deployments rekeying is something that can be observed, e.g., as
part of the parameter configuration. The particularity of this
is, that it often is a "broadcast configuration operation" where
new key material is supposed to be sent to everybody, and not just
a single router, e.g., leveraging the optimized flooding mechanism
of OLSRv2.
7. This Document does not Constrain how to Manage and Monitor MANETs
As explained in Section 1, this document describes how, what and why
some (typical) OLSRv2 networks are managed and monitored as of 2014.
As such, the document is reflexive, not prescriptive: it does not
stipulate requirements for how to manage OLSRv2 networks, nor does it
claim to be a complete list of all management patterns or protocols.
Other ways of managing an OLSRv2 network are very well imaginable -
now, or in future deployments of OLSRv2.
As an example of such a "future management scenario", rather than
managing and monitoring routers from a central NMS, a distributed,
autonomous management system between multiple routers can be
envisioned. In particular, monitoring data that is used to debug
network problems and to tweak inefficiencies could be distributed
amongst a group of routers in the same network. This would both
address problems of single point of failure when using only a single
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NMS, as well provide additional information about groups of multiple
routers, rather than a single router. An example use for such a
distributed information flow would be to identify areas of a network
wherein, e.g., due to different router densities, message sending
interval parameters could be exchanged and optimal values negotiated
between routers, so as to obtain locally optimized performance.
While such a management model is highly interesting, it is also at
present entirely fictional - at least outside the realm of research.
It is included to, both, indicate directions being explored (but not
exploited), and to insist that the intent of this document is not to
prescribe how MANETs are to be managed, in the presence or in the
future, but to describe the (known) state of how MANETs are managed,
presently.
8. Acknowledgments
The authors would like to gratefully acknowledge the following people
for intense technical discussions, early reviews, and comments on the
documents: Alan Cullen (BAE Systems), Christopher Dearlove (BAE
Systems), Adrian Farrel (Juniper), David Harrington (Comcast), and
Jurgen Schoenwalder (Jacobs University).
9. Informative References
[RFC3626] Clausen, T. and P. Jacquet, "The Optimized Link State
Routing Protocol", RFC 3626, October 2003.
[RFC5148] Clausen, T., Dearlove, C., and B. Adamson, "Jitter
Considerations in Mobile Ad Hoc Networks (MANETs)",
RFC 5148, February 2008.
[RFC5444] Clausen, T., Dearlove, C., Dean, J., and C. Adjih,
"Generalized MANET Packet/Message Format", RFC 5444,
February 2009.
[RFC5497] Clausen, T. and C. Dearlove, "Representing Multi-Value
Time in Mobile Ad Hoc Networks (MANETs)", RFC 5497,
March 2009.
[RFC5706] Harrington, D., "Guidelines for Considering Operations and
Management of New Protocols and Protocol Extensions",
RFC 5706, November 2009.
[RFC6130] Clausen, T., Dearlove, C., and J. Dean, "Mobile Ad Hoc
Network (MANET) Neighborhood Discovery Protocol (NHDP)",
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RFC 6130, April 2011.
[RFC6643] Schoenwaelder, J., "Translation of Structure of Management
Information Version 2 (SMIv2) MIB Modules to YANG
Modules", RFC 6643, July 2012.
[RFC6779] Herberg, U., Cole, R., and I. Chakeres, "Definition of
Managed Objects for the Neighborhood Discovery Protocol",
RFC 6779, May 2012.
[RFC7181] Clausen, T., Dearlove, C., Jacquet, P., and U. Herberg,
"The Optimized Link State Routing Protocol Version 2",
RFC 7181, April 2014.
[RFC7182] Herberg, U., Clausen, T., and C. Dearlove, "Integrity
Check Value and Timestamp TLV Definitions for Mobile Ad
Hoc Networks (MANETs)", RFC 7182, April 2014.
[RFC7183] Herberg, U., Dearlove, C., and T. Clausen, "Integrity
Protection for the Neighborhood Discovery Protocol (NHDP)
and Optimized Link State Routing Protocol Version 2
(OLSRv2)", RFC 7183, April 2014.
[RFC7184] Herberg, U., Cole, R., and T. Clausen, "Definition of
Managed Objects for the Optimized Link State Routing
Protocol Version 2", RFC 7184, April 2014.
Authors' Addresses
Thomas Clausen
LIX, Ecole Polytechnique
91128 Palaiseau Cedex,
France
Phone: +33-6-6058-9349
Email: T.Clausen@computer.org
URI: http://www.thomasclausen.org
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Ulrich Herberg
Fujitsu Laboratories of America
1240 E Arques Ave
Sunnyvale CA 94086,
US
Phone:
Email: ulrich@herberg.name
URI: http://www.herberg.name
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