draft-ietf-manet-issues-00.txt   draft-ietf-manet-issues-01.txt 
Internet Draft S. Corson Internet Draft S. Corson
Expiration: March 1998 University of Maryland Expiration: September 1998 University of Maryland
File: draft-ietf-manet-issues-00.txt J. Macker File: draft-ietf-manet-issues-01.txt J. Macker
Naval Research Laboratory Naval Research Laboratory
September 1997 March 1998
Mobile Ad hoc Networking (MANET): Mobile Ad hoc Networking (MANET):
Routing Protocol Performance Issues and Evaluation Considerations Routing Protocol Performance Issues and Evaluation Considerations
Status of this Memo Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working This document is an Internet-Draft. Internet-Drafts are working
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Summary Abstract
This memo describes the concept of mobile ad hoc networking--giving a This memo first describes the characteristics of Mobile Ad hoc
rationale for its existence and outlining the unique issues and Networks (MANETs), and their idiosyncrasies with respect to
challenges found in this form of purely wireless, mobile networking. traditional, hardwired packet networks. It then discusses the effect
these differences have on the design and evaluation of network
control protocols with an emphasis on routing performance evaluation
considerations.
1. Introduction 1. Introduction
With recent performance advancements in computer and wireless With recent performance advancements in computer and wireless
communications technologies, advanced mobile wireless computing is communications technologies, advanced mobile wireless computing is
expected to see increasingly widespread use and application, much of expected to see increasingly widespread use and application, much of
which will involve the use of the Internet Protocol (IP) suite. The which will involve the use of the Internet Protocol (IP) suite. The
vision of mobile ad hoc networking is to support robust and efficient vision of mobile ad hoc networking is to support robust and efficient
operation in mobile wireless networks by incorporating routing operation in mobile wireless networks by incorporating routing
functionality into mobile nodes. Such networks are envisioned to functionality into mobile nodes. Such networks are envisioned to
have dynamic, sometimes rapidly-changing, random, multihop topologies have dynamic, sometimes rapidly-changing, random, multihop topologies
which are likely composed of relatively bandwidth-constrained which are likely composed of relatively bandwidth-constrained
wireless links. wireless links.
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Within the Internet community, routing support for mobile hosts is Within the Internet community, routing support for mobile hosts is
presently being formulated as "mobile IP" technology. This is a presently being formulated as "mobile IP" technology. This is a
technology to support nomadic host "roaming", where a roaming host technology to support nomadic host "roaming", where a roaming host
may be connected through various means to the Internet other than its may be connected through various means to the Internet other than its
well known fixed-address domain space. The host may be directly well known fixed-address domain space. The host may be directly
physically connected to the fixed network on a foreign subnet, or be physically connected to the fixed network on a foreign subnet, or be
connected via a wireless link, dial-up line, etc. Supporting this connected via a wireless link, dial-up line, etc. Supporting this
form of host mobility (or nomadicity) requires address management, form of host mobility (or nomadicity) requires address management,
protocol interoperability enhancements and the like, but core network protocol interoperability enhancements and the like, but core network
functions such as hop-by-hop routing still presently rely upon pre- functions such as hop-by-hop routing still presently rely upon pre-
existing routing protocols operating within the fixed network. In existing routing protocols operating within the fixed network. In
contrast, the goal of mobile ad hoc networking is to extend mobility contrast, the goal of mobile ad hoc networking is to extend mobility
into the realm of autonomous, mobile, wireless domains, where the into the realm of autonomous, mobile, wireless domains, where a set
nodes themselves form the network routing infrastructure in an ad hoc of nodes--which may be combined routers and hosts--themselves form
fashion. the network routing infrastructure in an ad hoc fashion.
This memo first describes the characteristics of Mobile Ad hoc
Networks (MANETs), and their idiosyncrasies with respect to
traditional, hardwired packet networks. It then discusses the effect
these differences have on the design and evaluation of network
control protocols with an emphasis on routing.
2. Applications 2. Applications
The technology of Mobile Ad hoc Networking is somewhat synonomous The technology of Mobile Ad hoc Networking is somewhat synonymous
with Mobile Packet Radio Networking (a term coined via during early with Mobile Packet Radio Networking (a term coined via during early
military research in the 70's and 80's), Mobile Mesh Networking (a military research in the 70's and 80's), Mobile Mesh Networking (a
term that appeared in an article in The Economist regarding the term that appeared in an article in The Economist regarding the
structure of future military networks) and Mobile, Multihop, Wireless structure of future military networks) and Mobile, Multihop, Wireless
Networking (perhaps the most accurate term, although a bit Networking (perhaps the most accurate term, although a bit
cumbersome). cumbersome).
There is current and future need for dynamic ad hoc networking There is current and future need for dynamic ad hoc networking
technology. The emerging field of mobile and nomadic computing, with technology. The emerging field of mobile and nomadic computing, with
its current emphasis on mobile IP operation, should gradually broaden its current emphasis on mobile IP operation, should gradually broaden
and require highly adaptive mobile networking technology to and require highly-adaptive mobile networking technology to
effectively manage multihop, ad hoc network clusters which can effectively manage multihop, ad hoc network clusters which can
operate autonomously or, more than likely, be attached at some operate autonomously or, more than likely, be attached at some
point(s) to the fixed Internet. point(s) to the fixed Internet.
Some applications of MANET technology could include industrial and Some applications of MANET technology could include industrial and
commercial applications involving cooperative mobile data exchange. commercial applications involving cooperative mobile data exchange.
In addition, mesh-based mobile networks can be operated as robust, In addition, mesh-based mobile networks can be operated as robust,
inexpensive alternatives or enhancements to cell-based mobile network inexpensive alternatives or enhancements to cell-based mobile network
infrastructures. There are also existing and future military infrastructures. There are also existing and future military
networking requirements for robust, IP-compliant data services within networking requirements for robust, IP-compliant data services within
mobile wireless communication networks [1]--many of these networks mobile wireless communication networks [1]--many of these networks
consist of highly-dynamic autonomous topology segments. Also, the consist of highly-dynamic autonomous topology segments. Also, the
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developing technologies of "wearable" computing and communications developing technologies of "wearable" computing and communications
may provide applications for MANET technology. When properly combined may provide applications for MANET technology. When properly combined
with satellite-based information delivery, MANET technology can with satellite-based information delivery, MANET technology can
provide an extremely flexible method for establishing communications provide an extremely flexible method for establishing communications
for fire/safety/rescue operations or other scenarios requiring for fire/safety/rescue operations or other scenarios requiring
rapidly-deployable communications with survivable, efficient dynamic rapidly-deployable communications with survivable, efficient dynamic
networking. There are likely other applications for MANET technology networking. There are likely other applications for MANET technology
which are not presently realized or envisioned by the authors. It which are not presently realized or envisioned by the authors. It
is, simply put, efficient IP-based routing technology for highly is, simply put, improved IP-based networking technology for dynamic,
dynamic, autonomous wireless networks. autonomous wireless networks.
3. Characteristics of MANETs 3. Characteristics of MANETs
A MANET consists of mobile platforms (combined router, host and A MANET consists of mobile platforms (e.g., a router with multiple
wireless communications platforms)--herein simply referred to as hosts and wireless communications devices)--herein simply referred to
"nodes"--which are free to move about arbitrarily. The nodes may be as "nodes"--which are free to move about arbitrarily. The nodes may
located in or on airplanes, ships, trucks, cars, perhaps even on be located in or on airplanes, ships, trucks, cars, perhaps even on
people, and there may be multiple hosts per router. A MANET is an people or very small devices, and there may be multiple hosts per
autonomous system of mobile nodes. The system may operate in router. A MANET is an autonomous system of mobile nodes. The system
isolation, or may have gateways to and interface with a fixed may operate in isolation, or may have gateways to and interface with
network--typically envisioned to operate as a stub network connecting a fixed network. In the latter operational mode, it is typically
to a fixed internetwork. envisioned to operate as a "stub" network connecting to a fixed
internetwork. Stub networks carry traffic originating at and/or
destined for internal nodes, but do not permit exogenous traffic to
"transit" through the stub network.
The nodes are equipped with wireless transmitters and receivers using MANET nodes are equipped with wireless transmitters and receivers
antennas which may be omnidirectional (broadcast), highly-directional using antennas which may be omnidirectional (broadcast), highly-
(point-to-point) or some combination thereof. At a given point in directional (point-to-point), possibly steerable, or some combination
time, depending on the nodes' positions and their transmitter and thereof. At a given point in time, depending on the nodes' positions
receiver coverage patterns, transmission power levels and cochannel and their transmitter and receiver coverage patterns, transmission
interference levels, a wireless connectivity in the form of a random, power levels and co-channel interference levels, a wireless
multihop graph or "ad hoc" network exists between the nodes. This ad connectivity in the form of a random, multihop graph or "ad hoc"
hoc topology may change with time as the nodes move or adjust their network exists between the nodes. This ad hoc topology may change
transmission and reception parameters. with time as the nodes move or adjust their transmission and
reception parameters.
MANETs have several salient characteristics: MANETs have several salient characteristics:
1) Dynamic topologies: Nodes are free to move arbitrarily; thus, 1) Dynamic topologies: Nodes are free to move arbitrarily; thus,
the network topology--which is typically multihop--may change the network topology--which is typically multihop--may change
randomly and rapidly at unpredictable times, and may consist of randomly and rapidly at unpredictable times, and may consist of
both bidirectional and unidirectional links. both bidirectional and unidirectional links.
2) Bandwidth-constrained, variable capacity links: Wireless links 2) Bandwidth-constrained, variable capacity links: Wireless links
will continue to have significantly lower capacity than their will continue to have significantly lower capacity than their
hardwired counterparts. In addition, the realized throughput of hardwired counterparts. In addition, the realized throughput of
wireless communications--after accounting for the effects of wireless communications--after accounting for the effects of
multiple access, fading, noise, and interference conditions, multiple access, fading, noise, and interference conditions,
etc.--is often very much less than a radio's maximum transmission etc.--is often much less than a radio's maximum transmission rate.
rate.
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One effect of the relatively low to moderate link capacities is One effect of the relatively low to moderate link capacities is
that congestion is typically the norm rather than the exception, that congestion is typically the norm rather than the exception,
i.e. aggregate application demand will likely approach or exceed i.e. aggregate application demand will likely approach or exceed
network capacity frequently. As the mobile network is often simply network capacity frequently. As the mobile network is often simply
an extension of the fixed network infrastructure, mobile ad hoc an extension of the fixed network infrastructure, mobile ad hoc
users will demand similar services. These demands will continue to users will demand similar services. These demands will continue to
increase as multimedia computing and collaborative networking increase as multimedia computing and collaborative networking
applications rise. applications rise.
3) Power-constrained operation: Some or all of the nodes in a 3) Energy-constrained operation: Some or all of the nodes in a
MANET may rely on batteries for their energy. For these nodes, the MANET may rely on batteries or other exhaustible means for their
most important system design criteria for optimization may be energy. For these nodes, the most important system design criteria
power conservation. for optimization may be energy conservation.
4) Limited physical security: Mobile wireless networks are 4) Limited physical security: Mobile wireless networks are
generally more prone to physical security threats than are fixed- generally more prone to physical security threats than are fixed-
cable nets. The increased possibility of eavesdropping, spoofing, cable nets. The increased possibility of eavesdropping, spoofing,
and denial of service attacks should be carefully considered. and denial-of-service attacks should be carefully considered.
Existing link security techniques are often applied within Existing link security techniques are often applied within
wireless network to reduce security threats. As a benefit, the wireless networks to reduce security threats. As a benefit, the
decentralized nature of network control in MANETs provides decentralized nature of network control in MANETs provides
additional robustness against single points of failure of more additional robustness against the single points of failure of more
centralized approaches. centralized approaches.
In addition, some envisioned networks (e.g. mobile military networks In addition, some envisioned networks (e.g. mobile military networks
or highway networks) may be relatively large (e.g. tens or hundreds or highway networks) may be relatively large (e.g. tens or hundreds
of nodes per routing area). The need for scalability is not unique of nodes per routing area). The need for scalability is not unique
to MANETS. However, in light of the preceding characteristics, the to MANETS. However, in light of the preceding characteristics, the
mechanisms required to achieve scalability likely are. mechanisms required to achieve scalability likely are.
These characteristics create a set of underlying assumptions and These characteristics create a set of underlying assumptions and
performance concerns for protocol design which extend beyond those performance concerns for protocol design which extend beyond those
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topology of the fixed Internet. topology of the fixed Internet.
4. Goals of IETF Mobile Ad Hoc Network (manet) Working Group 4. Goals of IETF Mobile Ad Hoc Network (manet) Working Group
The intent of the newly formed IETF manet working group is to develop The intent of the newly formed IETF manet working group is to develop
a peer-to-peer mobile routing capability in a purely mobile, wireless a peer-to-peer mobile routing capability in a purely mobile, wireless
domain. This capability will exist beyond the fixed network (as domain. This capability will exist beyond the fixed network (as
supported by traditional IP networking) and beyond the one-hop fringe supported by traditional IP networking) and beyond the one-hop fringe
of the fixed network. of the fixed network.
The near-term goal of the manet working group is to standardize an The near-term goal of the manet working group is to standardize one
intra-domain unicast routing protocol which: (or more) intra-domain unicast routing protocol(s) or mode(s), and
related network-layer support technology which:
* provides a mode(s) of operation for effective operation in a
mobile networking "context". (a context is a set of defined
^L * provides for effective operation over a wide range of mobile
networking characteristics), networking "contexts" (a context is a set of characteristics
describing a mobile network and its environment);
* provides a standard "mode discovery" protocol so that newly- * provides a standard "protocol or mode discovery" algorithm so
arriving nodes may learn the mode in which a given MANET is that newly-arriving nodes may learn the mode in which a given
operating, MANET is operating;
* supports traditional, connectionless IP service, * supports traditional, connectionless IP service;
* reacts efficiently to topological changes while maintaining * reacts efficiently to topological changes and traffic demands
effective routing in a mobile networking context. while maintaining effective routing in a mobile networking
context.
The working group will also address issues pertaining to security and The working group will also consider issues pertaining to addressing,
interaction/interface with link-layer protocols and internet security security, and interaction/interfacing with lower and upper layer
protocols. In the longer term, the group may look at the issues of protocols. In the longer term, the group may look at the issues of
layering more advanced mobility services on top of the initial layering more advanced mobility services on top of the initial
unicast routing developed. These longer term issues will likely unicast routing developed. These longer term issues will likely
include investigating multicast and QoS extensions for a dynamic, include investigating multicast and QoS extensions for a dynamic,
mobile area. mobile area.
5. Why an IP-Layer Routing Solution? 5. IP-Layer Mobile Routing
A solution at the IP layer can provide a benefit similar to the An improved mobile routing capability at the IP layer can provide a
intention of the original Internet, viz. "an interoperable benefit similar to the intention of the original Internet, viz. "an
internetworking capability over a heterogeneous networking interoperable internetworking capability over a heterogeneous
infrastructure". In this case, the infrastructure is wireless, rather networking infrastructure". In this case, the infrastructure is
than hardwired, consisting of multiple wireless technologies, channel wireless, rather than hardwired, consisting of multiple wireless
access protocols, etc. Improved IP routing and related networking technologies, channel access protocols, etc. Improved IP routing and
services provide the glue to preserve the integrity of the mobile related networking services provide the glue to preserve the
internetwork segment in this more dynamic environment. integrity of the mobile internetwork segment in this more dynamic
environment.
In other words, a real benefit to using IP-level routing in a MANET
is to provide network-level consistency for multihop networks
composed of nodes using a *mixture* of physical-layer media; i.e. a
mixture of what are commonly thought of as subnet technologies. A
MANET node principally consists of a router, which may be physically
attached to multiple IP hosts (or IP-addressable devices), which has
potentially *multiple* wireless interfaces--each interface using a
*different* wireless technology. Thus, a MANET node with interfaces
using technologies A and B can communicate with any other MANET node
possessing an interface with technology A or B. The multihop
connectivity of technology A forms a physical-layer multihop
topology, the multihop connectivity of technology B forms *another*
physical-layer topology (which may differ from that of A's topology),
and the *union* of these topologies forms another topology (in graph
theoretic terms--a multigraph), termed the "IP routing fabric", of
the MANET. MANET nodes making routing decisions using the IP fabric
can intercommunicate using either or both physical-layer topologies
simultaneously. As new physical-layer technologies are developed,
new device drivers can be written and another physical-layer multihop
topology can be seamlessly added to the IP fabric. Likewise, older
technologies can easily be dropped. Such is the functionality and
architectural flexibility that IP-layer routing can support, which
brings with it hardware economies of scale.
The concept of a "router ID" (separate and apart from IP addressing)
is crucial to supporting the multigraph topology of the routing
fabric. It is what *unifies* a set of wireless IP interfaces (each
with their own IP address) and identifies them as belonging to the
same mobile platform. This approach permits maximum flexibility in
address assignment, and does not require that all IP addresses
attached to a given router fall under a common CIDR prefix. Router
IDs are used at the IP layer for routing computations. To enable IP
routing to hosts associated with the router, the subnet mask(s)
(encompassing the hosts on the mobile platform) should be advertised
with the router ID to permit routing table construction.
6. MANET Routing Protocol Performance Issues 6. MANET Routing Protocol Performance Issues
To judge the merit of a routing protocol, one needs metrics--both To judge the merit of a routing protocol, one needs metrics--both
qualitative and quantitative--with which to measure its suitability qualitative and quantitative--with which to measure its suitability
and performance. These metrics should be somewhat *independent* of and performance. These metrics should be *independent* of any given
any given routing protocol. routing protocol.
The following is a list of desirable qualitative properties: The following is a list of desirable qualitative properties of manet
routing protocols.
1) Distributed operation: This is an essential property, but it 1) Distributed operation: This is an essential property, but it
should be stated nonetheless. should be stated nonetheless.
2) Loop-freedom: Not required per se in light of certain 2) Loop-freedom: Not required per se in light of certain
quantitative measures (performance criteria), but generally quantitative measures (performance criteria), but generally
desirable to avoid problems such as worst-case phenomena, e.g. a desirable to avoid problems such as worst-case phenomena, e.g. a
small fraction of packets spinning around in the network for small fraction of packets spinning around in the network for
arbitrary time periods. Ad hoc solutions such as TTL values can arbitrary time periods. Ad hoc solutions such as TTL values can
bound the problem, but a more structured and well-formed approach bound the problem, but a more structured and well-formed approach
is generally desirable as it usually leads to better overall
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is generally desirable as it oftentimes leads to better overall
performance. performance.
3) Demand-based operation: Instead of assuming uniform traffic 3) Demand-based operation: Instead of assuming an uniform traffic
distribution within the network (and maintaining routing between distribution within the network (and maintaining routing between
all nodes at all times), let the routing algorithm adapt to the all nodes at all times), let the routing algorithm adapt to the
traffic pattern on a demand or need basis. If this is done traffic pattern on a demand or need basis. If this is done
intelligently, it will utilize network resources more efficiently. intelligently, it will utilize network energy and bandwidth
resources more efficiently.
4) Unidirectional link support: Bidirectional links are typically
assumed in the design of routing algorithms, and many algorithms
are incapable of functioning properly over unidirectional links.
Nevertheless, unidirectional links can and do occur in wireless
networks. Often times, a sufficient number of duplex links exist
so that usage of unidirectional links is of limited added value.
However, in situations where a pair of unidirectional links (in
opposite directions) form the *only* bidirectional connection
between two ad hoc clusters, the ability to make use of them is
invaluable.
5) Security: Without some form of network-level security or link 4) Security: Without some form of network-level or link-layer
layer security, a MANET routing protocol is vulnerable to many security, a MANET routing protocol is vulnerable to many forms of
forms of attack. It may be relatively simple to snoop network attack. It may be relatively simple to snoop network traffic,
traffic, replay transmissions, manipulate packet headers, and replay transmissions, manipulate packet headers, and redirect
redirect routing messages, within a wireless network without routing messages, within a wireless network without appropriate
appropriate security provisions. While these concerns exist within security provisions. While these concerns exist within wired
wired infrastructures and routing protocols as well, maintaining infrastructures and routing protocols as well, maintaining the
the "physical" security of of the transmission media is harder in "physical" security of of the transmission media is harder in
practice with MANETs. Sufficient security protection to prohibit practice with MANETs. Sufficient security protection to prohibit
distruption of modification of protocol operation is desired. disruption of modification of protocol operation is desired. This
This may be somewhat orthogonal to any particular routing protocol may be somewhat orthogonal to any particular routing protocol
approach, e.g. through the application of IP Security techniques. approach, e.g. through the application of IP Security techniques.
6) "Sleep" period operation: As a result of power conservation, 5) "Sleep" period operation: As a result of energy conservation,
or some other need to be inactive, nodes of a MANET may stop or some other need to be inactive, nodes of a MANET may stop
transmitting and/or receiving (even receiving requires power) for transmitting and/or receiving (even receiving requires power) for
arbitrary time periods. A routing protocol should be able to arbitrary time periods. A routing protocol should be able to
accomodate such sleep periods without overly adverse consequences. accommodate such sleep periods without overly adverse
This property may require close coupling with the link layer consequences. This property may require close coupling with the
protocol through a standardized interface. link-layer protocol through a standardized interface.
6) Unidirectional link support: Bidirectional links are typically
assumed in the design of routing algorithms, and many algorithms
are incapable of functioning properly over unidirectional links.
Nevertheless, unidirectional links can and do occur in wireless
networks. Oftentimes, a sufficient number of duplex links exist so
that usage of unidirectional links is of limited added value.
However, in situations where a pair of unidirectional links (in
opposite directions) form the only bidirectional connection
between two ad hoc clusters, the ability to make use of them is
valuable.
The following is a list of quantitative metrics that can be used to The following is a list of quantitative metrics that can be used to
assess the performance of any routing protocol. assess the performance of any routing protocol.
1) End-to-end data throughput and delay: Statistical measures of 1) End-to-end data throughput and delay: Statistical measures of
data routing performance (e.g., means, variances, distributions) data routing performance (e.g., means, variances, distributions)
are important. These are the measures of a routing policy's are important. These are the measures of a routing policy's
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effectiveness--how well it does its job--as measured from the effectiveness--how well it does its job--as measured from the
*external* perspective of other policies that make use of routing. *external* perspective of other policies that make use of routing.
2) Efficiency: If data routing effectiveness is the external 2) Route Acquisition Time: A particular form of *external* end-
to-end delay measurement--of particular concern with "on demand"
routing algorithms--is the time required to establish route(s)
when requested.
3) Efficiency: If data routing effectiveness is the external
measure of a policy's performance, efficiency is the *internal* measure of a policy's performance, efficiency is the *internal*
measure of its effectiveness. To achieve a given level of data measure of its effectiveness. To achieve a given level of data
routing performance, two different policies may expend differing routing performance, two different policies can expend differing
amounts of overhead, depending on their internal efficiency. amounts of overhead, depending on their internal efficiency.
Protocol efficiency may or may not directly affect data routing Protocol efficiency may or may not directly affect data routing
performance. If control and data traffic must share the same performance. If control and data traffic must share the same
channel, and the channel's capacity is limited, then excessive channel, and the channel's capacity is limited, then excessive
control traffic may impact data routing performance. control traffic often impacts data routing performance.
It is useful to track two ratios that illuminate the *internal* It is useful to track two ratios that illuminate the *internal*
efficiency of a protocol in doing its job (there may be others efficiency of a protocol in doing its job (there may be others
that the authors have not considered): that the authors have not considered):
* Average number of data bits transmitted/data bit delivered-- * Average number of data bits transmitted/data bit delivered--
this can be thought of as a measure of the efficiency of this can be thought of as a measure of the efficiency of
delivering data within the network. delivering data within the network.
* Average number of control bits transmitted/data bit * Average number of control bits transmitted/data bit
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topology is changing topology is changing
4) Link capacity--effective link speed measured in bits/second, 4) Link capacity--effective link speed measured in bits/second,
after accounting for losses due to multiple access, coding, after accounting for losses due to multiple access, coding,
framing, etc. framing, etc.
5) Fraction of unidirectional links--how effectively does a 5) Fraction of unidirectional links--how effectively does a
protocol perform as a function of the presence of unidirectional protocol perform as a function of the presence of unidirectional
links? links?
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6) Traffic patterns--how effective is a protocol in adapting to 6) Traffic patterns--how effective is a protocol in adapting to
non-uniform or bursty traffic patterns? non-uniform or bursty traffic patterns?
7) Mobility--when, and under what circumstances, is temporal and 7) Mobility--when, and under what circumstances, is temporal and
spatial topological correlation relevant to the performance of a spatial topological correlation relevant to the performance of a
routing protocol? In these cases, what is the most appropriate routing protocol? In these cases, what is the most appropriate
model for simulating node mobility in a MANET? model for simulating node mobility in a MANET?
8) Fraction and frequency of sleeping nodes--how does a protocol 8) Fraction and frequency of sleeping nodes--how does a protocol
perform in the presence of sleeping and awakening nodes? perform in the presence of sleeping and awakening nodes?
A MANET protocol should function effectively over a wide range of A MANET protocol should function effectively over a wide range of
networking contexts--from small, collaborative, ad hoc groups to networking contexts--from small, collaborative, ad hoc groups to
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its *advantages* and *limitations* should be mentioned so that the its *advantages* and *limitations* should be mentioned so that the
appropriate networking context(s) for its usage can be identified. appropriate networking context(s) for its usage can be identified.
These attributes of a protocol can typically be expressed These attributes of a protocol can typically be expressed
*qualitatively*, e.g., whether the protocol can or cannot support *qualitatively*, e.g., whether the protocol can or cannot support
shortest-path routing. Qualitative descriptions of this nature shortest-path routing. Qualitative descriptions of this nature
permit broad classification of protocols, and form a basis for more permit broad classification of protocols, and form a basis for more
detailed *quantitative* assessments of protocol performance. In detailed *quantitative* assessments of protocol performance. In
future documents, the group may put forth candidate recommendations future documents, the group may put forth candidate recommendations
regarding protocol design for MANETs. The metrics and the philosophy regarding protocol design for MANETs. The metrics and the philosophy
presented within this document are expected to continue to evolve as presented within this document are expected to continue to evolve as
MANET technology and efforts mature. MANET technology and related efforts mature.
6. References 6. References
[1] B. Adamson, "Tactical Radio Frequency Communication Requirements for [1] B. Adamson, "Tactical Radio Frequency Communication Requirements for
IPng," RFC 1677, Aug. 1994. IPng," RFC 1677, Aug. 1994.
Authors' Addresses Authors' Addresses
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M. Scott Corson M. Scott Corson
Institute for Systems Research Institute for Systems Research
University of Maryland University of Maryland
College Park, MD 20742 College Park, MD 20742
(301) 405-6630 (301) 405-6630
corson@isr.umd.edu corson@isr.umd.edu
Joseph Macker Joseph Macker
Information Technology Division Information Technology Division
Naval Research Laboratory Naval Research Laboratory
Washington, DC 20375 Washington, DC 20375
(202) 767-2001 (202) 767-2001
macker@itd.nrl.navy.mil macker@itd.nrl.navy.mil
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