draft-ietf-manet-issues-02.txt   rfc2501.txt 
Internet Draft S. Corson Network Working Group S. Corson
Expiration: April 1999 University of Maryland Request for Comments: 2501 University of Maryland
File: draft-ietf-manet-issues-02.txt J. Macker Category: Informational J. Macker
Naval Research Laboratory Naval Research Laboratory
October 1998 January 1999
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 memo provides information for the Internet community. It does
documents of the Internet Engineering Task Force (IETF), its areas, not specify an Internet standard of any kind. Distribution of this
and its working groups. Note that other groups may also distribute memo is unlimited.
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet- Drafts as reference
material or to cite them other than as "work in progress."
To view the entire list of current Internet-Drafts, please check the Copyright Notice
"1id-abstracts.txt" listing contained in the Internet-Drafts Shadow
Directories on ftp.is.co.za (Africa), ftp.nordu.net (Europe),
munnari.oz.au (Pacific Rim), ftp.ietf.org (US East Coast), or
ftp.isi.edu (US West Coast).
Distribution of this memo is unlimited. Copyright (C) The Internet Society (1999). All Rights Reserved.
Abstract Abstract
This memo first describes the characteristics of Mobile Ad hoc This memo first describes the characteristics of Mobile Ad hoc
Networks (MANETs), and their idiosyncrasies with respect to Networks (MANETs), and their idiosyncrasies with respect to
traditional, hardwired packet networks. It then discusses the effect traditional, hardwired packet networks. It then discusses the effect
these differences have on the design and evaluation of network these differences have on the design and evaluation of network
control protocols with an emphasis on routing performance evaluation control protocols with an emphasis on routing performance evaluation
considerations. 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.
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
skipping to change at page 4, line 49 skipping to change at page 4, line 40
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 one The near-term goal of the manet working group is to standardize one
(or more) intra-domain unicast routing protocol(s) or mode(s), and (or more) intra-domain unicast routing protocol(s), and related
related network-layer support technology which: network-layer support technology which:
* provides for effective operation over a wide range of mobile * provides for effective operation over a wide range of mobile
networking "contexts" (a context is a set of characteristics networking "contexts" (a context is a set of characteristics
describing a mobile network and its environment); describing a mobile network and its environment);
* provides a standard "protocol or mode discovery" algorithm so
that newly-arriving nodes may learn the mode in which a given
MANET is operating;
* supports traditional, connectionless IP service; * supports traditional, connectionless IP service;
* reacts efficiently to topological changes and traffic demands * reacts efficiently to topological changes and traffic demands
while maintaining effective routing in a mobile networking while maintaining effective routing in a mobile networking
context. context.
The working group will also consider issues pertaining to addressing, The working group will also consider issues pertaining to addressing,
security, and interaction/interfacing with lower and upper layer 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
skipping to change at page 6, line 13 skipping to change at page 5, line 49
theoretic terms--a multigraph), termed the "IP routing fabric", of theoretic terms--a multigraph), termed the "IP routing fabric", of
the MANET. MANET nodes making routing decisions using the IP fabric the MANET. MANET nodes making routing decisions using the IP fabric
can intercommunicate using either or both physical-layer topologies can intercommunicate using either or both physical-layer topologies
simultaneously. As new physical-layer technologies are developed, simultaneously. As new physical-layer technologies are developed,
new device drivers can be written and another physical-layer multihop new device drivers can be written and another physical-layer multihop
topology can be seamlessly added to the IP fabric. Likewise, older topology can be seamlessly added to the IP fabric. Likewise, older
technologies can easily be dropped. Such is the functionality and technologies can easily be dropped. Such is the functionality and
architectural flexibility that IP-layer routing can support, which architectural flexibility that IP-layer routing can support, which
brings with it hardware economies of scale. brings with it hardware economies of scale.
The concept of a "router ID" (separate and apart from IP addressing) The concept of a "node identifier" (separate and apart from the
is crucial to supporting the multigraph topology of the routing concept of an "interface identifier") is crucial to supporting the
fabric. It is what *unifies* a set of wireless IP interfaces (each multigraph topology of the routing fabric. It is what *unifies* a set
with their own IP address) and identifies them as belonging to the of wireless interfaces and identifies them as belonging to the same
same mobile platform. This approach permits maximum flexibility in mobile platform. This approach permits maximum flexibility in
address assignment, and does not require that all IP addresses address assignment. Node identifiers are used at the IP layer for
attached to a given router fall under a common CIDR prefix. Router routing computations.
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.
5.1. Interaction with Standard IP Routing 5.1. Interaction with Standard IP Routing
In the near term, it is currently envisioned that MANETs will In the near term, it is currently envisioned that MANETs will
function as *stub* networks, meaning that all traffic carried by function as *stub* networks, meaning that all traffic carried by
MANET nodes must either be sourced or sinked within the MANET. MANET nodes will either be sourced or sinked within the MANET.
Because of bandwidth and possibly power constraints, MANETs are not Because of bandwidth and possibly power constraints, MANETs are not
presently envisioned to function as *transit* networks carrying presently envisioned to function as *transit* networks carrying
traffic which enters and then leaves the MANET (although this traffic which enters and then leaves the MANET (although this
restriction may be removed by subsequent technology advances). This restriction may be removed by subsequent technology advances). This
substantially reduces the amount of route advertisement required for substantially reduces the amount of route advertisement required for
interoperation with the existing fixed Internet. For stub operation, interoperation with the existing fixed Internet. For stub operation,
routing interoperability in the near term may be achieved using some routing interoperability in the near term may be achieved using some
combination of mechanisms such as MANET-based anycast and mobile IP. combination of mechanisms such as MANET-based anycast and mobile IP.
Future interoperability may be achieved using mechanisms other than Future interoperability may be achieved using mechanisms other than
mobile IP. mobile IP.
skipping to change at page 7, line 4 skipping to change at page 6, line 35
usage of a common MANET addressing approach by all MANET routing usage of a common MANET addressing approach by all MANET routing
protocols. Development of such an approach is underway which permits protocols. Development of such an approach is underway which permits
routing through a multi-technology fabric, permits multiple hosts per routing through a multi-technology fabric, permits multiple hosts per
router and ensures long-term interoperability through adherence to router and ensures long-term interoperability through adherence to
the IP addressing architecture. Supporting these features appears the IP addressing architecture. Supporting these features appears
only to require identifying host and router interfaces with IP only to require identifying host and router interfaces with IP
addresses, identifying a router with a separate Router ID, and addresses, identifying a router with a separate Router ID, and
permitting routers to have multiple wired and wireless interfaces. permitting routers to have multiple wired and wireless interfaces.
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 *independent* of any given and performance. These metrics should be *independent* of any given
routing protocol. routing protocol.
The following is a list of desirable qualitative properties of manet The following is a list of desirable qualitative properties of MANET
routing protocols. 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 (i.e. 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 is generally desirable as it usually leads to better overall
performance. performance.
3) Demand-based operation: Instead of assuming an 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 energy and bandwidth intelligently, it can utilize network energy and bandwidth
resources more efficiently. resources more efficiently, at the cost of increased route
discovery delay.
4) Security: Without some form of network-level or link-layer 4) Proactive operation: The flip-side of demand-based operation.
In certain contexts, the additional latency demand-based operation
incurs may be unacceptable. If bandwidth and energy resources
permit, proactive operation is desirable in these contexts.
5) Security: Without some form of network-level or link-layer
security, a MANET routing protocol is vulnerable to many forms of security, a MANET routing protocol is vulnerable to many forms of
attack. It may be relatively simple to snoop network traffic, attack. It may be relatively simple to snoop network traffic,
replay transmissions, manipulate packet headers, and redirect replay transmissions, manipulate packet headers, and redirect
routing messages, within a wireless network without appropriate routing messages, within a wireless network without appropriate
security provisions. While these concerns exist within wired security provisions. While these concerns exist within wired
infrastructures and routing protocols as well, maintaining the infrastructures and routing protocols as well, maintaining 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
disruption of modification of protocol operation is desired. This disruption of modification of protocol operation is desired. 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.
5) "Sleep" period operation: As a result of energy conservation, 6) "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
accommodate such sleep periods without overly adverse accommodate such sleep periods without overly adverse
consequences. This property may require close coupling with the consequences. This property may require close coupling with the
link-layer protocol through a standardized interface. link-layer protocol through a standardized interface.
6) Unidirectional link support: Bidirectional links are typically 7) Unidirectional link support: Bidirectional links are typically
assumed in the design of routing algorithms, and many algorithms assumed in the design of routing algorithms, and many algorithms
are incapable of functioning properly over unidirectional links. are incapable of functioning properly over unidirectional links.
Nevertheless, unidirectional links can and do occur in wireless Nevertheless, unidirectional links can and do occur in wireless
networks. Oftentimes, a sufficient number of duplex links exist so networks. Oftentimes, a sufficient number of duplex links exist so
that usage of unidirectional links is of limited added value. that usage of unidirectional links is of limited added value.
However, in situations where a pair of unidirectional links (in However, in situations where a pair of unidirectional links (in
opposite directions) form the only bidirectional connection opposite directions) form the only bidirectional connection
between two ad hoc clusters, the ability to make use of them is between two ad hoc regions, the ability to make use of them is
valuable. 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
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.
skipping to change at page 8, line 45 skipping to change at page 8, line 34
4) Efficiency: If data routing effectiveness is the external 4) 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 can 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 often impacts 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 several ratios that illuminate the
efficiency of a protocol in doing its job (there may be others *internal* efficiency of a protocol in doing its job (there may be
that the authors have not considered): others 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 bit efficiency of
delivering data within the network. delivering data within the network. Indirectly, it also gives
the average hop count taken by data packets.
* Average number of control bits transmitted/data bit * Average number of control bits transmitted/data bit
delivered--this measures the efficiency of the protocol in delivered--this measures the bit efficiency of the protocol in
expending control overhead to delivery data packets. Note that expending control overhead to delivery data. Note that this
this should include not only the bits in the routing control should include not only the bits in the routing control
packets, but also the bits in the header of the data packets. packets, but also the bits in the header of the data packets.
In other words, anything that is not data is control overhead, In other words, anything that is not data is control overhead,
and should be counted in the control portion of the algorithm. and should be counted in the control portion of the algorithm.
* Average number of control and data packets transmitted/data
packet delivered--rather than measuring pure algorithmic
efficiency in terms of bit count, this measure tries to capture
a protocol's channel access efficiency, as the cost of channel
access is high in contention-based link layers.
Also, we must consider the networking *context* in which a protocol's Also, we must consider the networking *context* in which a protocol's
performance is measured. Essential parameters that should be varied performance is measured. Essential parameters that should be varied
include: include:
1) Network size--measured in the number of nodes 1) Network size--measured in the number of nodes
2) Network connectivity--the average degree of a node (i.e. the 2) Network connectivity--the average degree of a node (i.e. the
average number of neighbors of a node) average number of neighbors of a node)
3) Topological rate of change--the speed with which a network's 3) Topological rate of change--the speed with which a network's
skipping to change at page 10, line 42 skipping to change at page 10, line 41
inter-router authentication prior to the exchange of network control inter-router authentication prior to the exchange of network control
information. Several levels of authentication ranging from no information. Several levels of authentication ranging from no
security (always an option) and simple shared-key approaches, to full security (always an option) and simple shared-key approaches, to full
public key infrastructure-based authentication mechanisms will be public key infrastructure-based authentication mechanisms will be
explored by the group. As an adjunct to the working groups efforts, explored by the group. As an adjunct to the working groups efforts,
several optional authentication modes may be standardized for use in several optional authentication modes may be standardized for use in
MANETs. MANETs.
8. References 8. References
[1] B. Adamson, "Tactical Radio Frequency Communication Requirements for [1] Adamson, B., "Tactical Radio Frequency Communication Requirements
IPng," RFC 1677, Aug. 1994. for IPng", RFC 1677, August 1994.
Authors' Addresses Authors' Addresses
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
corson@isr.umd.edu Phone: (301) 405-6630
EMail: 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
macker@itd.nrl.navy.mil Phone: (202) 767-2001
EMail: macker@itd.nrl.navy.mil
Full Copyright Statement
Copyright (C) The Internet Society (1999). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
 End of changes. 26 change blocks. 
60 lines changed or deleted 57 lines changed or added

This html diff was produced by rfcdiff 1.41. The latest version is available from http://tools.ietf.org/tools/rfcdiff/