draft-ietf-intarea-adhoc-wireless-com-00.txt   draft-ietf-intarea-adhoc-wireless-com-01.txt 
Internet Area E. Baccelli Internet Area E. Baccelli
Internet-Draft INRIA Internet-Draft INRIA
Intended status: Informational C. Perkins Intended status: Informational C. Perkins
Expires: May 4, 2016 Futurewei Expires: July 15, 2016 Futurewei
November 1, 2015 January 12, 2016
Multi-hop Ad Hoc Wireless Communication Multi-hop Ad Hoc Wireless Communication
draft-ietf-intarea-adhoc-wireless-com-00 draft-ietf-intarea-adhoc-wireless-com-01
Abstract Abstract
This document describes characteristics of communication between This document describes characteristics of communication between
interfaces in a multi-hop ad hoc wireless network, that protocol interfaces in a multi-hop ad hoc wireless network, that protocol
engineers and system analysts should be aware of when designing engineers and system analysts should be aware of when designing
solutions for ad hoc networks at the IP layer. solutions for ad hoc networks at the IP layer.
Status of This Memo Status of This Memo
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Copyright Notice Copyright Notice
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document authors. All rights reserved. document authors. All rights reserved.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Multi-hop Ad Hoc Wireless Networks . . . . . . . . . . . . . 2 2. Multi-hop Ad Hoc Wireless Networks . . . . . . . . . . . . . 2
3. Common Packet Transmission Characteristics in Multi-hop Ad 3. Common Packet Transmission Characteristics in
Hoc Wireless Networks . . . . . . . . . . . . . . . . . . . . 3 Multi-hop Ad Hoc Wireless Networks . . . . . . . . . . . . . 3
3.1. Asymmetry, Time-Variation, and Non-Transitivity . . . . . 3 3.1. Asymmetry, Time-Variation, and Non-Transitivity . . . . . 4
3.2. Radio Range and Wireless Irregularities . . . . . . . . . 4 3.2. Radio Range and Wireless Irregularities . . . . . . . . . 4
4. Alternative Terminology . . . . . . . . . . . . . . . . . . . 7 4. Alternative Terminology . . . . . . . . . . . . . . . . . . . 7
5. Security Considerations . . . . . . . . . . . . . . . . . . . 8 5. Security Considerations . . . . . . . . . . . . . . . . . . . 8
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
7. Informative References . . . . . . . . . . . . . . . . . . . 8 7. Informative References . . . . . . . . . . . . . . . . . . . 9
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 11 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction 1. Introduction
Experience gathered with ad hoc routing protocol development, Experience gathered with ad hoc routing protocol development,
deployment and operation, shows that wireless communication presents deployment and operation, shows that wireless communication presents
specific challenges [RFC2501] [DoD01], which Internet protocol specific challenges [RFC2501] [DoD01], which Internet protocol
designers should be aware of, when designing solutions for ad hoc designers should be aware of, when designing solutions for ad hoc
networks at the IP layer. This document does not prescribe networks at the IP layer. This document does not prescribe
solutions, but instead briefly describes these challenges in hopes of solutions, but instead briefly describes these challenges in hopes of
increasing that awareness. For example, even though a wireless link increasing that awareness.
may experience high variability as a communications channel, such
variation does not mean that the link is "broken"; indeed many As background, RFC 3819 [RFC3819] provides an excellent reference for
layer-2 technologies serve to reduce error rates by various means. higher-level considerations when designing protocols for shared
Nevertheless, such errors as noted in this document may still become media. From MTU to subnet design, from security to considerations
visible above layer-2 and so become relevant to the operation of about retransmissions, RFC 3819 provides guidance and design
higher layer protocols. rationale to help with many aspects of higher-level protocol design.
The present document focuses more specifically on challenges in
multi-hop ad hoc wireless networking. For example, in that context,
even though a wireless link may experience high variability as a
communications channel, such variation does not mean that the link is
"broken"; indeed many layer-2 technologies serve to reduce error
rates by various means. Nevertheless, such errors as noted in this
document may still become visible above layer-2 and so become
relevant to the operation of higher layer protocols.
2. Multi-hop Ad Hoc Wireless Networks 2. Multi-hop Ad Hoc Wireless Networks
For the purposes of this document, a multi-hop ad hoc wireless For the purposes of this document, a multi-hop ad hoc wireless
network will be considered to be a collection of devices that each network will be considered to be a collection of devices that each
have a radio transceiver (i.e., wireless network interface), and that have a radio transceiver (i.e., wireless network interface), and that
are moreover configured to self-organize and provide store-and- are moreover configured to self-organize and provide store-and-
forward functionality as needed to enable communications. This forward functionality as needed to enable communications. This
document focuses on the characteristics of communications through document focuses on the characteristics of communications through
such a network interface. such a network interface.
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communications as defined in Section 3.1. communications as defined in Section 3.1.
Radio Ranges for Devices A and B Radio Ranges for Devices A and B
<~~~~~~~~~~~~~+~~~~~~~~~~~~~> <~~~~~~~~~~~~~+~~~~~~~~~~~~~>
| <~~~~~~+~~~~~~> | <~~~~~~+~~~~~~>
+--|--+ +--|--+ +--|--+ +--|--+
| A |======>| B | | A |======>| B |
+-----+ +-----+ +-----+ +-----+
Figure 1: Asymmetric wireless communication example. Device A can communicate with device B, but B cannot communicate with A. Figure 1: Asymmetric wireless communication: Device A can
communicate with device B, but B cannot communicate with A.
Another example, depicted in Figure 2, is known as the "Hidden Another example, depicted in Figure 2, is known as the "Hidden
Terminal" problem. Even though the devices all have equal power for Terminal" problem. Even though the devices all have equal power for
their radio transmissions, they cannot all detect one another. In their radio transmissions, they cannot all detect one another. In
the figure, devices A and B can detect one another, and devices A and the figure, devices A and B can detect one another, and devices A and
C can also detect one another. On the other hand, B and C cannot C can also detect one another. On the other hand, B and C cannot
detect one another. When B and C simultaneously try to communicate detect one another. When B and C simultaneously try to communicate
with A, their radio signals may collide. Device A may receive with A, their radio signals may collide. Device A may receive
incoherent noise, and may even be unable to determine the source of incoherent noise, and may even be unable to determine the source of
the noise. The hidden terminal problem illustrates the property of the noise. The hidden terminal problem illustrates the property of
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each other, and A is transmitting packets to B, thus A cannot detect each other, and A is transmitting packets to B, thus A cannot detect
device C -- but C can detect A. As shown in Figure 3, during the on- device C -- but C can detect A. As shown in Figure 3, during the on-
going transmission of A, device C cannot reliably communicate with going transmission of A, device C cannot reliably communicate with
device D because of interference within C's radio range due to A's device D because of interference within C's radio range due to A's
transmissions. Device C is then said to be "exposed", because it is transmissions. Device C is then said to be "exposed", because it is
exposed to co-channel interference from A and is thereby prevented exposed to co-channel interference from A and is thereby prevented
from reliably exchanging protocol messages with D -- even though from reliably exchanging protocol messages with D -- even though
these transmissions would not interfere with the reception of data these transmissions would not interfere with the reception of data
sent from A destined to B. sent from A destined to B.
Radio Ranges for Devices A, B, C, D Radio Ranges for Devices A, B, C, D
<~~~~~~~~~~~~+~~~~~~~~~~~~> <~~~~~~~~~~+~~~~~~~~~~~> <~~~~~~~~~~~~+~~~~~~~~~~~~> <~~~~~~~~~~+~~~~~~~~~~~>
|<~~~~~~~~~~~~+~~~~~~~~~~~~>|<~~~~~~~~~~~~+~~~~~~~~~> |<~~~~~~~~~~~~+~~~~~~~~~~~~>|<~~~~~~~~~~~~+~~~~~~~~~>
+--|--+ +--|--+ +--|--+ +--|--+ +--|--+ +--|--+ +--|--+ +--|--+
| B |<======| A | | C |======>| D | | B |<======| A | | C |======>| D |
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+
Figure 3: The exposed terminal problem. When device A is communicating Figure 3: The exposed terminal problem: when device A
with device B, and device C is "exposed". communicates with device B, device C is "exposed".
Hidden and exposed terminal situations are often observed in multi- Hidden and exposed terminal situations are often observed in multi-
hop ad hoc wireless networks. Asymmetry issues with wireless hop ad hoc wireless networks. Asymmetry issues with wireless
communication may also arise for reasons other than power inequality communication may also arise for reasons other than power inequality
(e.g., multipath interference). Such problems are often resolved by (e.g., multipath interference). Such problems are often resolved by
specific mechanisms below the IP layer, for example, CSMA/CA, which specific mechanisms below the IP layer, for example, CSMA/CA, which
ensures transmission in periods perceived to be unoccupied by other ensures transmission in periods perceived to be unoccupied by other
transmissions. However, depending on the link layer technology in transmissions. However, depending on the link layer technology in
use and the position of the devices, such problems may affect the IP use and the position of the devices, such problems may affect the IP
layer due to range-limitation and partial overlap . layer due to range-limitation and partial overlap .
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representative of the breadth of terminologies that have been used in representative of the breadth of terminologies that have been used in
various ways to explain the properties mentioned in Section 3. We do various ways to explain the properties mentioned in Section 3. We do
not discuss bidirectionality, but as a final observation it is not discuss bidirectionality, but as a final observation it is
worthwhile to note that bidirectionality is not synonymous with worthwhile to note that bidirectionality is not synonymous with
symmetry. For example, the error statistics in either direction are symmetry. For example, the error statistics in either direction are
often different for a link that is otherwise considered often different for a link that is otherwise considered
bidirectional. bidirectional.
5. Security Considerations 5. Security Considerations
This document does not make any detailed description about the Section 18 of RFC 3819 [RFC3819] provides an excellent overview of
security implications of wireless communications. Notably, security considerations at the subnetwork layer. Beyond the material
eavesdropping on a wireless link is much easier than for wired media there, multi-hop ad hoc wireless networking (i) is not limited to
(although significant progress has been made in the field of wireless subnetwork layer operation, and (ii) makes use of wireless
monitoring of wired transmissions). Nevertheless, the need for communications.
securing high-level (layer-3 and above) protocols for wireless media
is a priori independent from the need to secure the layer-2 and On one hand, a detailed description of security implications of
layer-1 protocols for such media. wireless communications in general is outside of the scope of this
document. Notably, however, eavesdropping on a wireless link is much
easier than for wired media (although significant progress has been
made in the field of wireless monitoring of wired transmissions). As
a result, traffic analysis attacks can be even more subtle and
difficult to defeat in this context. Furthermore, such
communications over a shared media are particularly prone to theft of
service and denial of service (DoS) attacks.
On the other hand, the potential multi-hop aspect of the networks we
consider in this document goes beyond traditional scope of subnetwork
design. In practice, unplanned relaying of network traffic (both
user traffic and control traffic) happens routinely. Due to the
physical nature of wireless media, Man in the Middle (MITM) attacks
are facilitated, which may significantly alter network performance.
This highlights the need to stick to the "end-to-end principle": L3
security, end-to-end, becomes a primary goal, independently of
securing layer-2 and layer-1 protocols (though L2 and L1 security can
indeed help to reach this goal).
6. IANA Considerations 6. IANA Considerations
This document does not have any IANA actions. This document does not have any IANA actions.
7. Informative References 7. Informative References
[RFC2501] Corson, S. and J. Macker, "Mobile Ad hoc Networking [RFC2501] Corson, S. and J. Macker, "Mobile Ad hoc Networking
(MANET): Routing Protocol Performance Issues and (MANET): Routing Protocol Performance Issues and
Evaluation Considerations", RFC 2501, Evaluation Considerations", RFC 2501,
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[RFC3626] Clausen, T., Ed. and P. Jacquet, Ed., "Optimized Link [RFC3626] Clausen, T., Ed. and P. Jacquet, Ed., "Optimized Link
State Routing Protocol (OLSR)", RFC 3626, State Routing Protocol (OLSR)", RFC 3626,
DOI 10.17487/RFC3626, October 2003, DOI 10.17487/RFC3626, October 2003,
<http://www.rfc-editor.org/info/rfc3626>. <http://www.rfc-editor.org/info/rfc3626>.
[RFC3684] Ogier, R., Templin, F., and M. Lewis, "Topology [RFC3684] Ogier, R., Templin, F., and M. Lewis, "Topology
Dissemination Based on Reverse-Path Forwarding (TBRPF)", Dissemination Based on Reverse-Path Forwarding (TBRPF)",
RFC 3684, DOI 10.17487/RFC3684, February 2004, RFC 3684, DOI 10.17487/RFC3684, February 2004,
<http://www.rfc-editor.org/info/rfc3684>. <http://www.rfc-editor.org/info/rfc3684>.
[RFC3819] Karn, P., Ed., Bormann, C., Fairhurst, G., Grossman, D.,
Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J., and L.
Wood, "Advice for Internet Subnetwork Designers", BCP 89,
RFC 3819, DOI 10.17487/RFC3819, July 2004,
<http://www.rfc-editor.org/info/rfc3819>.
[RFC4728] Johnson, D., Hu, Y., and D. Maltz, "The Dynamic Source [RFC4728] Johnson, D., Hu, Y., and D. Maltz, "The Dynamic Source
Routing Protocol (DSR) for Mobile Ad Hoc Networks for Routing Protocol (DSR) for Mobile Ad Hoc Networks for
IPv4", RFC 4728, DOI 10.17487/RFC4728, February 2007, IPv4", RFC 4728, DOI 10.17487/RFC4728, February 2007,
<http://www.rfc-editor.org/info/rfc4728>. <http://www.rfc-editor.org/info/rfc4728>.
[RFC4903] Thaler, D., "Multi-Link Subnet Issues", RFC 4903,
DOI 10.17487/RFC4903, June 2007,
<http://www.rfc-editor.org/info/rfc4903>.
[RFC5449] Baccelli, E., Jacquet, P., Nguyen, D., and T. Clausen, [RFC5449] Baccelli, E., Jacquet, P., Nguyen, D., and T. Clausen,
"OSPF Multipoint Relay (MPR) Extension for Ad Hoc "OSPF Multipoint Relay (MPR) Extension for Ad Hoc
Networks", RFC 5449, DOI 10.17487/RFC5449, February 2009, Networks", RFC 5449, DOI 10.17487/RFC5449, February 2009,
<http://www.rfc-editor.org/info/rfc5449>. <http://www.rfc-editor.org/info/rfc5449>.
[RFC5889] Baccelli, E., Ed. and M. Townsley, Ed., "IP Addressing
Model in Ad Hoc Networks", RFC 5889, DOI 10.17487/RFC5889,
September 2010, <http://www.rfc-editor.org/info/rfc5889>.
[RFC6250] Thaler, D., "Evolution of the IP Model", RFC 6250, [RFC6250] Thaler, D., "Evolution of the IP Model", RFC 6250,
DOI 10.17487/RFC6250, May 2011, DOI 10.17487/RFC6250, May 2011,
<http://www.rfc-editor.org/info/rfc6250>. <http://www.rfc-editor.org/info/rfc6250>.
[DoD01] Freebersyser, J. and B. Leiner, "A DoD perspective on [DoD01] Freebersyser, J. and B. Leiner, "A DoD perspective on
mobile ad hoc networks", Addison Wesley C. E. Perkins, mobile ad hoc networks", Addison Wesley C. E. Perkins,
Ed., 2001, pp. 29--51, 2001. Ed., 2001, pp. 29--51, 2001.
[FUNKFEUER] [FUNKFEUER]
"Austria Wireless Community Network, "Austria Wireless Community Network,
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