draft-ietf-intarea-adhoc-wireless-com-01.txt   draft-ietf-intarea-adhoc-wireless-com-02.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: July 15, 2016 Futurewei Expires: January 21, 2017 Futurewei
January 12, 2016 July 20, 2016
Multi-hop Ad Hoc Wireless Communication Multi-hop Ad Hoc Wireless Communication
draft-ietf-intarea-adhoc-wireless-com-01 draft-ietf-intarea-adhoc-wireless-com-02
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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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on July 15, 2016. This Internet-Draft will expire on January 21, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
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 3. Common Packet Transmission Characteristics in
Multi-hop Ad Hoc Wireless Networks . . . . . . . . . . . . . 3 Multi-hop Ad Hoc Wireless Networks . . . . . . . . . . . . . 3
3.1. Asymmetry, Time-Variation, and Non-Transitivity . . . . . 4 3.1. Asymmetry, Time-Variation, and Non-Transitivity . . . . . 4
3.2. Radio Range and Wireless Irregularities . . . . . . . . . 4 3.2. Radio Range and Wireless Irregularities . . . . . . . . . 5
4. Alternative Terminology . . . . . . . . . . . . . . . . . . . 7 4. Alternative Terminology . . . . . . . . . . . . . . . . . . . 7
5. Security Considerations . . . . . . . . . . . . . . . . . . . 8 5. Security Considerations . . . . . . . . . . . . . . . . . . . 8
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
7. Informative References . . . . . . . . . . . . . . . . . . . 9 7. Informative References . . . . . . . . . . . . . . . . . . . 9
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 12 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction 1. Introduction
Experience gathered with ad hoc routing protocol development, Experience gathered with ad hoc routing protocol development,
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As background, RFC 3819 [RFC3819] provides an excellent reference for As background, RFC 3819 [RFC3819] provides an excellent reference for
higher-level considerations when designing protocols for shared higher-level considerations when designing protocols for shared
media. From MTU to subnet design, from security to considerations media. From MTU to subnet design, from security to considerations
about retransmissions, RFC 3819 provides guidance and design about retransmissions, RFC 3819 provides guidance and design
rationale to help with many aspects of higher-level protocol design. rationale to help with many aspects of higher-level protocol design.
The present document focuses more specifically on challenges in The present document focuses more specifically on challenges in
multi-hop ad hoc wireless networking. For example, in that context, multi-hop ad hoc wireless networking. For example, in that context,
even though a wireless link may experience high variability as a even though a wireless link may experience high variability as a
communications channel, such variation does not mean that the link is communications channel, such variation does not mean that the link is
"broken"; indeed many layer-2 technologies serve to reduce error "broken". Many layer-2 technologies serve to reduce error rates by
rates by various means. Nevertheless, such errors as noted in this various means. Nevertheless, such errors as noted in this document
document may still become visible above layer-2 and so become may still become visible above layer-2 and so become relevant to the
relevant to the operation of higher layer protocols. 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 at least one radio transceiver (i.e., wireless network
are moreover configured to self-organize and provide store-and- interface), and that are moreover configured to self-organize and
forward functionality as needed to enable communications. This provide store-and-forward functionality as needed to enable
document focuses on the characteristics of communications through communications. This document focuses on the characteristics of
such a network interface. communications through such a network interface.
Although the characteristics of packet transmission over multi-hop ad Although the characteristics of packet transmission over multi-hop ad
hoc wireless networks, described below, are not the typical hoc wireless networks, described below, are not the typical
characteristics expected by IP [RFC6250], it is desirable and characteristics expected by IP [RFC6250], it is desirable and
possible to run IP over such networks, as demonstrated in certain possible to run IP over such networks, as demonstrated in certain
deployments currently in operation, such as Freifunk [FREIFUNK], and deployments currently in operation, such as Freifunk [FREIFUNK], and
Funkfeuer [FUNKFEUER]. These deployments use routers running IP Funkfeuer [FUNKFEUER]. These deployments use routers running IP
protocols e.g., OLSR (Optimized Link State Routing [RFC3626]) on top protocols e.g., OLSR (Optimized Link State Routing [RFC3626]) on top
of IEEE 802.11 in ad hoc mode with the same ESSID (Extended Service of IEEE 802.11 in ad hoc mode with the same ESSID (Extended Service
Set Identification) at the link layer. Multi-hop ad hoc wireless Set Identification) at the link layer. Multi-hop ad hoc wireless
networks may also run on link layers other than IEEE 802.11, and may networks may also run on link layers other than IEEE 802.11, and may
use routing protocols other than OLSR (for instance, AODV [RFC3561], use routing protocols other than OLSR. The following documents
TBRPF [RFC3684], DSR [RFC4728], or OSPF-MPR [RFC5449]). provide a number of examples: AODV [RFC3561], OLSRv2 [RFC7181], TBRPF
[RFC3684], OSPF ([RFC5449], [RFC5820] and [RFC7137]), or DSR
[RFC4728].
Note that in contrast, devices communicating via an IEEE 802.11 Note that in contrast, devices communicating via an IEEE 802.11
access point in infrastructure mode do not form a multi-hop ad hoc access point in infrastructure mode do not form a multi-hop ad hoc
wireless network, since the central role of the access point is wireless network, since the central role of the access point is
predetermined, and devices other than the access point do not predetermined, and devices other than the access point do not
generally provide store-and-forward functionality. generally provide store-and-forward functionality.
3. Common Packet Transmission Characteristics in Multi-hop Ad Hoc 3. Common Packet Transmission Characteristics in Multi-hop Ad Hoc
Wireless Networks Wireless Networks
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then say that B can "detect" A. Note that therefore, when B detects then say that B can "detect" A. Note that therefore, when B detects
A, an IP packet transmitted by A will be rigorously identical to the A, an IP packet transmitted by A will be rigorously identical to the
corresponding IP packet received by B. corresponding IP packet received by B.
Let S be the set of devices that detect device A through its wireless Let S be the set of devices that detect device A through its wireless
interface on network N. The following section gathers common interface on network N. The following section gathers common
characteristics concerning packet transmission over such networks, characteristics concerning packet transmission over such networks,
which were observed through experience with MANET routing protocol which were observed through experience with MANET routing protocol
development (for instance, OLSR[RFC3626], AODV[RFC3561], development (for instance, OLSR[RFC3626], AODV[RFC3561],
TBRPF[RFC3684], DSR[RFC4728], and OSPF-MPR[RFC5449]), as well as TBRPF[RFC3684], DSR[RFC4728], and OSPF-MPR[RFC5449]), as well as
deployment and operation (Freifunk[FREIFUNK], Funkfeuer[FUNKFEUER]). deployment and operation (e.g., Freifunk[FREIFUNK],
Funkfeuer[FUNKFEUER]).
3.1. Asymmetry, Time-Variation, and Non-Transitivity 3.1. Asymmetry, Time-Variation, and Non-Transitivity
First, even though a device C in set S can (by definition) detect First, even though a device C in set S can (by definition) detect
device A, there is no guarantee that C can, conversely, send IP device A, there is no guarantee that C can, conversely, send IP
packets directly to A. In other words, even though C can detect A packets directly to A. In other words, even though C can detect A
(since it is a member of set S), there is no guarantee that A can (since it is a member of set S), there is no guarantee that A can
detect C. Thus, multi-hop ad hoc wireless communications may be detect C. Thus, multi-hop ad hoc wireless communications may be
"asymmetric". Such cases are common. "asymmetric". Such cases are common.
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time. Thus, multi-hop ad hoc wireless communications may be "time- time. Thus, multi-hop ad hoc wireless communications may be "time-
variant". Time variation is often observed in multi-hop ad hoc variant". Time variation is often observed in multi-hop ad hoc
wireless networks due to variability of the wireless medium, and to wireless networks due to variability of the wireless medium, and to
device mobility. device mobility.
Now, conversely, let V be the set of devices which A detects. Now, conversely, let V be the set of devices which A detects.
Suppose that A is communicating at time t0 through its interface on Suppose that A is communicating at time t0 through its interface on
network N. As a consequence of time variation and asymmetry, we network N. As a consequence of time variation and asymmetry, we
observe that A: observe that A:
1. cannot assume that S = V, 1. cannot assume that S = V, and
2. cannot assume that S and/or V are unchanged at time t1 later than 2. cannot assume that S and/or V are unchanged at time t1 later than
t0. t0.
Furthermore, transitivity is not guaranteed over multi-hop ad hoc Furthermore, transitivity is not guaranteed over multi-hop ad hoc
wireless networks. Indeed, let's assume that, through their wireless networks. Suppose that, through their respective interfaces
respective interfaces within network N: within network N:
1. device B and device A can detect one another (i.e. B is a member 1. device B and device A can detect one another (i.e. B is a member
of sets S and V), and, of sets S and V), and,
2. device A and device C can also detect one another (i.e. C is a 2. device A and device C can also detect one another (i.e. C is a
also a member of sets S and V). also a member of sets S and V).
These assumptions do not imply that B can detect C, nor that C can These assumptions do not imply that B can detect C, nor that C can
detect B (through their interface on network N). Such "non- detect B (through their interface on network N). Such "non-
transitivity" is common on multi-hop ad hoc wireless networks. transitivity" is common on multi-hop ad hoc wireless networks.
In a nutshell: multi-hop ad hoc wireless communications can be In summary: multi-hop ad hoc wireless communications can be
asymmetric, non-transitive, and time-varying. asymmetric, non-transitive, and time-varying.
3.2. Radio Range and Wireless Irregularities 3.2. Radio Range and Wireless Irregularities
Section 3.1 presents an abstract description of some common Section 3.1 presents an abstract description of some common
characteristics concerning packet transmission over multi-hop ad hoc characteristics concerning packet transmission over multi-hop ad hoc
wireless networks. This section describes practical examples, which wireless networks. This section describes practical examples, which
illustrate the characteristics listed in Section 3.1 as well as other illustrate the characteristics listed in Section 3.1 as well as other
common effects. common effects.
Wireless communications are subject to limitations to the distance Wireless communications are particularly subject to limitations on
across which they may be established. The range-limitation factor the distance across which they may be established. The range-
creates specific problems on multi-hop ad hoc wireless networks. In limitation factor creates specific problems on multi-hop ad hoc
this context, the radio ranges of several devices often partially wireless networks. Due to the lack of isolation between the
overlap. Such partial overlap causes communication to be non- transmitters, the radio ranges of several devices often partially
transitive and/or asymmetric, as described in Section 3.1. Moreover, overlap, causing communication to be non-transitive and/or asymmetric
the range may vary from one device to another, depending on location as described in Section 3.1. Moreover, the range of each device may
and environmental factors. This is in addition to the time variation depend on location and environmental factors. This is in addition to
of range and signal strength caused by variability in the local possible time variations of range and signal strength.
environment.
For example, as depicted in Figure 1, it may happen that a device B
detects a device A which transmits at high power, whereas B transmits
at lower power. In such cases, B detects A, but A cannot detect B.
This examplifies the asymmetry in multi-hop ad hoc wireless
communications as defined in Section 3.1.
Radio Ranges for Devices A and B For example it may happen that a device B detects a device A which
transmits at high power, whereas B transmits at lower power. In such
cases, as depicted in Figure 1, B can detect A, but A cannot detect
B. This exemplifies asymmetry in wireless communications as defined
in Section 3.1.
<~~~~~~~~~~~~~+~~~~~~~~~~~~~> Radio Range for Device A
| <~~~~~~+~~~~~~> <~~~~~~~~~~~~~+~~~~~~~~~~~~~>
+--|--+ +--|--+ | Range for Device B
| A |======>| B | | <~~~~~~+~~~~~~>
+-----+ +-----+ +--|--+ +--|--+
| A |======>| B |
+-----+ +-----+
Figure 1: Asymmetric wireless communication: Device A can Figure 1: Asymmetric Wireless Communication
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. Nevertheless, B and C cannot detect
detect one another. When B and C simultaneously try to communicate one another. When B and C simultaneously try to communicate with A,
with A, their radio signals may collide. Device A may receive their radio signals collide. Device A may then receive incoherent
incoherent noise, and may even be unable to determine the source of noise, and may even be unable to determine the source of the noise.
the noise. The hidden terminal problem illustrates the property of The hidden terminal problem is a consequence of the property of non-
non-transitivity in multi-hop ad hoc wireless communications as transitivity in multi-hop ad hoc wireless communications as described
described in Section 3.1. in Section 3.1.
Radio Ranges for Devices A, B, C
Radio Range for Device B Radio Range for Device C
<~~~~~~~~~~~~~+~~~~~~~~~~~~~> <~~~~~~~~~~~~~+~~~~~~~~~~~~~> <~~~~~~~~~~~~~+~~~~~~~~~~~~~> <~~~~~~~~~~~~~+~~~~~~~~~~~~~>
| Radio Range for Device A |
|<~~~~~~~~~~~~~+~~~~~~~~~~~~~>| |<~~~~~~~~~~~~~+~~~~~~~~~~~~~>|
+--|--+ +--|--+ +--|--+ +--+--+ +--+--+ +--+--+
| B |=======>| A |<=======| C | | B |=======>| A |<=======| C |
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+
Figure 2: The hidden terminal problem. Devices C and B Figure 2: Hidden Terminal Problem
try to communicate with device A at the same time,
and their radio signals collide.
Another situation, shown in Figure 3, is known as the "Exposed Another situation, shown in Figure 3, is known as the "Exposed
Terminal" problem. In the figure, device A and device B can detect Terminal" problem. In the figure, device A and device B can detect
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 Range for Device B Range for Device C
<~~~~~~~~~~~~+~~~~~~~~~~~~> <~~~~~~~~~~+~~~~~~~~~~~> <~~~~~~~~~~~~+~~~~~~~~~~~~> <~~~~~~~~~~+~~~~~~~~~~~>
| Range for Device A | Range for Device D
|<~~~~~~~~~~~~+~~~~~~~~~~~~>|<~~~~~~~~~~~~+~~~~~~~~~> |<~~~~~~~~~~~~+~~~~~~~~~~~~>|<~~~~~~~~~~~~+~~~~~~~~~>
+--|--+ +--|--+ +--|--+ +--|--+ +--|--+ +--|--+ +--|--+ +--|--+
| B |<======| A | | C |======>| D | | B |<======| A | | C |======>| D |
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+ +-----+
Figure 3: The exposed terminal problem: when device A Figure 3: Exposed Terminal Problem
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; CSMA/CA, for example,
ensures transmission in periods perceived to be unoccupied by other requires that the physical medium be unoccupied from the point of
transmissions. However, depending on the link layer technology in view of both devices before starting transmission. Nevertheless,
use and the position of the devices, such problems may affect the IP depending on the link layer technology in use and the position of the
layer due to range-limitation and partial overlap . devices, such problems may affect the IP layer due to range
limitation and partial overlap.
Besides radio range limitations, wireless communications are affected Besides radio range limitations, wireless communications are affected
by irregularities in the shape of the geographical area over which by irregularities in the shape of the geographical area over which
devices may effectively communicate (see for instance [MC03], devices may effectively communicate (see for instance [MC03],
[MI03]). For example, even omnidirectional wireless transmission is [MI03]). For example, even omnidirectional wireless transmission is
typically non-isotropic (i.e. non-circular). Signal strength often typically non-isotropic (i.e. non-circular). Signal strength often
suffers frequent and significant variations, which are not a simple suffers frequent and significant variations, which do not have a
function of distance. Instead, it is a complex function of the simple dependence on distance. Instead, the dependence is a complex
environment including obstacles, weather conditions, interference, function of the environment including obstacles, weather conditions,
and other factors that change over time. Because wireless interference, and other factors that change over time. Because
communications have to encounter different terrain, path, wireless communications often encounter different terrain, path,
obstructions, atmospheric conditions and other phenomena, analytical obstructions, atmospheric conditions and other phenomena, analytical
formulation of signal strength is considered intractable [VTC99], and formulation of signal strength is considered intractable [VTC99].
the radio engineering community has thus developed numerous radio The radio engineering community has developed numerous radio
propagation models, relying on median values observed in specific propagation approximations, relying on median values observed in
environments [SAR03]. specific environments [SAR03].
The above irregularities also cause communications on multi-hop ad These irregularities cause communications on multi-hop ad hoc
hoc wireless networks to be non-transitive, asymmetric, or time- wireless networks to be non-transitive, asymmetric, or time-varying,
varying, as described in Section 3.1, and may impact protocols at the as described in Section 3.1, and may impact protocols at the IP layer
IP layer and above. There may be no indication to the IP layer when and above. There may be no indication to the IP layer when a
a previously established communication channel becomes unusable; previously established communication channel becomes unusable; "link
"link down" triggers are generally absent in multi-hop ad hoc down" triggers are often absent in multi-hop ad hoc wireless
wireless networks, since the absence of detectable radio energy networks, since the absence of detectable radio energy (e.g., in
(e.g., in carrier waves) may simply indicate that neighboring devices carrier waves) may simply indicate that neighboring devices are not
are not currently transmitting. Such an absence of detectable radio currently transmitting.
energy does not therefore indicate whether or not transmissions have
failed to reach the intended destination.
4. Alternative Terminology 4. Alternative Terminology
Many terms have been used in the past to describe the relationship of Many terms have been used in the past to describe the relationship of
devices in a multi-hop ad hoc wireless network based on their ability devices in a multi-hop ad hoc wireless network based on their ability
to send or receive packets to/from each other. The terms used in to send or receive packets to/from each other. The terms used in
previous sections of this document have been selected because the previous sections of this document have been selected because the
authors believe they are unambiguous, with respect to the goal of authors believe they are unambiguous, with respect to the goal of
this document (see Section 1). this document as formulated in Section 1.
In this section, we exhibit some other terms that describe the same In this section, we exhibit some other terms that describe the same
relationship between devices in multi-hop ad hoc wireless networks. relationship between devices in multi-hop ad hoc wireless networks.
In the following, let network N be, again, a multi-hop ad hoc In the following, let network N be, again, a multi-hop ad hoc
wireless network. Let the set S be, as before, the set of devices wireless network. Let the set S be, as before, the set of devices
that can directly receive packets transmitted by device A through its that can directly receive packets transmitted by device A through its
interface on network N. In other words, any device B belonging to S interface on network N. In other words, any device B belonging to S
can detect packets transmitted by A. Then, due to the asymmetric can detect packets transmitted by A. Then, due to the asymmetric
nature of wireless communications: nature of wireless communications:
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- We may say that device B "is adjacent to" device A. In this - We may say that device B "is adjacent to" device A. In this
terminology, there is no guarantee that A is adjacent to B, even terminology, there is no guarantee that A is adjacent to B, even
if B is adjacent to A. if B is adjacent to A.
- We may say that device B "is downstream from" device A. In this - We may say that device B "is downstream from" device A. In this
terminology, there is no guarantee that A is downstream from B, terminology, there is no guarantee that A is downstream from B,
even if B is downstream from A. even if B is downstream from A.
- We may say that device B "is a neighbor of" device A. In this - We may say that device B "is a neighbor of" device A. In this
terminology, there is no guarantee that A is a neighbor of B, even terminology, there is no guarantee that A is a neighbor of B, even
if B a neighbor of A. As it happens, terminology based on if B a neighbor of A. Terminology based on "neighborhood" is
"neighborhood" is quite confusing for multi-hop wireless quite confusing for multi-hop wireless communications. For
communications. For example, when B can detect A, but A cannot example, when B can detect A, but A cannot detect B, it is not
detect B, it is not clear whether B should be considered a clear whether or not B should be considered a neighbor of A; A
neighbor of A at all, since A would not necessarily be aware that would not necessarily be aware that B was a neighbor, as it cannot
B was a neighbor, as it cannot detect B. It is thus best to avoid detect B. It is thus best to avoid the "neighbor" terminology,
the "neighbor" terminology, except for when some level of symmetry except when bidirectionality has been established.
has been verified.
This list of alternative terminologies is given here for illustrative This list of alternative terminologies is given here for illustrative
purposes only, and is not suggested to be complete or even purposes only, and is not suggested to be complete or even
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. Note
not discuss bidirectionality, but as a final observation it is that bidirectionality is not synonymous with symmetry. For example,
worthwhile to note that bidirectionality is not synonymous with the error statistics in either direction are often different for a
symmetry. For example, the error statistics in either direction are link that is otherwise considered bidirectional.
often different for a link that is otherwise considered
bidirectional.
5. Security Considerations 5. Security Considerations
Section 18 of RFC 3819 [RFC3819] provides an excellent overview of Section 18 of RFC 3819 [RFC3819] provides an excellent overview of
security considerations at the subnetwork layer. Beyond the material security considerations at the subnetwork layer. Beyond the material
there, multi-hop ad hoc wireless networking (i) is not limited to there, multi-hop ad hoc wireless networking (i) is not limited to
subnetwork layer operation, and (ii) makes use of wireless subnetwork layer operation, and (ii) makes use of wireless
communications. communications.
On one hand, a detailed description of security implications of On one hand, a detailed description of security implications of
wireless communications in general is outside of the scope of this wireless communications in general is outside of the scope of this
document. Notably, however, eavesdropping on a wireless link is much document. It is true that eavesdropping on a wireless link is much
easier than for wired media (although significant progress has been easier than for wired media (although significant progress has been
made in the field of wireless monitoring of wired transmissions). As made in the field of wireless monitoring of wired transmissions). As
a result, traffic analysis attacks can be even more subtle and a result, traffic analysis attacks can be even more subtle and
difficult to defeat in this context. Furthermore, such difficult to defeat in this context. Furthermore, such
communications over a shared media are particularly prone to theft of communications over a shared media are particularly prone to theft of
service and denial of service (DoS) attacks. service and denial of service (DoS) attacks.
On the other hand, the potential multi-hop aspect of the networks we On the other hand, the potential multi-hop aspect of the networks we
consider in this document goes beyond traditional scope of subnetwork consider in this document goes beyond traditional scope of subnetwork
design. In practice, unplanned relaying of network traffic (both design. In practice, unplanned relaying of network traffic (both
user traffic and control traffic) happens routinely. Due to the user traffic and control traffic) happens routinely. Due to the
physical nature of wireless media, Man in the Middle (MITM) attacks physical nature of wireless media, Man in the Middle (MITM) attacks
are facilitated, which may significantly alter network performance. are facilitated, which may significantly alter network performance.
This highlights the need to stick to the "end-to-end principle": L3 This highlights the importance of the "end-to-end principle": L3
security, end-to-end, becomes a primary goal, independently of security, end-to-end, becomes a primary goal, independently of
securing layer-2 and layer-1 protocols (though L2 and L1 security can securing layer-2 and layer-1 protocols (though L2 and L1 security
indeed help to reach this goal). often 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,
skipping to change at page 10, line 26 skipping to change at page 10, line 10
[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>.
[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>.
[RFC5820] Roy, A., Ed. and M. Chandra, Ed., "Extensions to OSPF to
Support Mobile Ad Hoc Networking", RFC 5820,
DOI 10.17487/RFC5820, March 2010,
<http://www.rfc-editor.org/info/rfc5820>.
[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>.
[RFC7137] Retana, A. and S. Ratliff, "Use of the OSPF-MANET
Interface in Single-Hop Broadcast Networks", RFC 7137,
DOI 10.17487/RFC7137, February 2014,
<http://www.rfc-editor.org/info/rfc7137>.
[RFC7181] Clausen, T., Dearlove, C., Jacquet, P., and U. Herberg,
"The Optimized Link State Routing Protocol Version 2",
RFC 7181, DOI 10.17487/RFC7181, April 2014,
<http://www.rfc-editor.org/info/rfc7181>.
[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,
http://www.funkfeuer.at", 2013. http://www.funkfeuer.at", 2013.
[MC03] Corson, S. and J. Macker, "Mobile Ad hoc Networking: [MC03] Corson, S. and J. Macker, "Mobile Ad hoc Networking:
Routing Technology for Dynamic, Wireless Networks", IEEE Routing Technology for Dynamic, Wireless Networks", IEEE
skipping to change at page 12, line 8 skipping to change at page 12, line 8
Axioms of Wireless-Network Research", Dartmouth College Axioms of Wireless-Network Research", Dartmouth College
Computer Science Technical Report TR2003-467, 2003. Computer Science Technical Report TR2003-467, 2003.
[FREIFUNK] [FREIFUNK]
"Freifunk Wireless Community Networks, "Freifunk Wireless Community Networks,
http://www.freifunk.net", 2013. http://www.freifunk.net", 2013.
Appendix A. Acknowledgements Appendix A. Acknowledgements
This document stems from discussions with the following people, in This document stems from discussions with the following people, in
alphabetical order: Jari Arkko, Teco Boot, Carlos Jesus Bernardos alphabetical order: Jari Arkko, Teco Boot, Brian Carpenter, Carlos
Cano, Ian Chakeres, Thomas Clausen, Robert Cragie, Christopher Jesus Bernardos Cano, Zhen Cao, Ian Chakeres, Thomas Clausen, Robert
Dearlove, Ralph Droms, Brian Haberman, Ulrich Herberg, Paul Lambert, Cragie, Christopher Dearlove, Ralph Droms, Brian Haberman, Ulrich
Kenichi Mase, Thomas Narten, Erik Nordmark, Alexandru Petrescu, Stan Herberg, Paul Lambert, Kenichi Mase, Thomas Narten, Erik Nordmark,
Ratliff, Zach Shelby, Shubhranshu Singh, Fred Templin, Dave Thaler, Alexandru Petrescu, Stan Ratliff, Zach Shelby, Shubhranshu Singh,
Mark Townsley, Ronald Velt in't, and Seung Yi. Fred Templin, Dave Thaler, Mark Townsley, Ronald Velt in't, and Seung
Yi.
Authors' Addresses Authors' Addresses
Emmanuel Baccelli Emmanuel Baccelli
INRIA INRIA
EMail: Emmanuel.Baccelli@inria.fr EMail: Emmanuel.Baccelli@inria.fr
URI: http://www.emmanuelbaccelli.org/ URI: http://www.emmanuelbaccelli.org/
Charles E. Perkins Charles E. Perkins
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