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Versions: 00 01 02 draft-irtf-gaia-alternative-network-deployments

Global Access to the Internet for All                    J. Saldana, Ed.
Internet-Draft                                    University of Zaragoza
Intended status: Informational                            A. Arcia-Moret
Expires: July 25, 2015                          Universidad de Los Andes
                                                                B. Braem
                                                                  iMinds
                                                              L. Navarro
                                                U. Politecnica Catalunya
                                                         E. Pietrosemoli
                                                                    ICTP
                                                           C. Rey-Moreno
                                          University of the Western Cape
                                                         A. Sathiaseelan
                                                 University of Cambridge
                                                              M. Zennaro
                                                        Abdus Salam ICTP
                                                        January 21, 2015


    Alternative Network Deployments.  Taxonomy and characterization
               draft-manyfolks-gaia-community-networks-02

Abstract

   This document presents a taxonomy of "Alternative Network
   deployments", and a set of definitions and shared characteristics.
   This term includes a set of network access models emerged in the last
   decade with the aim of bringing Internet connectivity to people,
   using topological, architectural and business models different from
   the so-called "traditional" ones, where a company deploys the network
   infrastructure for connecting the users, who pay for it.

   Several initiatives throughout the world have built large scale
   networks that are alternative to the traditional network operator
   deployments using predominately wireless technologies (including long
   distance) due to the reduced cost of using the unlicensed spectrum.
   Wired technologies such as Fiber are also used in some of these
   alternate networks.  There are several types of such alternate
   network: networks such as community networks are self-organized and
   decentralized networks wholly owned by the community; networks owned
   by individuals who act as wireless internet service providers
   (WISPs), networks owned by individuals but leased out to network
   operators who use such networks as a low-cost medium to reach the
   underserved population and finally there are networks that provide
   connectivity by sharing wireless resources of the users.

   The emergence of these networks can be motivated by different causes
   such as the reluctance, or the impossibility, of network operators to



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   provide wired and cellular infrastructures to rural/remote areas.  In
   these cases, the networks have self sustainable business models that
   provide more localised communication services as well as Internet
   backhaul support through peering agreements with traditional network
   operators.  Some other times, networks are built as a complement and
   an alternative to commercial Internet access provided by
   "traditional" network operators.

   The present classification considers different existing network
   models such as Community Networks, open wireless services, user-
   extensible services, traditional local Internet Service Providers
   (ISPs), new global ISPs, etc.  Different criteria are used in order
   to build a classification as e.g., the ownership of the equipment,
   the way the network is organized, the participatory model, the
   extensibility, if they are driven by a community, a company or a
   local (public or private) stakeholder, etc.

   According to the developed taxonomy, a characterization of each kind
   of network is presented, in terms of specific network characteristics
   related to architecture, organization, etc.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   This Internet-Draft will expire on July 25, 2015.

Copyright Notice

   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect



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   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   5
   2.  Classification  . . . . . . . . . . . . . . . . . . . . . . .   5
     2.1.  Community Networks  . . . . . . . . . . . . . . . . . . .   5
       2.1.1.  Free Networks . . . . . . . . . . . . . . . . . . . .   6
     2.2.  Wireless Internet Service Providers WISPs . . . . . . . .   7
     2.3.  Shared infrastructure model . . . . . . . . . . . . . . .   7
     2.4.  Crowdshared approaches, led by the people and third party
           stakeholders  . . . . . . . . . . . . . . . . . . . . . .   8
     2.5.  Testbeds for research purposes  . . . . . . . . . . . . .   9
   3.  Scenarios where Alternative Networks are deployed . . . . . .   9
     3.1.  Digital Divide and Alternative Networks . . . . . . . . .   9
     3.2.  Urban vs. rural areas . . . . . . . . . . . . . . . . . .  11
   4.  Technologies employed . . . . . . . . . . . . . . . . . . . .  12
     4.1.  Wired . . . . . . . . . . . . . . . . . . . . . . . . . .  12
     4.2.  Wireless  . . . . . . . . . . . . . . . . . . . . . . . .  12
       4.2.1.  Antennas  . . . . . . . . . . . . . . . . . . . . . .  13
       4.2.2.  Link length . . . . . . . . . . . . . . . . . . . . .  14
         4.2.2.1.  Line-of-Sight . . . . . . . . . . . . . . . . . .  14
         4.2.2.2.  Transmitted and Received Power  . . . . . . . . .  15
         4.2.2.3.  Medium Access Protocol  . . . . . . . . . . . . .  16
       4.2.3.  Layer 2 . . . . . . . . . . . . . . . . . . . . . . .  16
         4.2.3.1.  802.11 (Wi-Fi)  . . . . . . . . . . . . . . . . .  16
         4.2.3.2.  GSM . . . . . . . . . . . . . . . . . . . . . . .  18
         4.2.3.3.  Dynamic Spectrum  . . . . . . . . . . . . . . . .  18
   5.  Network and architecture issues . . . . . . . . . . . . . . .  20
     5.1.  Layer 3 . . . . . . . . . . . . . . . . . . . . . . . . .  20
       5.1.1.  IP addressing . . . . . . . . . . . . . . . . . . . .  20
       5.1.2.  Routing protocols . . . . . . . . . . . . . . . . . .  20
         5.1.2.1.  Traditional routing protocols . . . . . . . . . .  21
         5.1.2.2.  Mesh routing protocols  . . . . . . . . . . . . .  21
     5.2.  Upper layers  . . . . . . . . . . . . . . . . . . . . . .  21
       5.2.1.  Services provided by Alternative Networks . . . . . .  22
         5.2.1.1.  Intranet services . . . . . . . . . . . . . . . .  22
         5.2.1.2.  Access to the Internet  . . . . . . . . . . . . .  23
     5.3.  Topology  . . . . . . . . . . . . . . . . . . . . . . . .  23
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  24
   7.  Contributing Authors  . . . . . . . . . . . . . . . . . . . .  24
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  25
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  25
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  25



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     10.1.  Normative References . . . . . . . . . . . . . . . . . .  25
     10.2.  Informative References . . . . . . . . . . . . . . . . .  28
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  32

1.  Introduction

   Several initiatives throughout the world have built large scale
   networks that are alternative to the traditional network operator
   deployments using predominately wireless technologies (including long
   distance) due to the reduced cost of using the unlicensed spectrum.
   Wired technologies such as Fiber are also used in some of these
   alternate networks.  There are several types of such alternate
   network: networks such as community networks are self-organized and
   decentralized networks wholly owned by the community; networks owned
   by individuals who act as wireless internet service providers
   (WISPs), networks owned by individuals but leased out to network
   operators who use such networks as a low cost medium to reach the
   underserved population and finally there are networks that provide
   connectivity by sharing wireless resources of the users.

   The emergence of these networks can be motivated by different causes,
   as the reluctance, or the impossibility, of network operators to
   provide wired and cellular infrastructures to rural/remote areas
   [Pietrosemoli].  In these cases, the networks have self sustainable
   business models that provide more localised communication services as
   well as Internet backhaul support through peering agreements with
   traditional network operators.  Some other times, they are built as a
   complement and an alternative to commercial Internet access provided
   by "traditional" network operators.

   One of the aims of the Global Access to the Internet for All (GAIA)
   IRTF initiative is "to document and share deployment experiences and
   research results to the wider community through scholarly
   publications, white papers, Informational and Experimental RFCs,
   etc."  In line with this objective, this document is intended to
   propose a classification of these "Alternative Network deployments".
   This term includes a set of network access models emerged in the last
   decade with the aim of bringing Internet connectivity to people,
   following topological, architectural and business models different
   from the so-called "traditional" ones, where a company deploys the
   infrastructure connecting the users, who pay for it.  The document is
   intended to be largely descriptive providing a broad overview of
   initiatives, technologies and approaches employed in these networks.
   Research references describing each kind of network are also
   provided.






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1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

2.  Classification

   This section classifies Alternative Networks (ANs) according to their
   intended usage.  Each of them has different incentive structures,
   maybe common technological challenges, but most importantly
   interesting usage challenges which feeds into the incentives as well
   as the technological challenges.

   This classification is agnostic from the technical point of view.
   Technology in this case must be taken as implementation.  Moreover,
   many of these networks are implemented in a way that several
   technologies (Ad-Hoc Wi-Fi, Infrastructure Wi-Fi, Optical Fiber,
   IPv4, IPv6, RFC1918, OLSR, BMX6, etc.) coexist.

2.1.  Community Networks

   Community Networks are large-scale, distributed, self-managed
   networks sharing these characteristics:

   - They are built and organized in a decentralized and open manner.

   - They start and grow organically, they are open to participation
   from everyone, sometimes agreeing to an open peering agreement.
   Community members directly contribute active network infrastructure
   (not just passive infrastructure).

   - Knowledge about building and maintaining the network and ownership
   of the network itself is decentralized and open.  Community members
   have an obvious and direct form of organizational control over the
   overall operation of the network in their community (not just their
   own participation in the network).

   - The network CAN serve as a backhaul for providing a whole range of
   services and applications, from completely free to even commercial
   services.

   Hardware and software used in Community Networks CAN be very diverse,
   even inside one network.  A Community Network CAN have both wired and
   wireless links.  The network CAN be managed by multiple routing
   protocols or network topology management systems.





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   These networks grow organically, since they are formed by the
   aggregation of nodes belonging to different users.  A minimum
   governance infrastructure is required in order to coordinate IP
   addressing, routing, etc.  A clear example of this kind of Community
   Network is described in [Braem].  These networks are effective in
   enhancing and extending digital Internet rights following a
   participatory model.

   The fact of the users adding new infrastructure (i.e. extensibility)
   can be used to formulate another definition: A Community Network is a
   network in which any participant in the system may add link segments
   to the network in such a way that the new network segments can
   support multiple nodes and adopt the same overall characteristics as
   those of the joined network, including the capacity to further extend
   the network.  Once these link segments are joined to the network,
   there is no longer a meaningful distinction between the previous
   extent of the network and the new extent of the network.

   In Community Networks, the profit can only be made by services and
   not by the infrastructure itself, because the infrastructure is
   neutral, free, and open (traditional Internet Service Providers,
   ISPs, base their business on the control of the infrastructure).  In
   Community Networks, everybody keeps the ownership of what he/she has
   contributed.

   Community Networks MAY also be called "Free Networks" or even
   "Network Commons".  [FNF].  The majority of Community Networks
   accomplishes the definition of Free Network, included in the next
   subsection.

2.1.1.  Free Networks

   A definition of Free Network (which MAY be the same as Community
   Network) is proposed by the Free Network Foundation (see
   http://thefnf.org) as:

   "A free network equitably grants the following freedoms to all:

   Freedom 0 - The freedom to communicate for any purpose, without
   discrimination, interference, or interception.

   Freedom 1 - The freedom to grow, improve, communicate across, and
   connect to the whole network.

   Freedom 2- The freedom to study, use, remix, and share any network
   communication mechanisms, in their most reusable forms."





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   The principles of Free, Open and Neutral Networks have also been
   summarized (see http://guifi.net/en/FONCC) this way:

   - You have the freedom to use the network for any purpose as long as
   you do not harm the operation of the network itself, the rights of
   other users, or the principles of neutrality that allow contents and
   services to flow without deliberate interference.

   - You have the right to understand the network, to know its
   components, and to spread knowledge of its mechanisms and principles.

   - You have the right to offer services and content to the network on
   your own terms.

   - You have the right to join the network, and the responsibility to
   extend this set of rights to anyone according to these same terms.

2.2.  Wireless Internet Service Providers WISPs

   WISPs are commercially-operated wireless Internet networks that
   provide Internet and/or Voice Over Internet (VoIP) services.  They
   are most common in areas not covered by incumbent telcos or ISPs.
   WISPs often use wireless point-to-point or point-to-multipoint in the
   unlicensed frequencies but licensed frequency use is common too
   especially in regions where unlicensed spectrum is either perceived
   as crowded or where unlicensed spectrum may have regulatory barriers
   impeding its use.

   Most WISPs are operated by local companies responding to a perceived
   market gap.  There is a small but growing number of WISPs, such as
   AirJaldi [Airjaldi] in India that have expanded from local service
   into multiple locations.

   Since 2006, the deployment of cloud-managed WISPs has been possible
   with companies like Meraki and later OpenMesh and others.  Until
   recently, however, most of these services have been aimed at
   industrialised markets.  Everylayer [Everylayer], launched in 2014,
   is the first cloud-managed WISP service aimed at emerging markets.

2.3.  Shared infrastructure model

   These networks are owned by individuals but leased out to network
   operators who use them as a low cost medium to reach the underserved
   population.







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2.4.  Crowdshared approaches, led by the people and third party
      stakeholders

   These networks can be defined as a set of nodes whose owners share
   common interests (e.g. sharing connectivity; resources; peripherals)
   regardless of their physical location.  The node location exhibits a
   space and time correlation which is the basis to establish a robust
   connectivity model over time.

   These networks conform to the following approach: the home router
   creates two wireless networks: one of them is normally used by the
   owner, and the other one is public.  A small fraction of the
   bandwidth is allocated to the public network, to be employed by any
   user of the service in the immediate area.  Some examples are
   described in [PAWS] and [Sathiaseelan_c].  Other example is
   constituted by the networks created and managed by City Councils
   (e.g., [Heer]).

   In the same way, some companies [Fon] develop and sell Wi-Fi routers
   with a dual access: a Wi-Fi network for the user, and a shared one.
   A user community is created, and people can join the network in
   different ways: they can buy a router, so they share their connection
   and in turn they get access to all the routers associated to the
   community.  Some users can even get some revenue every time another
   user connects to their Wi-Fi spot.  Other users can just buy some
   passes in order to use the network.  Some telecommunications
   operators can collaborate with the community, including in their
   routers the possibility of creating these two networks.

   A Virtual Private Network (VPN) is created for public traffic, so it
   is completely secure and separated from the owner's connection.  The
   network capacity shared may employ a low priority, a less-than-best-
   effort or scavenger approach, so as not to harm the traffic of the
   owner of the connection [Sathiaseelan_a].

   The elements involved in a crowd-shared network are summarised below:

   - Interest: a parameter capable of providing a measure (cost) of the
   attractiveness of a node towards a specific location, in a specific
   instance in time.

   - Resources: A physical or virtual element of a global system.  For
   instance, bandwidth; energy; data; devices.

   - The owner: End users who sign up for the service and share their
   network capacity.  As a counterpart, they can access another owners'
   home access for free.  The owner can be an end user or an entity




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   (e.g.  operator; virtual operator; municipality) that is to be made
   responsible for any actions concerning his/her device.

   - The user: a legal entity or an individual using or requesting a
   publicly available electronic communications' service for private or
   business purposes, without necessarily having subscribed to such
   service.

   - The Virtual Network Operator (VNO): An entity that acts in some
   aspects as a network coordinator.  It may provide services such as
   initial authentication or registering, and eventually, trust
   relationship storage.  A VNO is not an ISP given that it does not
   provide Internet access (e.g. infrastructure; naming).  A VNO is
   neither an Application Service Provider (ASP) since it does not
   provide user services.  Virtual Operators MAY also be stakeholders
   with socio-environmental objectives.  They CAN be a local government,
   grass root user communities, charities, or even content operators,
   smart grid operators, etc.  They are the ones who actually run the
   service.

   - Network operators, who have a financial incentive to lease out the
   unused capacity [Sathiaseelan_b] at lower cost to the VNOs.

   VNOs pay the sharers and the network operators, thus creating an
   incentive structure for all the actors: the end users get money for
   sharing their network, the network operators are paid by the VNOs,
   who in turn accomplish their socio-environmental role.

2.5.  Testbeds for research purposes

   In some cases, the initiative to start the network is not from the
   community, but from a research entity (e.g. a university), with the
   aim of using it for research purposes [Samanta], [Bernardi].

3.  Scenarios where Alternative Networks are deployed

   Alternative Network deployments are present in every part of the
   world.  Even in some high-income countries, these networks have been
   built as an alternative to commercial ones managed by traditional
   network operators.  This section discusses the scenarios where
   Alternative Networks have been deployed.

3.1.  Digital Divide and Alternative Networks

   There is no definition for what a developing country represents that
   has been recognized internationally, but the term is generally used
   to describe a nation with a low level of material well-being.  In
   this sense, one of the most commonly used classification is the one



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   by the World Bank, who ranks countries according to their Gross
   National Income (GNI) per Capita: low income, middle income, and high
   income, being those falling within the low and middle income groups
   considered developing economies.  Developing countries have also been
   defined as those which are in transition from traditional lifestyles
   towards the modern lifestyle which began in the Industrial
   Revolution.  Additionally, the Human Development Index, which
   considers not only the GNI but also life expectancy and education,
   has been proposed by the United Nations to rank countries according
   to their well-being and not solely based on economic terms.  These
   classifications are used to give strong signals to the international
   community about the need of special concessions in support of these
   countries, implying a correlation between development and increased
   well-being.

   However, at the beginning of the 90's the debates about how to
   quantify development in a country were shaken by the appearance of
   Internet and mobile phones, which many authors consider the beginning
   of the Information Society.  With the beginning of this Digital
   Revolution, defining development based on Industrial Society concepts
   started to be challenged, and links between digital development and
   its impact on human development started to flourish.  The following
   dimensions are considered to be meaningful when measuring the digital
   development state of a country: infrastructures (availability and
   affordability); ICT (Information and Communications Technology)
   sector (human capital and technological industry); digital literacy;
   legal and regulatory framework; and content and services.  The lack
   or less extent of digital development in one or more of these
   dimensions is what has been referred as Digital Divide.  This divide
   is a new vector of inequality which - as it happened during the
   Industrial Revolution - generates a lot of progress at the expense of
   creating a lot economic poverty and exclusion.  The Digital Divide is
   considered to be a consequence of other socio-economic divides,
   while, at the same time, a reason for their rise.

   In this context, the so-called "developing countries", in order not
   to be left behind of this incipient digital revolution, motivated the
   World Summit of the Information Society which aimed at achieving "a
   people-centred, inclusive and development-oriented Information
   Society, where everyone can create, access, utilize and share
   information and knowledge, enabling individuals, communities and
   peoples to achieve their full potential in promoting their
   sustainable development and improving their quality of life" [WSIS],
   and called upon "governments, private sector, civil society and
   international organisations" to actively engage to accomplish it
   [WSIS].





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   Most efforts from governments and international organizations focused
   initially on improving and extending the existing infrastructure in
   order not to leave their population behind.  As an example, one of
   the goals of the Digital Agenda for Europe [DAE] is "to increase
   regular internet usage from 60% to 75% by 2015, and from 41% to 60%
   among disadvantaged people."

   Universal Access and Service plans have taken different forms in
   different countries over the years, with very uneven success rates,
   but in most cases inadequate to the scale of the problem.  Given its
   incapacity to solve the problem, some governments included Universal
   Service and Access obligations to mobile network operators when
   liberalizing the telecommunications market.  In combination with the
   overwhelming and unexpected uptake of mobile phones by poor people,
   this has mitigated the low access indicators existing in many
   developing countries at the beginning of the 90s [Rendon].

   Although the contribution made by mobile network operators in
   decreasing the access gap is undeniable, their model presents some
   constraints that limit the development outcomes that increased
   connectivity promises to bring.  Prices, tailored for the more
   affluent part of the population, remain unaffordable to many, who
   invest large percentages of their disposable income in
   communications.  Additionally, the cost of prepaid packages, the only
   option available for the informal economies existing throughout
   developing countries, is high compared with the rate longer-term
   subscribers pay.

   The consolidation of many Alternative Networks (e.g.  Community
   Networks) in high income countries sets a precedent for civil society
   members from the so-called developing countries to become more active
   in the search for alternatives to provide themselves with affordable
   access.  Furthermore, Alternative Networks could contribute to other
   dimensions of the digital development like increased human capital
   and the creation of contents and services targeting the locality of
   each network.

3.2.  Urban vs. rural areas

   The Digital Divide presented in the previous section is not only
   present between countries, but within them too.  This is specially
   the case for rural inhabitants, which represents approximately 55% of
   the world's population, from which 78% inhabit in developing
   countries.  Although it is impossible to generalize among them, there
   exist some common features that have determined the availability of
   ICT infrastructure in these regions.  The disposable income of their
   dwellers is lower than those inhabiting urban areas, with many
   surviving on a subsistence economy.  Many of them are located in



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   geographies difficult to access and exposed to extreme weather
   conditions.  This has resulted in the almost complete lack of
   electrical infrastructure.  This context, together with their low
   population density, discourages telecommunications operators to
   provide similar services to those provided to urban dwellers, since
   they do not deem them profitable.

   The cost of the wireless infrastructure required to set up a network,
   including powering it via solar energy, is within the range of
   availability if not of individuals at least of entire communities.
   The social capital existing in these areas can allow for Alternative
   Network set-ups where a reduced number of nodes may cover communities
   whose dwellers share the cost of the infrastructure and the gateway
   and access it via inexpensive wireless devices.  Some examples are
   presented in [Pietrosemoli] and [Bernardi].

   In this case, the lack of awareness and confidence of rural
   communities to embark themselves in such tasks can become major
   barriers to their deployment.  Scarce technical skills in these
   regions have been also pointed as a challenge for their success, but
   the proliferation of urban Community Networks, where scarcity of
   spectrum, scale, and heterogeneity of devices pose tremendous
   challenges to their stability and the services they aim to provide,
   has fuelled the creation of robust low-cost low-consumption low-
   complexity off-the-shelf wireless devices which make much easier the
   deployment and maintenance of these alternative infrastructures in
   rural areas.

4.  Technologies employed

4.1.  Wired

   In many (developed or developing) countries it may happen that
   national service providers may decline to provide connectivity to
   tiny and isolated villages.  So in some cases the villagers have
   created their own optical fiber networks.  It is the case of
   Lowenstedt in Germany [Lowenstedt].

4.2.  Wireless

   Different wireless technologies [WNDW] can be employed in Alternative
   Network deployments.  Below we summarise topics to be considered in
   such deployments:








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4.2.1.  Antennas

   Three kinds of antennas are suitable to be used in these networks:
   omnidirectional, directional and high gain antennas.

   For local access, omnidirectional antennas are the most useful, since
   they provide the same coverage in all directions of the plane in
   which they are located.  Above and below this plane, the received
   signal will diminish, so the maximum benefits are obtained when the
   client is at approximately the same height as the Access Point.

   When using an omnidirectional antenna outdoors to provide
   connectivity to a large area, people often select high gain antennas
   located at the highest structure available to extend the coverage.
   In many cases this is counterproductive, since a high gain
   omnidirectional antenna will have a very narrow beamwidth in the
   vertical plane, meaning that clients that are below the plane of the
   antenna will receive a very weak signal (and by the reciprocity
   property of all antennas, the antenna will also receive a feeble
   signal from the client).  A moderate gain omnidirectional of about 8
   to 10 dBi is normally preferable.  Higher gain omnidirectional
   antennas are only advisable when the farthest way client is roughly
   in the same plane.

   For indoor clients, omnidirectional antennas are generally fine,
   because the numerous reflections normally found in indoor
   environments negate the advantage of using directional antennas.

   For outdoor clients, directional antennas can be quite useful to
   extend coverage to an Access Point fitted with an omnidirectional
   one.

   When building point-to-point links, the highest gain antennas are the
   best choice, since their narrow beamwidth mitigates interference from
   other users and can provide the longest links [Flickenger],
   [Zennaro].

   24 to 34 dBi antennas are commercially available at both the
   unlicensed 2.4 GHz and 5 GHz bands, and even higher gain antennas can
   be found in the newer unlicensed bands at 17 GHz and 24 GHz.

   Despite the fact that the free space loss is directly proportional to
   the square of the frequency, it is normally advisable to use higher
   frequencies for point-to-point links when there is a clear line of
   sight, because it is normally easier to get higher gain antennas at 5
   GHz.  Deploying high gain antennas at both ends will more than
   compensate for the additional free space loss.  Furthermore, higher
   frequencies can make do with lower altitude antenna placement since



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   the Fresnel ellipsoid (the volume around the optical line occuppied
   by radio waves, which should be free from obstacles), is inversely
   proportional to the square root of the frequency.

   On the contrary, lower frequencies offer advantages when the line of
   sight is blocked because they can leverage diffraction to reach the
   intended receiver.

   It is common to find dual radio Access Points, at two different
   frequency bands.  One way of benefiting from this arrangement is to
   attach a directional antenna to the high frequency radio for
   connection to the backbone and an omnidirectional one to the lower
   frequency to provide local access.

   In the case of mesh networking, where the antenna should connect to
   several other nodes, it is better to use omnidirectional antennas.

   The same type of polarisation must be used at both ends of any radio
   link.  For point-to-point links, some vendors use two radios
   operating at the same frequency but with orthogonal polarisations,
   thus doubling the achievable throughput, and also offering added
   protection to multipath and other transmission impairments.

4.2.2.  Link length

4.2.2.1.  Line-of-Sight

   For short distance transmission, there is no strict requirement of
   line of sight between the transmitter and the receiver, and multipath
   can guarantee communication despite the existence of obstacles in the
   direct path.

   For longer distances, the first requirement is the existence of an
   unobstructed line of sight between the transmitter and the receiver.
   For very long path the earth curvature is an obstacle that must be
   cleared, but the trajectory of the radio beam is not strictly a
   straight line due to the bending of the rays as a consequence of non-
   uniformities of the atmosphere.  Most of the time this bending will
   mean that the radio horizon extends further than the optical horizon.

   Another factor to be considered is that the Fresnel zone (the volume
   around the optical line) must be unencumbered from obstacles for the
   maximum signal to be captured at the receiver.  The size of the
   Fresnel ellipsoid grows with the distance between the end points and
   with the wavelength of the signal, which in turn is inversely
   proportional to the frequency.





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   For optimum signal reception the end points must be high enough to
   clear any obstacle in the path and leave extra "elbow room" for the
   Fresnel zone.  This can be achieved by using suitable masts at either
   end, or by taking advantage of existing structures or hills.

4.2.2.2.  Transmitted and Received Power

   Once a clear radio-electric line of sight (including the Fresnel zone
   clearance) is obtained, one must ascertain that the received power is
   well above the sensitivity of the receiver, by what is known as the
   "link margin".  The greater the link margin, the more reliable the
   link.  For mission critical applications 20 dB margin is suggested,
   but for non critical ones 10 dB might suffice.

   The sensitivity of the receiver decreases with the transmission
   speed, so more power is needed at greater transmission speeds.

   The received power is determined by the transmitted power, the gain
   of the transmitting and receiving antennas and the propagation loss.

   The propagation loss is the sum of the free space loss (proportional
   to the square of the the frequency and the square of the distance),
   plus additional factors like attenuation in the atmosphere by gases
   or meteorological effects (which are strongly frequency dependent),
   multipath and diffraction losses.

   Multipath is more pronounced in trajectories over water.  If they
   cannot be avoided special countermeasures should be taken.

   In order to achieve a given link margin (also called "fade margin"),
   one can:

   a) Increase the output power.The maximum transmitted power is
   specified by each country's regulation, and for unlicensed
   frequencies is much lower than for licensed frequencies.

   b) Increase the antenna gain.  There is no limit in the gain of the
   receiving antenna, but high gain antennas are bulkier, present more
   wind resistance and require sturdy mounts to comply with tighter
   alignment requirements.  The transmitter antenna gain is also
   regulated and can be different for point-to-point as for point-to-
   multipoint links.  Many countries impose a limit in the combination
   of transmitted power and antenna gain, EIRP (Equivalent Isotropically
   Irradiated Power) which can be different for point-to- point or
   point-to-multipoint links.

   c) Reduce the propagation loss, by using a more favorable frequency
   or a shorter path.



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   d) Use a more sensitive receiver.  Receiver sensitivity can be
   improved by using better circuits, but it is ultimately limited by
   the thermal noise, which is proportional to temperature and
   bandwidth.  One can increase the sensitivity by using a smaller
   receiving bandwidth, or by settling to lower throughput even in the
   same receiver bandwidth.  This step is often done automatically in
   many protocols, in which the transmission speed can be reduced from
   150 Mbit/s to 6 Mbit/s if the receiver power is not enough to sustain
   the maximum throughput.

4.2.2.3.  Medium Access Protocol

   A completely different limiting factor is related to the medium
   access protocol.  Wi-Fi was designed for short distance, and the
   transmitter expects the reception of an acknowledgment for each
   transmitted packet in a certain amount of time; if the waiting time
   is exceeded, the packet is retransmitted.  This will significantly
   reduce the throughput at long distance, so for long distance
   applications it is better to use a different medium access technique,
   in which the receiver does not wait for an acknowledgement of the
   transited packet.  This strategy of TDMA (Time Domain Multiple
   Access) has been adopted by many equipment vendors who offer
   proprietary protocols alongside the standard Wi-Fi in order to
   increase the throughput at longer distances.  Low cost equipment
   using TDMA can offer high throughput at distances over 100
   kilometers.

4.2.3.  Layer 2

4.2.3.1.  802.11 (Wi-Fi)

   Wireless standards ensure interoperability and usability to those who
   design, deploy and manage wireless networks.  The standards used in
   the vast majority of Community Networks come from the IEEE Standard
   Association's IEEE 802 Working Group.

   The standard we are most interested in is 802.11 a/b/g/n,
   [IEEE.802-11A.1999], [IEEE.802-11B.1999], [IEEE.802-11G.2003],
   [IEEE.802-11N.2009] as it defines the protocol for Wireless LAN.
   Different 802.11 amendments have been released, as shown in the table
   below, also including their frequencies and approximate ranges.










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   |802.11| Release | Freq |BWdth | Data Rate per  |  Approx range (m) |
   |prot  |  date   | (GHz)|(MHz) |stream (Mbit/s) | indoor |  outdoor |
   +------+---------+------+------+----------------+--------+----------+
   |  a   |Sep 1999 | 5    |  20  | 6,9,12, 18, 24,|    35  |    120   |
   |      |         |      |      | 36, 48, 54     |        |          |
   |  b   |Sep 1999 | 2.4  |  20  | 1, 2, 5.5, 11  |    35  |    140   |
   |  g   |Jun 2003 | 2.4  |  20  | 6,9,12, 18, 24,|    38  |    140   |
   |      |         |      |      | 36, 48, 54     |        |          |
   |  n   |Oct 2009 | 2.4/5|  20  | 7.2, 14.4, 21.7|    70  |    250   |
   |      |         |      |      | 28.9, 43.3,    |        |          |
   |      |         |      |      | 57.8, 65, 72.2 |        |          |
   |  n   |Oct 2009 | 2.4/5|  40  | 15, 30, 45, 60,|    70  |    250   |
   |      |         |      |      | 90, 120,       |        |          |
   |      |         |      |      | 135, 150       |        |          |
   |  ac  |Nov 2011 | 5    |  20  | Up to 87.6     |        |          |
   |  ac  |Nov 2011 | 5    |  40  | Up to 200      |        |          |
   |  ac  |Nov 2011 | 5    |  80  | Up to 433.3    |        |          |
   |  ac  |Nov 2011 | 5    |  160 | Up to 866.7    |        |          |

   In 2012 IEEE issued the 802.11-2012 Standard that consolidates all
   the previous amendments.  The document is freely downloadable from
   IEEE Standards [IEEE].

4.2.3.1.1.  Deployment planning for 802.11 wireless networks

   Before packets can be forwarded and routed to the Internet, layers
   one (the physical) and two (the data link) need to be connected.
   Without link local connectivity, network nodes cannot talk to each
   other and route packets.

   To provide physical connectivity, wireless network devices MUST
   operate in the same part of the radio spectrum.  This means that
   802.11a radios will talk to 802.11a radios at around 5 GHz, and
   802.11b/g radios will talk to other 802.11b/g radios at around 2.4
   GHz.  But an 802.11a device cannot interoperate with an 802.11b/g
   device, since they use completely different parts of the
   electromagnetic spectrum.  More specifically, wireless interfaces
   must agree on a common channel.  If one 802.11b radio card is set to
   channel 2 while another is set to channel 11, then the radios cannot
   communicate with each other.

   When two wireless interfaces are configured to use the same protocol
   on the same radio channel, then they are ready to negotiate data link
   layer connectivity.  Each 802.11a/b/g device can operate in one of
   four possible modes:

   1.  Master mode (also called AP or infrastructure mode) is used to
   create a service that looks like a traditional Access Point.  The



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   wireless interface creates a network with a specified name (called
   the SSID, Service Set IDentifier) and channel, and offers network
   services on it.  While in master mode, wireless interfaces manage all
   communications related to the network (authenticating wireless
   clients, handling channel contention, repeating packets, etc.)
   Wireless interfaces in master mode can only communicate with
   interfaces that are associated with them in managed mode.

   2.  Managed mode is sometimes also referred to as client mode.
   Wireless interfaces in managed mode will join a network created by a
   master, and will automatically change their channel to match it.
   They then present any necessary credentials to the master, and if
   those credentials are accepted, they are associated with the master.
   Managed mode interfaces do not communicate with each other directly,
   and only communicate with an associated master.

   3.  Ad-hoc mode creates a multipoint-to-multipoint network where
   there is no single master node or AP.  In ad-hoc mode, each wireless
   interface communicates directly with its neighbours.  Nodes must be
   in range of each other to communicate, and must agree on a network
   name and channel.  Ad-hoc mode is often also called Mesh Networking.

   4.  Monitor mode is used by some tools (such as Kismet) to passively
   listen to all radio traffic on a given channel.  When in monitor
   mode, wireless interfaces transmit no data.  This is useful for
   analysing problems on a wireless link or observing spectrum usage in
   the local area.  Monitor mode is not used for normal communications.

   When implementing a point-to-point or point-to-multipoint link, one
   radio will typically operate in master mode, while the other(s)
   operate in managed mode.  In a multipoint-to-multipoint mesh, the
   radios all operate in ad-hoc mode so that they can communicate with
   each other directly.  Managed mode clients cannot communicate with
   each other directly, so a high repeater site is required in master or
   ad-hoc mode.  Ad-hoc is more flexible but has a number of performance
   issues as compared to using the master / managed modes.

4.2.3.2.  GSM

   GSM has also been used in Alternative Networks as Layer 2 option, as
   explained in [Mexican].

4.2.3.3.  Dynamic Spectrum

   Some Alternative Networks make use of TV White Spaces - a set of UHF
   and VHF television frequencies that can be utilized by secondary
   users in locations where it is unused by licensed primary users such
   as television broadcasters.  Equipment that makes use of TV White



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   Spaces is required to detect the presence of existing unused TV
   channels by means of a spectrum database and/or spectrum sensing in
   order to ensure that no harmful interference is caused to primary
   users.  In order to smartly allocate interference-free channels to
   the devices, cognitive radios are used which are able to modify their
   frequency, power and modulation techniques to meet the strict
   operating conditions required for secondary users.

   The use of the term "White Spaces" is often used to describe "TV
   White Spaces" as the VHF and UHF television frequencies were the
   first to be exploited on a secondary use basis.  There are two
   dominant standards for TV white space communication: (i) the 802.11af
   standard [IEEE.802-11AF.2013] - an adaptation of the 802.11 standard
   for TV white space bands and (ii) the IEEE 802.22 standard
   [IEEE.802-22.2011] for long-range rural communication.

4.2.3.3.1.  802.11af

   802.11af [IEEE.802-11AF.2013] is a modified version of the 802.11
   standard operating in TV White Space bands using Cognitive Radios to
   avoid interference with primary users.  The standard is often
   referred to as White-Fi or Super WiFi and was approved in February
   2014. 802.11af contains much of the advances of all the 802.11
   standards including recent advances in 802.11ac such as up to four
   bonded channels, four spatial streams and very high rate 256-QAM
   modulation but with improved in-building penetration and outdoor
   coverage.  The maximum data rate achievable is 426.7 Mbps for
   countries with 6/7 MHz channels and 568.9 Mbps for countries with 8
   MHz channels.  Coverage is typically limited to 1km although longer
   range at lower throughput and using high gain antennas will be
   possible.

   Devices are designated as enabling stations (access points) or
   dependent stations (clients).  Enabling stations are authorized to
   control the operation of a dependent station and securely access a
   geolocation database.  Once the enabling station has received a list
   of available white space channels it can announce a chosen channel to
   the dependent stations for them to communicate with the enabling
   station. 802.11af also makes use of a registered location server - a
   local database that organizes the geographic location and operating
   parameters of all enabling stations.

4.2.3.3.2.  802.22

   802.22 [IEEE.802-22.2011] is a standard developed specifically for
   long range rural communications in TV white space frequencies and
   first approved in July 2011.  The standard is similar to the 802.16
   (WiMax) [IEEE.802-16.2008] standard with an added cognitive radio



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   ability.  The maximum throughput of 802.22 is 22.6 Mbps for a single
   8 MHz channel using 64-QAM modulation.  The achievable range using
   the default MAC scheme is 30 km, however 100 km is possible with
   special scheduling techniques.  The MAC of 802.22 is specifically
   customized for long distances - for example, slots in a frame
   destined for more distant CPEs are sent before slots destined for
   nearby CPEs.

   Base stations are required to have a GPS and a connection to the
   Internet in order to query a geolocation spectrum database.  Once the
   base station receives the allowed TV channels, it communicates a
   preferred operating white space TV channel with the Client Premises
   Equipment (CPE) devices.  The standard also has a co-existence
   mechanism that uses beacons to make other 802.22 base stations aware
   of the presence of a base station that is not part of the same
   network.

5.  Network and architecture issues

5.1.  Layer 3

5.1.1.  IP addressing

   Most known Alternative Networks started in or around the year 2000.
   IPv6 was fully specified by then, but almost all Alternative Networks
   still use IPv4.  A survey [Avonts] indicated that IPv6 rollout
   presents a challenge to Community Networks.

   Most Community Networks use private IPv4 address ranges, as defined
   by RFC 1918 [RFC1918].  The motivation for this was the lower cost
   and the simplified IP allocation because of the large available
   address ranges.

5.1.2.  Routing protocols

   Alternative Networks are composed of possibly different layer 2
   devices, resulting in a mesh of nodes.  Connection between different
   nodes is not guaranteed and the link stability can vary strongly over
   time.  To tackle this, some Alternative Networks use mesh network
   routing protocols while other networks use more traditional routing
   protocols.  Some networks operate multiple routing protocols in
   parallel.  For example, they use a mesh protocol inside different
   islands and use traditional routing protocols to connect islands.








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5.1.2.1.  Traditional routing protocols

   The BGP protocol, as defined by RFC 4271 [RFC4271] is used by a
   number of Community Networks, because of its well-studied behavior
   and scalability.

   For similar reasons, smaller networks opt to run the OSPF protocol,
   as defined by RFC 2328 [RFC2328].

5.1.2.2.  Mesh routing protocols

   A large number of Alternative Networks use the OLSR routing protocol
   as defined in RFC 3626 [RFC3626].  The pro-active link state routing
   protocol is a good match with Alternative Networks because it has
   good performance in mesh networks where nodes have multiple
   interfaces.

   The Better Approach To Mobile Adhoc Networking (BATMAN) [Abolhasan]
   protocol was developed by members of the Freifunk community.  The
   protocol handles all routing at layer 2, creating one bridged
   network.

   Parallel to BGP, some networks also run the BMX6 protocol [Neumann].
   This is an advanced version of the BATMAN protocol which is based on
   IPv6 and tries to exploit the social structure of Alternative
   Networks.

5.2.  Upper layers

   From crowdshared perspective, and considering just regular TCP
   connections during the critical sharing time, the Access Point
   offering the service is likely to be the bottleneck of the
   connection.  This is the main concern of sharers, having several
   implications.  There should be an adequate Active Queue Management
   (AQM) mechanism that implements a Less than Best Effort (LBE) policy
   for the user and protects the sharer.  Achieving LBE behaviour
   requires the appropriate tuning of the well known mechanisms such as
   ECN, or RED, or others more recent AQM mechanisms such as CoDel and
   PIE that aid on keeping low latency RFC 6297 [RFC6297].

   The user traffic should not interfere with the sharer's traffic.
   However, other bottlenecks besides client's access bottleneck may not
   be controlled by the previously mentioned protocols.  Therefore,
   recently proposed transport protocols like LEDBAT [Ros], [Komnios]
   with the purpose of transporting scavenger traffic may be a solution.
   LEDBAT requires the cooperation of both the client and the server to
   achieve certain target delay, therefore controlling the impact of the
   user along all the path.



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   There are applications that manage aspects of the network from the
   sharer side and from the client side.  From sharer's side, there are
   applications to centralise the management of the APs conforming the
   network that have been recently proposed by means of SDN
   [Sathiaseelan_a], [Suresh].  There are also other proposals such as
   Wi2Me [Lampropulos] that manage the connection to several Community
   Networks from the client's side.  These applications have shown to
   improve the client performance compared to a single-Community Network
   client.

   On the other hand, transport protocols inside a multiple hop wireless
   mesh network are likely to suffer performance degradation for
   multiple reasons, e.g., hidden terminal problem, unnecessary delays
   on the TCP ACK clocking that decrease the throughout or route
   changing [Hanbali].  There are some options for network
   configuration.  The implementation of an easy-to-adopt solution for
   TCP over mesh networks may be implemented from two different
   perspectives.  One way is to use a TCP-proxy to transparently deal
   with the different impairments (RFC 3135 [RFC3135]).  Another way is
   to adopt end-to-end solutions for monitoring the connection delay so
   that the receiver adapts the TCP reception window (rwnd)
   [Castignani_c].  Similarly, the ACK Congestion Control (ACKCC)
   mechanism RFC 5690 [RFC5690] could deal with TCP-ACK clocking
   impairments due to inappropriate delay on ACK packets.  ACKCC
   compensates in an end-to-end fashion the throughput degradation due
   to the effect of media contention as well as the unfairness
   experienced by multiple uplink TCP flows in a congested Wi-Fi access.

5.2.1.  Services provided by Alternative Networks

   This section provides an overview of the services between hosts
   inside the network.  They can be divided into Intranet services,
   connecting hosts between them, and Internet services, connecting to
   nodes outside the network.

5.2.1.1.  Intranet services

   Intranet services can include, but are not limited to:

   - VoIP (e.g. with SIP)

   - Remote desktop (e.g. using my home computer and my Internet
   connection when I am on holidays in a village).

   - FTP file sharing (e.g. distribution of Linux software).

   - P2P file sharing.




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   - Public video cameras.

   - DNS.

   - Online games servers.

   - Jabber instant messaging.

   - IRC chat.

   - Weather stations.

   - NTP.

   - Network monitoring.

   - Videoconferencing / streaming.

   - Radio streaming.

5.2.1.2.  Access to the Internet

5.2.1.2.1.  Web browsing proxies

   A number of federated proxies MAY provide web browsing service for
   the users.  Other services (file sharing, skype, etc.) are not
   usually allowed in many Alternative Networks due to bandwidth
   limitations.

5.2.1.2.2.  Use of VPNs

   Some "micro-ISPs" may use the network as a backhaul for providing
   Internet access, setting up VPNs from the client to a machine with
   Internet access.

5.3.  Topology

   Alternative Networks follow different topology patterns, as studied
   in [Vega].

   Regularly rural areas in these networks are connected through long-
   distance links (the so-called community mesh approach) which in turn
   convey the Internet connection to relevant organisations or
   institutions.  In contrast, in urban areas, users tend to share and
   require mobile access.  Since these areas are also likely to be
   covered by commercial ISPs, the provision of wireless access by
   Virtual Operators like [Fon] may constitute a way to extend the user




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   capacity (or gain connection) to the network.  Other proposals like
   Virtual Public Networks [Sathiaseelan_a] can also extend the service.

   As in the case of main Internet Service Providers in France,
   Community Networks for urban areas are conceived as a set of APs
   sharing a common SSID among the clients favouring the nomadic access.
   For users in France, ISPs promise to cause a little impact on their
   service agreement when the shared network service is activated on
   clients' APs.  Nowadays, millions of APs are deployed around the
   country performing services of nomadism and 3G offloading, however as
   some studies demonstrate, at walking speed, there is a fair chance of
   performing file transfers [Castignani_a], [Castignani_b].  Scenarios
   studied in France and Luxembourg show that the density of APs in
   urban areas (mainly in downtown and residential areas) is quite big
   and from different ISPs.  Moreover, performed studies reveal that
   aggregating available networks can be beneficial to the client by
   using an application that manages the best connection among the
   different networks.  For improving the scanning process (or topology
   recognition), which consumes the 90% of the connection/reconnection
   process to the Community Network, the client may implement several
   techniques for selecting the best AP [Castignani_c].

6.  Acknowledgements

   This work has been partially funded by the CONFINE European
   Commission Project (FP7 - 288535).

   The editor and the authors of this document wish to thank the
   following individuals who have participated in the drafting, review,
   and discussion of this memo:

   Paul M.  Aoki, Roger Baig, Jaume Barcelo, Steven G.  Huter, Rohan
   Mahy, Rute Sofia, Dirk Trossen.

   A special thanks to the GAIA Working Group chairs Matt Ford and
   Arjuna Sathiaseelan for their support and guidance.

7.  Contributing Authors













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   Ioannis Komnios
   Democritus University of Thrace
   Department of Electrical and Computer Engineering
   Kimmeria University Campus
   Xanthi 67100
   Greece

   Phone: +306945406585
   Email: ikomnios@ee.duth.gr


   Steve Song
   Village Telco Limited


   Halifax
   Canada

   Phone:
   Email: stevesong@nsrc.org


   David Lloyd Johnson
   Meraka, CSIR
   15 Lower Hope St
   Rosebank 7700
   South Africa

   Phone: +27 (0)21 658 2740
   Email: djohnson@csir.co.za

8.  IANA Considerations

   This memo includes no request to IANA.

9.  Security Considerations

   No security issues have been identified for this document.

10.  References

10.1.  Normative References









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   [IEEE.802-11A.1999]
              "Information technology - Telecommunications and
              information exchange between systems - Local and
              metropolitan area networks - Specific requirements - Part
              11: Wireless LAN Medium Access Control (MAC) and Physical
              Layer (PHY) specifications - High-speed Physical Layer in
              the 5 GHZ Band", IEEE Standard 802.11a, Sept 1999,
              <http://standards.ieee.org/getieee802/
              download/802.11a-1999.pdf>.

   [IEEE.802-11AF.2013]
              "Information technology - Telecommunications and
              information exchange between systems - Local and
              metropolitan area networks - Specific requirements - Part
              11: Wireless LAN Medium Access Control (MAC) and Physical
              Layer (PHY) specifications - Amendment 5: Television White
              Spaces (TVWS) Operation", IEEE Standard 802.11af, Oct
              2009, <http://standards.ieee.org/getieee802/
              download/802.11af-2013.pdf>.

   [IEEE.802-11B.1999]
              "Information technology - Telecommunications and
              information exchange between systems - Local and
              metropolitan area networks - Specific requirements - Part
              11: Wireless LAN Medium Access Control (MAC) and Physical
              Layer (PHY) specifications - Higher-Speed Physical Layer
              Extension in the 2.4 GHz Band", IEEE Standard 802.11b,
              Sept 1999, <http://standards.ieee.org/getieee802/
              download/802.11b-1999.pdf>.

   [IEEE.802-11G.2003]
              "Information technology - Telecommunications and
              information exchange between systems - Local and
              metropolitan area networks - Specific requirements - Part
              11: Wireless LAN Medium Access Control (MAC) and Physical
              Layer (PHY) specifications - Amendment 4: Further Higher
              Data Rate Extension in the 2.4 GHz Band", IEEE Standard
              802.11g, Jun 2003, <http://standards.ieee.org/getieee802/
              download/802.11g-2003.pdf>.












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   [IEEE.802-11N.2009]
              "Information technology - Telecommunications and
              information exchange between systems - Local and
              metropolitan area networks - Specific requirements - Part
              11: Wireless LAN Medium Access Control (MAC) and Physical
              Layer (PHY) specifications - Amendment 5: Enhancements for
              Higher Throughput", IEEE Standard 802.11n, Oct 2009,
              <http://standards.ieee.org/getieee802/
              download/802.11n-2009.pdf>.

   [IEEE.802-16.2008]
              "Information technology - Telecommunications and
              information exchange between systems - Broadband wireless
              metropolitan area networks (MANs) - IEEE Standard for Air
              Interface for Broadband Wireless Access Systems", IEEE
              Standard 802.16, Jun 2008,
              <http://standards.ieee.org/getieee802/
              download/802.16-2012.pdf>.

   [IEEE.802-22.2011]
              "Information technology - Telecommunications and
              information exchange between systems - Local and
              metropolitan area networks - Specific requirements - Part
              22: Cognitive Wireless RAN Medium Access Control (MAC) and
              Physical Layer (PHY) specifications: Policies and
              procedures for operation in the TV Bands", IEEE Standard
              802.22, Jul 2011, <http://standards.ieee.org/getieee802/
              download/802.11af-2013.pdf>.

   [RFC1918]  Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and
              E. Lear, "Address Allocation for Private Internets", BCP
              5, RFC 1918, February 1996.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2328]  Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.

   [RFC3135]  Border, J., Kojo, M., Griner, J., Montenegro, G., and Z.
              Shelby, "Performance Enhancing Proxies Intended to
              Mitigate Link-Related Degradations", RFC 3135, June 2001.

   [RFC3626]  Clausen, T. and P. Jacquet, "Optimized Link State Routing
              Protocol (OLSR)", RFC 3626, October 2003.

   [RFC4271]  Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
              Protocol 4 (BGP-4)", RFC 4271, January 2006.




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   [RFC5690]  Floyd, S., Arcia, A., Ros, D., and J. Iyengar, "Adding
              Acknowledgement Congestion Control to TCP", RFC 5690,
              February 2010.

   [RFC6297]  Welzl, M. and D. Ros, "A Survey of Lower-than-Best-Effort
              Transport Protocols", RFC 6297, June 2011.

10.2.  Informative References

   [Abolhasan]
              Abolhasan, M., Hagelstein, B., and J. Wang, "Real-world
              performance of current proactive multi-hop mesh
              protocols", In Communications, 2009. APCC 2009. 15th Asia-
              Pacific Conference on (pp. 44-47). IEEE. , 2009.

   [Airjaldi]
              Rural Broadband (RBB) Pvt. Ltd., Airjaldi., "Airjaldi
              service", Airjaldi web page, www.airjaldi.net , 2015.

   [Avonts]   Avonts, J., Braem, B., and C. Blondia, "A Questionnaire
              based Examination of Community Networks", Proceedings
              Wireless and Mobile Computing, Networking and
              Communications (WiMob), 2013 IEEE 8th International
              Conference on (pp. 8-15) , 2013.

   [Bernardi]
              Bernardi, B., Buneman, P., and M. Marina, "Tegola tiered
              mesh network testbed in rural Scotland", Proceedings of
              the 2008 ACM workshop on Wireless networks and systems for
              developing regions (WiNS-DR '08). ACM, New York, NY, USA,
              9-16 , 2008.

   [Braem]    Braem, B., Baig Vinas, R., Kaplan, A., Neumann, A., Vilata
              i Balaguer, I., Tatum, B., Matson, M., Blondia, C., Barz,
              C., Rogge, H., Freitag, F., Navarro, L., Bonicioli, J.,
              Papathanasiou, S., and P. Escrich, "A case for research
              with and on community networks", ACM SIGCOMM Computer
              Communication Review vol. 43, no. 3, pp. 68-73, 2013.

   [Castignani_a]
              Castignani, G., Loiseau, L., and N. Montavont, "An
              Evaluation of IEEE 802.11 Community Networks Deployments",
              Information Networking (ICOIN), 2011 International
              Conference on , vol., no., pp.498,503, 26-28 , 2011.







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   [Castignani_b]
              Castignani, G., Monetti, J., Montavont, N., Arcia-Moret,
              A., Frank, R., and T. Engel, "A Study of Urban IEEE 802.11
              Hotspot Networks: Towards a Community Access Network",
              Wireless Days (WD), 2013 IFIP , pp.1,8, 13-15 , 2013.

   [Castignani_c]
              Castignani, G., Arcia-Moret, A., and N. Montavont, "A
              study of the discovery process in 802.11 networks",
              SIGMOBILE Mob. Comput. Commun. Rev., vol. 15, no. 1, p. 25
              , 2011.

   [DAE]      European Commission, EC., "A Digital Agenda for Europe",
              Communication from the Commission of 19 May 2010 to the
              European Parliament, the Council, the European Economic
              and Social Committee and the Committee of the Regions - A
              Digital Agenda for Europe , 2010.

   [Everylayer]
              former Volo Broadband, Everylayer., "Everylayer",
              Everylayer web page, http://www.everylayer.com/ , 2015.

   [FNF]      The Free Network Foundation, FNF., "The Free Network
              Foundation", The Free Network Foundation web page,
              https://thefnf.org/ , 2014.

   [Flickenger]
              Flickenger, R., Okay, S., Pietrosemoli, E., Zennaro, M.,
              and C. Fonda, "Very Long Distance Wi-Fi Networks", NSDR
              2008, The Second ACM SIGCOMM Workshop on Networked Systems
              for Developing Regions. USA, 2008 , 2008.

   [Fon]      Fon Wireless Limited, Fon., "What is Fon", Fon web page,
              https://corp.fon.com/en , 2014.

   [Hanbali]  Hanbali, A., Altman, E., and P. Nain, "A Survey of TCP
              over Ad Hoc Networks", IEEE Commun. Surv. Tutorials, vol.
              7, pp. 22-36 , 2005.

   [Heer]     Heer, T., Hummen, R., Viol, N., Wirtz, H., Gotz, S., and
              K. Wehrle, "Collaborative municipal Wi-Fi networks-
              challenges and opportunities", Pervasive Computing and
              Communications Workshops (PERCOM Workshops), 2010 8th IEEE
              International Conference on (pp. 588-593). IEEE. , 2010.

   [IEEE]     Institute of Electrical and Electronics Engineers, IEEE,
              "IEEE Standards association", 2012.




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   [Komnios]  Komnios, I., Sathiaseelan, A., and J. Crowcroft, "LEDBAT
              performance in subpacket regimes", IEEE/IFIP WONS,
              Austria, April 2014 , 2014.

   [Lampropulos]
              Lampropulos, A., Castignani, G., Blanc, A., and N.
              Montavont, "Wi2Me: A Mobile Sensing Platform for Wireless
              Heterogeneous Networks", 32nd International Conference on
              Distributed Computing Systems Workshops (ICDCS Workshops),
              2012, pp. 108-113 , 2012.

   [Lowenstedt]
              Huggler, J., "Lowenstedt Villagers Built Own Fiber Optic
              Network", The Telegraph, 03 Jun 2014, available at
              http://www.telegraph.co.uk/news/worldnews/europe/
              germany/10871150/
              German-villagers-set-up-their-own-broadband-network.html ,
              2014.

   [Mexican]  Varma, S., "Lowenstedt Villagers Built Own Fiber Optic
              Network", The Times of India, 27 Aug 2013, available at
              http://timesofindia.indiatimes.com/world/rest-of-world/
              Ignored-by-big-companies-Mexican-village-creates-its-own-
              mobile-service/articleshow/22094736.cms , 2013.

   [Neumann]  Neumann, A., Lopez, E., and L. Navarro, "An evaluation of
              bmx6 for community wireless networks", In Wireless and
              Mobile Computing, Networking and Communications (WiMob),
              2012 IEEE 8th International Conference on (pp. 651-658).
              IEEE. , 2012.

   [PAWS]     Sathiaseelan, A., Crowcroft, J., Goulden, M.,
              Greiffenhagen, C., Mortier, R., Fairhurst, G., and D.
              McAuley, "Public Access WiFi Service (PAWS)", Digital
              Economy All Hands Meeting, Aberdeen , Oct 2012.

   [Pietrosemoli]
              Pietrosemoli, E., Zennaro, M., and C. Fonda, "Low cost
              carrier independent telecommunications infrastructure", In
              proc. 4th Global Information Infrastructure and Networking
              Symposium, Choroni, Venezuela , 2012.

   [Rendon]   Rendon, A., Ludena, P., and A. Martinez Fernandez,
              "Tecnologias de la Informacion y las Comunicaciones para
              zonas rurales Aplicacion a la atencion de salud en paises
              en desarrollo", CYTED. Programa Iberoamericano de Ciencia
              y Tecnologia para el Desarrollo , 2011.




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   [Ros]      Ros, D. and M. Welzl, "Assessing LEDBAT's Delay Impact",
              Communications Letters, IEEE , vol.17, no.5, pp.1044,1047,
              May 2013 , 2013.

   [Samanta]  Samanta, V., Knowles, C., Wagmister, J., and D. Estrin,
              "Metropolitan Wi-Fi Research Network at the Los Angeles
              State Historic Park", The Journal of Community
              Informatics, North America, 4 , May 2008.

   [Sathiaseelan_a]
              Sathiaseelan, A., Rotsos, C., Sriram, C., Trossen, D.,
              Papadimitriou, P., and J. Crowcroft, "Virtual Public
              Networks", In Software Defined Networks (EWSDN), 2013
              Second European Workshop on (pp. 1-6). IEEE. , 2013.

   [Sathiaseelan_b]
              Sathiaseelan, A. and J. Crowcroft, "LCD-Net: Lowest Cost
              Denominator Networking", ACM SIGCOMM Computer
              Communication Review , Apr 2013.

   [Sathiaseelan_c]
              Sathiaseelan, A., Mortier, R., Goulden, M., Greiffenhagen,
              C., Radenkovic, M., Crowcroft, J., and D. McAuley, "A
              Feasibility Study of an In-the-Wild Experimental Public
              Access WiFi Network", ACM DEV 5, Proceedings of the Fifth
              ACM Symposium on Computing for Development, San Jose , Dec
              2014 pp 33-42, 2014.

   [Suresh]   Suresh, L., Schulz-Zander, J., Merz, R., Feldmann, A., and
              T. Vazao, "Towards Programmable Enterprise WLANs with
              ODIN", In Proceedings of the first workshop on Hot topics
              in software defined networks (HotSDN '12). ACM, New York,
              NY, USA, 115-120 , 2012.

   [Vega]     Vega, D., Cerda-Alabern, L., Navarro, L., and R. Meseguer,
              "Topology patterns of a community network: Guifi. net.",
              Proceedings Wireless and Mobile Computing, Networking and
              Communications (WiMob), 2012 IEEE 8th International
              Conference on (pp. 612-619) , 2012.

   [WNDW]     Wireless Networking in the Developing World/Core
              Contributors, "Wireless Networking in the Developing
              World, 3rd Edition", The WNDW Project, available at
              wndw.net , 2013.







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   [WSIS]     International Telecommunications Union, ITU, "Declaration
              of Principles. Building the Information Society: A global
              challenge in the new millenium", World Summit on the
              Information Society, 2003, at http://www.itu.int/wsis,
              accessed 12 January 2004. , Dec 2013.

   [Zennaro]  Zennaro, M., Fonda, C., Pietrosemoli, E., Muyepa, A.,
              Okay, S., Flickenger, R., and S. Radicella, "On a long
              wireless link for rural telemedicine in Malawi", 6th
              International Conference on Open Access, Lilongwe, Malawi
              , Nov 2008.

Authors' Addresses

   Jose Saldana (editor)
   University of Zaragoza
   Dpt. IEC Ada Byron Building
   Zaragoza  50018
   Spain

   Phone: +34 976 762 698
   Email: jsaldana@unizar.es


   Andres Arcia-Moret
   Universidad de Los Andes
   Facultad de Ingenieria. Sector La Hechicera
   Merida  5101
   Venezuela

   Phone: +58 274 2402811
   Email: andres.arcia@ula.ve


   Bart Braem
   iMinds
   Gaston Crommenlaan 8 (bus 102)
   Gent  9050
   Belgium

   Phone: +32 3 265 38 64
   Email: bart.braem@iminds.be









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   Leandro Navarro
   U. Politecnica Catalunya
   Jordi Girona, 1-3, D6
   Barcelona  08034
   Spain

   Phone: +34 934016807
   Email: leandro@ac.upc.edu


   Ermanno Pietrosemoli
   ICTP
   Via Beirut 7
   Trieste  34151
   Italy

   Phone: +39 040 2240 471
   Email: ermanno@ictp.it


   Carlos Rey-Moreno
   University of the Western Cape
   Robert Sobukwe road
   Bellville  7535
   South Africa

   Phone: 0027219592562
   Email: crey-moreno@uwc.ac.za


   Arjuna Sathiaseelan
   University of Cambridge
   15 JJ Thomson Avenue
   Cambridge  CB30FD
   United Kingdom

   Phone: +44 (0)1223 763781
   Email: arjuna.sathiaseelan@cl.cam.ac.uk


   Marco Zennaro
   Abdus Salam ICTP
   Strada Costiera 11
   Trieste  34100
   Italy

   Phone: +39 040 2240 406
   Email: mzennaro@ictp.it



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