Global Access to the Internet for All                    J. Saldana, Ed.
Internet-Draft                                    University of Zaragoza
Intended status: Informational                            A. Arcia-Moret
Expires: April 9, 2015                          Universidad de Los Andes
                                                                B. Braem
                                                              L. Navarro
                                                U. Politecnica Catalunya
                                                         E. Pietrosemoli
                                        Escuela Latinoamericana de Redes
                                                           C. Rey-Moreno
                                          University of the Western Cape
                                                         A. Sathiaseelan
                                                 University of Cambridge
                                                              M. Zennaro
                                                        Abdus Salam ICTP
                                                         October 6, 2014

    Alternative Network Deployments.  Taxonomy and characterization


   This document presents a taxonomy of "alternative network
   deployments", and a set of definitions and shared characteristics.
   This term includes a set of network models emerged in the last
   decades 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 households of the users, who pay for

   Several initiatives throughout the World have built large scale
   networks that use wireless technologies (including long distance) due
   to the reduced cost of using the unlicensed spectrum.  Others rely on
   wired technologies.  Some of these networks are self-organized and
   decentralized, other ones are based on sharing wireless resources of
   the users.  The emergence of these networks can be motivated by
   different causes: Sometimes the reluctance, or the impossibility, of
   network operators to 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 providing 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

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   The classification considers different existing network models as
   e.g., community networks, open wireless services, user-extensible
   services, traditional local 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 network characteristics related
   to architecture, organization, etc.

Status of This Memo

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   This Internet-Draft will expire on April 9, 2015.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   4
   2.  Classification  . . . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  Community Networks  . . . . . . . . . . . . . . . . . . .   5
     2.2.  Crowdshared approaches, led by the people and third party
           stakeholders  . . . . . . . . . . . . . . . . . . . . . .   6
     2.3.  User-centric Networks . . . . . . . . . . . . . . . . . .   7
     2.4.  Testbed . . . . . . . . . . . . . . . . . . . . . . . . .   8
   3.  Scenarios where Alternative Networks are deployed . . . . . .   8
     3.1.  Alternative Networks depending on the income level of
           each country  . . . . . . . . . . . . . . . . . . . . . .   8
     3.2.  Urban vs. rural areas . . . . . . . . . . . . . . . . . .  10
   4.  Technologies employed . . . . . . . . . . . . . . . . . . . .  11
     4.1.  Wired . . . . . . . . . . . . . . . . . . . . . . . . . .  11
       4.1.1.  Optical Fiber . . . . . . . . . . . . . . . . . . . .  11
     4.2.  Wireless  . . . . . . . . . . . . . . . . . . . . . . . .  11
       4.2.1.  Antennas  . . . . . . . . . . . . . . . . . . . . . .  11
       4.2.2.  Link length . . . . . . . . . . . . . . . . . . . . .  13
       4.2.3.  Layer 2 . . . . . . . . . . . . . . . . . . . . . . .  15  802.11 (Wi-Fi)  . . . . . . . . . . . . . . . . .  15  GSM . . . . . . . . . . . . . . . . . . . . . . .  17
   5.  Network and architecture issues . . . . . . . . . . . . . . .  17
     5.1.  Layer 3 . . . . . . . . . . . . . . . . . . . . . . . . .  17
       5.1.1.  IP addressing . . . . . . . . . . . . . . . . . . . .  17
       5.1.2.  Routing protocols . . . . . . . . . . . . . . . . . .  18  Traditional routing protocols . . . . . . . . . .  18  Mesh routing protocols  . . . . . . . . . . . . .  18
     5.2.  Upper layers  . . . . . . . . . . . . . . . . . . . . . .  18
       5.2.1.  Services provided by these networks . . . . . . . . .  19  Intranet services . . . . . . . . . . . . . . . .  20  Access to the Internet  . . . . . . . . . . . . .  20
     5.3.  Topology  . . . . . . . . . . . . . . . . . . . . . . . .  21
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  21
   7.  Contributing Authors  . . . . . . . . . . . . . . . . . . . .  21
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  22
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  22
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  22
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  22
     10.2.  Informative References . . . . . . . . . . . . . . . . .  23
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  25

1.  Introduction

   Several initiatives throughout the World have built large scale
   networks that use wireless technologies (including long distance) due
   to the reduced cost of using the unlicensed spectrum.  Others rely on

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   wired technologies.  Some of them are self-organized and
   decentralized, other ones are based on sharing wireless resources of
   the users.  The emergence of these networks can be motivated by
   different causes: Sometimes 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 providing 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

   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 models emerged in the last
   decades 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 households of 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.

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [RFC2119].

2.  Classification

   This section classifies Alternative Networks according to their
   intended usage.  Each of them have different incentive structures,
   maybe common technological challenges, but most importantly
   interesting usage challenges which feeds into the incentives as well
   as 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 WiFi, Infrastructure WiFi, Optical Fibre, IPv4,
   IPv6, RFC1918, OLSR, BMX6, etc.) coexist.

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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 are directly contributing 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 a 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

   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.

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

   A free network equitably grants the following freedoms to all:

   Freedom 0 - 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."

   The principles of these networks have also been summarized (see this way:

   - You have the freedom to use the network for any purpose as long as
   you don't harm the operation of the network itself , the rights of

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   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.

   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 can be used to build
   another definition: 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 that sense, Community Networks can be called "user-
   extensible networks".

   These networks are also called sometimes "Free Networks" or even
   "Network Commons".  However, the most accepted name is Community

   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 ISPs base their business on the
   control of the infrastructure).  In Community Networks, everybody
   keeps the ownership of what he/she has contributed.

2.2.  Crowdshared approaches, led by the people and third party

   These networks follow the next approach: the home router creates two
   wireless networks, one of them to be normally used by the owner, and
   the other one is public.  A small fraction of the bandwidth is
   allocated to the public network (as e.g.  Less-than-best-effort or

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   scavenger traffic), to be employed by any user of the service in the
   immediate area.  An example is described in [PAWS].

   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 less-than-best-effort approach,
   so as not to harm the traffic of the owner of the connection

   There are three actors in the scenario:

   - End users who sign up for the service and share their network
   capacity.  As a counterpart, they can access anyone's home broadband
   for free.

   - Virtual Network Operators (VNOs) are 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.

2.3.  User-centric Networks

   A first example are the networks created and managed by City Councils
   (e.g., [Heer]).  Some companies [FON reference missing] 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, an people can join it
   different ways: they can buy a dual 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 revenues 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.

   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.

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

   - The owner: an entity (e.g. end-user; 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

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

   - The Virtual Operator: 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 VO is
   not an ISP given that it does not provide Internet access (e.g.
   infrastructure; naming).  A VO is neither an ASP since it does not
   provide user services.

2.4.  Testbed

   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].

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 are interesting or have been deployed.

3.1.  Alternative Networks depending on the income level of each country

   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
   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 been also
   defined as those which are in transition from traditional lifestyles

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   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 the well-being of a country and not solely based on economic
   terms.  These classifications are used to give strong signals to the
   international community to 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 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", worried of
   being 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

   Most efforts from governments and international organizations focused
   initially on improving and extending the existing infrastructure for
   not leaving their population behind.  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

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   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 it is undeniable the contribution made by mobile network
   operators in decreasing the access gap, its model presents some
   constraints that limits 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
   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 deemed them profitable

   The cost of the wireless infrastructure required to set up a network,
   including powering them via solar energy, is within the range of
   availability if not of individuals at least of entire communities.

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   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.  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 to that of the services they aim to provide, has
   fuelled the creation of robust low-cost low-consumption low-
   complexity off-the-self wireless devices which make much easier the
   deployment and maintenance of these alternative infrastructures in
   rural areas.

4.  Technologies employed

4.1.  Wired

   Some of the wired technologies employed in ANs are:

4.1.1.  Optical Fiber

   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

4.2.  Wireless

   Different wireless technologies [WNDW] can be employed in Alternative
   Network Deployments.

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.

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   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 omni will also receive a feeble signal
   from the client).  So a moderate gain omnidirectional of about 8 to
   10 dBi is normally preferable.  Higher gain omnis antennas are only
   advisable when the farthest way client are roughly in the same plane.

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

   For outdoor clients, directive antennas can be quite useful to extend
   coverage to an Access Point fitted with an omni.

   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 frequently 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 due with lower altitude antenna placement since
   the Fresnel zone is inversely proportional to the square root of the

   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 omni to the lower frequency to
   provide local access.

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   Of course, in the case of mesh networking, where the antenna should
   connect to several other nodes, it is better to use omnidirectional

   Keep also in mind that the same type of polarisation must be used at
   both ends of any radio link.  For point to point links, some vendor
   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

4.2.2.  Link length

   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 radio waves occuppy a volume
   around the optical line, which must be unencumbered from obstacles
   for the maximum signal to be captured at the receiver.  This volume
   is known as the Fresnel ellipsoid and its size grows with the
   distance between the end points and with the wavelength of the
   signal, which in turn is inversely proportional to the frequency.

   So, 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.

   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.

   Bear in mind that the sensitivity of the receiver decreases with the
   transmission speed, so more power is needed at greater transmission

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   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.

   So to achieve a given link margin (also called fade margin), one can:

   a) increase the output power.The maximum transmitted power is
   specified by the 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, the 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 favourable frequency
   or a shorter path.

   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.  So 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 say
   from 150 Mbit/s to 6 Mbit/s if the receiver power is not enough to
   sustain the maximum throughput.

   A completely different limiting factor is related with the medium
   access protocol.  WiFi 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 reduce
   significantly the throughput at long distance, so for long distance
   application it is better to use a different medium access technique,

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   in which the receiver does not wait for an acknowledge 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 WiFi in order to
   increase the throughput at longer distances.  Low cost equipment
   using TDMA can offer high throughput at distances over 100

4.2.3.  Layer 2  802.11 (Wi-Fi)

   Wireless standards ensure interoperability and usability by 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, 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.

   |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].

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Internet-Draft       Alternative Network Deployments        October 2014  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 is 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
   wireless interface creates a network with a specified name (called
   the SSID) 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 said to be associated with
   the master.  Managed mode interfaces do not communicate with each
   other directly, and will 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.

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   4.Monitor mode is used by some tools (such as Kismet) to passively
   listen to all radio traHc 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.  Remember that managed mode clients cannot
   communicate with each other directly, so it is likely that you will
   want to run a high repeater site 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.  802.11af (TVWS)

   Some Alternative Networks make use of TV White Spaces, using 802.11af
   standard.  GSM

   802.11 is not the only layer 2 option to be used in Alternative
   Networks.  Some of them use mobile technologies as e.g.  GSM.

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 most almost all Alternative
   Networks still use IPv4.  A community networks survey [Avonts]
   indicated that IPv6 rollout forms 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.

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5.1.2.  Routing protocols

   These networks are composed of possibly different layer 2 devices,
   resulting in a mesh of nodes.  Connection between different nodes is
   not guaranteed, the link stability can vary strongly over time.  To
   tackle this, some Community Networks use mesh network routing
   protocols while other networks use more traditional routing
   protocols.  Some networks operate multiple routing protocols in
   parallel.  E.g., they use a mesh protocol inside different islands
   and use traditional routing protocols to connect islands.  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 Community Networks opt to run the OSPF
   protocol, as defined by RFC 2328 [RFC2328].  Mesh routing protocols

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

   The Better Approach To Mobile Adhoc Networking (B.A.T.M.A.N.)
   [Abolhasan]protocol was developed by member 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 Community Networks.

5.2.  Upper layers

   From crowd shared 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 implement a Less than Best Effort policy for the
   user and protect the sharer.  Achieving LBE behaviour requieres 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].

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

   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.  This application have shown to
   improve the client performance compared to a single-Community Network

   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].  So, 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 WiFi access.

5.2.1.  Services provided by these networks

   This section provides an explaining 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.

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Internet-Draft       Alternative Network Deployments        October 2014  Intranet services

   - VoIP (e.g. with SIP)

   - remote desktop (e.g. using my 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.

   - public video cameras.

   - DNS.

   - online games servers.

   - jabber instant messaging.

   - IRC chat.

   - weather stations.

   - NTP.

   - Network monitoring.

   - videoconferencing / streaming.

   - Radio streaming.  Access to the Internet  Web browsing proxies

   A number of federated proxies provide web browsing service for the
   users.  Other services (file sharing, skype, etc.) are not usually
   allowed.  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.

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5.3.  Topology

   These networks follow different topology patterns, as studied in

   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 is the way to extend the user 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 peatonal speed, there is a fair chance
   of performing file transfers [Castignani_a] [Castignani_b].  In
   studied scenarios in France and Luxembourg the density of APs around
   the urban areas (mainly in downtown and residential areas) there is a
   crowded deployment of APs for the different ISPs.  Moreover,
   performed studies reveal that aggregating available networks can be
   beneficial to the client by using an application that manage 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

6.  Acknowledgements

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

7.  Contributing Authors

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   L. Aaron Kaplan
   1234 city

   Phone: +43 (0)699 11994786

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

   [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.

   [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.

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10.2.  Informative References

              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.

   [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.

   [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, 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.

              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, 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.

              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.

   [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.

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   [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.

              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.

   [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, 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.

   [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.

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

   [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
     , 2013.

   [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,
              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

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

   Phone: +34 976 762 698

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

   Phone: +58 274 2402811

   Bart Braem
   Gaston Crommenlaan 8 (bus 102)
   Gent  9050

   Phone: +32 3 265 38 64

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

   Phone: +34 934016807

   Ermanno Pietrosemoli
   Escuela Latinoamericana de Redes
   Apartado 514
   Merida  5101

   Phone: +58 0274 2403327

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

   Phone: 0027219592562

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

   Phone: +44 (0)1223 763781

   Marco Zennaro
   Abdus Salam ICTP
   Strada Costiera 11
   Trieste  34100

   Phone: +39 040 2240 406

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