wdiff rfc7962v1.txt rfc7962.txt

Internet Research Task Force (IRTF) J. Saldana, Ed.
Request for Comments: 7962 University of Zaragoza
Category: Informational A. Arcia-Moret
ISSN: 2070-1721 University of Cambridge
B. Braem
iMinds
E. Pietrosemoli
The Abdus Salam ICTP
A. Sathiaseelan
University of Cambridge
M. Zennaro
The Abdus Salam ICTP
August 2016

Alternative Network Deployments:
Taxonomy, Characterization, Technologies, and Architectures

Abstract

This document presents a taxonomy of a set of "Alternative Network
Deployments" that emerged in the last decade with the aim of bringing
Internet connectivity to people or providing a local communication
infrastructure to serve various complementary needs and objectives.
They employ architectures and topologies different from those of
mainstream networks and rely on alternative governance and business
models.

The document also surveys the technologies deployed in these
networks, and their differing architectural characteristics,
including a set of definitions and shared properties.

The classification considers models such as Community Networks,
Wireless Internet Service Providers (WISPs), networks owned by
individuals but leased out to network operators who use them as a
low-cost medium to reach the underserved population, networks that
provide connectivity by sharing wireless resources of the users, and
rural utility cooperatives.

Status of This Memo

This document is not an Internet Standards Track specification; it is
published for informational purposes.

This document is a product of the Internet Research Task Force
(IRTF). The IRTF publishes the results of Internet-related research
and development activities. These results might not be suitable for
deployment. This RFC represents the consensus of the Global Access
to the Internet for All Research Group of the Internet Research Task
Force (IRTF). Documents approved for publication by the IRSG are not
a candidate for any level of Internet Standard; see Section 2 of RFC
5741.

Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7962.

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
to this document.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Mainstream Networks . . . . . . . . . . . . . . . . . . . 4
1.2. Alternative Networks . . . . . . . . . . . . . . . . . . 4
2. Terms Used in This Document . . . . . . . . . . . . . . . . . 5
3. Scenarios Where Alternative Networks Are Deployed . . . . . . 7 6
3.1. Urban vs. Rural Areas . . . . . . . . . . . . . . . . . . 8
3.2. Topology Patterns Followed by Alternative Networks . . . 9
4. Classification Criteria . . . . . . . . . . . . . . . . . . . 9
4.1. Entity behind the Network . . . . . . . . . . . . . . . . 9
4.2. Purpose . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.3. Governance and Sustainability Model . . . . . . . . . . . 11
4.4. Technologies Employed . . . . . . . . . . . . . . . . . . 12 11
4.5. Typical Scenarios . . . . . . . . . . . . . . . . . . . . 12
5. Classification of Alternative Networks . . . . . . . . . . . 12
5.1. Community Networks . . . . . . . . . . . . . . . . . . . 13 12
5.2. Wireless Internet Service Providers (WISPs) . . . . . . . 15 14
5.3. Shared Infrastructure Model . . . . . . . . . . . . . . . 16 15
5.4. Crowdshared Approaches Led by the Users and Third-Party
Stakeholders . . . . . . . . . . . . . . . . . . . . . . 17
5.5. Rural Utility Cooperatives . . . . . . . . . . . . . . . 19
5.6. Testbeds for Research Purposes . . . . . . . . . . . . . 20
6. Technologies Employed . . . . . . . . . . . . . . . . . . . . 20
6.1. Wired . . . . . . . . . . . . . . . . . . . . . . . . . . 20
6.2. Wireless . . . . . . . . . . . . . . . . . . . . . . . . 21
6.2.1. Media Access Control (MAC) Protocols for Wireless
Links . . . . . . . . . . . . . . . . . . . . . . . . 21
6.2.1.1. 802.11 (Wi-Fi) . . . . . . . . . . . . . . . . . 21
6.2.1.2. Mobile Technologies . . . . . . . . . . . . . . . 22
6.2.1.3. Dynamic Spectrum . . . . . . . . . . . . . . . . 22
7. Upper Layers . . . . . . . . . . . . . . . . . . . . . . . . 24
7.1. Layer 3 . . . . . . . . . . . . . . . . . . . . . . . . . 24
7.1.1. IP Addressing . . . . . . . . . . . . . . . . . . . . 24
7.1.2. Routing Protocols . . . . . . . . . . . . . . . . . . 24
7.1.2.1. Traditional Routing Protocols . . . . . . . . . . 25
7.1.2.2. Mesh Routing Protocols . . . . . . . . . . . . . 25
7.2. Transport Layer . . . . . . . . . . . . . . . . . . . . . 25
7.2.1. Traffic Management When Sharing Network Resources . . 25
7.3. Services Provided . . . . . . . . . . . . . . . . . . . . 26
7.3.1. Use of VPNs . . . . . . . . . . . . . . . . . . . . . 27
7.3.2. Other Facilities . . . . . . . . . . . . . . . . . . 27
7.4. Security Considerations . . . . . . . . . . . . . . . . . 28
8. Informative References . . . . . . . . . . . . . . . . . . . 28
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 38
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 40

1. Introduction

One of the aims of the Global Access to the Internet for All (GAIA)
IRTF Research Group is "to document and share deployment experiences
and research results to the wider community through scholarly
publications, white papers, Informational and Experimental RFCs,
etc." [GAIA]. In line with this objective, this document proposes a
classification of "Alternative Network Deployments". This term
includes a set of network access models that have emerged in the last
decade with the aim of providing Internet connections, following
topological, architectural, governance, and business models that
differ from the so-called "mainstream" ones, where a company deploys
the infrastructure connecting the users, who pay a subscription fee
to be connected and make use of it.

Several initiatives throughout the world have built these large-scale
networks, using predominantly wireless technologies (including long
distance links) due to the reduced cost of using unlicensed spectrum.
Wired technologies such as fiber are also used in some of these
networks.

The classification considers several types of alternate deployments:
Community Networks are self-organized networks wholly owned by the
community; networks acting 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; networks that provide connectivity by sharing
wireless resources of the users; and finally there are some rural
utility cooperatives also connecting their members to the Internet.

The emergence of these networks has been motivated by a variety of
factors such as the lack of wired and cellular infrastructures in
rural/remote areas [Pietrosemoli]. In some cases, alternative
networks Alternative
Networks may provide more localized communication services as well as
Internet backhaul support through peering agreements with mainstream
network operators. In other cases, they are built as a complement or
an alternative to commercial Internet access provided by mainstream
network operators.

The present document is intended to provide a broad overview of
initiatives, technologies, and approaches employed in these networks,
including some real examples. References describing each kind of
network are also provided.

1.1. Mainstream Networks

In this document, we will use the term "mainstream networks" to
denote those networks sharing these characteristics:

o Regarding scale, they are usually large networks spanning entire
regions.

o Top-down control of the network and centralized approach.

o They require a substantial investment in infrastructure.

o Users in mainstream networks do not participate in the network
design, deployment, operation, governance, and maintenance.

o Ownership of the network is never vested in the users themselves.

1.2. Alternative Networks

The term "Alternative Network" proposed in this document refers to
the networks that do not share the characteristics of "mainstream
network deployments". Therefore, they may share some of the
following characteristics:

o Relatively small scale (i.e., not spanning entire regions).

o Administration may not follow a centralized approach.

o They may require a reduced investment in infrastructure, which may
be shared by the users and commercial and non-commercial entities.

o Users in alternative networks Alternative Networks may participate in the network
design, deployment, operation, and maintenance.

o Ownership of the network is often vested in the users.

2. Terms Used in This Document

Considering the role that the Internet currently plays in everyday
life, this document touches on complex social, political, and
economic issues. Some of the concepts and terminology used have been
the subject of study of various disciplines outside the field of
networking and are responsible for long debates whose resolution is
out of the scope of this document.

o "Global north" and "global south". Although there is no consensus
on the terms to be used when talking about the different
development level of countries, we will employ the term "global
south" to refer to nations with a relatively lower standard of
living. This distinction is normally intended to reflect basic
economic country conditions. In common practice, Japan in Asia,
Canada and the United States in northern America, Australia and
New Zealand in Oceania, and Europe are considered "developed"
regions or areas [UN], so we will employ the term "global north"
when talking about them.

o The "Digital Divide". The following dimensions are considered to
be meaningful when measuring the digital development state of a
country: infrastructures (availability and affordability), the
Information and Communications Technology (ICT) sector (human
capital and technological industry), digital literacy, legal and
regulatory framework, and content and services. A lack of digital
development in one or more of these dimensions is what has been
referred as the "Digital Divide" [Norris]. It should be noted
that this "Divide" is not only present between different countries
but between zones of the same country, despite its degree of
development.

o "Urban" and "rural" zones. There is no single definition of
"rural" or "urban", as each country and various international
organizations define these terms differently, mainly based on the
number of inhabitants, the population density, and the distance
between houses [UNStats]. For networking purposes, the primary
distinction is likely the average distance between customers,
typically measured by population density, as well as the distance
to the nearest Internet point-of-presence, i.e., the distance to
be covered by "middle mile" or backhaul connectivity. Some
regions with low average population density may cluster almost all
inhabitants into a small number of relatively dense small towns,
for example, while residents may be dispersed more evenly in
others.

o Demand. In economics, it describes a consumer's desire and
willingness to pay a price for a specific good or service.

o Provision is the act of making an asset available for sale. In
this document, we will mainly use it as the act of making a
network service available to the inhabitants of a zone.

o Underserved area. Area in which the telecommunication market
permanently fails to provide the information and communications
services demanded by the population.

o "Free Networks". A definition of Free Network is proposed by the
Free Network Foundation [FNF] as the one that "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."

o The principles of free, Free, open, and neutral networks networks. Their principles have also been
summarized this way [Baig]:

* 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.

3. Scenarios Where Alternative Networks Are Deployed

Different studies have reported that as much as 60% of the people on
the planet do not have Internet connectivity [Sprague]
[InternetStats]. In addition, those unconnected are unevenly
distributed: only 31% of the population in "global south" countries
had access in 2014, against 80% in "global north" countries
[WorldBank2016]. This is one of the reasons behind the inclusion of
the objective to "significantly increase access to information and
communications technology and strive to provide universal and
affordable access to the Internet in least developed countries by
2020," as one of the targets in the Sustainable Development Goals
(SDGs) [SDG], considered as a part of "Goal 9. Build resilient
infrastructure, promote inclusive and sustainable industrialization
and foster innovation."

For the purpose of this document, a distinction between "global
north" and "global south" zones is made, highlighting the factors
related to ICT, which can be quantified in terms of:

o The availability of both national and international bandwidth, as
well as equipment.

o The difficulty in paying for the services and the devices required
to access the ICTs.

o The instability and/or lack of power supply.

o The scarcity of qualified staff.

o The existence of a policy and regulatory framework that hinders
the development of these models in favor of state monopolies or
incumbents.

In this context, the World Summit of the Information Society [WSIS]
aimed at achieving "a people-centred, inclusive and development-
oriented Information Society, where everyone can create, access,
utilize and share information and knowledge. Therefore, enabling
individuals, communities and people to achieve their full potential
in promoting their sustainable development and improving their
quality of life". It also called upon "governments, private sector,
civil society and international organizations" to actively engage to
work towards the bridging of the digital divide.

Some Alternative Networks have been deployed in underserved areas,
where citizens may be compelled to take a more active part in the
design and implementation of ICT solutions. However, Alternative
Networks (e.g., [Baig]) are also present in some "global north"
countries, being built as an alternative to commercial ones managed
by mainstream network operators.

The consolidation of a number of mature Alternative Networks (e.g.,
Community Networks) sets a precedent for civil society members to
become more active in the search for alternatives to provide
themselves with affordable access. Furthermore, Alternative Networks
could contribute to bridge the digital divide by increasing human
capital and promoting the creation of localized content and services.

3.1. Urban vs. Rural Areas

The differences presented in the previous section are not only
present between countries, but within them too. This is especially
the case for rural inhabitants, who represent approximately 55% of
the world's population [IFAD2011], with 78% of them in "global south"
countries [ITU2011]. According to the World Bank, adoption gaps
"between rural and urban populations are falling for mobile phones
but increasing for the internet" [WorldBank2016].

Although it is impossible to generalize among them, there exist some
common features in rural areas that have prevented incumbent
operators from providing access and that, at the same time, challenge
the deployment of alternative infrastructures [Brewer] [Nungu]
[Simo_c]. For example, a high network latency was reported in
[Johnson_b], which could be in the order of seconds during some
hours.

These challenges include:

o Low per capita income, as the local economy is mainly based on
subsistence agriculture, farming, and fishing.

o Scarcity or absence of basic infrastructures, such as electricity,
water, and access roads.

o Low population density and distance (spatial or effective) between
population clusters.

o Underdeveloped social services, such as healthcare and education.

o Lack of adequately educated and trained technicians, and high
potential for those (few) trained to leave the community
incentivized by better opportunities, higher salaries, or the
possibility of starting their own companies [McMahon].

o High cost of Internet access [Mathee].

o Harsh environments leading to failure in electronic communication
devices [Johnson_a], which reduces the reliability of the network.

Some of these factors challenge the stability of Alternative Networks
and the services they provide: scarcity of spectrum, scale, and
heterogeneity of devices. However, the proliferation of Alternative
Networks [Baig] together with the raising of low-cost, low-
consumption, low-complexity off-the-shelf wireless devices have
allowed and simplified the deployment and maintenance of alternative
infrastructures in rural areas.

3.2. Topology Patterns Followed by Alternative Networks

Alternative Networks, considered self-managed and self-sustained,
follow different topology patterns [Vega_a]. Generally, these
networks grow spontaneously and organically, that is, the network
grows without specific planning and deployment strategy and the
routing core of the network tends to fit a power law distribution.
Moreover, these networks are composed of a high number of
heterogeneous devices with the common objective of freely connecting
and increasing the network coverage and the reliability. Although
these characteristics increase the entropy (e.g., by increasing the
number of routing protocols), they have resulted in an inexpensive
solution to effectively increase the network size. One such example
is Guifi.net [Vega_a], which has had an exponential growth rate in
the number of operating nodes during the last decade.

Regularly, rural areas in these networks are connected through long-
distance links and/or wireless mesh networks, which in turn convey
the Internet connection to relevant organizations 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 capacity
to the network. Other proposals like "Virtual Public Networks"
[Sathiaseelan_a] can also extend the service.

4. Classification Criteria

The classification of Alternative Network Deployments, presented in
this document, is based on the following criteria:

4.1. Entity behind the Network

The entity (or entities) or individuals behind an Alternative Network
can be:

o A community of users.

o A public stakeholder.

o A private company.

o Supporters of a crowdshared approach.

o A community that already owns the infrastructure and shares it
with an operator, who, in turn, may also use it for backhauling
purposes.

o A research or academic entity.

The above actors may play different roles in the design, financing,
deployment, governance, and promotion of an alternative network. Alternative Network. For
example, each of the members of a community network Community Network maintains the
ownership over the equipment they have contributed, whereas in others
there is a single entity, e.g., a private company who owns the
equipment, or at least a part of it.

4.2. Purpose

Alternative Networks can be classified according to their purpose and
the benefits they bring compared to mainstream solutions, regarding
economic, technological, social, or political objectives. These
benefits could be enjoyed mostly by the actors involved (e.g.,
lowering costs or gaining technical expertise) or by the local
community (e.g., Internet access in underserved areas) or by the
society as a whole (e.g., network neutrality).

The benefits provided by Alternative Networks include, but are not
limited to:

o Extending coverage to underserved areas (users and communities).

o Providing affordable Internet access for all.

o Reducing initial capital expenditures (for the network and the end
user, or both).

o Providing additional sources of capital (beyond the traditional
carrier-based financing).

o Reducing ongoing operational costs (such as backhaul or network
administration).

o Leveraging expertise and having a place for experimentation and
teaching.

o Reducing hurdles to adoption (e.g., digital literacy, literacy in
general, and relevance).

o Providing an alternative service in case of natural disasters and
other extreme situations.

o Community building, social cohesion, and quality of life
improvement.

o Experimentation with alternative governance and ownership models
for treating network infrastructures as a commons.

o Raising awareness of political debates around issues like network
neutrality, knowledge sharing, access to resources, and more.

Note that the different purposes of alternative networks Alternative Networks can be more
or less explicitly stated and they could also evolve over time based
on the internal dynamics and external events. For example, the Red
Hook WIFI network in Brooklyn [Redhook] started as a community
network Community
Network focusing more on local applications and community building
[TidePools], but it became widely known when it played a key role as
an alternative service available during the Sandy storm [Tech]
[NYTimes].

Moreover, especially for those networks with more open and horizontal
governance models, the underlying motivations of those involved may
be very diverse, ranging from altruistic ones related to the desire
of free sharing of Internet connectivity and various forms of
activism to personal benefits from the experience and expertise
through the active participation in the deployment and management of
a real and operational network.

4.3. Governance and Sustainability Model

Different governance models are present in Alternative Networks.
They may range from some open and horizontal models, with an active
participation of the users (e.g., Community Networks) to a more
centralized model, where a single authority (e.g., a company or a
public stakeholder) plans and manages the network, even if it is
(total or partially) owned by a community.

Regarding sustainability, some networks grow "organically" as a
result of the new users who join and extend the network, contributing
their own hardware. In some other cases, the existence of previous
infrastructure (owned by the community or the users) may lower the
capital expenditures of an operator, who can therefore provide the
service with better economic conditions.

4.4. Technologies Employed

o Standard Wi-Fi. Many Alternative Networks are based on the
standard IEEE 802.11 [IEEE.802.11] using the Distributed
Coordination Function.

o Wi-Fi modified for long distances (WiLD). It Wi-Fi-based Long Distance (WiLD) networks. These can work with
either Carrier Sense Multiple Access with Collision Avoidance
(CSMA/CA) or an alternative Time Division Multiple Access (TDMA)
Media Access Control (MAC) [Simo_b].

o TDMA. It can be combined with a Wi-Fi protocol, in a non-standard
way [airMAX]. This configuration allows each client to send and
receive data using pre-designated timeslots.

o 802.16-compliant (Worldwide Interoperability for Microwave Access
(WiMax)) [IEEE.802.16] systems over non-licensed bands.

o Dynamic Spectrum Solutions (e.g., based on the use of TV white
spaces). White
Spaces). A set of television frequencies that can be utilized by
secondary users in locations where they are unused, e.g., IEEE
802.11af [IEEE.802.11AF] or 802.22 [IEEE.802.22].

o Satellite solutions can also be employed to give coverage to wide
areas, as proposed in the RIFE project (https://rife-project.eu/).

o Low-cost optical fiber systems are also used to connect households
in different places.

4.5. Typical Scenarios

The scenarios where Alternative Networks are usually deployed can be
classified as:

o Urban/rural areas.

o "Global north" / "global south" countries.

5. Classification of Alternative Networks

This section classifies Alternative Networks according to the
criteria explained previously. Each of them has different incentive
structures, maybe common technological challenges, but most
importantly interesting usage challenges that feed into the
incentives as well as the technological challenges.

At the beginning of each subsection, a table is presented including a
classification of each network according to the criteria listed in
the "Classification Criteria" subsection. Real examples of each kind
of Alternative Network are cited.

Table 1: Characteristics Summary for Community Networks

Community Networks are non-centralized, self-managed networks sharing
these characteristics:

o They start and grow organically, and they are open to
participation from everyone, sharing an open participation
agreement. Community members directly contribute active (not just
passive) network infrastructure. The network grows as new hosts
and links are added.

o Knowledge about building and maintaining the network and ownership
of the network itself is non-centralized and open. Different
degrees of centralization can be found in Community Networks. In
some of them, a shared platform (e.g., a website) may exist where
minimum coordination is performed. Community members with the
right permissions have an obvious and direct form of
organizational control over the overall organization of the
network (e.g., IP addresses, routing, etc.) in their community
(not just their own participation in the network).

o 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
and customized, even inside one network. A Community Network can
have both wired and wireless links. Multiple routing protocols or
network topology management systems may coexist in the network.

These networks grow organically, since they are formed by the
aggregation of nodes belonging to different users. A minimal
governance infrastructure is required in order to coordinate IP
addressing, routing, etc. Several examples of Community Networks are
described in [Braem]. A technological analysis of a community
network Community
Network is presented in [Vega_b], which focuses on technological
network diversity, topology characteristics, the evolution of the
network over time, robustness and reliability, and networking service
availability.

These networks follow a participatory administration model, which has
been shown to be effective in connecting geographically dispersed
people, thus enhancing and extending digital Internet rights.

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 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 and the new
extent of the network. The term "participant" refers to an
individual, who may become the user, provider, and manager of the
network at the same time.

In Community Networks, profit can only be made by offering services
and not simply by supplying the infrastructure, because the
infrastructure is neutral, free, and open (mainstream Internet
Service Providers base their business on the control of the
infrastructure). In Community Networks, everybody usually keeps the
ownership of what he/she has contributed or leaves the stewardship of
the equipment to the network as a whole (the commons), even loosing
track of the ownership of a particular equipment itself, in favor of
the community.

The majority of Community Networks comply with the definition of Free
Network, included in Section 2.

Table 2: Characteristics Summary for 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 mainstream telecommunications
companies or ISPs. WISPs mostly use wireless point-to-multipoint
links using unlicensed spectrum but often must resort to licensed
frequencies. Use of licensed frequencies is common in regions where
unlicensed spectrum is either perceived to be crowded or too
unreliable to offer commercial services, or where unlicensed spectrum
faces 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] in India, that have expanded from local service into
multiple locations.

Since 2006, the deployment of cloud-managed WISPs has been possible
with hardware from companies such as [Meraki] and later [OpenMesh]
and others. Until recently, however, most of these services have
been aimed at "global north" markets. In 2014, a cloud-managed WISP
service aimed at "global south" markets was launched [Everylayer].

Table 3: Characteristics Summary for Shared Infrastructure

In mainstream networks, the operator usually owns the
telecommunications infrastructure required for the service or
sometimes rents infrastructure to/from other companies. The problem
arises in large areas with low population density, in which neither
the operator nor the other companies have deployed infrastructure and
such deployments are not likely to happen due to the low potential
return on investment.

When users already own deployed infrastructure, either individually
or as a community, sharing that infrastructure with an operator can
benefit both parties and is a solution that has been deployed in some
areas. For the operator, this provides a significant reduction in
the initial investment needed to provide services in small rural
localities because capital expenditure is only associated with the
access network. Renting capacity in the users' network for
backhauling only requires an increment in the operating expenditure.
This approach also benefits the users in two ways: they obtain
improved access to telecommunications services that would not be
accessible otherwise, and they can derive some income from the
operator that helps to offset the network's operating costs,
particularly for network maintenance.

One clear example of the potential of the "shared infrastructure
model" nowadays is the deployment of 3G services in rural areas in
which there is a broadband rural community network. Community Network. Since the
inception of femtocells (small, low-power cellular base stations),
there are complete technical solutions for low-cost 3G coverage using
the Internet as a backhaul. If a user or community of users has an
IP network connected to the Internet with some excess capacity,
placing a femtocell in the user premises benefits both the user and
the operator, as the user obtains better coverage and the operator
does not have to support the cost of the backhaul infrastructure.
Although this paradigm was conceived for improved indoor coverage,
the solution is feasible for 3G coverage in underserved rural areas
with low population density (i.e., villages), where the number of
simultaneous users and the servicing area are small enough to use
low-cost femtocells. Also, the amount of traffic produced by these
cells can be easily transported by most community broadband rural
networks.

Some real examples can be referenced in the TUCAN3G project, which
deployed demonstrator networks in two regions in the Amazon forest in
Peru [Simo_d]. In these networks [Simo_a], the operator and several
rural communities cooperated to provide services through rural
networks built up with WiLD links [WiLD]. In these cases, the
networks belonged to the public health authorities and were deployed
with funds that came from international cooperation for telemedicine
purposes. Publications that justify the feasibility of this approach
can also be found on that website.

5.4. Crowdshared Approaches Led by the Users and Third-Party
Stakeholders

Table 4: Characteristics Summary for Crowdshared Approaches
These networks can be defined as a set of nodes whose owners share
common interests (e.g., sharing connectivity; resources; and
peripherals) regardless of their physical location. They 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 examples are found in the networks created and managed by city
councils (e.g., [Heer]). The "openwireless movement"
(https://openwireless.org/) also promotes the sharing of private
wireless networks.

Some companies [Fon] also promote the use of Wi-Fi routers with dual
access: a Wi-Fi network for the user and a shared one. Adequate
Authentication, Authorization, and Accounting (AAA) policies are
implemented, so people can join the network in different ways: they
can buy a router, so they can share their connection and in turn,
they get access to all the routers associated with the community.
Some users can even get some revenue every time another user connects
to their Wi-Fi Access Point. Users that are not part of the
community can buy passes in order to use the network. Some
mainstream telecommunications operators collaborate with these
communities by including the functionality required to create the two
access networks in their routers. Some of these efforts are surveyed
in [Shi].

The elements involved in a crowdshared network are summarized below:

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

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

o The owner: End users who sign up for the service and share their
network capacity. As a counterpart, they can access another
owner's home network capacity for free. The owner can be an end
user or an entity (e.g., operator; virtual mobile network
operator; or municipality) that is to be made responsible for any
actions concerning his/her device.

o 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.

o The VNO: An entity that acts in some aspects as a network
coordinator. It may provide services such as initial
authentication or registration and, eventually, trust relationship
storage. A VNO is not an ISP given that it does not provide
Internet access (e.g., infrastructure or naming). A VNO is not an
Application Service Provider (ASP) either since it does not
provide user services. Virtual Operators VNOs may also be stakeholders with socio-environmental socio-
environmental objectives. They can be local governments,
grassroots user communities, charities, or even content operators,
smart grid operators, etc. They are the ones who actually run the
service.

o Network operators: They have a financial incentive to lease out
unused capacity [Sathiaseelan_b] at a 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, and the network operators are paid by the
VNOs, who in turn accomplish their socio-environmental role.

5.5. Rural Utility Cooperatives

Table 5: Characteristics Summary for Rural Utility Cooperatives

A utility cooperative is a type of cooperative that delivers a public
utility to its members. For example, in the United States, rural
electric cooperatives have provided electric service starting in the
1930s, especially in areas where investor-owned utility would not
provide service, believing there would be insufficient revenue to
justify the capital expenditures required. Similarly, in many
regions with low population density, traditional Internet Service
Providers such as telephone companies or cable TV companies are
either not providing service at all or only offering low-speed DSL
service. Some rural electric cooperatives started installing fiber
optic lines to run their smart grid applications, but they found they
could provide fiber-based broadband to their members at little
additional cost [Cash]. In some of these cases, rural electric
cooperatives have partnered with local ISPs to provide Internet
connection to their members [Carlson]. More information about these
utilities and their management can be found in [NewMexico] and
[Mitchell].

5.6. Testbeds for Research Purposes

Table 6: Characteristics Summary for Testbeds

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].

The administration of these networks may start being centralized in
most cases (administered by the academic entity) and may end up in a
non-centralized model in which other local stakeholders assume part
of the network administration [Rey]. (for example, see [Rey]).

6. Technologies Employed

6.1. Wired

In many ("global north" or "global south") countries, it may happen
that national service providers decline to provide connectivity to
tiny and isolated villages. So in some cases, the villagers have
created their own optical fiber networks. This is the case in
Lowenstedt, Germany [Lowenstedt] or in some parts of Guifi.net
[Cerda-Alabern].

6.2. Wireless

The vast majority of Alternative Network Deployments are based on
different wireless technologies [WNDW]. Below we summarize the
options and trends when using these features in Alternative Networks.

6.2.1. Media Access Control (MAC) Protocols for Wireless Links

Different protocols for MAC, which also include physical layer (PHY)
recommendations, are widely used in Alternative Network Deployments.
Wireless standards ensure interoperability and usability to those who
design, deploy, and manage wireless networks. In addition, they then
ensure the low cost of equipment due to economies of scale and mass
production.

The standards used in the vast majority of Alternative Networks come
from the IEEE Standard Association's IEEE 802 Working Group.
Standards developed by other international entities can also be used,
such as, e.g., the European Telecommunications Standards Institute
(ETSI).

6.2.1.1. 802.11 (Wi-Fi)

The standard we are most interested in is 802.11 a/b/g/n/ac, as it
defines the protocol for Wireless LAN. It is also known as "Wi-Fi".
The original release (a/b) was issued in 1999 and allowed for rates
up to 54 Mbit/s. The latest release (802.11ac) approved in 2013
reaches up to 866.7 Mbit/s. In 2012, the IEEE issued the an 802.11
standard that consolidates consolidated all the previous amendments. amendments [IEEE.802.11].
The document is freely downloadable from the IEEE Standards
Association [IEEE].

The MAC protocol in 802.11 is called CSMA/CA and was designed for
short distances; the transmitter expects the reception of an
acknowledgment for each transmitted unicast packet and if a certain
waiting time is exceeded, the packet is retransmitted. This behavior
makes necessary the adaptation of several MAC parameters when 802.11
is used in long links [Simo_b]. Even with this adaptation, distance
has a significant negative impact on performance. For this reason,
many vendors implement alternative medium access techniques that are
offered alongside the standard CSMA/CA in their outdoor 802.11
products. These alternative proprietary MAC protocols usually employ
some type of TDMA. Low-cost equipment using these techniques can
offer high throughput at distances above 100 kilometers.

Different specifications of 802.11 operate in different frequency
bands. 802.11b/g/n operates in 2.4 GHz, but 802.11a/n/ac operates in
5 GHz. This fact is used in some Community Networks in order to
separate ordinary and "backbone" nodes:

o Typical routers running mesh firmware in homes, offices, and
public spaces operate at 2.4 GHz.

o Special routers running mesh firmware as well but broadcasting and
receiving on the 5 GHz band are used in point-to-point connections
only. They are helpful to create a "backbone" on the network that
can both connect neighborhoods to one another when reasonable
connections with 2.4 GHz nodes are not possible, and they ensure
that users of 2.4 GHz nodes are within a few hops to strong and
stable connections to the rest of the network.

6.2.1.2. Mobile Technologies

Global System for Mobile Communications (GSM), from ETSI, has also
been used in Alternative Networks as a Layer 2 option, as explained
in [Mexican], [Village], and [Heimerl]. Open source GSM code
projects such as OpenBTS (http://openbts.org) or OpenBSC
(http://openbsc.osmocom.org/trac/) have created an ecosystem with the
participation of several companies such as, e.g., [Rangenetworks],
[Endaga], and [YateBTS]. This enables deployments of voice, SMS, and
Internet services over alternative networks Alternative Networks with an IP-based
backhaul.

Internet navigation is usually restricted to relatively low bit rates
(see, e.g., [Osmocom]). However, leveraging on the evolution of
Third Generation Partnership Project (3GPP) standards, a trend can be
observed towards the integration of 4G [Spectrum] [YateBTS] or 5G
[Openair] functionalities, with significant increase of achievable
bit rates.

Depending on factors such as the allocated frequency band, the
adoption of licensed spectrum can have advantages over the eventually
higher frequencies used for Wi-Fi, in terms of signal propagation
and, consequently, coverage. Other factors favorable to 3GPP
technologies, especially GSM, are the low cost and energy consumption
of handsets, which facilitate its use by low-income communities.

6.2.1.3. Dynamic Spectrum

Some Alternative Networks make use of TV White Spaces [Lysko] -- a
set of UHF and VHF television frequencies that can be utilized by
secondary users in locations where they are unused by licensed
primary users such as television broadcasters. Equipment that makes
use of TV White 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 that 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 White Space communication: (i) the 802.11af
standard [IEEE.802.11AF] -- an adaptation of the 802.11 standard for
TV white space White Space bands -- and (ii) the IEEE 802.22 standard
[IEEE.802.22] for long-range rural communication.

6.2.1.3.1. 802.11af

802.11af [IEEE.802.11AF] 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 Wi-Fi" 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
(Quadrature Amplitude Modulation) but with improved in-building
penetration and outdoor coverage. The maximum data rate achievable
is 426.7 Mbit/s for countries with 6/7 MHz channels and 568.9 Mbit/s
for countries with 8 MHz channels. Coverage is typically limited to
1 km 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 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.

6.2.1.3.2. 802.22

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

The maximum throughput of 802.22 is 22.6 Mbit/s 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 Consumer Premises Equipment (CPE) are sent before slots
destined for nearby CPEs.

Base stations are required to have a Global Positioning System (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 TV white space White Space
channel with the CPE devices. The standard also includes a
coexistence 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.

7. Upper Layers

7.1. Layer 3

7.1.1. IP Addressing

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

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
presented a challenge to Community Networks. However, some of them
have already adopted it, such as ninux.org.

7.1.2. Routing Protocols

As stated in previous sections, Alternative Networks are composed of
possibly different Layer 2 devices, resulting in a mesh of nodes. A
connection between different nodes is not guaranteed, and the link
stability can vary strongly over time. To tackle this, some
Alternative Networks use mesh routing protocols for Mobile Ad Hoc
Networks (MANETs), while other ones use more traditional routing
protocols. Some networks operate multiple routing protocols in
parallel. For example, they may use a mesh protocol inside different
islands and rely on traditional routing protocols to connect these
islands.

7.1.2.1. Traditional Routing Protocols

The Border Gateway Protocol (BGP), as defined by [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 Open Shortest
Path First (OSPF) protocol, as defined by [RFC2328].

7.1.2.2. Mesh Routing Protocols

A large number of Alternative Networks use customized versions of the
Optimized Link State Routing (OLSR) Protocol [RFC3626]. The open
source project [OLSR] has extended the protocol with the Expected
Transmission Count (ETX) metric [Couto] and other features for its
use in Alternative Networks, especially wireless ones. A new version
of the protocol, named OLSRv2 [RFC7181], is becoming used in some
community networks
Community Networks [Barz].

Better Approach To Mobile Ad Hoc Networking (B.A.T.M.A.N.) Advanced
[Seither] is a Layer 2 routing protocol, which creates a bridged
network and allows seamless roaming of clients between wireless
nodes.

Some networks also run the BatMan-eXperimental Version 6 (BMX6)
protocol [Neumann_a], which is based on IPv6 and tries to exploit the
social structure of Alternative Networks.

Babel [RFC6126] is a Layer 3 loop-avoiding distance-vector routing
protocol that is robust and efficient both in wired and wireless mesh
networks.

In [Neumann_b], a study of three proactive mesh routing protocols
(BMX6, OLSR, and Babel) is presented, in terms of scalability,
performance, and stability.

7.2. Transport Layer

7.2.1. Traffic Management When Sharing Network Resources

When network resources are shared (as, e.g., in the networks
explained in Section 5.4), special care has to be taken with the
management of the traffic at upper layers. From a 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. In
some cases, an adequate Active Queue Management (AQM) mechanism that
implements a Less-than-Best-Effort (LBE) [RFC6297] policy for the
user is used to protect the sharer. Achieving LBE behavior requires
the appropriate tuning of well-known mechanisms such as Explicit
Congestion Notification (ECN) [RFC3168], Random Early Detection (RED)
[RFC2309],
[RFC7567], or other more recent AQM mechanisms that aid low latency
such as Controlled Delay (CoDel) [CoDel] and Proportional Integral
controller Enhanced (PIE) [PIE] design.

7.3. Services Provided

This section provides an overview of the services provided by the
network. Many Alternative Networks can be considered Autonomous
Systems, being (or aspiring to be) a part of the Internet.

The services provided can include, but are not limited to:

o Web browsing.

o Email.

o Remote desktop (e.g., using my home computer and my Internet
connection when I am away).

o FTP file sharing (e.g., distribution of software and media).

o VoIP (e.g., with SIP).

o Peer-to-Peer (P2P) file sharing.

o Public video cameras.

o DNS.

o Online game servers.

o Jabber instant messaging.

o Weather stations.

o Network monitoring.

o Videoconferencing/streaming.

o Radio streaming.

o Message/bulletin board.

o Local cloud storage services.

Due to bandwidth limitations, some services (file sharing, VoIP,
etc.) may not be allowed in some Alternative Networks. In some of
these cases, a number of federated proxies provide web-browsing
service for the users.

Some specialized services have been specifically developed for
Alternative Networks:

o Inter-network peering/VPNs
(e.g., https://wiki.freifunk.net/IC-VPN).

o Community-oriented portals (e.g., http://tidepools.co/).

o Network monitoring/deployment/maintenance platforms.

o VoIP sharing between networks, allowing cheap calls between
countries.

o Sensor networks and citizen science built by adding sensors to
devices.

o Community radio/TV stations.

Other services (e.g., local wikis as used in community portals; see
https://localwiki.org) can also provide useful information when
supplied through an alternative network, Alternative Network, although they were not
specifically created for them.

7.3.1. 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.

Many community networks Community Networks also use VPNs to connect multiple disjoint
parts of their networks together. In some others, every node
establishes a VPN tunnel as well.

7.3.2. Other Facilities

Other facilities, such as NTP or Internet Relay Chat (IRC) servers
may also be present in Alternative Networks.

7.4. Security Considerations

No security issues have been identified for this document.

8. Informative References

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Acknowledgements

This work has been partially funded by the CONFINE European
Commission project (FP7 - 288535). Arjuna Sathiaseelan and Andres
Arcia Moret were funded by the EU H2020 RIFE project (Grant Agreement
no: 644663). Jose Saldana was funded by the EU H2020 Wi-5 project
(Grant Agreement no: 644262).

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: Panayotis Antoniadis, Paul M. Aoki,
Roger Baig, Jaume Barcelo, Steven G. Huter, Aldebaro Klautau, Rohan
Mahy, Vesna Manojlovic, Mitar Milutinovic, Henning Schulzrinne, Rute
Sofia, and Dirk Trossen.

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

Contributors

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

Phone: +34 934016807 93 401 6807
Email: leandro@ac.upc.edu

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

Phone: 0027219592562 +27 (0)21 959 2562
Email: crey-moreno@uwc.ac.za

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
Network Startup Resource Center
Lunenburg, Nova Scotia
Canada

Phone: +1 902 529 0046
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
Javier Simo-Reigadas
Escuela Tecnica Superior de Ingenieria de Telecomunicacion
Campus de Fuenlabrada
Universidad Rey Juan Carlos
Madrid
Spain

Phone: +34 91 488 8428
Fax: +34 91 488 7500
Email: javier.simo@urjc.es

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
University of Cambridge
15 JJ Thomson Avenue
Cambridge FE04
United Kingdom

Phone: +44 (0) 1223 763610
Email: andres.arcia@cl.cam.ac.uk

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

Phone: +32 3 265 38 64
Email: bart.braem@iminds.be
Ermanno Pietrosemoli
The Abdus Salam ICTP
Via Beirut 7
Trieste 34151
Italy

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

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
The Abdus Salam ICTP
Strada Costiera 11
Trieste 34100
Italy

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