Global Access to the Internet for All J. Saldana, Ed.
Internet-Draft University of Zaragoza
Intended status: Informational A. Arcia-Moret
Expires: October 28, 2016 University of Cambridge
B. Braem
iMinds
E. Pietrosemoli
The Abdus Salam ICTP
A. Sathiaseelan
University of Cambridge
M. Zennaro
The Abdus Salam ICTP
April 26, 2016

Alternative Network Deployments: Taxonomy, characterization, technologies and architectures
draft-irtf-gaia-alternative-network-deployments-05

Abstract

This document presents a taxonomy of a set of "Alternative Network Deployments" emerged in the last decade with the aim of bringing Internet connectivity to people or of 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, and networks that provide connectivity by sharing wireless resources of the users.

Status of This Memo

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This Internet-Draft will expire on October 28, 2016.

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Table of Contents

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 connection, 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) 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; and finally there are networks that provide connectivity by sharing wireless resources of the users.

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 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:

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 next characteristics:

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 responsible for long debates whose resolution is out of the scope of this document.

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 percent of the population in "global south" countries had access in 2014, against 80 percent in "global north" countries [WorldBank2016]. This is one of the reasons behind the inclusion of the objective of providing "significantly increase access to ICT and strive to provide universal and affordable access to Internet in LDCs (Less 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 (Information and Communication Technologies), which can be quantified in terms of:

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 localised 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], 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 for 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:

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] has fuelled the creation of low-cost, low-consumption, low-complexity off-the-shelf wireless devices. These devices can simplify 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 example corresponds to Guifi.net [Vega_a] with 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 (the so-called community mesh approach) which in turn conveys 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. Commercial model / promoter

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

The above actors may play different roles in the design, financing, deployment, governance, and promotion of an alternative network. For example, each of the members of a 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. Goals and motivation

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 society as a whole (e.g., Internet access in underserved areas or network neutrality).

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

The underlying motivations of users for developing these networks may include their desire of free sharing of Internet connectivity; the experience of becoming active participants in the deployment and management of a real and operational network; various forms of activism as e.g. looking for network neutrality guarantees, anti-censorship, decentralization to minimize control; creating and sharing of "commons" (i.e. information and knowledge resources that are collectively shared); preferring alternative ownership model (co-owning, co-operating) of the networking infrastructure, etc.

4.3. Administrative model

4.4. Technologies employed

4.5. Typical scenarios

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

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 which 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.






































































































5.1. Community Networks

Community Networks' characteristics summary
Commercial model/promoter community
Goals and motivation all the goals listed in Section 4.2 may be present
Administration non-centralized
Technologies Wi-Fi [IEEE.802-11-2012] (standard and non-standard versions), optical fiber
Typical scenarios urban and rural

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

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. An example of this kind of Community Network is described in [Braem]. A technological analysis of a community network is presented in [Vega_b], focused on technological network diversity, topology characteristics, evolution of the network over time, robustness and reliability, and networking service availability.

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

The fact of the users adding new infrastructure (i.e. extensibility) can be used to formulate another definition: A Community Network is a network in which any participant in the system may add link segments to the network in such a way that the new 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 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 network as a whole, 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.




















































5.2. Wireless Internet Service Providers, WISPs

WISPs' characteristics summary
Commercial model/promoter company
Goals and motivation to serve underserved areas; to reduce capital expenditures in Internet access; to provide additional sources of capital
Administration centralized
Technologies wireless e.g. [IEEE.802-11-2012], [IEEE.802-16.2008], unlicensed frequencies
Typical scenarios rural (urban deployments also exist)

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 telcos 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].






































































































5.3. Shared infrastructure model

Shared infrastructure characteristics summary
Commercial model/promoter shared: companies and users
Goals and motivation to eliminate a capital expenditures barrier (to operators); lower the operating expenses (supported by the community); to extend coverage to underserved areas
Administration Non-centralized
Technologies wireless in non-licensed bands, [WiLD] and/or low-cost fiber, mobile femtocells
Typical scenarios rural areas, and more particularly rural areas in "global south" regions

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 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. 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 belong to the public health authorities and were deployed with funds come 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

Crowdshared approaches characteristics summary
Commercial model/promoter community, public stakeholders, private companies, supporters of a crowdshared approach
Goals and motivation sharing connectivity and resources
Administration Non-centralized
Technologies Wi-Fi [IEEE.802-11-2012]
Typical scenarios urban and rural

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. 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 AAA policies are implemented, so people can join the network in different ways: they can buy a router, so they share their connection and in turn they get access to all the routers associated 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 crowd-shared network are summarized below:

  • 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.
  • Resources: A physical or virtual element of a global system. For instance, bandwidth; energy; data; devices.
  • The owner: End users who sign up for the service and share their network capacity. As a counterpart, they can access another owners' home network capacity for free. The owner can be an end user or an entity (e.g. operator; virtual operator; municipality) that is to be made responsible for any actions concerning his/her device.
  • The user: a legal entity or an individual using or requesting a publicly available electronic communications' service for private or business purposes, without necessarily having subscribed to such service.
  • The Virtual Network Operator (VNO): An entity that acts in some aspects as a network coordinator. It may provide services such as initial authentication or registration, and eventually, trust relationship storage. A VNO is not an ISP given that it does not provide Internet access (e.g. infrastructure; naming). A VNO is not an Application Service Provider (ASP) either since it does not provide user services. Virtual Operators may also be stakeholders with socio-environmental objectives. They can be local governments, grass-roots 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 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.






































































































5.5. Testbeds for research purposes

Testbeds' characteristics summary
Commercial model/promoter research / academic entity
Goals and motivation research
Administration centralized initially, but it may end up in a non-centralized model.
Technologies wired and wireless
Typical scenarios urban and rural

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].

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 in Germany [Lowenstedt], or 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 Media Access Control, 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, then ensure 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, 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 802.11-2012 Standard that consolidates all the previous amendments. The document is freely downloadable from IEEE Standards [IEEE].

The MAC protocol in 802.11 is called CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) and was designed for short distances; the transmitter expects the reception of an acknowledgment for each transmitted unicast packet; 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 (Time Division Multiple Access). 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 5GHz. This fact is used in some Community Networks in order to separate ordinary and "backbone" nodes:

  • Typical routers running mesh firmware in homes, offices, public spaces operate on 2.4 GHz.
  • 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 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

GSM (Global System for Mobile Communications), from ETSI, has also been used in Alternative Networks as a Layer 2 option, as explained in [Mexican], [Village], [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 as e.g. [Rangenetworks], [Endaga], [YateBTS]. This enables deployments of voice, SMS and Internet services over 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 3rd 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 – 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 which are able to modify their frequency, power and modulation techniques to meet the strict operating conditions required for secondary users.

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

6.2.1.3.1. 802.11af

802.11af [IEEE.802-11AF.2013] is a modified version of the 802.11 standard operating in TV White Space bands using Cognitive Radios to avoid interference with primary users. The standard is often referred to as White-Fi or "Super 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 modulation but with improved in-building penetration and outdoor coverage. The maximum data rate achievable is 426.7 Mbps for countries with 6/7 MHz channels and 568.9 Mbps for countries with 8 MHz channels. Coverage is typically limited to 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 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.802-22.2011] is a standard developed specifically for long range rural communications in TV white space frequencies and first approved in July 2011. The standard is similar to the 802.16 (WiMax) [IEEE.802-16.2008] standard with an added cognitive radio ability. The maximum throughput of 802.22 is 22.6 Mbps for a single 8 MHz channel using 64-QAM modulation. The achievable range using the default MAC scheme is 30 km, however 100 km is possible with special scheduling techniques. The MAC of 802.22 is specifically customized for long distances – for example, slots in a frame destined for more distant Consumer Premises Equipment (CPEs) 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 white space TV channel with the CPE devices. The standard also includes a co-existence mechanism that uses beacons to make other 802.22 base stations aware of the presence of a base station that is not part of the same network.

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 as e.g. 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. Connection between different nodes is not guaranteed and the link stability can vary strongly over time. To tackle this, some Alternative Networks use mesh network routing protocols while other networks use more traditional routing protocols. Some networks operate multiple routing protocols in parallel. For example, they 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 Protocol (OLSR) [RFC3626]. The [olsr.org] open source project has extended the protocol with the Expected Transmission Count metric (ETX) [Couto] and other features, for its use in Alternative Networks, especially wireless ones. A new version of the protocol, named OLSRv2 [RFC7188] is becoming used in some community networks [Barz].

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 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 Lower-than-best-effort (LBE) [RFC6297] policy for the user is used to protect the sharer. Achieving LBE behavior requires the appropriate tuning of the well known mechanisms such as Explicit Congestion Notification (ECN) [RFC3168], or Random Early Detection (RED) [RFC2309], or other more recent AQM mechanisms such as Controlled Delay (CoDel) and [I-D.ietf-aqm-codel] PIE (Proportional Integral controller Enhanced) [I-D.ietf-aqm-pie] that aid low latency.

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:

  • Web browsing.
  • e-mail.
  • Remote desktop (e.g. using my home computer and my Internet connection when I am away).
  • FTP file sharing (e.g. distribution of software and media).
  • VoIP (e.g. with SIP).
  • P2P file sharing.
  • Public video cameras.
  • DNS.
  • Online games servers.
  • Jabber instant messaging.
  • Weather stations.
  • Network monitoring.
  • Videoconferencing / streaming.
  • Radio streaming.
  • Message / Bulletin board.

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 especifically developed for Alternative Networks:

  • Inter-network peering/VPNs (e.g. https://wiki.freifunk.net/IC-VPN).
  • Local wikis (e.g. https://localwiki.org).
  • Community oriented portals (e.g. http://tidepools.co/).
  • Network monitoring/deployment/maintenance platforms.
  • VoIP sharing between networks, allowing cheap calls between countries.
  • Sensor networks and citizen science build by adding sensors to devices.
  • Community radio/TV stations.

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.

7.3.2. Other facilities

Other facilities, as NTP or IRC servers may also be present in Alternative Networks.

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

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

9. Contributing Authors

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

Phone: +34 934016807
Email: leandro@ac.upc.edu  
Carlos Rey-Moreno
University of the Western Cape
Robert Sobukwe road
Bellville  7535
South Africa

Phone: 0027219592562
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 Técnica Superior de Ingeniería de Telecomunicación
Campus de Fuenlabrada
Universidad Rey Juan Carlos
Madrid
Spain

Phone: 91 488 8428 / 7500
Email: javier.simo@urjc.es

10. IANA Considerations

This memo includes no request to IANA.

11. Security Considerations

No security issues have been identified for this document.

12. Informative References

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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