Alternative Network Deployments: Taxonomy, characterization, technologies and architectures
draft-irtf-gaia-alternative-network-deployments-03

Abstract

This document presents a taxonomy of "Alternative Network Deployments", and a set of definitions and shared properties. It also surveys the technologies employed in these networks, and their differing architectural characteristics.

The term "Alternative Network Deployments" includes a set of network access models that have emerged in the last decade. These networks aim to bring Internet connectivity to people, using topological, architectural and business models different from the so-called "traditional" ones, where a company deploys or leases the network infrastructure for connecting the users, who pay a subscription fee to be connected and make use of it.

Several initiatives throughout the world have built large scale Alternative 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 alternate networks.

The emergence of these networks has been motivated by a variety of factors such as the reluctance of network operators to provide wired and cellular infrastructures to rural/remote areas. In these cases, the networks have self-sustaining business models that provide more localized communication services as well as Internet backhaul support through peering agreements with traditional network operators. In other cases, networks are built as a complement to commercial Internet access provided by "traditional" network operators.

The present classification considers extant network models such as Community Networks, which are self-organized and decentralized networks wholly owned by the community; networks owned by individuals who act as Wireless Internet Service Providers (WISPs); networks owned by individuals but leased out to network operators who use them 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.

Different criteria are used in order to build a classification e.g., the ownership of the equipment, the way the network is organized, the participatory model, the extensibility, if they are driven by a community, a company or a local stakeholder (public or private), etc.

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

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Table of Contents

• 1. Introduction
• 1.1. Traditional networks
• 1.2. Alternative Networks
• 2. General Considerations Regarding Alternative Networks
• 2.1. Digital Divide and Alternative Networks
• 2.2. Urban vs. Rural Areas
• 2.3. Gap between Demand and Provision of Communications Services
• 2.4. Topology patterns followed by Alternative Networks
• 3. Classification criteria
• 3.1. Commercial model / promoter
• 3.2. Goals and motivation
• 3.3. Administrative model
• 3.4. Technologies employed
• 3.5. Typical scenarios
• 4. Classification of Alternative Networks
• 4.1. Community Networks
• 4.1.1. Free Networks
• 4.2. Wireless Internet Service Providers WISPs
• 4.3. Shared infrastructure model
• 4.4. Crowdshared approaches, led by the users and third party stakeholders
• 4.5. Testbeds for research purposes
• 5. Technologies employed
• 5.1. Wired
• 5.2. Wireless
• 5.2.1. Media Access Control (MAC) Protocols for Wireless Links
• 5.2.1.1. 802.11 (Wi-Fi)
• 5.2.1.2. GSM
• 5.2.1.3. Dynamic Spectrum
• 6. Upper layers
• 6.1. Layer 3
• 6.1.1. IP addressing
• 6.1.2. Routing protocols
• 6.1.2.1. Traditional routing protocols
• 6.1.2.2. Mesh routing protocols
• 6.2. Transport layer
• 6.2.1. Traffic Management when sharing network resources
• 6.3. Services provided
• 6.3.1. Intranet services
• 6.3.2. Access to the Internet
• 6.3.2.1. Web browsing proxies
• 6.3.2.2. Use of VPNs
• 7. Acknowledgements
• 8. Contributing Authors
• 9. IANA Considerations
• 10. Security Considerations
• 11. Informative References
• Authors' Addresses

1. Introduction

Several initiatives throughout the world have built 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 alternate networks. These networks constitute an alternative to traditional network operator deployments.

There are several types of alternate deployments: Community Networks are self-organized and decentralized networks wholly owned by the community; networks owned by individuals who act as Wireless Internet Service Providers (WISPs); networks owned by individuals but leased out to network operators who use such networks as a low cost medium to reach the underserved population, and finally there are networks that provide connectivity by sharing wireless resources of the users.

The emergence of these networks has been motivated by a variety of factors such as the reluctance of network operators to provide wired and cellular infrastructures to rural/remote areas [Pietrosemoli]. In these cases, the networks have self-sustaining business models that provide more localized communication services as well as Internet backhaul support through peering agreements with traditional network operators. In other cases, they are built as a complement and an alternative to commercial Internet access provided by "traditional" network operators.

One of the aims of the Global Access to the Internet for All (GAIA) IRTF 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." In line with this objective, this document proposes a classification of these "Alternative Network Deployments". This term includes a set of network access models that have emerged in the last decade with the aim of bringing Internet connectivity to people, following topological, architectural and business models that differ from the so-called "traditional" ones, where a company deploys the infrastructure connecting the users, who pay a subscription fee to be connected and make use of it. The present document is intended to provide a broad overview of initiatives, technologies and approaches employed in these networks. References describing each kind of network are also provided.

1.1. Traditional networks

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

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

- Top-down control of the network and centralized approaches are used.

- They require a substantial investment in infrastructure.

- Users in traditional networks tend to be passive consumers, as opposed to active stakeholders, in the network design, deployment, operation and maintenance.

1.2. Alternative Networks

The definition of an "alternative network" in this document is negative: a network that does not have the characteristics of "traditional networks".

2. General Considerations Regarding Alternative Networks

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

2.1. Digital Divide and Alternative Networks

Although there is no consensus on a precise definition for the term "developing country", it is generally used to refer to nations with a relatively lower standard of living. Developing countries have also been defined as those which are in transition from traditional lifestyles towards the modern lifestyle which began in the Industrial Revolution. When it comes to quantify to which extent a country is a developing country, the Human Development Index has been proposed by the United Nations in order to consider the Gross National Income (GNI), the life expectancy and the education level of the population in a single indicator. Additionally, the Gini Index (World Bank estimate) may be used to measure the inequality, as it estimates the dispersion of the national income (see http://data.worldbank.org/indicator/SI.POV.GINI).

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

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

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

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

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

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

2.2. Urban vs. Rural Areas

The Digital Divide presented in the previous section is not only present between countries, but within them too. This is especially the case for rural inhabitants, who represent approximately 55% of the world's population, 78% of them in developing countries. Although it is impossible to generalize among them, there exist some common features that have determined the availability of ICT infrastructure in these regions. The disposable income of rural dwellers is lower than those inhabiting urban areas, with many surviving on a subsistence economy. Many of them are located in geographies difficult to access and exposed to extreme weather conditions. This has resulted in the almost complete lack of electrical infrastructure. This context, together with relatively low population density, discourages telecommunications operators from providing similar services to those provided to urban dwellers, since they do not deem them profitable.

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

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

2.3. Gap between Demand and Provision of Communications Services

Beyond the Digital Divide, either international or domestic, there are many situations in which the market fails to provide the information and communications services demanded by the population. When this happens permanently in an area, citizens may be compelled to take a more active part in the design and implementation of ICT solutions, hence promoting Alternative Networks.

2.4. Topology patterns followed by Alternative Networks

Alternative Networks, considered self-managed and self-sustained, follow different topology patterns [Vega]. 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. 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] 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.

3. Classification criteria

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

3.1. Commercial model / promoter

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

• A community of users.
• A public stakeholder.
• A private company.
• Supporters of a crowdshared approach.
• A community that already owns some infrastructure shares it with an operator, which uses it for backhauling purposes.
• A research or academic entity.

3.2. Goals and motivation

Alternative networks can also be classified according to the underlying motivation for them, e.g., addressing deployment and usage hurdles:

• Reducing initial capital expenditures (for the network and the end user, or both).
• Providing additional sources of capital (beyond the traditional carrier-based financing).
• Reducing on-going operational costs (such as backhaul or network administration)
• Leveraging expertise.
• Reducing hurdles to adoption (digital literacy; literacy in general; relevance, etc.)
• Extending coverage to underserved areas (users and communities).
• Network neutrality guarantees.

3.3. Administrative model

• Centralized.
• Distributed.

3.4. Technologies employed

• Standard Wi-Fi.
• Wi-Fi modified for long distances (WiLD), either with CSMA/CA or with an alternative TDMA MAC [Simo_b].
• 802.16-compliant systems over non-licensed bands.
• Dynamic Spectrum Solutions (e.g. based on the use of white spaces).
• Satellite solutions.
• Low-cost optical fiber systems.

3.5. Typical scenarios

The scenarios where Alternative Networks are usually deployed can be:

• Urban.
• Rural.
• Rural in developing countries.

4. 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.

In some cases, real examples of Alternative Networks are cited.

4.1. Community Networks

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
Village Telco Limited


Halifax
Canada

Phone:
Email: stevesong@nsrc.org  

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

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

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