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Is this intentional? Checking references for intended status: Informational ---------------------------------------------------------------------------- == Outdated reference: A later version (-10) exists of draft-ietf-aqm-codel-02 == Outdated reference: A later version (-10) exists of draft-ietf-aqm-pie-03 -- Obsolete informational reference (is this intentional?): RFC 2309 (Obsoleted by RFC 7567) -- Obsolete informational reference (is this intentional?): RFC 6126 (Obsoleted by RFC 8966) Summary: 0 errors (**), 0 flaws (~~), 5 warnings (==), 3 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Global Access to the Internet for All J. Saldana, Ed. 3 Internet-Draft University of Zaragoza 4 Intended status: Informational A. Arcia-Moret 5 Expires: January 18, 2017 University of Cambridge 6 B. Braem 7 iMinds 8 E. Pietrosemoli 9 The Abdus Salam ICTP 10 A. Sathiaseelan 11 University of Cambridge 12 M. Zennaro 13 The Abdus Salam ICTP 14 July 17, 2016 16 Alternative Network Deployments: Taxonomy, characterization, 17 technologies and architectures 18 draft-irtf-gaia-alternative-network-deployments-08 20 Abstract 22 This document presents a taxonomy of a set of "Alternative Network 23 Deployments" that emerged in the last decade with the aim of bringing 24 Internet connectivity to people or for providing local communication 25 infrastructure to serve various complementary needs and objectives. 26 They employ architectures and topologies different from those of 27 mainstream networks, and rely on alternative governance and business 28 models. 30 The document also surveys the technologies deployed in these 31 networks, and their differing architectural characteristics, 32 including a set of definitions and shared properties. 34 The classification considers models such as Community Networks, 35 Wireless Internet Service Providers (WISPs), networks owned by 36 individuals but leased out to network operators who use them as a 37 low-cost medium to reach the underserved population, networks that 38 provide connectivity by sharing wireless resources of the users and 39 rural utility cooperatives. 41 Status of This Memo 43 This Internet-Draft is submitted in full conformance with the 44 provisions of BCP 78 and BCP 79. 46 Internet-Drafts are working documents of the Internet Engineering 47 Task Force (IETF). Note that other groups may also distribute 48 working documents as Internet-Drafts. The list of current Internet- 49 Drafts is at http://datatracker.ietf.org/drafts/current/. 51 Internet-Drafts are draft documents valid for a maximum of six months 52 and may be updated, replaced, or obsoleted by other documents at any 53 time. It is inappropriate to use Internet-Drafts as reference 54 material or to cite them other than as "work in progress." 56 This Internet-Draft will expire on January 18, 2017. 58 Copyright Notice 60 Copyright (c) 2016 IETF Trust and the persons identified as the 61 document authors. All rights reserved. 63 This document is subject to BCP 78 and the IETF Trust's Legal 64 Provisions Relating to IETF Documents 65 (http://trustee.ietf.org/license-info) in effect on the date of 66 publication of this document. Please review these documents 67 carefully, as they describe your rights and restrictions with respect 68 to this document. Code Components extracted from this document must 69 include Simplified BSD License text as described in Section 4.e of 70 the Trust Legal Provisions and are provided without warranty as 71 described in the Simplified BSD License. 73 Table of Contents 75 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 76 1.1. Mainstream networks . . . . . . . . . . . . . . . . . . . 4 77 1.2. Alternative Networks . . . . . . . . . . . . . . . . . . 4 78 2. Terms used in this document . . . . . . . . . . . . . . . . . 5 79 3. Scenarios where Alternative Networks are deployed . . . . . . 7 80 3.1. Urban vs. Rural Areas . . . . . . . . . . . . . . . . . . 8 81 3.2. Topology patterns followed by Alternative Networks . . . 9 82 4. Classification criteria . . . . . . . . . . . . . . . . . . . 9 83 4.1. Entity behind the network . . . . . . . . . . . . . . . . 10 84 4.2. Purpose . . . . . . . . . . . . . . . . . . . . . . . . . 10 85 4.3. Governance and sustainability model . . . . . . . . . . . 11 86 4.4. Technologies employed . . . . . . . . . . . . . . . . . . 12 87 4.5. Typical scenarios . . . . . . . . . . . . . . . . . . . . 12 88 5. Classification of Alternative Networks . . . . . . . . . . . 13 89 5.1. Community Networks . . . . . . . . . . . . . . . . . . . 13 90 5.2. Wireless Internet Service Providers, WISPs . . . . . . . 15 91 5.3. Shared infrastructure model . . . . . . . . . . . . . . . 16 92 5.4. Crowdshared approaches, led by the users and third party 93 stakeholders . . . . . . . . . . . . . . . . . . . . . . 18 94 5.5. Rural utility cooperatives . . . . . . . . . . . . . . . 20 95 5.6. Testbeds for research purposes . . . . . . . . . . . . . 21 97 6. Technologies employed . . . . . . . . . . . . . . . . . . . . 21 98 6.1. Wired . . . . . . . . . . . . . . . . . . . . . . . . . . 21 99 6.2. Wireless . . . . . . . . . . . . . . . . . . . . . . . . 21 100 6.2.1. Media Access Control (MAC) Protocols for Wireless 101 Links . . . . . . . . . . . . . . . . . . . . . . . . 22 102 6.2.1.1. 802.11 (Wi-Fi) . . . . . . . . . . . . . . . . . 22 103 6.2.1.2. Mobile technologies . . . . . . . . . . . . . . . 23 104 6.2.1.3. Dynamic Spectrum . . . . . . . . . . . . . . . . 23 105 7. Upper layers . . . . . . . . . . . . . . . . . . . . . . . . 25 106 7.1. Layer 3 . . . . . . . . . . . . . . . . . . . . . . . . . 25 107 7.1.1. IP addressing . . . . . . . . . . . . . . . . . . . . 25 108 7.1.2. Routing protocols . . . . . . . . . . . . . . . . . . 25 109 7.1.2.1. Traditional routing protocols . . . . . . . . . . 25 110 7.1.2.2. Mesh routing protocols . . . . . . . . . . . . . 26 111 7.2. Transport layer . . . . . . . . . . . . . . . . . . . . . 26 112 7.2.1. Traffic Management when sharing network resources . . 26 113 7.3. Services provided . . . . . . . . . . . . . . . . . . . . 27 114 7.3.1. Use of VPNs . . . . . . . . . . . . . . . . . . . . . 28 115 7.3.2. Other facilities . . . . . . . . . . . . . . . . . . 28 116 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 28 117 9. Contributing Authors . . . . . . . . . . . . . . . . . . . . 29 118 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 30 119 11. Security Considerations . . . . . . . . . . . . . . . . . . . 30 120 12. Informative References . . . . . . . . . . . . . . . . . . . 30 121 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 41 123 1. Introduction 125 One of the aims of the Global Access to the Internet for All (GAIA) 126 IRTF research group is "to document and share deployment experiences 127 and research results to the wider community through scholarly 128 publications, white papers, Informational and Experimental RFCs, 129 etc." [GAIA]. In line with this objective, this document proposes a 130 classification of "Alternative Network Deployments". This term 131 includes a set of network access models that have emerged in the last 132 decade with the aim of providing Internet connections, following 133 topological, architectural, governance and business models that 134 differ from the so-called "mainstream" ones, where a company deploys 135 the infrastructure connecting the users, who pay a subscription fee 136 to be connected and make use of it. 138 Several initiatives throughout the world have built these large scale 139 networks, using predominantly wireless technologies (including long 140 distance links) due to the reduced cost of using unlicensed spectrum. 141 Wired technologies such as fiber are also used in some of these 142 networks. 144 The classification considers several types of alternate deployments: 145 Community Networks are self-organized networks wholly owned by the 146 community; networks acting as Wireless Internet Service Providers 147 (WISPs); networks owned by individuals but leased out to network 148 operators who use such networks as a low cost medium to reach the 149 underserved population; networks that provide connectivity by sharing 150 wireless resources of the users; and finally there are some rural 151 utility cooperatives also connecting their members to the Internet. 153 The emergence of these networks has been motivated by a variety of 154 factors such as the lack of wired and cellular infrastructures in 155 rural/remote areas [Pietrosemoli]. In some cases, alternative 156 networks may provide more localized communication services as well as 157 Internet backhaul support through peering agreements with mainstream 158 network operators. In other cases, they are built as a complement or 159 an alternative to commercial Internet access provided by mainstream 160 network operators. 162 The present document is intended to provide a broad overview of 163 initiatives, technologies and approaches employed in these networks, 164 including some real examples. References describing each kind of 165 network are also provided. 167 1.1. Mainstream networks 169 In this document, we will use the term "mainstream networks" to 170 denote those networks sharing these characteristics: 172 o Regarding scale, they are usually large networks spanning entire 173 regions. 175 o Top-down control of the network and centralized approach. 177 o They require a substantial investment in infrastructure. 179 o Users in mainstream networks do not participate in the network 180 design, deployment, operation, governance and maintenance. 182 o Ownership of the network is never vested in the users themselves. 184 1.2. Alternative Networks 186 The term "Alternative Network" proposed in this document refers to 187 the networks that do not share the characteristics of "mainstream 188 network deployments". Therefore, they may share some of the 189 following characteristics: 191 o Relatively small scale (i.e. not spanning entire regions). 193 o Administration may not follow a centralized approach. 195 o They may require a reduced investment in infrastructure, which may 196 be shared by the users, commercial and non-commercial entities. 198 o Users in alternative networks may participate in the network 199 design, deployment, operation and maintenance. 201 o Ownership of the network is often vested in the users. 203 2. Terms used in this document 205 Considering the role that the Internet currently plays in everyday 206 life, this document touches on complex social, political, and 207 economic issues. Some of the concepts and terminology used have been 208 the subject of study of various disciplines outside the field of 209 networking, and responsible for long debates whose resolution is out 210 of the scope of this document. 212 o "Global north" and "global south". Although there is no consensus 213 on the terms to be used when talking about the different 214 development level of countries, we will employ the term "global 215 south" to refer to nations with a relatively lower standard of 216 living. This distinction is normally intended to reflect basic 217 economic country conditions. In common practice, Japan in Asia, 218 Canada and the United States in northern America, Australia and 219 New Zealand in Oceania, and Europe are considered "developed" 220 regions or areas [UN], so we will employ the term "global north" 221 when talking about them. 223 o The "Digital Divide". The following dimensions are considered to 224 be meaningful when measuring the digital development state of a 225 country: infrastructures (availability and affordability), 226 Information and Communications Technology (ICT) sector (human 227 capital and technological industry), digital literacy, legal and 228 regulatory framework and, content and services. A lack of digital 229 development in one or more of these dimensions is what has been 230 referred as the "Digital Divide" [Norris]. It should be noted 231 that this "Divide" is not only present between different 232 countries, but between zones of the same country, despite its 233 degree of development. 235 o "Urban" and "rural" zones. There is no single definition of 236 "rural" or "urban", as each country and various international 237 organizations define these terms differently, mainly based on the 238 number of inhabitants, the population density and the distance 239 between houses [UNStats]. For networking purposes, the primary 240 distinction is likely the average distance between customers, 241 typically measured by population density, as well as the distance 242 to the nearest Internet point-of-presence, i.e., the distance to 243 be covered by "middle mile" or back haul connectivity. Some 244 regions with low average population density may cluster almost all 245 inhabitants into a small number of relatively-dense small towns, 246 for example, while residents may be dispersed more evenly in 247 others. 249 o Demand. In economics, it describes a consumer's desire and 250 willingness to pay a price for a specific good or service. 252 o Provision is the act of making an asset available for sale. In 253 this document we will mainly use it as the act of making a network 254 service available to the inhabitants of a zone. 256 o Underserved area. Area in which the telecommunication market 257 permanently fails to provide the information and communications 258 services demanded by the population. 260 o "Free Networks" [FNF]. A definition of Free Network is proposed 261 by the Free Network Foundation (see https://thefnf.org) as the one 262 that "equitably grants the following freedoms to all: 264 * Freedom 0 - The freedom to communicate for any purpose, without 265 discrimination, interference, or interception. 267 * Freedom 1 - The freedom to grow, improve, communicate across, 268 and connect to the whole network. 270 * Freedom 2- The freedom to study, use, remix, and share any 271 network communication mechanisms, in their most reusable 272 forms." 274 o The principles of Free, Open and Neutral Networks have also been 275 summarized [Baig] this way: 277 * You have the freedom to use the network for any purpose as long 278 as you do not harm the operation of the network itself, the 279 rights of other users, or the principles of neutrality that 280 allow contents and services to flow without deliberate 281 interference. 283 * You have the right to understand the network, to know its 284 components, and to spread knowledge of its mechanisms and 285 principles. 287 * You have the right to offer services and content to the network 288 on your own terms. 290 * You have the right to join the network, and the responsibility 291 to extend this set of rights to anyone according to these same 292 terms. 294 3. Scenarios where Alternative Networks are deployed 296 Different studies have reported that as much as 60% of the people on 297 the planet do not have Internet connectivity [Sprague], 298 [InternetStats]. In addition, those unconnected are unevenly 299 distributed: only 31 percent of the population in "global south" 300 countries had access in 2014, against 80 percent in "global north" 301 countries [WorldBank2016]. This is one of the reasons behind the 302 inclusion of the objective of providing "significantly increase 303 access to ICT and strive to provide universal and affordable access 304 to Internet in LDCs (Less Developed Countries) by 2020," as one of 305 the targets in the Sustainable Development Goals (SDGs) [SDG], 306 considered as a part of "Goal 9. Build resilient infrastructure, 307 promote inclusive and sustainable industrialization and foster 308 innovation." 310 For the purpose of this document, a distinction between "global 311 north" and "global south" zones is made, highlighting the factors 312 related to ICT (Information and Communication Technologies), which 313 can be quantified in terms of: 315 o The availability of both national and international bandwidth, as 316 well as equipment. 318 o The difficulty in paying for the services and the devices required 319 to access the ICTs. 321 o The instability and/or lack of power supply. 323 o The scarcity of qualified staff. 325 o The existence of a policy and regulatory framework that hinders 326 the development of these models in favor of state monopolies or 327 incumbents. 329 In this context, the World Summit of the Information Society [WSIS] 330 aimed at achieving "a people-centred, inclusive and development- 331 oriented Information Society, where everyone can create, access, 332 utilize and share information and knowledge. Therefore, enabling 333 individuals, communities and people to achieve their full potential 334 in promoting their sustainable development and improving their 335 quality of life". It also called upon "governments, private sector, 336 civil society and international organizations" to actively engage to 337 work towards the bridging of the digital divide. 339 Some Alternative Networks have been deployed in underserved areas, 340 where citizens may be compelled to take a more active part in the 341 design and implementation of ICT solutions. However, Alternative 342 Networks (e.g. [Baig]) are also present in some "global north" 343 countries, being built as an alternative to commercial ones managed 344 by mainstream network operators. 346 The consolidation of a number of mature Alternative Networks (e.g. 347 Community Networks) sets a precedent for civil society members to 348 become more active in the search for alternatives to provide 349 themselves with affordable access. Furthermore, Alternative Networks 350 could contribute to bridge the digital divide by increasing human 351 capital and promoting the creation of localised content and services. 353 3.1. Urban vs. Rural Areas 355 The differences presented in the previous section are not only 356 present between countries, but within them too. This is especially 357 the case for rural inhabitants, who represent approximately 55% of 358 the world's population [IFAD2011], 78% of them in "global south" 359 countries [ITU2011]. According to the World Bank, adoption gaps 360 "between rural and urban populations are falling for mobile phones 361 but increasing for the Internet" [WorldBank2016]. 363 Although it is impossible to generalize among them, there exist some 364 common features in rural areas that have prevented incumbent 365 operators from providing access and that, at the same time, challenge 366 the deployment of alternative infrastructures [Brewer], [Nungu], 367 [Simo_c]. For example, a high network latency was reported in 368 [Johnson_b], which could be in the order of seconds during some 369 hours. 371 These challenges include: 373 o Low per capita income, as the local economy is mainly based on 374 subsistence agriculture, farming and fishing. 376 o Scarcity or absence of basic infrastructures, such as electricity, 377 water and access roads. 379 o Low population density and distance (spatial or effective) between 380 population clusters. 382 o Underdeveloped social services, such as healthcare and education. 384 o Lack of adequately educated and trained technicians, and high 385 potential for those (few) trained to leave the community 386 incentivized by better opportunities, higher salaries or the 387 possibility to start their own companies [McMahon]. 389 o High cost of Internet access [Mathee]. 391 o Harsh environments leading to failure in electronic communication 392 devices [Johnson_a], which reduces the reliability of the network. 394 Some of these factors challenge the stability of Alternative Networks 395 and the services they provide: scarcity of spectrum, scale, and 396 heterogeneity of devices. However, the proliferation of Alternative 397 Networks [Baig] together with the raising of low-cost, low- 398 consumption, low-complexity off-the-shelf wireless devices, have 399 allowed and simplified the deployment and maintenance of alternative 400 infrastructures in rural areas. 402 3.2. Topology patterns followed by Alternative Networks 404 Alternative Networks, considered self-managed and self-sustained, 405 follow different topology patterns [Vega_a]. Generally, these 406 networks grow spontaneously and organically, that is, the network 407 grows without specific planning and deployment strategy and the 408 routing core of the network tends to fit a power law distribution. 409 Moreover, these networks are composed of a high number of 410 heterogeneous devices with the common objective of freely connecting 411 and increasing the network coverage and the reliability. Although 412 these characteristics increase the entropy (e.g., by increasing the 413 number of routing protocols), they have resulted in an inexpensive 414 solution to effectively increase the network size. One such example 415 is Guifi.net [Vega_a] which has had an exponential growth rate in the 416 number of operating nodes during the last decade. 418 Regularly, rural areas in these networks are connected through long- 419 distance links and/or wireless mesh networks, which in turn conveys 420 the Internet connection to relevant organizations or institutions. 421 In contrast, in urban areas, users tend to share and require mobile 422 access. Since these areas are also likely to be covered by 423 commercial ISPs, the provision of wireless access by Virtual 424 Operators like [Fon] may constitute a way to extend the user capacity 425 to the network. Other proposals like Virtual Public Networks 426 [Sathiaseelan_a] can also extend the service. 428 4. Classification criteria 430 The classification of Alternative Network Deployments, presented in 431 this document, is based on the following criteria: 433 4.1. Entity behind the network 435 The entity (or entities) or individuals behind an Alternative Network 436 can be: 438 o A community of users. 440 o A public stakeholder. 442 o A private company. 444 o Supporters of a crowdshared approach. 446 o A community that already owns the infrastructure and shares it 447 with an operator, who, in turn, may also use it for backhauling 448 purposes. 450 o A research or academic entity. 452 The above actors may play different roles in the design, financing, 453 deployment, governance, and promotion of an alternative network. For 454 example, each of the members of a community network maintains the 455 ownership over the equipment they have contributed, whereas in others 456 there is a single entity, e.g., a private company who owns the 457 equipment, or at least a part of it. 459 4.2. Purpose 461 Alternative Networks can be classified according to their purpose and 462 the benefits they bring compared to mainstream solutions, regarding 463 economic, technological, social or political objectives. These 464 benefits could be enjoyed mostly by the actors involved (e.g., 465 lowering costs or gaining technical expertise) or by the local 466 community (e.g., Internet access in underserved areas) or by the 467 society as a whole (e.g., network neutrality). 469 The benefits provided by Alternative Networks include, but are not 470 limited to: 472 o Extending coverage to underserved areas (users and communities). 474 o Providing affordable Internet access for all. 476 o Reducing initial capital expenditures (for the network and the end 477 user, or both). 479 o Providing additional sources of capital (beyond the traditional 480 carrier-based financing). 482 o Reducing on-going operational costs (such as backhaul or network 483 administration). 485 o Leveraging expertise, and having a place for experimentation and 486 teaching. 488 o Reducing hurdles to adoption (e.g., digital literacy, literacy in 489 general, relevance). 491 o Providing an alternative service in case of natural disasters and 492 other extreme situations. 494 o Community building, social cohesion and quality of life 495 improvement. 497 o Experimentation with alternative governance and ownership models 498 for treating network infrastructures as a commons. 500 o Raising awareness of political debates around issues like network 501 neutrality, knowledge sharing, access to resources, and more. 503 Note that the different purposes of alternative networks can be more 504 or less explicitly stated and they could also evolve over time based 505 on the internal dynamics and external events. For example, the 506 Redhook WiFi network in Brooklyn [Redhook] started as a community 507 network focusing more on local applications and community building 508 [TidePools] but it became widely known when it played a key role as 509 an alternative service available during the Sandy storm [Tech] 510 [NYTimes]. 512 Moreover, especially for those networks with more open and horizontal 513 governance models, the underlying motivations of those involved may 514 be very diverse, ranging from altruistic ones related to the desire 515 of free sharing of Internet connectivity and various forms of 516 activism, to personal benefits from the experience and expertise 517 through the active participation in the deployment and management of 518 a real and operational network. 520 4.3. Governance and sustainability model 522 Different governance models are present in Alternative Networks. 523 They may range from some open and horizontal models, with an active 524 participation of the users (e.g. Community Networks) to a more 525 centralized model, where a single authority (e.g. a company, a public 526 stakeholder) plans and manages the network, even if it is (total or 527 partially) owned by a community. 529 Regarding sustainability, some networks grow "organically," as a 530 result of the new users who join and extend the network, contributing 531 their own hardware. In some other cases, the existence of previous 532 infrastructure (owned by the community or the users) may lower the 533 capital expenditures of an operator, who can therefore provide the 534 service with better economic conditions. 536 4.4. Technologies employed 538 o Standard Wi-Fi. Many Alternative Networks are based on the 539 standard IEEE 802.11 [IEEE.802-11-2012] using the Distributed 540 Coordination Function. 542 o Wi-Fi modified for long distances (WiLD). It can work with either 543 CSMA/CA or an alternative TDMA MAC [Simo_b]. 545 o Time Division Multiple Access (TDMA). It can be combined with a 546 Wi-Fi protocol, in a non-standard way [airMAX]. This 547 configuration allows each client to send and receive data using 548 pre-designated timeslots. 550 o 802.16-compliant (WiMax) [IEEE.802-16.2008] systems over non- 551 licensed bands. 553 o Dynamic Spectrum Solutions (e.g. based on the use of TV white 554 spaces), a set of television frequencies that can be utilized by 555 secondary users in locations where they are unused, e.g., IEEE 556 802.11af [IEEE.802-11AF.2013] or 802.22 [IEEE.802-22.2011]. 558 o Satellite solutions can also be employed to give coverage to wide 559 areas, as proposed in the RIFE project (https://rife-project.eu/). 561 o Low-cost optical fiber systems are also used to connect households 562 in different places. 564 4.5. Typical scenarios 566 The scenarios where Alternative Networks are usually deployed can be 567 classified as: 569 o Urban / Rural areas. 571 o "Global north" / "Global south" countries. 573 5. Classification of Alternative Networks 575 This section classifies Alternative Networks according to the 576 criteria explained previously. Each of them has different incentive 577 structures, maybe common technological challenges, but most 578 importantly interesting usage challenges which feed into the 579 incentives as well as the technological challenges. 581 At the beginning of each subsection, a table is presented including a 582 classification of each network according to the criteria listed in 583 the "Classification criteria" subsection. Real examples of each kind 584 of Alternative Network are cited. 586 5.1. Community Networks 588 +----------------+--------------------------------------------------+ 589 | Entity behind | community | 590 | the network | | 591 +----------------+--------------------------------------------------+ 592 | Purpose | all the goals listed in Section 4.2 may be | 593 | | present | 594 +----------------+--------------------------------------------------+ 595 | Governance and | participatory administration model: non- | 596 | sustainability | centralized and open building and maintenance; | 597 | model | users may contribute their own hardware | 598 +----------------+--------------------------------------------------+ 599 | Technologies | Wi-Fi [IEEE.802-11-2012] (standard and non- | 600 | employed | standard versions), optical fiber | 601 +----------------+--------------------------------------------------+ 602 | Typical | urban and rural | 603 | scenarios | | 604 +----------------+--------------------------------------------------+ 606 Table 1: Community Networks' characteristics summary 608 Community Networks are non-centralized, self-managed networks sharing 609 these characteristics: 611 o They start and grow organically, they are open to participation 612 from everyone, sharing an open participation agreement. Community 613 members directly contribute active (not just passive) network 614 infrastructure. The network grows as new hosts and links are 615 added. 617 o Knowledge about building and maintaining the network and ownership 618 of the network itself is non-centralized and open. Different 619 degrees of centralization can be found in Community Networks. In 620 some of them, a shared platform (e.g. a web site) may exist where 621 minimum coordination is performed. Community members with the 622 right permissions have an obvious and direct form of 623 organizational control over the overall organization of the 624 network (e.g. IP addresses, routing, etc.) in their community 625 (not just their own participation in the network). 627 o The network can serve as a backhaul for providing a whole range of 628 services and applications, from completely free to even commercial 629 services. 631 Hardware and software used in Community Networks can be very diverse 632 and customized, even inside one network. A Community Network can 633 have both wired and wireless links. Multiple routing protocols or 634 network topology management systems may coexist in the network. 636 These networks grow organically, since they are formed by the 637 aggregation of nodes belonging to different users. A minimal 638 governance infrastructure is required in order to coordinate IP 639 addressing, routing, etc. Several examples of Community Networks are 640 described in [Braem]. A technological analysis of a community 641 network is presented in [Vega_b], focused on technological network 642 diversity, topology characteristics, the evolution of the network 643 over time, robustness and reliability, and networking service 644 availability. 646 These networks follow a participatory administration model, which has 647 been shown to be effective in connecting geographically dispersed 648 people, thus enhancing and extending digital Internet rights. 650 Users adding new infrastructure (i.e. extensibility) can be used to 651 formulate another definition: A Community Network is a network in 652 which any participant in the system may add link segments to the 653 network in such a way that the new segments can support multiple 654 nodes and adopt the same overall characteristics as those of the 655 joined network, including the capacity to further extend the network. 656 Once these link segments are joined to the network, there is no 657 longer a meaningful distinction between the previous and the new 658 extent of the network. The term "participant" refers to an 659 individual, who may become the user, provider and manager of the 660 network at the same time. 662 In Community Networks, profit can only be made by offering services 663 and not simply by supplying the infrastructure, because the 664 infrastructure is neutral, free, and open (mainstream Internet 665 Service Providers base their business on the control of the 666 infrastructure). In Community Networks, everybody usually keeps the 667 ownership of what he/she has contributed, or leaves the stewardship 668 of the equipment to the network as a whole, (the commons), even 669 loosing track of the ownership of a particular equipment itself, in 670 favor of the community. 672 The majority of Community Networks comply with the definition of Free 673 Network, included in Section 2. 675 5.2. Wireless Internet Service Providers, WISPs 677 +-----------------+-------------------------------------------------+ 678 | Entity behind | company | 679 | the network | | 680 +-----------------+-------------------------------------------------+ 681 | Purpose | to serve underserved areas; to reduce capital | 682 | | expenditures in Internet access; to provide | 683 | | additional sources of capital | 684 +-----------------+-------------------------------------------------+ 685 | Governance and | operated by a company that provides the | 686 | sustainability | equipment; centralized administration | 687 | model | | 688 +-----------------+-------------------------------------------------+ 689 | Technologies | wireless e.g. [IEEE.802-11-2012], | 690 | employed | [IEEE.802-16.2008], unlicensed frequencies | 691 +-----------------+-------------------------------------------------+ 692 | Typical | rural (urban deployments also exist) | 693 | scenarios | | 694 +-----------------+-------------------------------------------------+ 696 Table 2: WISPs' characteristics summary 698 WISPs are commercially-operated wireless Internet networks that 699 provide Internet and/or Voice Over Internet (VoIP) services. They 700 are most common in areas not covered by mainstream telcos or ISPs. 701 WISPs mostly use wireless point-to-multipoint links using unlicensed 702 spectrum but often must resort to licensed frequencies. Use of 703 licensed frequencies is common in regions where unlicensed spectrum 704 is either perceived to be crowded, or too unreliable to offer 705 commercial services, or where unlicensed spectrum faces regulatory 706 barriers impeding its use. 708 Most WISPs are operated by local companies responding to a perceived 709 market gap. There is a small but growing number of WISPs, such as 710 [Airjaldi] in India, that have expanded from local service into 711 multiple locations. 713 Since 2006, the deployment of cloud-managed WISPs has been possible 714 with hardware from companies such as [Meraki] and later [OpenMesh] 715 and others. Until recently, however, most of these services have 716 been aimed at "global north" markets. In 2014 a cloud-managed WISP 717 service aimed at "global south" markets was launched [Everylayer]. 719 5.3. Shared infrastructure model 721 +----------------+--------------------------------------------------+ 722 | Entity behind | shared: companies and users | 723 | the network | | 724 +----------------+--------------------------------------------------+ 725 | Purpose | to eliminate a capital expenditures barrier (to | 726 | | operators); lower the operating expenses | 727 | | (supported by the community); to extend coverage | 728 | | to underserved areas | 729 +----------------+--------------------------------------------------+ 730 | Governance and | the community rents the existing infrastructure | 731 | sustainability | to an operator | 732 | model | | 733 +----------------+--------------------------------------------------+ 734 | Technologies | wireless in non-licensed bands, [WiLD] and/or | 735 | employed | low-cost fiber, mobile femtocells | 736 +----------------+--------------------------------------------------+ 737 | Typical | rural areas, and more particularly rural areas | 738 | scenarios | in "global south" regions | 739 +----------------+--------------------------------------------------+ 741 Table 3: Shared infrastructure characteristics summary 743 In mainstream networks, the operator usually owns the 744 telecommunications infrastructure required for the service, or 745 sometimes rents infrastructure to/from other companies. The problem 746 arises in large areas with low population density, in which neither 747 the operator nor other companies have deployed infrastructure and 748 such deployments are not likely to happen due to the low potential 749 return on investment. 751 When users already own deployed infrastructure, either individually 752 or as a community, sharing that infrastructure with an operator can 753 benefit both parties and is a solution that has been deployed in some 754 areas. For the operator, this provides a significant reduction in 755 the initial investment needed to provide services in small rural 756 localities because capital expenditure is only associated with the 757 access network. Renting capacity in the users' network for 758 backhauling only requires an increment in the operating expenditure. 759 This approach also benefits the users in two ways: they obtain 760 improved access to telecommunications services that would not be 761 accessible otherwise, and they can derive some income from the 762 operator that helps to offset the network's operating costs, 763 particularly for network maintenance. 765 One clear example of the potential of the "shared infrastructure 766 model" nowadays is the deployment of 3G services in rural areas in 767 which there is a broadband rural community network. Since the 768 inception of femtocells (small, low-power cellular base stations), 769 there are complete technical solutions for low-cost 3G coverage using 770 the Internet as a backhaul. If a user or community of users has an 771 IP network connected to the Internet with some excess capacity, 772 placing a femtocell in the user premises benefits both the user and 773 the operator, as the user obtains better coverage and the operator 774 does not have to support the cost of the backhaul infrastructure. 775 Although this paradigm was conceived for improved indoor coverage, 776 the solution is feasible for 3G coverage in underserved rural areas 777 with low population density (i.e. villages), where the number of 778 simultaneous users and the servicing area are small enough to use 779 low-cost femtocells. Also, the amount of traffic produced by these 780 cells can be easily transported by most community broadband rural 781 networks. 783 Some real examples can be referenced in the TUCAN3G project, which 784 deployed demonstrator networks in two regions in the Amazon forest in 785 Peru [Simo_d]. In these networks [Simo_a], the operator and several 786 rural communities cooperated to provide services through rural 787 networks built up with WiLD links [WiLD]. In these cases, the 788 networks belong to the public health authorities and were deployed 789 with funds come from international cooperation for telemedicine 790 purposes. Publications that justify the feasibility of this approach 791 can also be found on that website. 793 5.4. Crowdshared approaches, led by the users and third party 794 stakeholders 796 +----------------+--------------------------------------------------+ 797 | Entity behind | community, public stakeholders, private | 798 | the network | companies, supporters of a crowdshared approach | 799 +----------------+--------------------------------------------------+ 800 | Purpose | sharing connectivity and resources | 801 +----------------+--------------------------------------------------+ 802 | Governance and | users share their capacity, coordinated by a | 803 | sustainability | Virtual Network Operator (VNO); different models | 804 | model | may exist, depending on the nature of the VNO | 805 +----------------+--------------------------------------------------+ 806 | Technologies | Wi-Fi [IEEE.802-11-2012] | 807 | employed | | 808 +----------------+--------------------------------------------------+ 809 | Typical | urban and rural | 810 | scenarios | | 811 +----------------+--------------------------------------------------+ 813 Table 4: Crowdshared approaches characteristics summary 815 These networks can be defined as a set of nodes whose owners share 816 common interests (e.g. sharing connectivity; resources; peripherals) 817 regardless of their physical location. They conform to the following 818 approach: the home router creates two wireless networks: one of them 819 is normally used by the owner, and the other one is public. A small 820 fraction of the bandwidth is allocated to the public network, to be 821 employed by any user of the service in the immediate area. Some 822 examples are described in [PAWS] and [Sathiaseelan_c]. Other 823 examples are found in the networks created and managed by City 824 Councils (e.g., [Heer]). The "openwireless movement" 825 (https://openwireless.org/) also promotes the sharing of private 826 wireless networks. 828 Some companies [Fon] also promote the use of Wi-Fi routers with dual 829 access: a Wi-Fi network for the user, and a shared one. Adequate AAA 830 policies are implemented, so people can join the network in different 831 ways: they can buy a router, so they share their connection and in 832 turn they get access to all the routers associated with the 833 community. Some users can even get some revenue every time another 834 user connects to their Wi-Fi access point. Users that are not part 835 of the community can buy passes in order to use the network. Some 836 mainstream telecommunications operators collaborate with these 837 communities, by including the functionality required to create the 838 two access networks in their routers. Some of these efforts are 839 surveyed in [Shi]. 841 The elements involved in a crowd-shared network are summarized below: 843 o Interest: a parameter capable of providing a measure (cost) of the 844 attractiveness of a node in a specific location, at a specific 845 instance in time. 847 o Resources: A physical or virtual element of a global system. For 848 instance, bandwidth; energy; data; devices. 850 o The owner: End users who sign up for the service and share their 851 network capacity. As a counterpart, they can access another 852 owners' home network capacity for free. The owner can be an end 853 user or an entity (e.g. operator; virtual operator; municipality) 854 that is to be made responsible for any actions concerning his/her 855 device. 857 o The user: a legal entity or an individual using or requesting a 858 publicly available electronic communications' service for private 859 or business purposes, without necessarily having subscribed to 860 such service. 862 o The Virtual Network Operator (VNO): An entity that acts in some 863 aspects as a network coordinator. It may provide services such as 864 initial authentication or registration, and eventually, trust 865 relationship storage. A VNO is not an ISP given that it does not 866 provide Internet access (e.g. infrastructure; naming). A VNO is 867 not an Application Service Provider (ASP) either since it does not 868 provide user services. Virtual Operators may also be stakeholders 869 with socio-environmental objectives. They can be local 870 governments, grass-roots user communities, charities, or even 871 content operators, smart grid operators, etc. They are the ones 872 who actually run the service. 874 o Network operators, who have a financial incentive to lease out 875 unused capacity [Sathiaseelan_b] at a lower cost to the VNOs. 877 VNOs pay the sharers and the network operators, thus creating an 878 incentive structure for all the actors: the end users get money for 879 sharing their network, the network operators are paid by the VNOs, 880 who in turn accomplish their socio-environmental role. 882 5.5. Rural utility cooperatives 884 +----------------------+--------------------------------------------+ 885 | Entity behind the | rural utility cooperative | 886 | network | | 887 +----------------------+--------------------------------------------+ 888 | Purpose | to serve underserved areas; to reduce | 889 | | capital expenditures in Internet access | 890 +----------------------+--------------------------------------------+ 891 | Governance and | the cooperative partners with an ISP who | 892 | sustainability model | manages the network | 893 +----------------------+--------------------------------------------+ 894 | Technologies | wired (fiber) and wireless | 895 | employed | | 896 +----------------------+--------------------------------------------+ 897 | Typical scenarios | rural | 898 +----------------------+--------------------------------------------+ 900 Table 5: Rural utility cooperatives' characteristics summary 902 A utility cooperative is a type of cooperative that delivers a public 903 utility to its members. For example, in the United States, rural 904 electric cooperatives have provided electric service starting in the 905 1930s, especially in areas where investor-owned utility would not 906 provide service, believing there would be insufficient revenue to 907 justify the capital expenditures required. Similarly, in many 908 regions with low population density, traditional Internet services 909 providers such as telephone companies or cable TV companies are 910 either not providing service at all or only offer low-speed DSL 911 service. Some rural electric cooperatives started installing fiber 912 optic lines to run their smart grid applications, but they found they 913 could provide fiber-based broadband to their members at little 914 additional cost [Cash]. In some of these cases, rural electric 915 cooperatives have partnered with local ISPs to provide Internet 916 connection to their members [Carlson]. More information about these 917 utilities and their management can be found in [NewMexico] and 918 [Mitchell]. 920 5.6. Testbeds for research purposes 922 +------------------+------------------------------------------------+ 923 | Entity behind | research / academic entity | 924 | the network | | 925 +------------------+------------------------------------------------+ 926 | Purpose | research | 927 +------------------+------------------------------------------------+ 928 | Governance and | the management is initially coordinated by the | 929 | sustainability | research entity, but it may end up in a | 930 | model | different model | 931 +------------------+------------------------------------------------+ 932 | Technologies | wired and wireless | 933 | employed | | 934 +------------------+------------------------------------------------+ 935 | Typical | urban and rural | 936 | scenarios | | 937 +------------------+------------------------------------------------+ 939 Table 6: Testbeds' characteristics summary 941 In some cases, the initiative to start the network is not from the 942 community, but from a research entity (e.g. a university), with the 943 aim of using it for research purposes [Samanta], [Bernardi]. 945 The administration of these networks may start being centralized in 946 most cases (administered by the academic entity) and may end up in a 947 non-centralized model in which other local stakeholders assume part 948 of the network administration [Rey]. 950 6. Technologies employed 952 6.1. Wired 954 In many ("global north" or "global south") countries it may happen 955 that national service providers decline to provide connectivity to 956 tiny and isolated villages. So in some cases the villagers have 957 created their own optical fiber networks. This is the case in 958 Lowenstedt in Germany [Lowenstedt], or some parts of Guifi.net 959 [Cerda-Alabern]. 961 6.2. Wireless 963 The vast majority of Alternative Network Deployments are based on 964 different wireless technologies [WNDW]. Below we summarize the 965 options and trends when using these features in Alternative Networks. 967 6.2.1. Media Access Control (MAC) Protocols for Wireless Links 969 Different protocols for Media Access Control, which also include 970 physical layer (PHY) recommendations, are widely used in Alternative 971 Network Deployments. Wireless standards ensure interoperability and 972 usability to those who design, deploy and manage wireless networks. 973 In addition, they then ensure low-cost of equipment due to economies 974 of scale and mass production. 976 The standards used in the vast majority of Alternative Networks come 977 from the IEEE Standard Association's IEEE 802 Working Group. 978 Standards developed by other international entities can also be used, 979 such as e.g. the European Telecommunications Standards Institute 980 (ETSI). 982 6.2.1.1. 802.11 (Wi-Fi) 984 The standard we are most interested in is 802.11 a/b/g/n/ac, as it 985 defines the protocol for Wireless LAN. It is also known as "Wi-Fi". 986 The original release (a/b) was issued in 1999 and allowed for rates 987 up to 54 Mbit/s. The latest release (802.11ac) approved in 2013 988 reaches up to 866.7 Mbit/s. In 2012, the IEEE issued the 802.11-2012 989 Standard that consolidates all the previous amendments. The document 990 is freely downloadable from IEEE Standards [IEEE]. 992 The MAC protocol in 802.11 is called CSMA/CA (Carrier Sense Multiple 993 Access with Collision Avoidance) and was designed for short 994 distances; the transmitter expects the reception of an acknowledgment 995 for each transmitted unicast packet; if a certain waiting time is 996 exceeded, the packet is retransmitted. This behavior makes necessary 997 the adaptation of several MAC parameters when 802.11 is used in long 998 links [Simo_b]. Even with this adaptation, distance has a 999 significant negative impact on performance. For this reason, many 1000 vendors implement alternative medium access techniques that are 1001 offered alongside the standard CSMA/CA in their outdoor 802.11 1002 products. These alternative proprietary MAC protocols usually employ 1003 some type of TDMA (Time Division Multiple Access). Low cost 1004 equipment using these techniques can offer high throughput at 1005 distances above 100 kilometers. 1007 Different specifications of 802.11 operate in different frequency 1008 bands. 802.11b/g/n operates in 2.4 GHz, but 802.11a/n/ac operates in 1009 5GHz. This fact is used in some Community Networks in order to 1010 separate ordinary and "backbone" nodes: 1012 o Typical routers running mesh firmware in homes, offices, public 1013 spaces operate at 2.4 GHz. 1015 o Special routers running mesh firmware as well, but broadcasting 1016 and receiving on the 5 GHz band are used in point-to-point 1017 connections only. They are helpful to create a "backbone" on the 1018 network that can both connect neighborhoods to one another when 1019 reasonable connections with 2.4 GHz Nodes are not possible, and 1020 ensure that users of 2.4 GHz nodes are within a few hops to strong 1021 and stable connections to the rest of the network. 1023 6.2.1.2. Mobile technologies 1025 GSM (Global System for Mobile Communications), from ETSI, has also 1026 been used in Alternative Networks as a Layer 2 option, as explained 1027 in [Mexican], [Village], [Heimerl]. Open source GSM code projects 1028 such as OpenBTS (http://openbts.org) or OpenBSC 1029 (http://openbsc.osmocom.org/trac/) have created an ecosystem with the 1030 participation of several companies as e.g. [Rangenetworks], 1031 [Endaga], [YateBTS]. This enables deployments of voice, SMS and 1032 Internet services over alternative networks with an IP-based 1033 backhaul. 1035 Internet navigation is usually restricted to relatively low bit rates 1036 (see e.g. [Osmocom]). However, leveraging on the evolution of 3rd 1037 Generation Partnership Project (3GPP) standards, a trend can be 1038 observed towards the integration of 4G [Spectrum], [YateBTS] or 5G 1039 [Openair] functionalities, with significant increase of achievable 1040 bit rates. 1042 Depending on factors such as the allocated frequency band, the 1043 adoption of licensed spectrum can have advantages over the eventually 1044 higher frequencies used for Wi-Fi, in terms of signal propagation 1045 and, consequently, coverage. Other factors favorable to 3GPP 1046 technologies, especially GSM, are the low cost and energy consumption 1047 of handsets, which facilitate its use by low-income communities. 1049 6.2.1.3. Dynamic Spectrum 1051 Some Alternative Networks make use of TV White Spaces [Lysko] - a set 1052 of UHF and VHF television frequencies that can be utilized by 1053 secondary users in locations where they are unused by licensed 1054 primary users such as television broadcasters. Equipment that makes 1055 use of TV White Spaces is required to detect the presence of existing 1056 unused TV channels by means of a spectrum database and/or spectrum 1057 sensing in order to ensure that no harmful interference is caused to 1058 primary users. In order to smartly allocate interference-free 1059 channels to the devices, cognitive radios are used which are able to 1060 modify their frequency, power and modulation techniques to meet the 1061 strict operating conditions required for secondary users. 1063 The use of the term "White Spaces" is often used to describe "TV 1064 White Spaces" as the VHF and UHF television frequencies were the 1065 first to be exploited on a secondary use basis. There are two 1066 dominant standards for TV white space communication: (i) the 802.11af 1067 standard [IEEE.802-11AF.2013] - an adaptation of the 802.11 standard 1068 for TV white space bands and (ii) the IEEE 802.22 standard 1069 [IEEE.802-22.2011] for long-range rural communication. 1071 6.2.1.3.1. 802.11af 1073 802.11af [IEEE.802-11AF.2013] is a modified version of the 802.11 1074 standard operating in TV White Space bands using Cognitive Radios to 1075 avoid interference with primary users. The standard is often 1076 referred to as White-Fi or "Super Wi-Fi" and was approved in February 1077 2014. 802.11af contains much of the advances of all the 802.11 1078 standards including recent advances in 802.11ac such as up to four 1079 bonded channels, four spatial streams and very high rate 256-QAM 1080 modulation but with improved in-building penetration and outdoor 1081 coverage. The maximum data rate achievable is 426.7 Mbps for 1082 countries with 6/7 MHz channels and 568.9 Mbps for countries with 8 1083 MHz channels. Coverage is typically limited to 1 km although longer 1084 range at lower throughput and using high gain antennas will be 1085 possible. 1087 Devices are designated as enabling stations (Access Points) or 1088 dependent stations (clients). Enabling stations are authorized to 1089 control the operation of a dependent station and securely access a 1090 geolocation database. Once the enabling station has received a list 1091 of available white space channels it can announce a chosen channel to 1092 the dependent stations for them to communicate with the enabling 1093 station. 802.11af also makes use of a registered location server - a 1094 local database that organizes the geographic location and operating 1095 parameters of all enabling stations. 1097 6.2.1.3.2. 802.22 1099 802.22 [IEEE.802-22.2011] is a standard developed specifically for 1100 long range rural communications in TV white space frequencies and 1101 first approved in July 2011. The standard is similar to the 802.16 1102 (WiMax) [IEEE.802-16.2008] standard with an added cognitive radio 1103 ability. The maximum throughput of 802.22 is 22.6 Mbps for a single 1104 8 MHz channel using 64-QAM modulation. The achievable range using 1105 the default MAC scheme is 30 km, however 100 km is possible with 1106 special scheduling techniques. The MAC of 802.22 is specifically 1107 customized for long distances - for example, slots in a frame 1108 destined for more distant Consumer Premises Equipment (CPEs) are sent 1109 before slots destined for nearby CPEs. 1111 Base stations are required to have a Global Positioning System (GPS) 1112 and a connection to the Internet in order to query a geolocation 1113 spectrum database. Once the base station receives the allowed TV 1114 channels, it communicates a preferred operating white space TV 1115 channel with the CPE devices. The standard also includes a co- 1116 existence mechanism that uses beacons to make other 802.22 base 1117 stations aware of the presence of a base station that is not part of 1118 the same network. 1120 7. Upper layers 1122 7.1. Layer 3 1124 7.1.1. IP addressing 1126 Most Community Networks use private IPv4 address ranges, as defined 1127 by [RFC1918]. The motivation for this was the lower cost and the 1128 simplified IP allocation because of the large available address 1129 ranges. 1131 Most known Alternative Networks started in or around the year 2000. 1132 IPv6 was fully specified by then, but almost all Alternative Networks 1133 still use IPv4. A survey [Avonts] indicated that IPv6 rollout 1134 presented a challenge to Community Networks. However, some of them 1135 have already adopted it as e.g. ninux.org. 1137 7.1.2. Routing protocols 1139 As stated in previous sections, Alternative Networks are composed of 1140 possibly different layer 2 devices, resulting in a mesh of nodes. A 1141 onnection between different nodes is not guaranteed and the link 1142 stability can vary strongly over time. To tackle this, some 1143 Alternative Networks use mesh routing protocols for Mobile Ad Hoc 1144 Networks (MANETs), while other ones use more traditional routing 1145 protocols. Some networks operate multiple routing protocols in 1146 parallel. For example, they may use a mesh protocol inside different 1147 islands and rely on traditional routing protocols to connect these 1148 islands. 1150 7.1.2.1. Traditional routing protocols 1152 The Border Gateway Protocol (BGP), as defined by [RFC4271] is used by 1153 a number of Community Networks, because of its well-studied behavior 1154 and scalability. 1156 For similar reasons, smaller networks opt to run the Open Shortest 1157 Path First (OSPF) protocol, as defined by [RFC2328]. 1159 7.1.2.2. Mesh routing protocols 1161 A large number of Alternative Networks use customized versions of the 1162 Optimized Link State Routing Protocol (OLSR) [RFC3626]. The 1163 [olsr.org] open source project has extended the protocol with the 1164 Expected Transmission Count metric (ETX) [Couto] and other features, 1165 for its use in Alternative Networks, especially wireless ones. A new 1166 version of the protocol, named OLSRv2 [RFC7181] is becoming used in 1167 some community networks [Barz]. 1169 B.A.T.M.A.N. Advanced [Seither] is a layer-2 routing protocol, which 1170 creates a bridged network and allows seamless roaming of clients 1171 between wireless nodes. 1173 Some networks also run the BMX6 protocol [Neumann_a], which is based 1174 on IPv6 and tries to exploit the social structure of Alternative 1175 Networks. 1177 Babel [RFC6126] is a layer-3 loop-avoiding distance-vector routing 1178 protocol that is robust and efficient both in wired and wireless mesh 1179 networks. 1181 In [Neumann_b] a study of three proactive mesh routing protocols 1182 (BMX6, OLSR, and Babel) is presented, in terms of scalability, 1183 performance, and stability. 1185 7.2. Transport layer 1187 7.2.1. Traffic Management when sharing network resources 1189 When network resources are shared (as e.g. in the networks explained 1190 in Section 5.4), special care has to be taken with the management of 1191 the traffic at upper layers. From a crowdshared perspective, and 1192 considering just regular TCP connections during the critical sharing 1193 time, the Access Point offering the service is likely to be the 1194 bottleneck of the connection. 1196 This is the main concern of sharers, having several implications. In 1197 some cases, an adequate Active Queue Management (AQM) mechanism that 1198 implements a Lower-than-best-effort (LBE) [RFC6297] policy for the 1199 user is used to protect the sharer. Achieving LBE behavior requires 1200 the appropriate tuning of the well known mechanisms such as Explicit 1201 Congestion Notification (ECN) [RFC3168], or Random Early Detection 1202 (RED) [RFC2309], or other more recent AQM mechanisms such as 1203 Controlled Delay (CoDel) and [I-D.ietf-aqm-codel] PIE (Proportional 1204 Integral controller Enhanced) [I-D.ietf-aqm-pie] that aid low 1205 latency. 1207 7.3. Services provided 1209 This section provides an overview of the services provided by the 1210 network. Many Alternative Networks can be considered Autonomous 1211 Systems, being (or aspiring to be) a part of the Internet. 1213 The services provided can include, but are not limited to: 1215 o Web browsing. 1217 o e-mail. 1219 o Remote desktop (e.g. using my home computer and my Internet 1220 connection when I am away). 1222 o FTP file sharing (e.g. distribution of software and media). 1224 o VoIP (e.g. with SIP). 1226 o P2P file sharing. 1228 o Public video cameras. 1230 o DNS. 1232 o Online games servers. 1234 o Jabber instant messaging. 1236 o Weather stations. 1238 o Network monitoring. 1240 o Videoconferencing / streaming. 1242 o Radio streaming. 1244 o Message / Bulletin board. 1246 o Local cloud storage services. 1248 Due to bandwidth limitations, some services (file sharing, VoIP, 1249 etc.) may not be allowed in some Alternative Networks. In some of 1250 these cases, a number of federated proxies provide web browsing 1251 service for the users. 1253 Some specialized services have been specifically developed for 1254 Alternative Networks: 1256 o Inter-network peering/VPNs (e.g. https://wiki.freifunk.net/IC- 1257 VPN). 1259 o Community oriented portals (e.g. http://tidepools.co/). 1261 o Network monitoring/deployment/maintenance platforms. 1263 o VoIP sharing between networks, allowing cheap calls between 1264 countries. 1266 o Sensor networks and citizen science built by adding sensors to 1267 devices. 1269 o Community radio/TV stations. 1271 Other services (e.g. Local wikis as https://localwiki.org used in 1272 community portals) can also provide useful information when supplied 1273 through an alternative network, although they were not specifically 1274 created for them. 1276 7.3.1. Use of VPNs 1278 Some "micro-ISPs" may use the network as a backhaul for providing 1279 Internet access, setting up VPNs from the client to a machine with 1280 Internet access. 1282 Many community networks also use VPNs to connect multiple disjoint 1283 parts of their networks together. In some others, every node 1284 establishes a VPN tunnel as well. 1286 7.3.2. Other facilities 1288 Other facilities, such as NTP or IRC servers may also be present in 1289 Alternative Networks. 1291 8. Acknowledgements 1293 This work has been partially funded by the CONFINE European 1294 Commission Project (FP7 - 288535). Arjuna Sathiaseelan and Andres 1295 Arcia Moret were funded by the EU H2020 RIFE project (Grant Agreement 1296 no: 644663). Jose Saldana was funded by the EU H2020 Wi-5 project 1297 (Grant Agreement no: 644262). 1299 The editor and the authors of this document wish to thank the 1300 following individuals who have participated in the drafting, review, 1301 and discussion of this memo: Paul M. Aoki, Roger Baig, Jaume 1302 Barcelo, Steven G. Huter, Rohan Mahy, Rute Sofia, Dirk Trossen, 1303 Aldebaro Klautau, Vesna Manojlovic, Mitar Milutinovic, Henning 1304 Schulzrinne, Panayotis Antoniadis. 1306 A special thanks to the GAIA Working Group chairs Mat Ford and Arjuna 1307 Sathiaseelan for their support and guidance. 1309 9. Contributing Authors 1311 Leandro Navarro 1312 U. Politecnica Catalunya 1313 Jordi Girona, 1-3, D6 1314 Barcelona 08034 1315 Spain 1317 Phone: +34 934016807 1318 Email: leandro@ac.upc.edu 1320 Carlos Rey-Moreno 1321 University of the Western Cape 1322 Robert Sobukwe road 1323 Bellville 7535 1324 South Africa 1326 Phone: 0027219592562 1327 Email: crey-moreno@uwc.ac.za 1329 Ioannis Komnios 1330 Democritus University of Thrace 1331 Department of Electrical and Computer Engineering 1332 Kimmeria University Campus 1333 Xanthi 67100 1334 Greece 1336 Phone: +306945406585 1337 Email: ikomnios@ee.duth.gr 1339 Steve Song 1340 Network Startup Resource Center 1341 Lunenburg, Nova Scotia 1342 CANADA 1344 Phone: +1 902 529 0046 1345 Email: stevesong@nsrc.org 1346 David Lloyd Johnson 1347 Meraka, CSIR 1348 15 Lower Hope St 1349 Rosebank 7700 1350 South Africa 1352 Phone: +27 (0)21 658 2740 1353 Email: djohnson@csir.co.za 1355 Javier Simo-Reigadas 1356 Escuela Tecnica Superior de Ingenieria de Telecomunicacion 1357 Campus de Fuenlabrada 1358 Universidad Rey Juan Carlos 1359 Madrid 1360 Spain 1362 Phone: 91 488 8428 / 7500 1363 Email: javier.simo@urjc.es 1365 10. IANA Considerations 1367 This memo includes no request to IANA. 1369 11. Security Considerations 1371 No security issues have been identified for this document. 1373 12. Informative References 1375 [Airjaldi] 1376 Rural Broadband (RBB) Pvt. Ltd., Airjaldi., "Airjaldi 1377 service", Airjaldi web page, https://airjaldi.com/, 2015. 1379 [airMAX] Ubiquiti Networks, Inc., airMAX., "airMAX", airMAX web 1380 page, https://www.ubnt.com/broadband/, 2016. 1382 [Avonts] Avonts, J., Braem, B., and C. Blondia, "A Questionnaire 1383 based Examination of Community Networks", Proceedings IEEE 1384 8th International Conference on Wireless and Mobile 1385 Computing, Networking and Communications (WiMob) pp. 8-15, 1386 2013. 1388 [Baig] Baig, R., Roca, R., Freitag, F., and L. Navarro, 1389 "guifi.net, a crowdsourced network infrastructure held in 1390 common", Computer Networks, vol. 90, no. 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Lear, "Address Allocation for Private Internets", 1665 BCP 5, RFC 1918, DOI 10.17487/RFC1918, February 1996, 1666 . 1668 [RFC2309] Braden, B., Clark, D., Crowcroft, J., Davie, B., Deering, 1669 S., Estrin, D., Floyd, S., Jacobson, V., Minshall, G., 1670 Partridge, C., Peterson, L., Ramakrishnan, K., Shenker, 1671 S., Wroclawski, J., and L. Zhang, "Recommendations on 1672 Queue Management and Congestion Avoidance in the 1673 Internet", RFC 2309, DOI 10.17487/RFC2309, April 1998, 1674 . 1676 [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, 1677 DOI 10.17487/RFC2328, April 1998, 1678 . 1680 [RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition 1681 of Explicit Congestion Notification (ECN) to IP", 1682 RFC 3168, DOI 10.17487/RFC3168, September 2001, 1683 . 1685 [RFC3626] Clausen, T., Ed. and P. Jacquet, Ed., "Optimized Link 1686 State Routing Protocol (OLSR)", RFC 3626, 1687 DOI 10.17487/RFC3626, October 2003, 1688 . 1690 [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. 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IEC Ada Byron Building 1863 Zaragoza 50018 1864 Spain 1866 Phone: +34 976 762 698 1867 Email: jsaldana@unizar.es 1869 Andres Arcia-Moret 1870 University of Cambridge 1871 15 JJ Thomson Avenue 1872 Cambridge FE04 1873 United Kingdom 1875 Phone: +44 (0) 1223 763610 1876 Email: andres.arcia@cl.cam.ac.uk 1878 Bart Braem 1879 iMinds 1880 Gaston Crommenlaan 8 (bus 102) 1881 Gent 9050 1882 Belgium 1884 Phone: +32 3 265 38 64 1885 Email: bart.braem@iminds.be 1887 Ermanno Pietrosemoli 1888 The Abdus Salam ICTP 1889 Via Beirut 7 1890 Trieste 34151 1891 Italy 1893 Phone: +39 040 2240 471 1894 Email: ermanno@ictp.it 1895 Arjuna Sathiaseelan 1896 University of Cambridge 1897 15 JJ Thomson Avenue 1898 Cambridge CB30FD 1899 United Kingdom 1901 Phone: +44 (0)1223 763781 1902 Email: arjuna.sathiaseelan@cl.cam.ac.uk 1904 Marco Zennaro 1905 The Abdus Salam ICTP 1906 Strada Costiera 11 1907 Trieste 34100 1908 Italy 1910 Phone: +39 040 2240 406 1911 Email: mzennaro@ictp.it