idnits 2.17.1 draft-manyfolks-gaia-community-networks-00.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The exact meaning of the all-uppercase expression 'MAY NOT' is not defined in RFC 2119. If it is intended as a requirements expression, it should be rewritten using one of the combinations defined in RFC 2119; otherwise it should not be all-uppercase. == The expression 'MAY NOT', while looking like RFC 2119 requirements text, is not defined in RFC 2119, and should not be used. Consider using 'MUST NOT' instead (if that is what you mean). Found 'MAY NOT' in this paragraph: A Community Network MAY or MAY NOT be organized as a company, but in any case this document only considers those operated and owned by the community members (e.g. as a cooperative). The fact of setting up a company is sometimes an advantage: it not only permits the provision of the service within the current regulatory framework (in some countries, in order to charge for the services, even in a cost-recovery mode only, you need to have a licence), but it also allows to obtain wholesale prices from other operators when peering, which are way cheaper than those offered for normal clients, prices which influence greatly on the uptake of the service and in the financial sustainability of the Community Network. -- The document date (June 18, 2014) is 3597 days in the past. Is this intentional? Checking references for intended status: Informational ---------------------------------------------------------------------------- == Unused Reference: 'Abolhasan' is defined on line 883, but no explicit reference was found in the text Summary: 0 errors (**), 0 flaws (~~), 3 warnings (==), 2 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: December 20, 2014 Universidad de Los Andes 6 B. Braem 7 University of Antwerp - iMinds 8 L. Navarro 9 U. Politecnica Catalunya 10 E. Pietrosemoli 11 Escuela Latinoamericana de Redes 12 C. Rey-Moreno 13 University of the Western Cape 14 A. Sathiaseelan 15 University of Cambridge 16 M. Zennaro 17 Abdus Salam ICTP 18 June 18, 2014 20 Community Networks. Definition and taxonomy 21 draft-manyfolks-gaia-community-networks-00 23 Abstract 25 Several communities have developed initiatives to build large scale, 26 self-organized and decentralized community wireless networks that use 27 wireless technologies (including long distance) due to the reduced 28 cost of using the unlicensed spectrum. This can be motivated by 29 different causes: Sometimes the reluctance, or the impossibility, of 30 network operators to provide wired and cellular infrastructures to 31 rural/remote areas has motivated the rise of these networks. Some 32 other times, they are built as a complement and an alternative to 33 wired Internet access. 35 These community wireless networks have self sustainable business 36 models that provide more localised communication services as well as 37 providing Internet backhaul support through peering agreements with 38 traditional network operators who see such community led networks as 39 a way to extend their reach to rural/remote areas at lower cost. 41 This document defines these networks, summarizes their technological 42 characteristics and classifies them, also talking about their socio- 43 economic sustainability models. 45 There exist other networks, also based on sharing wireless resources 46 of the users, but not built upon the initiative of the users 47 themselves, nor owned by them. The characterization of these 48 networks is not the objective of this document. 50 Status of This Memo 52 This Internet-Draft is submitted in full conformance with the 53 provisions of BCP 78 and BCP 79. 55 Internet-Drafts are working documents of the Internet Engineering 56 Task Force (IETF). Note that other groups may also distribute 57 working documents as Internet-Drafts. The list of current Internet- 58 Drafts is at http://datatracker.ietf.org/drafts/current/. 60 Internet-Drafts are draft documents valid for a maximum of six months 61 and may be updated, replaced, or obsoleted by other documents at any 62 time. It is inappropriate to use Internet-Drafts as reference 63 material or to cite them other than as "work in progress." 65 This Internet-Draft will expire on December 20, 2014. 67 Copyright Notice 69 Copyright (c) 2014 IETF Trust and the persons identified as the 70 document authors. All rights reserved. 72 This document is subject to BCP 78 and the IETF Trust's Legal 73 Provisions Relating to IETF Documents 74 (http://trustee.ietf.org/license-info) in effect on the date of 75 publication of this document. Please review these documents 76 carefully, as they describe your rights and restrictions with respect 77 to this document. Code Components extracted from this document must 78 include Simplified BSD License text as described in Section 4.e of 79 the Trust Legal Provisions and are provided without warranty as 80 described in the Simplified BSD License. 82 Table of Contents 84 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 85 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4 86 1.2. Definition . . . . . . . . . . . . . . . . . . . . . . . 4 87 1.3. Scenarios . . . . . . . . . . . . . . . . . . . . . . . . 4 88 1.3.1. Developing countries . . . . . . . . . . . . . . . . 4 89 1.3.2. Rural areas . . . . . . . . . . . . . . . . . . . . . 6 90 2. Technologies employed . . . . . . . . . . . . . . . . . . . . 7 91 2.1. Antennas . . . . . . . . . . . . . . . . . . . . . . . . 7 92 2.2. Link length . . . . . . . . . . . . . . . . . . . . . . . 8 93 2.3. Layer 2 . . . . . . . . . . . . . . . . . . . . . . . . . 10 94 2.3.1. The 802.11 standard . . . . . . . . . . . . . . . . . 10 95 2.3.2. Deployment planning for 802.11 wireless networks . . 11 96 2.3.3. 802.11af (TVWS) . . . . . . . . . . . . . . . . . . . 13 97 2.3.4. Other options . . . . . . . . . . . . . . . . . . . . 13 99 2.4. Layer 3 . . . . . . . . . . . . . . . . . . . . . . . . . 13 100 2.4.1. IP addressing . . . . . . . . . . . . . . . . . . . . 13 101 2.4.2. Routing protocols . . . . . . . . . . . . . . . . . . 13 102 2.4.2.1. Traditional routing protocols . . . . . . . . . . 13 103 2.4.2.2. Mesh routing protocols . . . . . . . . . . . . . 14 104 2.5. Upper layers . . . . . . . . . . . . . . . . . . . . . . 14 105 2.5.1. Services provided by these networks . . . . . . . . . 15 106 2.5.1.1. Intranet services . . . . . . . . . . . . . . . . 15 107 2.5.1.2. Access to the Internet . . . . . . . . . . . . . 16 108 3. Topology . . . . . . . . . . . . . . . . . . . . . . . . . . 16 109 4. Classification . . . . . . . . . . . . . . . . . . . . . . . 17 110 4.1. Community led Wireless Mesh, led by the people . . . . . 17 111 4.2. Crowdshared approaches, led by the people and third party 112 stakeholders . . . . . . . . . . . . . . . . . . . . . . 17 113 4.3. Testbed . . . . . . . . . . . . . . . . . . . . . . . . . 18 114 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 18 115 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 116 7. Security Considerations . . . . . . . . . . . . . . . . . . . 18 117 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 18 118 8.1. Normative References . . . . . . . . . . . . . . . . . . 18 119 8.2. Informative References . . . . . . . . . . . . . . . . . 19 120 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22 122 1. Introduction 124 Several communities have developed initiatives to build large scale, 125 self-organized and decentralized community wireless networks that use 126 wireless technology (including long distance) due to the reduced cost 127 of using the unlicensed spectrum. This can be motivated by different 128 causes: Sometimes the reluctance, or the impossibility, of network 129 operators to provide wired and cellular infrastructures to rural/ 130 remote areas has motivated the rise of these networks [Pietrosemoli]. 131 Some other times, they are built as a complement and an alternative 132 to wired Internet access. 134 These community wireless networks have self sustainable business 135 models that provide more localised communication services as well as 136 providing Internet backhaul support through peering agreements with 137 traditional network operators who see such community led networks as 138 a way to extend their reach to rural/remote areas at lower cost. 140 A Community Network MAY or MAY NOT be organized as a company, but in 141 any case this document only considers those operated and owned by the 142 community members (e.g. as a cooperative). The fact of setting up a 143 company is sometimes an advantage: it not only permits the provision 144 of the service within the current regulatory framework (in some 145 countries, in order to charge for the services, even in a cost- 146 recovery mode only, you need to have a licence), but it also allows 147 to obtain wholesale prices from other operators when peering, which 148 are way cheaper than those offered for normal clients, prices which 149 influence greatly on the uptake of the service and in the financial 150 sustainability of the Community Network. 152 There exist other networks, also based on sharing wireless resources 153 of the users, but not built upon the initiative of the users 154 themselves, nor owned by them. The characterization of these 155 networks is not the objective of this document. 157 1.1. Requirements Language 159 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 160 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 161 document are to be interpreted as described in RFC 2119 [RFC2119]. 163 1.2. Definition 165 Community Networks are large-scale, distributed, self-managed 166 networks which are built and organized in a decentralized and open 167 manner. Community Networks start and grow organically, they are open 168 to participation from everyone agreeing to an open peering agreement. 169 Knowledge about building and maintaining the network and ownership of 170 the network itself is decentralized and open. Hardware and software 171 used in community networks CAN be very diverse, even inside one 172 network. A Community Network CAN have both wired and wireless links. 173 The network CAN be managed by multiple routing protocols or network 174 topology management systems. The network CAN serve as a backhaul for 175 providing a whole range of services and applications, from completely 176 free to even commercial services. 178 1.3. Scenarios 180 Scenarios where CNs are interesting or have been deployed. 182 1.3.1. Developing countries 184 There is no definition for what a developing country represents that 185 has been recognized internationally, but the term is generally used 186 to describe a nation with a low level of material well-being. In 187 this sense, one of the most commonly used classification is the one 188 by the World Bank, who ranks countries according to their Gross 189 National Income (GNI) per Capita: low income, middle income, and high 190 income, being those falling within the low and middle income groups 191 considered developing economies. Developing countries have been also 192 defined as those which are in transition from traditional lifestyles 193 towards the modern lifestyle which began in the Industrial 194 Revolution. Additionally, the Human Development Index, which 195 considers not only the GNI but also life expectancy and education, 196 has been proposed by the United Nations to rank countries according 197 to the well-being of a country and not solely based on economic 198 terms. These classifications are used to give strong signals to the 199 international community to the need of special concessions in support 200 of these countries, implying a correlation between development and 201 increased well-being. 203 However, at the beginning of the 90's the debates about how to 204 quantify development in a country were shaken by the appearance of 205 Internet and mobile phones, which many authors consider the beginning 206 of the Information Society. With the beginning of this Digital 207 Revolution, defining development based on Industrial Society concepts 208 started to be challenged, and links between digital development and 209 its impact on human development started to flourish. The following 210 dimensions are considered to be meaningful when measuring the digital 211 development state of a country: infrastructures (availability and 212 affordability); ICT sector (human capital and technological 213 industry); digital literacy; legal and regulatory framework; and 214 content and services. The lack or less extent of digital development 215 in one or more of these dimensions is what has been referred as 216 Digital Divide. This divide is a new vector of inequality which - as 217 it happened during the Industrial Revolution - generates a lot of 218 progress at the expense of creating a lot economic poverty and 219 exclusion. The Digital Divide is considered to be a consequence of 220 other socio-economic divides, while, at the same time, a reason for 221 their rise. 223 In this context, the so-called developing countries, worried of being 224 left behind of this incipient digital revolution, motivated the World 225 Summit of the Information Society which aimed at achieving "a people- 226 centred, inclusive and development-oriented Information Society, 227 where everyone can create, access, utilize and share information and 228 knowledge, enabling individuals, communities and peoples to achieve 229 their full potential in promoting their sustainable development and 230 improving their quality of life" [WSIS], and called upon 231 "governments, private sector, civil society and international 232 organisations" to actively engage to accomplish it [WSIS]. 234 Most efforts from governments and international organizations focused 235 initially on improving and extending the existing infrastructure for 236 not leaving their population behind. Universal Access and Service 237 plans have taken different forms in different countries over the 238 years, with very uneven success rates, but in most cases inadequate 239 to the scale of the problem. Given its incapacity to solve the 240 problem, some governments included Universal Service and Access 241 obligations to mobile network operators when liberalizing the 242 telecommunications market. In combination with the overwhelming and 243 unexpected uptake of mobile phones by poor people, this has mitigated 244 the low access indicators existing in many developing countries at 245 the beginning of the 90s [Rendon]. 247 Although it is undeniable the contribution made by mobile network 248 operators in decreasing the access gap, its model presents some 249 constraints that limits the development outcomes that increased 250 connectivity promises to bring. Prices, tailored for the more 251 affluent part of the population, remain unaffordable to many, who 252 invest large percentages of their disposable income in 253 communications. Additionally, the cost of prepaid packages, the only 254 option available for the informal economies existing throughout 255 developing countries, is high compared with the rate longer-term 256 subscribers pay. 258 The consolidation of many Community Networks in high income countries 259 sets a precedent for civil society members from the so-called 260 developing countries to become more active in the search for 261 alternatives to provide themselves with affordable access. 262 Furthermore, Community Networks could contribute to other dimensions 263 of the digital development like increased human capital and the 264 creation of contents and services targeting the locality of each 265 network. 267 1.3.2. Rural areas 269 The Digital Divide presented in the previous section is not only 270 present between countries, but within them too. This is specially 271 the case for rural inhabitants, which represents approximately 55% of 272 the World's population, from which 78% inhabit in developing 273 countries. Although it is impossible to generalize among them, there 274 exist some common features that have determined the availability of 275 ICT infrastructure in these regions. The disposable income of their 276 dwellers is lower than those inhabiting urban areas, with many 277 surviving on a subsistence economy. Many of them are located in 278 geographies difficult to access and exposed to extreme weather 279 conditions. This has resulted in the almost complete lack of 280 electrical infrastructure. This context, together with their low 281 population density, discourages telecommunications operators to 282 provide similar services to those provided to urban dwellers, since 283 they do not deemed them profitable 285 The cost of the wireless infrastructure required to set up a 286 Community Network, including powering them via solar energy, is 287 within the range of availability if not of individuals at least of 288 entire communities. The social capital existing in these areas can 289 allow for Community Network set-ups where a reduced number of nodes 290 may cover communities whose dwellers share the cost of the 291 infrastructure and the gateway and access it via inexpensive wireless 292 devices. In this case, the lack of awareness and confidence of rural 293 communities to embark themselves in such tasks can become major 294 barriers to their deployment. Scarce technical skills in these 295 regions have been also pointed as a challenge for their success, but 296 the proliferation of urban Community Networks, where scarcity of 297 spectrum, scale, and heterogeneity of devices pose tremendous 298 challenges to their stability and to that of the services they aim to 299 provide, has fuelled the creation of robust low-cost low-consumption 300 low-complexity off-the-self wireless devices which make much easier 301 the deployment and maintenance of these alternative infrastructures 302 in rural areas. 304 2. Technologies employed 306 These networks employ different technologies [WNDW]. They can be 307 classified according to different criteria: 309 2.1. Antennas 311 Three kinds of antennas are suitable to be used in community 312 networks: omnidirectional, directional and high gain antennas. 314 For local access, omnidirectional antennas are the most useful, since 315 they provide the same coverage in all directions of the plane in 316 which they are located. Above and below this plane, the received 317 signal will diminish, so the maximum benefits are obtained when the 318 client is at approximately the same height as the Access Point. 320 When using an omnidirectional antenna outdoors to provide 321 connectivity to a large area, people often select high gain antennas 322 located at the highest structure available to extend the coverage. 323 In many cases this is counterproductive, since a high gain 324 omnidirectional antenna will have a very narrow beamwidth in the 325 vertical plane, meaning that clients that are below the plane of the 326 antenna will receive a very weak signal (and by the reciprocity 327 property of all antennas, the omni will also receive a feeble signal 328 from the client). So a moderate gain omnidirectional of about 8 to 329 10 dBi is normally preferable. Higher gain omnis antennas are only 330 advisable when the farthest way client are roughly in the same plane. 332 For indoor clients, omnis are generally fine, because the numerous 333 reflections normally found in indoor environments negate the 334 advantage of using directive antennas. 336 For outdoor clients, directive antennas can be quite useful to extend 337 coverage to an Access Point fitted with an omni. 339 When building point to point links, the highest gain antennas are the 340 best choice, since their narrow beamwidth mitigates interference from 341 other users and can provide the longest links [Flickenger] [Zennaro]. 343 24 to 34 dBi antennas are commercially available at both the 344 unlicensed 2.4 GHz and 5 GHz bands, and even higher gain antennas can 345 be found in the newer unlicensed bands at 17 GHz and 24 GHz. 347 Despite the fact that the free space loss is directly proportional to 348 the square of the frequency, it is normally advisable to use higher 349 frequencies for point to point links when there is a clear line of 350 sight, because it is frequently easier to get higher gain antennas at 351 5 GHz. Deploying high gain antennas at both ends will more than 352 compensate for the additional free space loss. Furthermore, higher 353 frequencies can make due with lower altitude antenna placement since 354 the Fresnel zone is inversely proportional to the square root of the 355 frequency. 357 On the contrary, lower frequencies offer advantages when the line of 358 sight is blocked because they can leverage diffraction to reach the 359 intended receiver. 361 It is common to find dual radio Access Points, at two different 362 frequency bands. One way of benefiting from this arrangement is to 363 attach a directional antenna to the high frequency radio for 364 connection to the backbone and an omni to the lower frequency to 365 provide local access. 367 Of course, in the case of mesh networking, where the antenna should 368 connect to several other nodes, it is better to use omnidirectional 369 antennas. 371 Keep also in mind that the same type of polarisation must be used at 372 both ends of any radio link. For point to point links, some vendor 373 use two radios operating at the same frequency but with orthogonal 374 polarisations, thus doubling the achievable throughput, and also 375 offering added protection to multipath and other transmission 376 impairments. 378 2.2. Link length 380 For short distance transmission, there is no strict requirement of 381 line of sight between the transmitter and the receiver, and multipath 382 can guarantee communication despite the existence of obstacles in the 383 direct path. 385 For longer distances, the first requirement is the existence of an 386 unobstructed line of sight between the transmitter and the receiver. 388 For very long path the earth curvature is an obstacle that must be 389 cleared, but the trajectory of the radio beam is not strictly a 390 straight line due to the bending of the rays as a consequence of non- 391 uniformities of the atmosphere. Most of the time this bending will 392 mean that the radio horizon extends further than the optical horizon. 394 Another factor to be considered is that radio waves occuppy a volume 395 around the optical line, which must be unencumbered from obstacles 396 for the maximum signal to be captured at the receiver. This volume 397 is known as the Fresnel ellipsoid and its size grows with the 398 distance between the end points and with the wavelength of the 399 signal, which in turn is inversely proportional to the frequency. 401 So, for optimum signal reception the end points must be high enough 402 to clear any obstacle in the path and leave extra "elbow room" for 403 the Fresnel zone. This can be achieved by using suitable masts at 404 either end, or by taking advantage of existing structures or hills. 406 Once a clear radio-electric line of sight (including the Fresnel zone 407 clearance) is obtained, one must ascertain that the received power is 408 well above the sensitivity of the receiver, by what is known as the 409 link margin. The greater the link margin, the more reliable the 410 link. For mission critical applications 20 dB margin is suggested, 411 but for non critical ones 10 dB might suffice. 413 Bear in mind that the sensitivity of the receiver decreases with the 414 transmission speed, so more power is needed at greater transmission 415 speeds. 417 The received power is determined by the transmitted power, the gain 418 of the transmitting and receiving antennas and the propagation loss. 420 The propagation loss is the sum of the free space loss (proportional 421 to the square of the the frequency and the square of the distance), 422 plus additional factors like attenuation in the atmosphere by gases 423 or meteorological effects (which are strongly frequency dependent), 424 multipath and diffraction losses. 426 Multipath is more pronounced in trajectories over water, if they 427 cannot be avoided special countermeasures should be taken. 429 So to achieve a given link margin (also called fade margin), one can: 431 a) increase the output power.The maximum transmitted power is 432 specified by the country's regulation, and for unlicensed frequencies 433 is much lower than for licensed frequencies. 435 b) Increase the antenna gain. There is no limit in the gain of the 436 receiving antenna, but high gain antennas are bulkier, present more 437 wind resistance and require sturdy mounts to comply with tighter 438 alignment requirements. The transmitter antenna gain is also 439 regulated and can be different for point to point as for point to 440 multipoint links. Many countries impose a limit in the combination 441 of transmitted power and antenna gain, the EIRP (Equivalent 442 Isotropically Irradiated Power) which can be different for point to 443 point or point to multipoint links. 445 c) Reduce the propagation loss, by using a more favourable frequency 446 or a shorter path. 448 d) Use a more sensitive receiver. Receiver sensitivity can be 449 improved by using better circuits, but it is ultimately limited by 450 the thermal noise, which is proportional to temperature and 451 bandwidth. So one can increase the sensitivity by using a smaller 452 receiving bandwidth, or by settling to lower throughput even in the 453 same receiver bandwidth. This step is often done automatically in 454 many protocols, in which the transmission speed can be reduced say 455 from 150 Mbit/s to 6 Mbit/s if the receiver power is not enough to 456 sustain the maximum throughput. 458 A completely different limiting factor is related with the medium 459 access protocol. WiFi was designed for short distance, and the 460 transmitter expects the reception of an acknowledgment for each 461 transmitted packet in a certain amount of time, if the waiting time 462 is exceeded, the packet is retransmitted. This will reduce 463 significantly the throughput at long distance, so for long distance 464 application it is better to use a different medium access technique, 465 in which the receiver does not wait for an acknowledge of the 466 transited packet. This strategy of TDMA (Time Domain Multiple 467 Access) has been adopted by many equipment vendors who offer 468 proprietary protocols alongside the standard WiFi in order to 469 increase the throughput at longer distances. Low cost equipment 470 using TDMA can offer high throughput at distances over 100 471 kilometres. 473 2.3. Layer 2 475 2.3.1. The 802.11 standard 477 Wireless standards ensure interoperability and usability by those who 478 design, deploy and manage wireless networks. The Standards used in 479 the vast majority of Community Networks come from the IEEE Standard 480 Association's IEEE 802 Working Group. 482 The standard we are most interested in is 802.11 a/b/g/n, as it 483 defines the protocol for Wireless LAN. Different 802.11 amendments 484 have been released, as shown in the table below, also including their 485 frequencies and approximate ranges. 487 |802.11| Release | Freq |BWdth | Data Rate per | Approx range (m) | 488 |prot | date | (GHz)|(MHz) |stream (Mbit/s) | indoor | outdoor | 489 +------+---------+------+------+----------------+--------+----------+ 490 | a |Sep 1999 | 5 | 20 | 6,9,12, 18, 24,| 35 | 120 | 491 | | | | | 36, 48, 54 | | | 492 | b |Sep 1999 | 2.4 | 20 | 1, 2, 5.5, 11 | 35 | 140 | 493 | g |Jun 2003 | 2.4 | 20 | 6,9,12, 18, 24,| 38 | 140 | 494 | | | | | 36, 48, 54 | | | 495 | n |Oct 2009 | 2.4/5| 20 | 7.2, 14.4, 21.7| 70 | 250 | 496 | | | | | 28.9, 43.3, | | | 497 | | | | | 57.8, 65, 72.2 | | | 498 | n |Oct 2009 | 2.4/5| 40 | 15, 30, 45, 60,| 70 | 250 | 499 | | | | | 90, 120, | | | 500 | | | | | 135, 150 | | | 501 | ac |Nov 2011 | 5 | 20 | Up to 87.6 | | | 502 | ac |Nov 2011 | 5 | 40 | Up to 200 | | | 503 | ac |Nov 2011 | 5 | 80 | Up to 433.3 | | | 504 | ac |Nov 2011 | 5 | 160 | Up to 866.7 | | | 506 In 2012 IEEE issued the 802.11-2012 Standard that consolidates all 507 the previous amendments. The document is freely downloadable from 508 IEEE standards [IEEE]. 510 2.3.2. Deployment planning for 802.11 wireless networks 512 Before packets can be forwarded and routed to the Internet, layers 513 one (the physical) and two (the data link) need to be connected. 514 Without link local connectivity, network nodes cannot talk to each 515 other and route packets. 517 To provide physical connectivity, wireless network devices must 518 operate in the same part of the radio spectrum. This is means that 519 802.11a radios will talk to 802.11a radios at around 5 GHz, and 520 802.11b/g radios will talk to other 802.11b/g radios at around 2.4 521 GHz. But an 802.11a device cannot interoperate with an 802.11b/g 522 device, since they use completely different parts of the 523 electromagnetic spectrum. More specifically, wireless interfaces 524 must agree on a common channel. If one 802.11b radio card is set to 525 channel 2 while another is set to channel 11, then the radios cannot 526 communicate with each other. 528 When two wireless interfaces are configured to use the same protocol 529 on the same radio channel, then they are ready to negotiate data link 530 layer connectivity. Each 802.11a/b/g device can operate in one of 531 four possible modes: 533 1.Master mode (also called AP or infrastructure mode) is used to 534 create a service that looks like a traditional access point. The 535 wireless interface creates a network with a specified name (called 536 the SSID) and channel, and offers network services on it. While in 537 master mode, wireless interfaces manage all communications related to 538 the network (authenticating wireless clients, handling channel 539 contention, repeating packets, etc.) Wireless interfaces in master 540 mode can only communicate with interfaces that are associated with 541 them in managed mode. 543 2.Managed mode is sometimes also referred to as client mode. 544 Wireless interfaces in managed mode will join a network created by a 545 master, and will automatically change their channel to match it. 546 They then present any necessary credentials to the master, and if 547 those credentials are accepted, they are said to be associated with 548 the master. Managed mode interfaces do not communicate with each 549 other directly, and will only communicate with an associated master. 551 3.Ad-hoc mode creates a multipoint-to-multipoint network where there 552 is no single master node or AP. In ad-hoc mode, each wireless 553 interface communicates directly with its neighbours. Nodes must be 554 in range of each other to communicate, and must agree on a network 555 name and channel. Ad-hoc mode is often also called Mesh Networking. 557 4.Monitor mode is used by some tools (such as Kismet) to passively 558 listen to all radio traHc on a given channel. When in monitor mode, 559 wireless interfaces transmit no data. This is useful for analysing 560 problems on a wireless link or observing spectrum usage in the local 561 area. Monitor mode is not used for normal communications. 563 When implementing a point-to-point or point-to-multipoint link, one 564 radio will typically operate in master mode, while the other(s) 565 operate in managed mode. In a multipoint-to-multipoint mesh, the 566 radios all operate in ad-hoc mode so that they can communicate with 567 each other directly. Remember that managed mode clients cannot 568 communicate with each other directly, so it is likely that you will 569 want to run a high repeater site in master or ad-hoc mode. Ad-hoc is 570 more flexible but has a number of performance issues as compared to 571 using the master / managed modes. 573 2.3.3. 802.11af (TVWS) 575 Some Community Networks make use of TV White Spaces, using 802.11af 576 standard. 578 2.3.4. Other options 580 802.11 is not the only layer 2 option to be used in Community 581 Networks. 583 2.4. Layer 3 585 2.4.1. IP addressing 587 Most known Community Networks started in or around the year 2000. 588 IPv6 was fully specified by then, but most almost all Community 589 Networks still use IPv4. A community networks survey [Avonts] 590 indicated that IPv6 rollout forms a challenge to Community Networks. 592 Most Community Networks use private IPv4 address ranges, as defined 593 by RFC 1918 [RFC1918]. The motivation for this was the lower cost 594 and the simplified IP allocation because of the large available 595 address ranges. 597 2.4.2. Routing protocols 599 Community Networks are composed of possibly different layer 2 600 devices, resulting in a mesh of Community Network nodes. Connection 601 between different nodes is not guaranteed, the link stability can 602 vary strongly over time. To tackle this, some Community Networks use 603 mesh network routing protocols while other networks use more 604 traditional routing protocols. Some networks operate multiple 605 routing protocols in parallel. E.g., they use a mesh protocol inside 606 different islands and use traditional routing protocols to connect 607 islands. 609 2.4.2.1. Traditional routing protocols 611 The BGP protocol, as defined by RFC 4271 [RFC4271] is used by a 612 number of Community Networks, because of its well-studied behavior 613 and scalability. 615 For similar reasons, smaller Community Networks opt to run the OSPF 616 protocol, as defined by RFC 2328 [RFC2328]. 618 2.4.2.2. Mesh routing protocols 620 A large number of Community Networks use the OLSR routing protocol as 621 defined in RFC 3626 [RFC3626]. The pro-active link state routing 622 protocol is a good match with Community Networks because it has good 623 performance in mesh networks where nodes have multiple interfaces. 625 The Better Approach To Mobile Adhoc Networking (B.A.T.M.A.N.) 626 [Abolhasan]protocol was developed by member of the Freifunk 627 community. The protocol handles all routing at layer 2, creating one 628 bridged network. 630 Parallel to BGP, some networks also run the BMX6 protocol [Neumann]. 631 This is an advanced version of the BATMAN protocol which is based on 632 IPv6 and tries to exploit the social structure of Community Networks. 634 2.5. Upper layers 636 From crowd shared perspective, and considering just regular TCP 637 connections during the critical sharing time, the Access Point 638 offering the CN service is likely to be the bottleneck of the 639 connection. This is the main concern of sharers, having several 640 implications. There should be an adequate Active Queue Management 641 (AQM) mechanism that implement a Less than Best Effort policy for the 642 CN user and protect the sharer. Achieving LBE behaviour requieres 643 the appropriate tuning of the well known mechanisms such as ECN, or 644 RED, or others more recent AQM mechanisms such as CoDel and PIE that 645 aid on keeping low latency RFC 6297 [RFC6297]. 647 The CN user traffic should not interfere with the sharers traffic. 648 However, other bottlenecks besides client's access bottleneck may not 649 be controlled by previously mentioned protocols. And so, recently 650 proposed transport protocols like LETBAT [reference required] with 651 the purpose of transporting scavenger traffic may be a solution. 652 LEDBAT requieres the cooperation of both the client and the server to 653 achieve certain target delay, therefore controlling the impact of the 654 CN user all along the path. 656 There are applications that manage aspects of CN from the sharer side 657 and from the client side. From sharer's side, there are applications 658 to centralise the management of the APs conforming the CN that have 659 been recently proposed by means of SDN [Sathiaseelan_a] [Suresh]. 660 There are also other proposals such as Wi2Me [Lampropulos] that 661 manage the connection to several CNs from the client's side. This 662 application have shown to improve the client performance compared to 663 a single-CN client. 665 On the other hand, transport protocols inside a multiple hop wireless 666 mesh network are likely to suffer performance degradation for 667 multiple reasons, e.g., hidden terminal problem, unnecessary delays 668 on the TCP ACK clocking that decrease the throughout or route 669 changing [Hanbali]. So, there are some options for network 670 configuration. The implementation of an easy-to-adopt solution for 671 TCP over mesh networks may be implemented from two different 672 perspectives. One way is to use a TCP-proxy to transparently deal 673 with the different impairments RFC 3135 [RFC3135]. Another way is to 674 adopt end-to-end solutions for monitoring the connection delay so 675 that the receiver adapts the TCP reception window (rwnd) 676 [Castignani_c]. Similarly, the ACK Congestion Control (ACKCC) 677 mechanism RFC 5690 [RFC5690] could deal with TCP-ACK clocking 678 impairments due to inappropriate delay on ACK packets. ACKCC 679 compensates in an end-to-end fashion the throughput degradation due 680 to the effect of media contention as well as the unfairness 681 experienced by multiple uplink TCP flows in a congested WiFi access. 683 2.5.1. Services provided by these networks 685 This section provides an explaining of the services between hosts 686 inside the CN. They can be divided into Intranet services, 687 connecting hosts between them, and Internet services, connecting to 688 nodes outside the network. 690 2.5.1.1. Intranet services 692 - VoIP (e.g. with SIP) 694 - remote desktop (e.g. using my computer and my Internet connection 695 when I am on holidays in a village). 697 - FTP file sharing (e.g. distribution of Linux software). 699 - P2P file sharing. 701 - public video cameras. 703 - DNS. 705 - online games servers. 707 - jabber instant messaging. 709 - IRC chat. 711 - weather stations. 713 - NTP. 715 - Network monitoring. 717 - videoconferencing / streaming. 719 - Radio streaming. 721 2.5.1.2. Access to the Internet 723 2.5.1.2.1. Web browsing proxies 725 A number of federated proxies provide web browsing service for the 726 users. Other services (file sharing, skype, etc.) are not usually 727 allowed. 729 2.5.1.2.2. Use of VPNs 731 Some "micro-ISPs" may use the CN as a backhaul for providing Internet 732 access, setting up VPNs from the client to a machine with Internet 733 access. 735 3. Topology 737 These networks follow different topology patterns, as studied in 738 [Vega]. 740 Regularly rural areas in CNs are connected through long-distance 741 links (the so-called community mesh approach) which in turn convey 742 the Internet connection to relevant organisations or institutions. 743 In contrast, in urban areas, users tend to share and require mobile 744 access. Since these areas are also likely to be covered by 745 commercial ISPs, the provision of wireless access by Virtual 746 Operators like FON is the way to extend the user capacity (or gain 747 connection) to the network. Other proposals like Virtual Public 748 Networks [Sathiaseelan_a] can also extend the service. 750 As in the case of main Internet Service Providers in France, 751 Community Networks for urban areas are conceived as a set of APs 752 sharing a common SSID among the clients favouring the nomadic access. 753 For CNs users in France, ISPs promise to cause a little impact on 754 their service agreement when the CN service is activated on clients' 755 APs. Nowadays, millions of APs are deployed around the country 756 performing services of nomadism and 3G offloading, however as some 757 studies demonstrate, at peatonal speed, there is a fair chance of 758 performing file transfers [Castignani_a] [Castignani_b]. In studied 759 scenarios in France and Luxembourg the density of APs around the 760 urban areas (mainly in downtown and residential areas) there is a 761 crowded deployment of APs for the different ISPs. Moreover, 762 performed studies reveal that aggregating available networks can be 763 beneficial to the client by using an application that manage the best 764 connection among the different CNs. For improving the scanning 765 process (or topology recognition), which consumes the 90% of the 766 connection/reconnection process to the Community Network, the client 767 may implement several techniques for selecting the best AP 768 [Castignani_c]. 770 4. Classification 772 This section classifies Community Networks according to their 773 intended usage. Each of them have different incentive structures, 774 maybe common technological challenges but most importantly 775 interesting usage challenges which feeds into the incentives as well 776 as technological challenges 778 Some networks exist, which they are outside the scope of the present 779 document. A first example are the networks created and managed by 780 City Councils (e.g., [Heer]).Some companies [FON reference missing] 781 develop and sell Wi-Fi routers with a dual access: a Wi-Fi network 782 for the user, and a shared one. A user community is created, an 783 people can join it different ways: they can buy a dual router, so 784 they share their connection and in turn they get access to all the 785 routers associated to the community. Some users can even get some 786 revenues every time another user connects to their Wi-Fi spot. Other 787 users can just buy some passes in order to use the network. Some 788 telecommunications operators can collaborate with the community, 789 including in their routers the possibility of creating these two 790 networks. 792 4.1. Community led Wireless Mesh, led by the people 794 These networks grow organically, since they are formed by the 795 aggregation of nodes belonging to different users. A minimum 796 governance infrastructure is required in order to coordinate IP 797 addressing, routing, etc. A clear example of this kind of Community 798 Network is described in [Braem]. 800 4.2. Crowdshared approaches, led by the people and third party 801 stakeholders 803 These networks follow the next approach: the home router creates two 804 wireless networks, one of them to be normally used by the owner, and 805 the other one is public. A small fraction of the bandwidth is 806 allocated to the public network (as e.g. Less-than-best-effort or 807 scavenger traffic), to be employed by any user of the service in the 808 immediate area. An example is described in [PAWS]. 810 A Virtual Private Network (VPN) is created for public traffic, so it 811 is completely secure and separated from the owner's connection. The 812 network capacity shared may employ a less-than-best-effort approach, 813 so as not to harm the traffic of the owner of the connection 814 [Sathiaseelan_a]. 816 There are three actors in the scenario: 818 - End users who sign up for the service and share their network 819 capacity. As a counterpart, they can access anyone's home broadband 820 for free. 822 - Virtual Network Operators (VNOs) are stakeholders with socio- 823 environmental objectives. They can be a local government, grass root 824 user communities, charities, or even content operators, smart grid 825 operators, etc. They are the ones who actually run the service. 827 - Network operators, who have a financial incentive to lease out the 828 unused capacity [Sathiaseelan_b] at lower cost to the VNOs. 830 VNOs pay the sharers and the network operators, thus creating an 831 incentive structure for all the actors: the end users get money for 832 sharing their network, the network operators are paid by the VNOs, 833 who in turn accomplish their socio-environmental role. 835 4.3. Testbed 837 In some cases, the initiative to start the network is not from the 838 community, but from a research entity (e.g., a university), with the 839 aim of using it for research purposes [Samanta]. 841 5. Acknowledgements 843 6. IANA Considerations 845 This memo includes no request to IANA. 847 7. Security Considerations 849 No security issues have been identified for this document. 851 8. References 853 8.1. Normative References 855 [RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and 856 E. Lear, "Address Allocation for Private Internets", BCP 857 5, RFC 1918, February 1996. 859 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 860 Requirement Levels", BCP 14, RFC 2119, March 1997. 862 [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998. 864 [RFC3135] Border, J., Kojo, M., Griner, J., Montenegro, G., and Z. 865 Shelby, "Performance Enhancing Proxies Intended to 866 Mitigate Link-Related Degradations", RFC 3135, June 2001. 868 [RFC3626] Clausen, T. and P. Jacquet, "Optimized Link State Routing 869 Protocol (OLSR)", RFC 3626, October 2003. 871 [RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway 872 Protocol 4 (BGP-4)", RFC 4271, January 2006. 874 [RFC5690] Floyd, S., Arcia, A., Ros, D., and J. Iyengar, "Adding 875 Acknowledgement Congestion Control to TCP", RFC 5690, 876 February 2010. 878 [RFC6297] Welzl, M. and D. Ros, "A Survey of Lower-than-Best-Effort 879 Transport Protocols", RFC 6297, June 2011. 881 8.2. Informative References 883 [Abolhasan] 884 Abolhasan, M., Hagelstein, B., and J. Wang, "Real-world 885 performance of current proactive multi-hop mesh 886 protocols", In Communications, 2009. APCC 2009. 15th Asia- 887 Pacific Conference on (pp. 44-47). IEEE. , 2009. 889 [Avonts] Avonts, J., Braem, B., and C. Blondia, "A Questionnaire 890 based Examination of Community Networks", Proceedings 891 Wireless and Mobile Computing, Networking and 892 Communications (WiMob), 2013 IEEE 8th International 893 Conference on (pp. 8-15) , 2013. 895 [Braem] Braem, B., Baig Vinas, R., Kaplan, A., Neumann, A., Vilata 896 i Balaguer, I., Tatum, B., Matson, M., Blondia, C., Barz, 897 C., Rogge, H., Freitag, F., Navarro, L., Bonicioli, J., 898 Papathanasiou, S., and P. Escrich, "A case for research 899 with and on community networks", ACM SIGCOMM Computer 900 Communication Review vol. 43, no. 3, pp. 68-73, 2013. 902 [Castignani_a] 903 Castignani, G., Loiseau, L., and N. Montavont, "An 904 Evaluation of IEEE 802.11 Community Networks Deployments", 905 Information Networking (ICOIN), 2011 International 906 Conference on , vol., no., pp.498,503, 26-28 , 2011. 908 [Castignani_b] 909 Castignani, G., Monetti, J., Montavont, N., Arcia-Moret, 910 A., Frank, R., and T. Engel, "A Study of Urban IEEE 802.11 911 Hotspot Networks: Towards a Community Access Network", 912 Wireless Days (WD), 2013 IFIP , pp.1,8, 13-15 , 2013. 914 [Castignani_c] 915 Castignani, G., Arcia-Moret, A., and N. Montavont, "A 916 study of the discovery process in 802.11 networks", 917 SIGMOBILE Mob. Comput. Commun. Rev., vol. 15, no. 1, p. 25 918 , 2011. 920 [Flickenger] 921 Flickenger, R., Okay, S., Pietrosemoli, E., Zennaro, M., 922 and C. Fonda, "Very Long Distance Wi-Fi Networks", NSDR 923 2008, The Second ACM SIGCOMM Workshop on Networked Systems 924 for Developing Regions. USA, 2008 , 2008. 926 [Hanbali] Hanbali, A., Altman, E., and P. Nain, "A Survey of TCP 927 over Ad Hoc Networks", IEEE Commun. Surv. Tutorials, vol. 928 7, pp. 22-36 , 2005. 930 [Heer] Heer, T., Hummen, R., Viol, N., Wirtz, H., Gotz, S., and 931 K. Wehrle, "Collaborative municipal Wi-Fi networks- 932 challenges and opportunities", Pervasive Computing and 933 Communications Workshops (PERCOM Workshops), 2010 8th IEEE 934 International Conference on (pp. 588-593). IEEE. , 2010. 936 [IEEE] Institute of Electrical and Electronics Engineers, IEEE, 937 "IEEE Standards association", 2012. 939 [Lampropulos] 940 Lampropulos, A., Castignani, G., Blanc, A., and N. 941 Montavont, "Wi2Me: A Mobile Sensing Platform for Wireless 942 Heterogeneous Networks", 32nd International Conference on 943 Distributed Computing Systems Workshops (ICDCS Workshops), 944 2012, pp. 108-113 , 2012. 946 [Neumann] Neumann, A., Lopez, E., and L. Navarro, "An evaluation of 947 bmx6 for community wireless networks", In Wireless and 948 Mobile Computing, Networking and Communications (WiMob), 949 2012 IEEE 8th International Conference on (pp. 651-658). 950 IEEE. , 2012. 952 [PAWS] Sathiaseelan, A., Crowcroft, J., Goulden, M., 953 Greiffenhagen, C., Mortier, R., Fairhurst, G., and D. 954 McAuley, "Public Access WiFi Service (PAWS)", Digital 955 Economy All Hands Meeting, Aberdeen , Oct 2012. 957 [Pietrosemoli] 958 Pietrosemoli, E., Zennaro, M., and C. Fonda, "Low cost 959 carrier independent telecommunications infrastructure", In 960 proc. 4th Global Information Infrastructure and Networking 961 Symposium, Choroni, Venezuela , 2012. 963 [Rendon] Rendon, A., Ludena, P., and A. Martinez Fernandez, 964 "Tecnologias de la Informacion y las Comunicaciones para 965 zonas rurales Aplicacion a la atencion de salud en paises 966 en desarrollo", CYTED. Programa Iberoamericano de Ciencia 967 y Tecnologia para el Desarrollo , 2011. 969 [Samanta] Samanta, V., Knowles, C., Wagmister, J., and D. Estrin, 970 "Metropolitan Wi-Fi Research Network at the Los Angeles 971 State Historic Park", The Journal of Community 972 Informatics, North America, 4 , May 2008. 974 [Sathiaseelan_a] 975 Sathiaseelan, A., Rotsos, C., Sriram, C., Trossen, D., 976 Papadimitriou, P., and J. Crowcroft, "Virtual Public 977 Networks", In Software Defined Networks (EWSDN), 2013 978 Second European Workshop on (pp. 1-6). IEEE. , 2013. 980 [Sathiaseelan_b] 981 Sathiaseelan, A. and J. Crowcroft, "LCD-Net: Lowest Cost 982 Denominator Networking", ACM SIGCOMM Computer 983 Communication Review , Apr 2013. 985 [Suresh] Suresh, L., Schulz-Zander, J., Merz, R., Feldmann, A., and 986 T. Vazao, "Towards Programmable Enterprise WLANs with 987 ODIN", In Proceedings of the first workshop on Hot topics 988 in software defined networks (HotSDN '12). ACM, New York, 989 NY, USA, 115-120 , 2012. 991 [Vega] Vega, D., Cerda-Alabern, L., Navarro, L., and R. Meseguer, 992 "Topology patterns of a community network: Guifi. net.", 993 Proceedings Wireless and Mobile Computing, Networking and 994 Communications (WiMob), 2012 IEEE 8th International 995 Conference on (pp. 612-619) , 2012. 997 [WNDW] Wireless Networking in the Developing World/Core 998 Contributors, "Wireless Networking in the Developing 999 World, 3rd Edition", The WNDW Project, available at 1000 wndw.net , 2013. 1002 [WSIS] International Telecommunications Union, ITU, "Declaration 1003 of Principles. Building the Information Society: A global 1004 challenge in the new millenium", World Summit on the 1005 Information Society, 2003, at http://www.itu.int/wsis, 1006 accessed 12 January 2004. , Dec 2013. 1008 [Zennaro] Zennaro, M., Fonda, C., Pietrosemoli, E., Muyepa, A., 1009 Okay, S., Flickenger, R., and S. Radicella, "On a long 1010 wireless link for rural telemedicine in Malawi", 6th 1011 International Conference on Open Access, Lilongwe, Malawi 1012 , Nov 2008. 1014 Authors' Addresses 1016 Jose Saldana (editor) 1017 University of Zaragoza 1018 Dpt. IEC Ada Byron Building 1019 Zaragoza 50018 1020 Spain 1022 Phone: +34 976 762 698 1023 Email: jsaldana@unizar.es 1025 Andres Arcia-Moret 1026 Universidad de Los Andes 1027 Facultad de Ingenieria. Sector La Hechicera 1028 Merida 5101 1029 Venezuela 1031 Phone: +58 274 2402811 1032 Email: andres.arcia@ula.ve 1034 Bart Braem 1035 University of Antwerp - iMinds 1036 Middelheimlaan 1 1037 Antwerp B-2020 1038 Belgium 1040 Phone: +32 (0)3 265.38.64 1041 Email: bart.braem@iminds.be 1042 Leandro Navarro 1043 U. Politecnica Catalunya 1044 Jordi Girona, 1-3, D6 1045 Barcelona 08034 1046 Spain 1048 Phone: +34 934016807 1049 Email: leandro@ac.upc.edu 1051 Ermanno Pietrosemoli 1052 Escuela Latinoamericana de Redes 1053 Apartado 514 1054 Merida 5101 1055 Venezuela 1057 Phone: +58 0274 2403327 1058 Email: ermanno@ula.ve 1060 Carlos Rey-Moreno 1061 University of the Western Cape 1062 Robert Sobukwe road 1063 Bellville 7535 1064 South Africa 1066 Phone: 0027219592562 1067 Email: crey-moreno@uwc.ac.za 1069 Arjuna Sathiaseelan 1070 University of Cambridge 1071 15 JJ Thomson Avenue 1072 Cambridge CB30FD 1073 United Kingdom 1075 Phone: +44 (0)1223 763781 1076 Email: arjuna.sathiaseelan@cl.cam.ac.uk 1078 Marco Zennaro 1079 Abdus Salam ICTP 1080 Strada Costiera 11 1081 Trieste 34100 1082 Italy 1084 Phone: +39 040 2240 406 1085 Email: mzennaro@ictp.it