6. Technologies Employed
In many ("global north" or "global south") countries, it may happen
that national service providers decline to provide connectivity to
tiny and isolated villages. So in some cases, the villagers have
created their own optical fiber networks. This is the case in
Lowenstedt, Germany [Lowenstedt] or in some parts of Guifi.net
The vast majority of Alternative Network Deployments are based on
different wireless technologies [WNDW]. Below we summarize the
options and trends when using these features in Alternative Networks.
6.2.1. Media Access Control (MAC) Protocols for Wireless Links
Different protocols for MAC, which also include physical layer (PHY)
recommendations, are widely used in Alternative Network Deployments.
Wireless standards ensure interoperability and usability to those who
design, deploy, and manage wireless networks. In addition, they then
ensure the low cost of equipment due to economies of scale and mass
The standards used in the vast majority of Alternative Networks come
from the IEEE Standard Association's IEEE 802 Working Group.
Standards developed by other international entities can also be used,
such as, e.g., the European Telecommunications Standards Institute
220.127.116.11. 802.11 (Wi-Fi)
The standard we are most interested in is 802.11 a/b/g/n/ac, as it
defines the protocol for Wireless LAN. It is also known as "Wi-Fi".
The original release (a/b) was issued in 1999 and allowed for rates
up to 54 Mbit/s. The latest release (802.11ac) approved in 2013
reaches up to 866.7 Mbit/s. In 2012, the IEEE issued an 802.11
standard that consolidated all the previous amendments [IEEE.802.11].
The document is freely downloadable from the IEEE Standards
The MAC protocol in 802.11 is called CSMA/CA and was designed for
short distances; the transmitter expects the reception of an
acknowledgment for each transmitted unicast packet and if a certain
waiting time is exceeded, the packet is retransmitted. This behavior
makes necessary the adaptation of several MAC parameters when 802.11
is used in long links [Simo_b]. Even with this adaptation, distance
has a significant negative impact on performance. For this reason,
many vendors implement alternative medium access techniques that are
offered alongside the standard CSMA/CA in their outdoor 802.11
products. These alternative proprietary MAC protocols usually employ
some type of TDMA. Low-cost equipment using these techniques can
offer high throughput at distances above 100 kilometers.
Different specifications of 802.11 operate in different frequency
bands. 802.11b/g/n operates in 2.4 GHz, but 802.11a/n/ac operates in
5 GHz. This fact is used in some Community Networks in order to
separate ordinary and "backbone" nodes:
o Typical routers running mesh firmware in homes, offices, and
public spaces operate at 2.4 GHz.
o Special routers running mesh firmware as well but broadcasting and
receiving on the 5 GHz band are used in point-to-point connections
only. They are helpful to create a "backbone" on the network that
can both connect neighborhoods to one another when reasonable
connections with 2.4 GHz nodes are not possible, and they ensure
that users of 2.4 GHz nodes are within a few hops to strong and
stable connections to the rest of the network.
18.104.22.168. Mobile Technologies
Global System for Mobile Communications (GSM), from ETSI, has also
been used in Alternative Networks as a Layer 2 option, as explained
in [Mexican], [Village], and [Heimerl]. Open source GSM code
projects such as OpenBTS (http://openbts.org) or OpenBSC
(http://openbsc.osmocom.org/trac/) have created an ecosystem with the
participation of several companies such as, e.g., [Rangenetworks],
[Endaga], and [YateBTS]. This enables deployments of voice, SMS, and
Internet services over Alternative Networks with an IP-based
Internet navigation is usually restricted to relatively low bit rates
(see, e.g., [Osmocom]). However, leveraging on the evolution of
Third Generation Partnership Project (3GPP) standards, a trend can be
observed towards the integration of 4G [Spectrum] [YateBTS] or 5G
[Openair] functionalities, with significant increase of achievable
Depending on factors such as the allocated frequency band, the
adoption of licensed spectrum can have advantages over the eventually
higher frequencies used for Wi-Fi, in terms of signal propagation
and, consequently, coverage. Other factors favorable to 3GPP
technologies, especially GSM, are the low cost and energy consumption
of handsets, which facilitate its use by low-income communities.
22.214.171.124. Dynamic Spectrum
Some Alternative Networks make use of TV White Spaces [Lysko] -- a
set of UHF and VHF television frequencies that can be utilized by
secondary users in locations where they are unused by licensed
primary users such as television broadcasters. Equipment that makes
use of TV White Spaces is required to detect the presence of existing
unused TV channels by means of a spectrum database and/or spectrum
sensing in order to ensure that no harmful interference is caused to
primary users. In order to smartly allocate interference-free
channels to the devices, cognitive radios are used that are able to
modify their frequency, power, and modulation techniques to meet the
strict operating conditions required for secondary users.
The use of the term "White Spaces" is often used to describe "TV
White Spaces" as the VHF and UHF television frequencies were the
first to be exploited on a secondary use basis. There are two
dominant standards for TV White Space communication: (i) the 802.11af
standard [IEEE.802.11AF] -- an adaptation of the 802.11 standard for
TV White Space bands -- and (ii) the IEEE 802.22 standard
[IEEE.802.22] for long-range rural communication.
802.11af [IEEE.802.11AF] is a modified version of the 802.11 standard
operating in TV White Space bands using cognitive radios to avoid
interference with primary users. The standard is often referred to
as "White-Fi" or "Super Wi-Fi" and was approved in February 2014.
802.11af contains much of the advances of all the 802.11 standards
including recent advances in 802.11ac such as up to four bonded
channels, four spatial streams, and very high-rate 256 QAM
(Quadrature Amplitude Modulation) but with improved in-building
penetration and outdoor coverage. The maximum data rate achievable
is 426.7 Mbit/s for countries with 6/7 MHz channels and 568.9 Mbit/s
for countries with 8 MHz channels. Coverage is typically limited to
1 km although longer range at lower throughput and using high gain
antennas will be possible.
Devices are designated as enabling stations (Access Points) or
dependent stations (clients). Enabling stations are authorized to
control the operation of a dependent station and securely access a
geolocation database. Once the enabling station has received a list
of available White Space channels, it can announce a chosen channel
to the dependent stations for them to communicate with the enabling
station. 802.11af also makes use of a registered location server -- a
local database that organizes the geographic location and operating
parameters of all enabling stations.
802.22 [IEEE.802.22] is a standard developed specifically for long-
range rural communications in TV White Space frequencies and was
first approved in July 2011. The standard is similar to the 802.16
(WiMax) [IEEE.802.16] standard with an added cognitive radio ability.
The maximum throughput of 802.22 is 22.6 Mbit/s for a single 8 MHz
channel using 64-QAM modulation. The achievable range using the
default MAC scheme is 30 km; however, 100 km is possible with special
scheduling techniques. The MAC of 802.22 is specifically customized
for long distances -- for example, slots in a frame destined for more
distant Consumer Premises Equipment (CPE) are sent before slots
destined for nearby CPEs.
Base stations are required to have a Global Positioning System (GPS)
and a connection to the Internet in order to query a geolocation
spectrum database. Once the base station receives the allowed TV
channels, it communicates a preferred operating TV White Space
channel with the CPE devices. The standard also includes a
coexistence mechanism that uses beacons to make other 802.22 base
stations aware of the presence of a base station that is not part of
the same network.
7. Upper Layers
7.1. Layer 3
7.1.1. IP Addressing
Most Community Networks use private IPv4 address ranges, as defined
by [RFC1918]. The motivation for this was the lower cost and the
simplified IP allocation because of the large available address
Most known Alternative Networks started in or around the year 2000.
IPv6 was fully specified by then, but almost all Alternative Networks
still use IPv4. A survey [Avonts] indicated that IPv6 rollout
presented a challenge to Community Networks. However, some of them
have already adopted it, such as ninux.org.
7.1.2. Routing Protocols
As stated in previous sections, Alternative Networks are composed of
possibly different Layer 2 devices, resulting in a mesh of nodes. A
connection between different nodes is not guaranteed, and the link
stability can vary strongly over time. To tackle this, some
Alternative Networks use mesh routing protocols for Mobile Ad Hoc
Networks (MANETs), while other ones use more traditional routing
protocols. Some networks operate multiple routing protocols in
parallel. For example, they may use a mesh protocol inside different
islands and rely on traditional routing protocols to connect these
126.96.36.199. Traditional Routing Protocols
The Border Gateway Protocol (BGP), as defined by [RFC4271], is used
by a number of Community Networks because of its well-studied
behavior and scalability.
For similar reasons, smaller networks opt to run the Open Shortest
Path First (OSPF) protocol, as defined by [RFC2328].
188.8.131.52. Mesh Routing Protocols
A large number of Alternative Networks use customized versions of the
Optimized Link State Routing (OLSR) Protocol [RFC3626]. The open
source project [OLSR] has extended the protocol with the Expected
Transmission Count (ETX) metric [Couto] and other features for its
use in Alternative Networks, especially wireless ones. A new version
of the protocol, named OLSRv2 [RFC7181], is becoming used in some
Community Networks [Barz].
Better Approach To Mobile Ad Hoc Networking (B.A.T.M.A.N.) Advanced
[Seither] is a Layer 2 routing protocol, which creates a bridged
network and allows seamless roaming of clients between wireless
Some networks also run the BatMan-eXperimental Version 6 (BMX6)
protocol [Neumann_a], which is based on IPv6 and tries to exploit the
social structure of Alternative Networks.
Babel [RFC6126] is a Layer 3 loop-avoiding distance-vector routing
protocol that is robust and efficient both in wired and wireless mesh
In [Neumann_b], a study of three proactive mesh routing protocols
(BMX6, OLSR, and Babel) is presented, in terms of scalability,
performance, and stability.
7.2. Transport Layer
7.2.1. Traffic Management When Sharing Network Resources
When network resources are shared (as, e.g., in the networks
explained in Section 5.4), special care has to be taken with the
management of the traffic at upper layers. From a crowdshared
perspective, and considering just regular TCP connections during the
critical sharing time, the Access Point offering the service is
likely to be the bottleneck of the connection.
This is the main concern of sharers, having several implications. In
some cases, an adequate Active Queue Management (AQM) mechanism that
implements a Less-than-Best-Effort (LBE) [RFC6297] policy for the
user is used to protect the sharer. Achieving LBE behavior requires
the appropriate tuning of well-known mechanisms such as Explicit
Congestion Notification (ECN) [RFC3168], Random Early Detection (RED)
[RFC7567], or other more recent AQM mechanisms that aid low latency
such as Controlled Delay (CoDel) [CoDel] and Proportional Integral
controller Enhanced (PIE) [PIE] design.
7.3. Services Provided
This section provides an overview of the services provided by the
network. Many Alternative Networks can be considered Autonomous
Systems, being (or aspiring to be) a part of the Internet.
The services provided can include, but are not limited to:
o Web browsing.
o Remote desktop (e.g., using my home computer and my Internet
connection when I am away).
o FTP file sharing (e.g., distribution of software and media).
o VoIP (e.g., with SIP).
o Peer-to-Peer (P2P) file sharing.
o Public video cameras.
o Online game servers.
o Jabber instant messaging.
o Weather stations.
o Network monitoring.
o Radio streaming.
o Message/bulletin board.
o Local cloud storage services.
Due to bandwidth limitations, some services (file sharing, VoIP,
etc.) may not be allowed in some Alternative Networks. In some of
these cases, a number of federated proxies provide web-browsing
service for the users.
Some specialized services have been specifically developed for
o Inter-network peering/VPNs
o Community-oriented portals (e.g., http://tidepools.co/).
o Network monitoring/deployment/maintenance platforms.
o VoIP sharing between networks, allowing cheap calls between
o Sensor networks and citizen science built by adding sensors to
o Community radio/TV stations.
Other services (e.g., local wikis as used in community portals; see
https://localwiki.org) can also provide useful information when
supplied through an Alternative Network, although they were not
specifically created for them.
7.3.1. Use of VPNs
Some "micro-ISPs" may use the network as a backhaul for providing
Internet access, setting up VPNs from the client to a machine with
Many Community Networks also use VPNs to connect multiple disjoint
parts of their networks together. In some others, every node
establishes a VPN tunnel as well.
7.3.2. Other Facilities
Other facilities, such as NTP or Internet Relay Chat (IRC) servers
may also be present in Alternative Networks.
7.4. Security Considerations
No security issues have been identified for this document.
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This work has been partially funded by the CONFINE European
Commission project (FP7 - 288535). Arjuna Sathiaseelan and Andres
Arcia Moret were funded by the EU H2020 RIFE project (Grant Agreement
no: 644663). Jose Saldana was funded by the EU H2020 Wi-5 project
(Grant Agreement no: 644262).
The editor and the authors of this document wish to thank the
following individuals who have participated in the drafting, review,
and discussion of this memo: Panayotis Antoniadis, Paul M. Aoki,
Roger Baig, Jaume Barcelo, Steven G. Huter, Aldebaro Klautau, Rohan
Mahy, Vesna Manojlovic, Mitar Milutinovic, Henning Schulzrinne, Rute
Sofia, and Dirk Trossen.
A special thanks to the GAIA Working Group chairs Mat Ford and Arjuna
Sathiaseelan for their support and guidance.
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