IEEE 802.11s

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IEEE 802.11s is Wireless LAN standard and an IEEE 802.11 amendment for mesh networking, defining how wireless devices can interconnect to create a WLAN mesh network, which may be used for relatively fixed (not mobile) topologies and wireless ad hoc networks. The IEEE 802.11s working group draws upon volunteers from university and industry to provide specifications and possible design solutions for wireless mesh networking. As a standard, the document was iterated and revised many times prior to finalization.

Contents

802.11 is a set of IEEE standards that govern wireless networking transmission methods. They are commonly used today in their 802.11a, 802.11b, 802.11g, 802.11n, 802.11ac, and 802.11ax versions to provide wireless connectivity in the home, office and some commercial establishments.

Description

802.11s extends the IEEE 802.11 MAC standard by defining an architecture and protocol that supports both broadcast/multicast and unicast delivery using "radio-aware metrics over self-configuring multi-hop topologies."

802.11s inherently depends on one of 802.11a, 802.11b, 802.11g, 802.11n, 802.11ac, or 802.11ax carrying the actual traffic. One or more routing protocols suitable to the actual network physical topology are required. 802.11s requires Hybrid Wireless Mesh Protocol, or HWMP, [1] be supported as a default. However, other mesh, ad hoc (Associativity-Based Routing, Zone Routing Protocol, and location based routing) or dynamically link-state routed (OLSR, B.A.T.M.A.N. [ citation needed ]) may be supported or even static routing (WDS, OSPF). See the more detailed description below comparing these routing protocols.

A mesh often consists of many small nodes. When mobile users or heavy loads are concerned, there will often be a handoff from one base station to another, and not only from 802.11 but from other (GSM, Bluetooth, PCS and other cordless phone) networks. Accordingly, IEEE 802.21, which specifies this handoff between nodes both obeying 802.11s and otherwise, may be required. This is especially likely if a longer-range lower-bandwidth service is deployed to minimize mesh dead zones, e.g. GSM routing based on OpenBTS.

Mesh networking often involves network access by previously unknown parties, especially when a transient visitor population is being served. Thus the accompanying IEEE 802.11u standard will be required by most mesh networks to authenticate these users without pre-registration or any prior offline communication. Pre-standard captive portal approaches are also common. See the more detailed description below of mesh security.

Timeline

802.11s started as a Study Group of IEEE 802.11 in September 2003. It became a Task Group in July 2004. A call for proposals was issued in May 2005, which resulted in the submission of 15 proposals submitted to a vote in July 2005. After a series of eliminations and mergers, the proposals dwindled to two (the "SEE-Mesh" and "Wi-Mesh" proposals), which became a joint proposal in January 2006. This merged proposal was accepted as draft D0.01 after a unanimous confirmation vote in March 2006.

The draft evolved through informal comment resolution until it was submitted for a Letter Ballot in November 2006 as Draft D1.00. Draft D2.00 was submitted in March 2008 which failed with only 61% approval. A year was spent clarifying and pruning until Draft D3.00 was created which reached WG approval with 79% in March 2009.

The Task Groups stated goal for the May 2009 802.11 meeting is to start resolving comments from its new Letter Ballot.

In June 2011 the fifth recirculation Sponsor Ballot, on TGs Draft 12.0, was closed. The Draft met with 97.2% approval rate. [2]

The 2012 release of the 802.11 specification (802.11-2012) [3] directly incorporates Mesh Routing functionality. The IEEE page for 802.11s lists that specification as superseded.

A wireless mesh network architecture allowing otherwise out-of-range nodes 1-4 to still connect to the Internet. A key characteristic is the presence of multiple-hop links and using intermediate nodes to relay packets for others. XO internet access.jpg
A wireless mesh network architecture allowing otherwise out-of-range nodes 1–4 to still connect to the Internet. A key characteristic is the presence of multiple-hop links and using intermediate nodes to relay packets for others.

802.11 mesh architecture

An 802.11s wireless mesh network device is labelled as Mesh Station (mesh STA), or simply an ad hoc node. Mesh STAs form mesh links with one another, over which mesh paths can be established using an ad hoc mobile routing protocol. A key aspect of this architecture is the presence of multi-hop wireless links and routing of packets through other nodes towards the destination nodes.

Routing protocols

This should be expanded into a treatment of all the compatible routing protocols.

802.11s defines a default mandatory routing protocol (Hybrid Wireless Mesh Protocol, or HWMP), [1] yet allows vendors to operate using alternate routing protocols. HWMP is inspired by a combination of AODV (RFC 3561 [4] ), which uses on-demand ad hoc routing approach and tree-based routing. Examples of on-demand ad hoc routing are Dynamic Source Routing and Associativity-Based Routing. AODV route discovery and localized route repair approaches are identical to Associativity-based Routing. Prior work [5] [6] [7] [8] has discussed and compared these various routing protocols in detail. [9]

Mesh STAs are individual devices using mesh services to communicate with other devices in the network. They can also collocate with 802.11 Access Points (APs) and provide access to the mesh network to 802.11 stations (STAs), which have broad market availability. Also, mesh STAs can collocate with an 802.11 portal that implements the role of a gateway and provides access to one or more non-802.11 networks. In both cases, 802.11s provides a proxy mechanism to provide addressing support for non-mesh 802 devices, allowing for end-points to be cognizant of external addresses.

802.11s also includes mechanisms to provide deterministic network access, a framework for congestion control and power save.

Mesh security

There are no defined roles in a mesh — no clients and servers, no initiators and responders. Security protocols used in a mesh must, therefore, be true peer-to-peer protocols where either side can initiate to the other or both sides can initiate simultaneously.

Peer authentication methods

Between peers, 802.11s defines the secure password-based authentication and key establishment protocol Simultaneous Authentication of Equals (SAE). SAE is based on Diffie–Hellman key exchange using finite cyclic groups which can be a primary cyclic group or an elliptic curve. [10] The problem on using Diffie–Hellman key exchange is that it does not have an authentication mechanism. So the resulting key is influenced by a pre-shared key and the MAC addresses of both peers to solve the authentication problem.

When peers discover each other (and security is enabled) they take part in an SAE exchange. If SAE completes successfully, each peer knows the other party possesses the mesh password and, as a by-product of the SAE exchange, the two peers establish a cryptographically strong key. This key is used with the "Authenticated Mesh Peering Exchange" (AMPE) to establish a secure peering and derive a session key to protect mesh traffic, including routing traffic.

Usage

IEEE 802.11s amendment is supported by many products such as open80211s, OLPC. [11] In open80211s smaller meshes of under 32 nodes [12] are supported. Some of the projects are based on earlier (draft) versions.

Linux

A reference implementation of the 802.11s draft is available as part of the mac80211 layer in the Linux kernel, starting with version 2.6.26. [13] The Linux community, with its many diverse distributions, provides a heterogenous testing ground for protocols like Hybrid Wireless Mesh Protocol. [14] OpenWrt, a Linux distribution for routers, supports mesh networking. [15]  · [16]

BSD

In FreeBSD, 802.11s draft is supported starting with FreeBSD 8.0. [17]

Google Wifi

The Google Wifi router uses the 802.11s mesh networking protocol. [18]

MeshPoint.One

The MeshPoint.One router uses 802.11s mesh networking protocol [19]

See also

Related Research Articles

Wireless LAN Computer network that links devices using wireless communication within a limited area

A wireless LAN (WLAN) is a wireless computer network that links two or more devices using wireless communication to form a local area network (LAN) within a limited area such as a home, school, computer laboratory, campus, or office building. This gives users the ability to move around within the area and remain connected to the network. Through a gateway, a WLAN can also provide a connection to the wider Internet.

Zigbee IEEE 802.15.4-based specification for a suite of high-level communication protocols

ZigBee is an IEEE 802.15.4-based specification for a suite of high-level communication protocols used to create personal area networks with small, low-power digital radios, such as for home automation, medical device data collection, and other low-power low-bandwidth needs, designed for small scale projects which need wireless connection. Hence, ZigBee is a low-power, low data rate, and close proximity wireless ad hoc network.

Wireless mesh network network topology

A wireless mesh network (WMN) is a communications network made up of radio nodes organized in a mesh topology. It is also a form of wireless ad hoc network.

Service set (802.11 network) group of all devices on the same wireless network

In IEEE 802.11 wireless local area networking standards, a service set is a group of wireless network devices which are identified by the same SSID. SSIDs serve as "network names" and are typically natural language labels. A service set forms a logical network -- that is operating with the same level 2 networking parameters -- they are on the same logical network segment.

Mesh networking type of computer network

A mesh network is a local network topology in which the infrastructure nodes connect directly, dynamically and non-hierarchically to as many other nodes as possible and cooperate with one another to efficiently route data from/to clients. This lack of dependency on one node allows for every node to participate in the relay of information. Mesh networks dynamically self-organize and self-configure, which can reduce installation overhead. The ability to self-configure enables dynamic distribution of workloads, particularly in the event a few nodes should fail. This in turn contributes to fault-tolerance and reduced maintenance costs.

Optimized Link State Routing Protocol

The Optimized Link State Routing Protocol (OLSR) is an IP routing protocol optimized for mobile ad hoc networks, which can also be used on other wireless ad hoc networks. OLSR is a proactive link-state routing protocol, which uses hello and topology control (TC) messages to discover and then disseminate link state information throughout the mobile ad hoc network. Individual nodes use this topology information to compute next hop destinations for all nodes in the network using shortest hop forwarding paths.

Ad hoc On-Demand Distance Vector (AODV) Routing is a routing protocol for mobile ad hoc networks (MANETs) and other wireless ad hoc networks. It was jointly developed on July 2003 in Nokia Research Center, University of California, Santa Barbara and University of Cincinnati by C. Perkins, E. Belding-Royer and S. Das.

Wireless network interface controller Controller card for a wireless network interface

A wireless network interface controller (WNIC) is a network interface controller which connects to a wireless radio-based computer network, rather than a wired network, such as Token Ring or Ethernet. A WNIC, just like other NICs, works on the Layer 1 and Layer 2 of the OSI Model. This card uses an antenna to communicate via microwave radiation. A WNIC in a desktop computer is traditionally connected using the PCI bus. Other connectivity options are USB and PC card. Integrated WNICs are also available,.

The IEEE 802.21 refers to Media Independent Handoff (MIH) and is an IEEE standard published in 2008. The standard supports algorithms enabling seamless handover between wired and wireless networks of the same type as well as handover between different wired and wireless network types also called Media independent handover (MIH) or vertical handover. Vertical handover was first introduced by Mark Stemn and Randy Katz at U C Berkeley. The standard provides information to allow handing over to and from wired 802.3 network to wireless 802.11, 802.15, 802.16, 3GPP and 3GPP2 networks through different handover mechanisms.

Wireless security prevention of unauthorized access or damage to computers or data using wireless networks, which include Wi-Fi networks

Wireless security is the prevention of unauthorized access or damage to computers or data using wireless networks, which include Wi-Fi networks. The most common type is Wi-Fi security, which includes Wired Equivalent Privacy (WEP) and Wi-Fi Protected Access (WPA). WEP is a notoriously weak security standard: the password it uses can often be cracked in a few minutes with a basic laptop computer and widely available software tools. WEP is an old IEEE 802.11 standard from 1997, which was superseded in 2003 by WPA, or Wi-Fi Protected Access. WPA was a quick alternative to improve security over WEP. The current standard is WPA2; some hardware cannot support WPA2 without firmware upgrade or replacement. WPA2 uses an encryption device that encrypts the network with a 256-bit key; the longer key length improves security over WEP. Enterprises often enforce security using a certificate-based system to authenticate the connecting device, following the standard 802.1X.

IEEE 802.11u-2011 is an amendment to the IEEE 802.11-2007 standard to add features that improve interworking with external networks.

hostapd is a user space daemon software enabling a network interface card to act as an access point and authentication server. There are three implementations: Jouni Malinen's hostapd, OpenBSD's hostapd and Devicescape's hostapd.

In wireless networking, On-Demand Multicast Routing Protocol is a protocol for routing multicast and unicast traffic throughout Ad hoc wireless mesh networks.

6LoWPAN is an acronym of IPv6 over Low -Power Wireless Personal Area Networks. 6LoWPAN is the name of a concluded working group in the Internet area of the IETF.

A wireless ad hoc network (WANET) or Mobile ad hoc network (MANET) is a decentralized type of wireless network. The network is ad hoc because it does not rely on a pre-existing infrastructure, such as routers in wired networks or access points in managed (infrastructure) wireless networks. Instead, each node participates in routing by forwarding data for other nodes, so the determination of which nodes forward data is made dynamically on the basis of network connectivity and the routing algorithm in use.

B.A.T.M.A.N. routing protocol

The Better Approach To Mobile Adhoc Networking (B.A.T.M.A.N.) is a routing protocol for multi-hop mobile ad hoc networks which is under development by the German "Freifunk" community and intended to replace the Optimized Link State Routing Protocol (OLSR).

Hybrid Wireless Mesh Protocol (HWMP) defined in IEEE 802.11s, is a basic routing protocol for a wireless mesh network. It is based on AODV and tree-based routing. It relies on a Peer Link Management protocol by which each Mesh Point discovers and tracks neighboring nodes. If any of these are connected to a wired backhaul, there is no need for HWMP, which selects paths from those assembled by compiling all mesh point peers into one composite map.

Associativity-based routing is a mobile routing protocol invented for wireless ad hoc networks, also known as mobile ad hoc networks (MANETs) and wireless mesh networks. ABR was invented in 1993, filed for a U.S. patent in 1996, and granted the patent in 1999. ABR was invented by Chai Keong Toh while doing his Ph.D. at Cambridge University.

CBRP, or Cluster Based Routing Protocol, is a routing protocol for wireless mesh networks. CBRP was originally designed in mid 1998 by the National University of Singapore and subsequently published as an Internet Draft in August 1998. CBRP is one of the earlier hierarchical ad-hoc routing protocols. In CBRP, nodes dynamically form clusters to maintain structural routing support and to minimize excessive discovery traffic typical for ad-hoc routing.

References

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  3. 2012 release of the 802.11 specification (802.11-2012)
  4. "RFC 3561 Ad hoc On-Demand Distance Vector (AODV) Routing". Mobile Ad Hoc Networking Working Group of the Internet Engineering Task Force. July 2003. Retrieved 2007-03-03.
  5. "A Simulation Study of Table-Driven and On-Demand Routing Protocols for Mobile Ad Hoc Network - S J Lee, et. al., 1999" (PDF).
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  9. "Routing Protocols for Ad Hoc Mobile Wireless Networks by Padmini Misra".
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  19. "MeshPoint.One technical specification" . Retrieved 2019-08-11.