IEEE 802.11s is a draft IEEE 802.11 amendment for mesh networking, defining how wireless devices can interconnect to create a WLAN mesh network, which may be used for static topologies and ad-hoc network.

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, and 802.11n versions to provide wireless connectivity in the home, office and some commercial establishments.

[edit] Description

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

[edit] 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.

A mesh architectures allowing otherwise out-of-range nodes 1–4 to still connect to the Internet

[edit] 802.11 mesh architecture

An 802.11s mesh network device is labelled as Mesh Station (mesh STA). Mesh STAs form mesh links with one another, over which mesh paths can be established using a routing protocol. 802.11s defines a default mandatory routing protocol (Hybrid Wireless Mesh Protocol, or HWMP)^[1], yet allows vendors to operate using alternate protocols. HWMP is inspired by a combination of AODV (RFC 3561^[2]) and tree-based routing.

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.

[edit] 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.

802.11s defines a secure password-based authentication and key establishment protocol called "Simultaneous Authentication of Equals" (SAE). SAE is based on a zero knowledge proof and is resistant to active attack, passive attack, and dictionary attack.

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 Peering Exchange" (APE) to establish a secure peering and a derive a session key to protect mesh traffic, including routing traffic.

[edit] Usage

While still in a preliminary development stage, the 802.11s draft is supported by a wide variety of industry leaders. The One Laptop per Child^[3] project uses the 802.11s draft standard for its OLPC XO laptop and OLPC XS school server networking. 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^[4]. In FreeBSD, 802.11s draft is supported starting with FreeBSD 8.0^[5].

[edit] References

[edit] See also

• Wireless mesh network

[edit] External links

• Status of 802.11s
• Open80211s.org
• WifiMesh - FreeBSD Wiki