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* Introduction [1]
* Scope [2]
* Requirements [3]
* Mesh routing principles [4]
* Issues [5]
* Management [6]
* Hierarchy [7]
INTRODUCTION
Melbourne wireless aims to set up a community network. Unlike many
other wireless groups, our focus is not on free internet connection
sharing, but on actually establishing a large network of wide area
links with little emphasis on Internet connectivity. This places us in
a distinct niche (well, a slightly cramped niche along with Brisbane,
Madrid & Seattle wireless).
SCOPE
To provide a routing architecture and deployment specification for
community wireless netwoorks. Scope includes both internal routing
within a regional mesh, as well as peering via a smaller set of
wireless links, Internet tunnels or other mechanisms to other regional
meshes and Internet Protocol based internetworks.
REQUIREMENTS
MESH ROUTING PRINCIPLES
(1) Nodes within a region _must_ cooperate in order to forward
packets to the ultimate destination on behalf of peers.
(2) Any solution must be scalable to thousands of nodes within an
individual regional mesh
(3) Nodes must be able to support host networks attached via fixed or
wireless technologies.
(4) The mesh must be able to be inter-connected to other regional
meshes and Internet Protocol based internetworks.
ISSUES
(1) This is mostly straight-forward. The nodes in the mesh must
either switch or route packets towards their destination. Switching is
largely impractical except for bridging in special circumstances (such
as a repeater). In order to route, the node must support an operating
system with routing functionality, e.g. *NIX, Win2K, Cisco IOS. Merely
having 802.11 IBSS implementation is not enough as 802.11 does not
(contrary to some beliefs) specify any mechanism for forwarding
frames.
(2) There are a large number of difficulties to achieving the
scalability critieria. Firstly, scalable networks rely upon hierarchy.
Secondly in order to grow a network to this size requires minimal
management.
MANAGEMENT
Addition of a new node to the mesh should be achieved with minimum or
zero configuration changes on adjacent nodes. This implies a number of
things, but foremost, it requires that a dynamic routing protocal is
needed.
HIERARCHY
Hierarchy is difficult to achieve. Community wireless mesh networks
exhibit a graph structure that is approximately related to
geographical positioning of the nodes. Nodes that are in geographic
proximity are more likely to be linked than nodes that are distant.
This feature of the network topology makes the imposition of hierarchy
extremely difficult. Secondly, wireless technology is such that most
links will have the same order of magnitude of bandwidth. This makes
aggregation, a key principle of hierarchies, even more difficult. The
inability to easily impose hierarchy will limit the scalability of the
mesh. A good technical reference on scalability issues of routing
protocols is available from a North American Network Operators' Group
- nanog - talk [8].
(3) This is another relatively simple issue, easily solved again
through the use of a dynamic routing protocol that can advertise
reachability information into the mesh.
(4) This is where it starts to look a little more like an enterprise
network. Techniques from the Internet and enterprise networking worlds
are readily applicable.
Links:
------
[1] http://melbournewireless.org.au/#introduction
[2] http://melbournewireless.org.au/#scope
[3] http://melbournewireless.org.au/#requirements
[4] http://melbournewireless.org.au/#mesh_routing_principles
[5] http://melbournewireless.org.au/#issues
[6] http://melbournewireless.org.au/#management
[7] http://melbournewireless.org.au/#hierarchy
[8] http://www.nanog.org/mtg-0110/retana.html
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