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NodeTypes
Introduction
While the wireless network in Melbourne is in it's infancy other communities have very well developed infrastructure. In the US community networks are not nescessary providing an alternative network to the ISP provided ones but are rather providing wireless access for community members whereever they are.These networks are successful as there is no bandwidth limits from the regular ISP's and every coffe shop is able to hook up a DSL modem and an AP to become a node.In the well developed "geek" centres (Bay Area, Seattle, Austin among others) the local wireless orgs assist the setup of nodes to enlarge the coverage of the network. That's not to say they don't build backbone infrastructure as it is also high on their objectives but citywide access for members seems to be the driving factor.
Here in AUS it's a little different as the lack of competition means that most ISP's still gouge their customers and aply fairly draconian conditions (about what you can hook up, sharing your bandwidth, etc.).
The Melbourne Wireless network is pretty fragmented at the moment. There are pools of linked nodes but no city wide backbone yet. That seems to be the primary goal for the group at the moment. Creating a backbone is very dependant on individuals that want ot be part of it.
So what is a node and do you have one yet?
Seattle Wireless probably has the best classification of node types:
These node definitons really need to be applied a bit loosely as in reality a node will start out as one type and morph into a different type depending on the availability of other nodes to link to. Perhaps the most common variation would be a hybrid BxCx that would have links to other nodes and support either ClientNodes or CxNodes on the BSS interface.
Another common evolution would be a node that starts out running a BSS interface and has a number of other nodes pointng their uplink links to it. In this case the links may be sub-optimal but are likely to suffice for the ammount of traffic and usage of the connected nodes. (Note that as the discrete areas of connectivity coalesce and the network becomes used more that these types of "shared" connections will become bottlnecks in the network).
Logical view of different nodes:
ClientNodes
A ClientNode is a node that connects to a DxNode or CxNode, typically using BSS mode. It could be a PC, laptop or handheld device. A ClientNode could be fixed or mobile.DxNode
DxNodes is a node without any upstream connection, this is typically the node you install at home when you want to get wireless in your house. It allows your wireless devices to be part of your home LAN and you may have internet access for your own personal use. In this scenario you keep the node closed and may use some form of encryption (weak though it may be).+-----------------+ | | | | | +-----+ | | BSS |---\/\--- to ClientNodes | +-----+ | | | | +-----------------+
CxNode
CxNode is a node with one upstream connection. A CxNode connects to a single BxNode. The CxNode accepts connections from ClientNodes and routes thouse requests to it's upstream connection. At this level routing is easy. The CxNode is the on-ramp to the local wireless network.+-----------------+ | | | | | +------+ | | BSS | ---\/\--- to ClientNodes | +------+ | | | +------+ | | IBSS | +++++++++ to upstream BxNode | +------+ | | | | +-----------------+
BxNode
BxNodes support a pool of CxNodes and have two links to other BxNodes provides DHCP to the client CxNodes and intellegent routing. So a BxNode has 3 radios, one for supporting the CxNode pool and two more for making redundant links to the rest of the backbone using two other BxNodes.+-----------------+ | | | | | +------+ | | BSS | ---\/\--- to CxNodes | +------+ | | | +------+ | | IBSS | +++++++++ to peer BxNode | +------+ | | | +------+ | | IBSS | +++++++++ to peer BxNode | +------+ | | | | +-----------------+
AxNode
AxNodes or Super BxNodes have more then 3 radios and tend not to support a client cloud ( no CxNodes hanging of it). It provides routing between it's multiple interfaces.Variations
A number of variations of this classification exist. Perhaps the most common are nodes that provide a hybrid functionality betwen a CxNode and a BXNode. This is common in a young network such as ours as it is more important to get some links in place than to do it in a strictlu herachical sense.BxCx Hybrid
A node that could qualify as a BXNode is more of well linked CxNode. This node has the typical CientNodes but also has a link (or two) to other BxNodes on the same interface. The ideal situation would be for this node to have a dedicated raido(s) for the links to the BxNodes but for the time being the conncetion is established using the omni interface of the node.Re-trans
A re-trans is a pair of radios that provide linkage between two nodes that would not otherwise be able to connect. A retrans may be desirable due to terrain and the lack of suitable nodes in the location.Hypothetical example
In this example a number of BxNodes are configured in the same manner. They use Ch 6 in IBBS mode to communicate to one or more CxNodes that in turn use Ch12 in BSS mode to commuicate with a number of ClientNodes. This is kind of an ideal situation, each BxNode has 3 radios with dedicated links. In reality many of our Nodes will be less optimal.| +-----+IBBS +------+ | BxN |---\/\--- -->|Client| +-----+Ch 6 / +------+ IBBS|Ch 1 / +-----+IBSS +-----+BSS / +------+ | BxN |---\/\--->| CxN |---\/\--->|Client| +-----+Ch 6 +-----+Ch12\ +------+ | \ | \ +------+ This client could roam between the IBBS|Ch 11 -->|Client| the two CxN if they used the same ESSID | / +------+ | / +-----+IBSS +-----+BSS / +------+ | BxN |---\/\--->| CxN |---\/\--->|Client| +-----+Ch 6 +-----+Ch 1\ +------+ IBBS|Ch 1 \ +-----+IBBS \ +------+ | BxN |---\/\--- -->|Client| +-----+ +------+ |
Link types
It is possible to create a link in different ways, the commonest ways are supported in most wireless devices (cards and APs). The simplest links are those that use BSS mode where an AP is the hub for all transmissions. This is fine for the DxNode you use in the house and for connecting ClientNodes to a CxNode but has some limitations when trying to use it for backbone links (the major one being that all traffic is routed through the AP)In the backbone it is useful to build redundancy through multiple connections. Some of thes connections are achieved with multiple physical radios but as the density of nodes increases it is possible that multiple nodes can provide alternative routes for traffic.
Not all links are equal. The typs of link are discussed here in increasing order of preference.
- BSS
- WDS
- Bridge
- IBBS
Node Examples
Looking at the node finder we can see that there is not a lot of linkage activity in our network yet. Some areas are well on the way to creating isolated BxNodes that serve potential CxNodes but we don't have much in the way of BxNode linkage.Version 1 (old) modified Mon, 26 Jul 2021 12:49:29 +0000 by dna0xff
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