Network Architecture
Version 8 (Pau Escrich, 10/04/2013 08:38 am)
| 1 | 1 | Pau Escrich | h1. NetworkArchitecture |
|---|---|---|---|
| 2 | 1 | Pau Escrich | |
| 3 | 5 | Pau Escrich | h2. The basics |
| 4 | 5 | Pau Escrich | |
| 5 | 2 | Pau Escrich | The network architecture designed for libre-mesh is based in two layers: |
| 6 | 2 | Pau Escrich | * The cloud layer 2 which runs Batman-Adv |
| 7 | 2 | Pau Escrich | * The network layer 3 which runs BMX6 |
| 8 | 2 | Pau Escrich | |
| 9 | 1 | Pau Escrich | !network1.png! |
| 10 | 3 | Pau Escrich | |
| 11 | 4 | Pau Escrich | All nodes are runing BMX6 and BATADV at same time in the same WiFi devices but different VLANS. |
| 12 | 4 | Pau Escrich | The BMX6 VLAN is always the same, so all link-layer connected nodes will see each other. |
| 13 | 4 | Pau Escrich | The BATADV VLAN depends on the cloud identifier (CID) which is calculed (by default) from the AP SSID. |
| 14 | 4 | Pau Escrich | |
| 15 | 3 | Pau Escrich | !network2.png! |
| 16 | 4 | Pau Escrich | |
| 17 | 4 | Pau Escrich | This configuration allows to isolate the layer 2 clouds. |
| 18 | 4 | Pau Escrich | For instance a neighborhood, a company complex or a street level hotsposts network can choose isolate their LAN from the rest of the network. |
| 19 | 4 | Pau Escrich | However at the same time, they will be able to reach the rest of the community network using the layer 3 routed network. |
| 20 | 4 | Pau Escrich | |
| 21 | 4 | Pau Escrich | In case an entire network community wants to have a single cloud, they can just use the same CID. |
| 22 | 5 | Pau Escrich | |
| 23 | 5 | Pau Escrich | h2. The details |
| 24 | 5 | Pau Escrich | |
| 25 | 7 | Pau Escrich | All WiFi Access Points from the same layer 2 cloud share the same SSID, a special anycast IPv4/IPv6 address and a special anycast MAC address. |
| 26 | 7 | Pau Escrich | It will allow real roaming inside the network, so the clients does not need to renew their IP configuration when they change from one AP to the other. |
| 27 | 7 | Pau Escrich | |
| 28 | 5 | Pau Escrich | !network3.png! |
| 29 | 6 | Pau Escrich | |
| 30 | 7 | Pau Escrich | All mesh nodes have a DHCP/RA server to provide valid IPs from the cloud to the clients. |
| 31 | 7 | Pau Escrich | The DHCP leasses file is shared among the cloud to prevent colisions (using A.L.F.R.E.D). |
| 32 | 7 | Pau Escrich | As long as all nodes share the same anycast MAC/IP, from the client point of view it is fully transparent. Thus the gateway is always the same nonetheless the mesh node where they are attached is different. |
| 33 | 7 | Pau Escrich | |
| 34 | 6 | Pau Escrich | !network4.png! |
| 35 | 7 | Pau Escrich | |
| 36 | 7 | Pau Escrich | When a client wants to reach the Internet or any other network which is not the one used in the layer 2 cloud, it sends the packet to the anycast gateway address. |
| 37 | 7 | Pau Escrich | An ebtables rule in the LAN/AP bridge prevents the layer 2 packets propagation in the cloud sent to the anycast address. So the mesh node where the client is associated gets the packet but not the others. |
| 38 | 1 | Pau Escrich | |
| 39 | 1 | Pau Escrich | !network5.png! |
| 40 | 8 | Pau Escrich | |
| 41 | 8 | Pau Escrich | The packet is routed throw the BMX6 layer 3 network to the best Internet gateway (according to the BMX6 metrics). It may be a node from the same cloud or any other from another far away cloud. |
| 42 | 8 | Pau Escrich | In the way back the packet will arreive to some node in the cloud but it may not be the same, it will depend on the routing protocol metrics. |
| 43 | 8 | Pau Escrich | |
| 44 | 8 | Pau Escrich | !network6.png! |