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185 lines
6.3 KiB
Markdown
185 lines
6.3 KiB
Markdown
ZEP packet dispatcher
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=====================
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The ZEP dispatcher is a simple daemon that forwards ZEP packets to all connected
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nodes.
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```
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usage: zep_dispatch [-t topology] [-s seed] [-g graphviz_out] <address> <port>
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```
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By default the dispatcher will forward every packet it receives to every other
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connected node (flat topology).
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Advanced Topology Mode
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----------------------
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It is possible to simulate a more complex topology as well as packet loss by
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specifying a topology file.
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The file format is:
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```
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<node_a> <node_b> [weight_ab] [weight_ba]
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```
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This line defines a connection between <node_a> and <node_b>.
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The weight of the edge <node_a> -> <node_b> is <weight_ab>.
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An edge weight is a float value between 0 and 1 that represents the probability of
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a successful packet transmission on that path.
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A weight of `0` would mean no connection, whereas a weight of `1` would be a perfect
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connection. Intermediate values are possible, e.g. `0.6` would result in a packet
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loss probability of 40%.
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The weights can be omitted.
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If both weights are omitted, a perfect connection is assumed.
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If <weight_ba> is omitted, a symmetric connection is assumed and <weight_ab> is used
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for both directions.
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refer to the file `example.topo` for an example.
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There can only be as many nodes connected to the dispatcher as have been named in
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the topology file.
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Any additional nodes that try to connect will be ignored.
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Packet capture
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--------------
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To view traffic in Wireshark you need to create a virtual 802.15.4 device to which
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the network traffic is sent. This can then be selected as a capture source in Wireshark.
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To create the virtual device, load the `mac802154_hwsim` module
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sudo modprobe mac802154_hwsim
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This will create two wpan devices, `wpan0` and `wpan1`.
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If you then run the dispatcher with
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sudo zep_dispatch -w wpan0 ::1 17754
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all traffic on the simulated network will be also sent to the virtual `wpan0` interface
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where it can be captures with Wireshark.
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Network visualization
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---------------------
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It is possible to generate a graph of the current simulated network by executing the
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make graph
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target. This sends a USR1 signal to the `zep_dispatch` process to generate a graph in
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Graphviz format.
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### Foren6
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For real-time visualization of the (RPL) network, the [Foren6](https://cetic.github.io/foren6/)
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tool can be used.
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Support for ZEP dispatcher is currently only available through [a fork](https://github.com/benpicco/foren6).
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#### Foren6 setup
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Start `foren6` with the `make run` target and in the 'Manage Sources' menu, add a ZEP sniffer:
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The 'target' field takes a hostname:port combination, but you can leave it blank. In that case the default `[::1]:17754` will be used.
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#### Foren6 usage
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Foren6 will connect to a running ZEP dispatcher. If the dispatcher started after Foren6 or
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if the dispatcher was restarted, you have to re-connect by stopping the current capture ('Stop' button)
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and starting it again ('Start' button).
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You should see a view of the DODAG with all nodes in the network as they send packets.
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#### RIOT setup
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A proper simulated network will need a border router and some mesh nodes.
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The `gnrc_border_router` and `gnrc_networking` can serve as a starting point for those.
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By default the border router example will start the ZEP dispatcher with a flat topology, that is
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each node is connected to every other node.
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This makes for a very boring topology where no RPL is needed.
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To run the ZEP dispatcher with a custom topology, simply run it before the `gnrc_border_router`
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example. You can use the `make run` target which will default to the `example.topo` topology.
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This can be changed with the `TOPOLOGY` environment variable.
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Next, start the border router example with RPL enabled:
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USEMODULE=gnrc_rpl make -C examples/gnrc_border_router all term
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Verify that the border router got a prefix on it's downstream interface with `ifconfig`.
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```
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Iface 7 HWaddr: 36:DE Channel: 26 NID: 0x23
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Long HWaddr: BE:92:89:04:D7:B4:B6:DE
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L2-PDU:102 MTU:1280 HL:64 RTR
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RTR_ADV 6LO IPHC
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Source address length: 8
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Link type: wireless
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inet6 addr: fe80::bc92:8904:d7b4:b6de scope: link VAL
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--> inet6 addr: 2001:db8::bc92:8904:d7b4:b6de scope: global VAL
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inet6 group: ff02::2
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inet6 group: ff02::1
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inet6 group: ff02::1:ffb4:b6de
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inet6 group: ff02::1a
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Iface 6 HWaddr: 7A:37:FC:7D:1A:AF
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L2-PDU:1500 MTU:1500 HL:64 RTR
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Source address length: 6
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Link type: wired
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inet6 addr: fe80::7837:fcff:fe7d:1aaf scope: link VAL
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inet6 addr: fe80::2 scope: link VAL
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inet6 group: ff02::2
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inet6 group: ff02::1
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inet6 group: ff02::1:ff7d:1aaf
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inet6 group: ff02::1:ff00:2
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```
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Now start as many `gnrc_networking` nodes as you have mesh nodes defined in your topology file:
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USE_ZEP=1 make -C examples/gnrc_networking all term
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USE_ZEP=1 make -C examples/gnrc_networking all term
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…
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The node should be able to join the DODAG as you can verify with the `rpl` command:
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```
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instance table: [X]
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parent table: [X] [ ] [ ]
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instance [0 | Iface: 7 | mop: 2 | ocp: 0 | mhri: 256 | mri 0]
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dodag [2001:db8::bc92:8904:d7b4:b6de | R: 768 | OP: Router | PIO: on | TR(I=[8,20], k=10, c=119)]
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parent [addr: fe80::6467:2e89:b035:d51f | rank: 512]
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```
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This should also be visible in Foren6.
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Topology generation
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-------------------
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To generate a random topology use the `topogen.sh` script.
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This will randomly distribute *N* nodes on on a *W* × *H* map.
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Each node has a radio range *R* ± *V* where *V* is a random variance that can also be set to 0.
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The further away a node is from a sending node, the higher the packet loss probability.
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Nodes outside the sending radius have a zero probability of receiving a packet.
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If you have `gnuplot` installed this will also generate a plot of the resulting node distribution:
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A light color means that a node only has a one-way connection to the network, gray means a node is
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entirely isolated.
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