The Contiki netstacks
Three network stacks
The Contiki netstack
1. Network layer - NETSTACK_RADIO
2. MAC (Medium Access Control) layer - NETSTACK_MAC
3. RDC (Radio Duty Cycling) layer - NETSTACK_RDC
4. Radio layer - NETSTACK_RADIO
The packet buffer - packetbuf
- One buffer, holds a single packet.
- All layers of the netstack operate on the packetbuf.
- Large enough to hold a single radio packet - PACKETBUF_CONF_LEN
Queue buffers - queuebuf
- The packetbuf only holds the current packet.
- To store packets on queues, use a queuebuf.
- Use a list to keep track of them.
uIP packet buffer - uip_buf
Framers - NETSTACK_FRAMER
- The framer module converts link-layer headers to packet attributes - parse()
- And packet attributes to link-layer headers - create()
Network & Routing Layer
- Contiki automatically forms a wireless IPv6 network with the help of routing protocol called RPL (Routing Protocol for Low-power and Lossy Networks (LLNs)).
- RPL forms routing graph from root node or AP (Access Point). It builds acyclic graph from root node called DODAG (Destination Oriented Directed Acyclic Graph).
- DIO (DODAG Information Object) messages are broadcast by all nodes starting from the root node. It includes the node's rank, ETX, DAG version number etc.
- The node selects a parent based on the received DIO messages and calculates its rank.