The SWANS network entity receives upcalls from the link entity and passes them to the appropriate packet handler, based on the packet protocol information. The SWANS network entity also receives downcalls from the routing and transport entities, which it enqueues and eventually passes to the link entity. Thus, the network entity is the nexus of multiple network interfaces and multiple network packet handlers. The network interfaces are indexed sequentially from zero. The packet handlers are associated with IETF standard protocol numbers, but are mapped onto a smaller index space, to conserve memory, through a dynamic protocol mapper that is shared across the entire simulation. Each network interface is associated with a packet queue, which can handle packet priorities and perform RED. The packets are dequeued and sent to the appropriate link entity using a token protocol to ensure that only one packet is transmitted at a time per interface. The network layer sends packets to the routing entity to receive next hop information and allows the routing entity to peek at all incoming packets. It also encapsulates message with the appropriate IP packet header. The network layer uses an IPv4 implementation. Loopback and broadcast are implemented.
|PacketLoss||Zero||zero network layer packet loss|
|Uniform||independent, random drop with fixed probability|
|MessageQueue||outgoing message queues|