Editing Wormhole switching (section)

== Example ==

[[File:Wormhole-Three-Flows-Interfering.gif|thumb|upright=2|alt=An animation of the wormhole switching with three flows.|Three flows on 2x2 network using wormhole switching]] Consider the 2x2 network of the figure on the right, with 3 packets to be sent: a pink one, made of 4 flits, 'UVWX', from C to D; a blue one, made of 4 flits 'abcd', from A to F; and a green one, made of 4 flits 'ijkl', from E to H. We assume that the routing has been computed, as drawn, and implies a conflict of a buffer, in the bottom-left router. The throughput is of one flit per time unit.

First, consider the pink flow: at time 1, the flit 'U' is sent to the first buffer; at time 2, the flit 'U' goes through the next buffer (assuming the computation of the route takes no time), and the flit 'V' is sent to the first buffer, and so on.

The blue and green flows requires a step by step presentation:
* Time 1: Both the blue and green flows send theirs first flits, 'i' and 'a'.
* Time 2: The flit 'i' can go on into the next buffer. But a buffer is dedicated to a packet from its first to its last flit, and so, the 'a' flit can not be forwarded. This is the start of a ''back-pressure'' effect. The 'j' flit can replace the 'i' flit. The 'b' flit can be sent. 
* Time 3: The green packet goes on. The blue 'c' flit can not be forwarded (the buffer is occupied with the 'b' and 'a' flits): this back-pressure effect reaches the packet source.
* Time 4: As in time 3
* Time 5: The green packet no longer uses the left-down buffer. The blue packet is unblocked and can be forwarded (assuming that the 'unblocked' information can be forwarded in null time)
* Time 6-10: The blue packet goes through the network.