Wormhole switching

[2][3] The wormhole technique does not dictate the route to the destination but decides when the packet moves forward from a router.

Wormhole switching is widely used in multicomputers because of its low latency and small requirements at the nodes.

[3]: 376 Wormhole routing supports very low-latency, high-speed, guaranteed delivery of packets suitable for real-time communication.

In most respects, wormhole is very similar to ATM or MPLS forwarding, with the exception that the cell does not have to be queued.

This reduces latency (delay) noticeably compared to store-and-forward switching that waits for the whole packet before forwarding.

More recently, wormhole flow control has found its way to applications in network-on-chip systems (NOCs), of which multi-core processors are one flavor.

Here, many processor cores, or on a lower level, even functional units can be connected in a network on a single IC package.

As wire delays and many other non-scalable constraints on linked processing elements become the dominating factor for design, engineers are looking to simplify organized interconnection networks, in which flow control methods play an important role.

Each unidirectional virtual channel is realized by an independently managed pair of (flit) buffers.

Virtual channels were originally introduced to avoid the deadlock problem, but they can be also used to reduce wormhole blocking, improving network latency and throughput.

The packet sender may choose to use source routing to explicitly specify the complete path through the network to the final destination in this fashion.