Satoshi is discussing the reliability and speed of broadcasting blocks in the Bitcoin network.

In this context, a "broadcast" refers to the transmission of a new block to all nodes on the network. Satoshi is saying that these broadcasts are expected to be very reliable, meaning that the data will almost always reach its destination without being lost or corrupted. This is because the underlying technology, TCP (Transmission Control Protocol), is robust and rarely drops transmissions.

Furthermore, the Bitcoin protocol has a built-in retry mechanism that allows nodes to retrieve data from other nodes if they miss a broadcast. This ensures that all nodes on the network will eventually receive the new block.

However, Satoshi notes that if the broadcasts are slower than expected, it may be necessary to increase the target time between blocks. This is because nodes need to receive and process new blocks quickly, so they can focus on generating new blocks rather than wasting resources on obsolete ones.

In essence, Satoshi wants the block propagation time to be much faster than the block generation time. If blocks take too long to propagate, nodes will spend too much time working on blocks that are no longer valid, which would be inefficient and waste resources.

This highlights the importance of efficient block propagation in the Bitcoin network, as it directly affects the overall performance and scalability of the system.