At the moment, sc-network contains a pretty generic low-level networking stack, on top of which the syncing and transaction protocols are implemented.
sc-network exposes both the API of the low-level networking stack, but also an API for syncing and transaction-related actions.

I think it would make sense to move the syncing and transaction out of sc-network.

I focused on the syncing in the issue title, because transactions are already more or less segregated from the rest.