1+1/1:1 is a type of network protection technique. Under 1+1, a copy of data signal is transmitted respectively on a working and a protection channel. At the receiver side, the receiver can make a decision to accept which copy of signal based on the signal quality. In contrast to 1+1, 1:1 sends a copy of signal on a working channel only, while the protection channel is reserved for future use in case that the working channel gets failed. In normal time, the protection channel can also be used for low priority data traffic transmission. Only when a failure occurs on the working channel, a preempt operation is carried out to take over the protection channel to carry the traffic from the failed working channel. 1:1 generally has better efficiency in the protection capacity usage; however, it needs an additional action to switch over the traffic from a working channel to a protection channel, thereby affecting restoration speed.

Depending on the location that this type of protection mechanism is used, 1+1/1:1 can be implemented as a link-based 1+1/1:1 or path-based 1+1/1:1.