In a lambda switch, which we can also describe as an LSC interface with a GMPLS control plane, the goal is to reduce the time taken to establish optical paths from months to minutes. Once established, the wavelengths will remain in place for a relatively long time – perhaps months or even years. In this timescale, it’s quite acceptable to use traditional, reliable signaling techniques – notably RSVP (resource reservation protocol) and CR-LDP (constraint-based routing-label distribution protocol), which are being extended for use in GMPLS. Signaling can be out of band, using a low-speed overlay such as fast Ethernet. In OBS, the goal is to set up lambdas so that a single burst of data can be transmitted. As noted previously, a 1-Mbyte file transmitted at 10 G bit/s only requires a lambda for 1ms. The burst has to be buffered by the OEO edge device while the lambda is being set up, so the signaling has to be very fast indeed, and it looks as though we won’t have time for traditional handshakes.