JDSU Core level field testers enable a broad set of test and measurement capabilities, from basic bit error rate (BER) tests to in-line optical monitoring (seeing both East and West directions) for SONET/SDH rings, FC, and Gigabit Ethernet (GigE) services. JDSU testers also provide end-to-end L4 Transmission Control Protocol/User Datagram Protocol (TCP/UDP) Traffic Blasting that measures throughput, loss, and delay, as well as TCP state.