ing of encryption keys between access points and associated wireless stations. Transport Control Protocol (TCP): TCP manages the transport of mes- sages over a network, including the fragmentation into packets, in sequence reconstruction from received packets, error checking and requests to retransmit missing packets. Tunnelling: Tunnelling creates a secure link across an unsecured network by encapsulating data packets structured according to one protocol with a wrapper defined by another protocol. Tunnelling involves three different protocols; a carrier protocol used by the network that the data is transmit- ted over (e.g. IP), an encapsulating protocol that provides the wrapper and the passenger protocol that structures the original data packet. Turbo codes: Turbo codes are error correction codes that rely on the com- putation of two independent parity checks on each data block. On decod- ing, the two check codes are used to independently verify the received data block. If the two decoders disagree on the data block an iterative exchange of information takes place until they converge on a single solution. User Datagram Protocol (UDP): UDP is a data transport protocol that performs similar functions to TCP, but does not check for the arrival of all Glossary data packets or request retransmission if any packets are missed. UDP is used in applications such as VoIP or media streaming, where recovery of missed packets is of no value and they are simply dropped. Unicast: A unicast message is transmitted to a single identified receiving station, in contrast to multicast and broadcast messages (q.v.). Unshielded Twisted Pair (UTP): Unshielded twisted pair is the most common type of cabling for wired Ethernet connections and consists of four twisted copper wire pairs, terminated with an RJ45 connector. Different cat- egories of UTP cabling are defined for different network speeds from Cat 1 for low speed (1 Mbps), Cat 5 the most common Ethernet cabling for 100 Mbps, up to Cat 7 for ultra-fast Ethernet at 10 Gbps. Ultra 