UA: User Adaptation Layers
User Adaptation Layers (UA) are a collection of the Signaling User Adaptation Layers in the SIGTRAN protocol suite. UA includes: SS7 TCAP-User Adaptation Layer (TUA), SS7 SCCP-User Adaptation Layer (SUA), SS7 ISUP-User Adaptation Layer (ISUA), SS7 MTP3-User Adaptation Layer (M3UA), SS7 MTP2-User Adaptation Layer (M2UA), SS7 MTP2-User Peer-to-Peer Adaptation Layer (M2PA), ISDN-User Adaptation Layer (IUA), and Tekelec's Transport Adapter Layer Interface (TALI).
Standard Organization: IETF

UB Net/One: Ungermann-Bass Net/One
Ungermann-Bass Net/One (UB Net/One) is a routing protocol developed by UB Networks, that uses hello packets and a path-delay metric, with end nodes communicating using the XNS protocol. There are a number of differences between the manner in which Net/One uses the XNS protocol and the usage common among other XNS nodes.
Standard Organization: UB Networks

UDLP: UniDirectional Link Protocol
UniDirectional Link Protocol (UDLP) is used by inexpensive, receive-only antennas to receive data via satellite.

UDP Port Numbers
UDP Port Numbers are designed to distinguish multiple applications running on a single device with one IP address from one another. In the UDP header, there are "SourcePort" and "DestinationPort" fields which are used to indicate the message sending process and receiving process identities defined. The combination of the IP address and the port number is called "socket".
Standard Organization: IANA

UDP: User Datagram Protocol
User Datagram Protocol (UDP) is a connectionless transport layer (layer 4) protocol in the OSI model which provides a simple and unreliable message service for transaction-oriented services. UDP is basically an interface between IP and upper-layer processes. UDP protocol ports distinguish multiple applications running on a single device from one another.
Standard Organization: IETF
Reference Document: RFC 768

UMTS: Universal Mobile Telecommunication System
Universal Mobile Telecommunications System (UMTS) is a 3G cellular network technology that uses WCDMA (Wideband Code Division Multiple Access), which was operating in 25 countries as of mid-2005. The transmission rates range from a theoretical 384K bit/sec. for phones that are moving up to 2M bit/sec. for stationary devices.
Standard Organization: ETSI

UNI: User Network Interface
The User-to-Network Interface (UNI) signaling protocol within the Signalling ATM Adaptation Layer (SAAL) are responsible for ATM call and connection control, including call establishment, call clearing, status enquiry and point-to-multipoint control between ATM end users and a private ATM switch, or between a private ATM switch and the public carrier ATM network. ATM UNI signaling message uses the Q.931 message format, which is made up of a message header and a variable number of Information Elements.
Standard Organization: ITU-T

URL: Uniform Resource Locator
Uniform Resource Locator (URL) is the global address of documents and other resources on the World Wide Web. The first part of the address indicates what protocol used, and the second part specifies the IP address or the domain name where the resource is located.
Standard Organization: IETF
Reference Document: RFC 1738

UTS: Universal Terminal Support
Universal Terminal Support(UTS) is a data link layer protocol (P1024C) that runs in full-duplex mode over synchronous serial (V.24) lines and uses the ASCII character set.

UWB: Ultra-Wide-Band
Ultra-Wide-Band (UWB), also called digital pulse, is a wireless technology defined in IEEE 802.15.3 for transmitting digital data over a wide swath of the radio frequency spectrum with very low power. Because of the low power requirement, it can carry signals through doors and other obstacles that tend to reflect signals at more limited bandwidths and a higher power. It can carry large amounts of data (maximum bandwidth of 1Gbps) and can be used for multimedia content transfer, high-resolution radar, ground-penetrating radar, and radio locations systems.
Standard Organization: IEEE
Reference Document: 802.15.3