Cisco Cisco IOS Software Release 12.2(8)T

UDP— User Datagram Protocol. Connectionless transport layer protocol in the TCP/IP protocol stack. 
UDP is a simple protocol that exchanges datagrams without acknowledgments or guaranteed delivery, 
requiring that error processing and retransmission be handled by other protocols. UDP is defined in 
RFC-768.

URL—Universal Resource Locator. Standard address of any resource on the Internet that is part of the 
World Wide Web (WWW).

User Agent—A combination of UAS and UAC that initiates and receives calls. See UAS and UAC.

VoIP—Voice over IP. The ability to carry normal telephone-style voice over an IP-based Internet with 
POTS-like functionality, reliability, and voice quality. VoIP is a blanket term that generally refers to the 
Cisco standards-based approach (for example, H.323) to IP voice traffic.