ubiquitous WiFi, 523, 552
UCLA, 79, 371
UDP. See User Datagram Protocol
UDP segment, 501
UDP services, 95
UDP socket programming, 158, 159–164
client, 161–163
port numbers, 195–196
server, 163–164
UDP streaming, 681, 683
UMTS (Universal Mobile Telecommunications Service), 555, 556
unchoked peers, 146
undetected bit errors, 445
unguided media, 19
unidirectional data transfer, 208
unlicensed spectrum, 523
unreliable services, 192
unshielded twisted pair (UTP), 19
URG bit, 237
urgent data pointer field, 237
URLs, SIP, 705–706
user agents, 116
User Datagram Protocol (UDP), 191, 192, 200–206
advantages of, 201–202
checksum, 204–206
connectionless nature of, 201
DNS using, 201
fairness and, 281–282
Internet checksum in, 448
multimedia applications using, 202–203
multiplexing and demultiplexing, 195–196
reliability with, 203–204
RTP and, 700–701
segment structure, 204
Skype use of, 95, 697
in VoIP, 689
user state, cookies, 108–110
utilization, 219
UTP. See unshielded twisted pair