Both protocols are part of the TCP/IP stack. TCP= Connection oriented; Reliable; Re-transmission on loss; higher overhead than UDP; Suitable for Small-Very large data; hi-speed ex. SSH, FTP, TELNET, SMTP, POP UDP= Connectionless; unreliable; no re-transmission on loss; lower overhead; suitable for small to moderate data volume; very high speed ex. SNMP, DNS, RTP, VPN/Tunneling

TCP is sent specifically to logical addresses (HTTP, FTP), UDP is broadcast to everyone (DNS)