UDP (User Datagram Protocol)
- Unreliable, connectionless
- No three-way-handshake
- No guaranteed delivery of data
- Provides no error checking, sequencing, or flow control
- More efficient than TCP
- Useful for live audio or video
- More efficient for carrying messages that fit within one packet
- Header only contains four fields
- Source port
- Destination port
- Length
- Checksum
- Optional in IPv4, required in IPv6