1. Microsoft Windows Server 2003 TCP/IP Protocols and Services Technical Reference Slide: 1 Lesson 11 User Datagram Protocol (UDP)

2. Microsoft Windows Server 2003 TCP/IP Protocols and Services Technical Reference Slide: 2 User Datagram Protocol (UDP) Introduction to UDP UDP message UDP header UDP ports

3. Microsoft Windows Server 2003 TCP/IP Protocols and Services Technical Reference Slide: 3 Introduction to UDP Characteristics of UDP: Connectionless Unreliable Provides identification of Application Layer protocols Provides checksum of UDP message UDP does not provide: Buffering Segmentation Flow control

4. Microsoft Windows Server 2003 TCP/IP Protocols and Services Technical Reference Slide: 4 Uses for UDP Lightweight protocol Low overhead for a simple exchange of messages Reliability already provided by the Application Layer protocol TFTP and NFS Reliability not required due to periodic advertisement process RIP periodic advertising One-to-many delivery Broadcast or multicast

5. Microsoft Windows Server 2003 TCP/IP Protocols and Services Technical Reference Slide: 5 UDP Message Encapsulation IP headerMessage UDP message IP datagram Network Interface header Network Interface trailer Network Interface Layer frame UDP header

6. Microsoft Windows Server 2003 TCP/IP Protocols and Services Technical Reference Slide: 6 The UDP Header Source Port Destination Port Length Checksum

7. Microsoft Windows Server 2003 TCP/IP Protocols and Services Technical Reference Slide: 7 UDP Pseudo Header Source IP Address Destination IP Address Unused Protocol Length = 0 = 17

8. Microsoft Windows Server 2003 TCP/IP Protocols and Services Technical Reference Slide: 8 Quantity for UDP Checksum Calculation UDP pseudo header UDP header Message 12 bytes8 bytes0 to 65,507 bytesPadding (1 byte) UDP message

9. Microsoft Windows Server 2003 TCP/IP Protocols and Services Technical Reference Slide: 9 UDP Ports Defines a location or message queue for the delivery of messages Well-known port numbers: 53 DNS 67 BOOTP client (Dynamic Host Configuration Protocol [DHCP]) 68 BOOTP server (DHCP) 137 NetBIOS Name Service 138 NetBIOS Datagram Service 445 Direct hosting of Server Message Block (SMB) datagrams over TCP/IP 1812, 1813 Remote Authentication Dial-In User Service (RADIUS) Client process may listen on dynamically allocated UDP port number

10. Microsoft Windows Server 2003 TCP/IP Protocols and Services Technical Reference Slide: 10 UDP Port Demultiplexing Domain Name System (DNS) UDP Port 53 Trivial File Transfer Protocol (TFTP) UDP Port 69 NetBIOS Name Service UDP Port 137 NetBIOS Datagram Service UDP Port 138 UDP IP Protocol 17

11. Microsoft Windows Server 2003 TCP/IP Protocols and Services Technical Reference Slide: 11 Review Introduction to UDP UDP message UDP header UDP ports