User Datagram Protocol (UDP)
- an alternative to TCP
- no guaranteed delivery
- no preservation of sequence
- no protection against duplication
- minimum overhead
- adds port addressing to IP
In addition to TCP, there is one other transport-level protocol that is in common use as part of the TCP/IP protocol suite: the User Datagram Protocol (UDP). UDP does not guarantee delivery, preservation of sequence, or protection against duplication. UDP enables a procedure to send messages to other procedures with a minimum of protocol mechanism. Some transaction-oriented applications make use of UDP; eg SNMP (Simple Network Management Protocol). Because it is connectionless, UDP has very little to do. Essentially, it adds a port addressing capability to IP.
UDP Header
Because it is connectionless, UDP has very little to do. just adding a port addressing capability to IP. This is best seen by examining the UDP header, shown in Stallings DCC8e Figure 2.3b. The UDP header also includes a checksum to verify that no error occurs in the data; the use of the checksum is optional.
For decades, the keystone of the TCP/IP protocol architecture has been IP. Stallings DCC8e Figure 2.4a shows the IP header format, which is a minimum of 20 octets, or 160 bits. The header, together with the segment from the transport layer, forms an IP-level PDU referred to as an IP datagram or an IP packet. The header includes 32-bit source and destination addresses. The Header Checksum field is used to detect errors in the header to avoid misdelivery. The Protocol field indicates which higher-layer protocol is using IP. The ID, Flags, and Fragment Offset fields are used in the fragmentation and reassembly process. Chapter 18 provides more detail.
For decades, the keystone of the TCP/IP protocol architecture has been IP. Stallings DCC8e Figure 2.4a shows the IP header format, which is a minimum of 20 octets, or 160 bits. The header, together with the segment from the transport layer, forms an IP-level PDU referred to as an IP datagram or an IP packet. The header includes 32-bit source and destination addresses. The Header Checksum field is used to detect errors in the header to avoid misdelivery. The Protocol field indicates which higher-layer protocol is using IP. The ID, Flags, and Fragment Offset fields are used in the fragmentation and reassembly process. Chapter 18 provides more detail.
