Week 4: CST 311 Intro to Computer Networks

This week, we mostly prepared for the midterm. In the future, I will try harder to watch the course overview video at the beginning of the week to avoid missing deadlines.

We learned about the UDP transport protocol which is a connectionless/streamlined protocol. When a host receives a UDP segment, they will check the destination port number and direct it to the socket with that port number so IP datagrams with the same destination port number but different source IP addresses or source port numbers are directed to the same socket at the destination. In general, UDP or the User Datagram Protocol is a basic internet transport protocol used mostly for streaming, DNS, and SNMP. There is no handshaking between the UDP sender and receiver, and each segment is handled independently of the others. The segments can be lost or delivered out of order, but reliable transfer can be added at the application layer.

The UDP segment header is 32 bits long and includes the source port number, the destination port number, length, and checksum. The rest is the application data or payload. UDPs good parts are there is no connection establishment, its simple, has a small header size, and has no congestion control. Its checksum is to check for errors in the transmitted segment. The segment is treated as a sequence of 16-bit integers and uses one’s complement of the contents, inserts it into the header. The receiver then computes the segment checksum and checks if the computed checksum equals the checksum field value.

In the lab, we learned how to find UDP packets, what content is in the header, what information the length contains, the maximum number of bytes in a UDP payload, the largest source port number, and the protocol number for UDP.