Chapter Summary
The key points covered in this chapter are as follows.
- TCP is a connection-oriented protocol that provides services such as packet acknowledgment, flow control, error detection and correction, and segmentation.
- Establishing a TCP connection between two systems requires a three-way handshake, during which each computer supplies the other with the sequence number it will assign to its messages, plus its maximum segment size.
- To transmit large amounts of data over a TCP connection, a system divides a byte stream into multiple segments, each of which is transmitted in a separate message.
- The system receiving the data segments acknowledges them with occasional messages used for that purpose. Unacknowledged messages are eventually retransmitted.
- Acknowledgment messages inform the other system how much data it can transmit. This is called flow control.
- TCP messages contain a checksum that the receiving system uses to detect transmission errors.
- Closing a TCP connection requires the systems to exchange termination (FIN) messages and acknowledgments.
- UDP is a connectionless protocol that provides error detection through checksums, but it provides none of the other services found in TCP.
- SPX is NetWare's connection-oriented protocol, which includes most of the same features as TCP, but is used far less often than NCP.
- NCP is the transport layer protocol most often used by NetWare systems, because it supports a great many functions, including client/server file sharing and NDS communications.