TCP and UDP Protocols Flashcards

Vocabulary flashcards covering key concepts, header formats, handshake sequences, and teardown states for TCP and UDP transport layer protocols.

TCP (Transmission Control Protocol)

A connection-oriented, point-to-point transport layer protocol that provides a reliable, in-order byte stream with full duplex data flow, flow control, and congestion control.

Maximum Segment Size (MSS)

The maximum amount of application-layer data, specified in bytes, that TCP can transmit in a single segment.

Cumulative ACK

An acknowledgement mechanism in TCP where the receiver acknowledges data by sending the sequence number of the next byte expected from the sender.

TCP Sequence Number

The byte stream number assigned to the first byte of data in a TCP segment's payload.

TCP Receive Window (rwnd)

A 16-bit header field used for flow control that indicates the number of data bytes the receiver is currently willing to accept.

TCP Header Flags

Control bits in the TCP header including C and E (congestion notification), U (URG), A (ACK), P (PSH), R (RST), S (SYN), and F (FIN) used for state management and data handling.

TCP Segment Header Structure

The 20-byte baseline header structure of TCP containing source/destination ports, sequence number, acknowledgement number, header length, flags, receive window size, checksum, urgent pointer, and optional fields.

In-Flight Data

Bytes within the sender sequence number space that have been sent to the receiver but not yet acknowledged (ACKed).

Half-Open Connection

A connection state failure occurring in a 2-way handshake where a retransmitted connection request establishes a state at the server after the client has already terminated.

TCP 3-Way Handshake Sequence

The connection establishment protocol exchange consisting of: 1) Client sends $SYNbit=1, Seq=x$, 2) Server responds with $SYNbit=1, Seq=y, ACKbit=1, ACKnum=x+1$, and 3) Client sends $ACKbit=1, ACKnum=y+1$.

TCP Connection Teardown Diagram

The procedure for terminating a TCP connection where each side independently sends a FIN segment and receives an ACK, progressing through states like FIN_WAIT_1, CLOSE_WAIT, FIN_WAIT_2, LAST_ACK, TIME_WAIT, and CLOSED.

User Datagram Protocol (UDP)

A connectionless, lightweight transport protocol that provides best-effort, unordered, and un-throttled data delivery without handshaking or connection state.

UDP Segment Format Diagram

A 8-byte fixed transport header consisting of source port #, dest port #, length (in bytes of UDP segment including header), and checksum, followed by the application payload.