Transport Layer

Difference Between TCP and UDP

TCP is a connection-oriented transport protocol that guarantees reliable, ordered, error-checked delivery through a handshake and acknowledgements, while UDP i…

What is the OSI Model?

The OSI (Open Systems Interconnection) model is a conceptual framework that standardizes network communication into seven layers — Physical, Data Link, Network…

What is the TCP Three-Way Handshake?

The TCP three-way handshake is the process a client and server use to establish a reliable connection before exchanging data: the client sends a SYN, the serve…

TCP/IP Model vs OSI Model

The OSI model is a seven-layer conceptual reference used for teaching and troubleshooting, while the TCP/IP model is a four-layer practical model that actually…

What is a Socket?

A socket is an endpoint for network communication, uniquely identified by the combination of an IP address, a port number, and a transport protocol (TCP or UDP…

What is a Port in Networking?

A port is a 16-bit number (0–65535) that identifies a specific process or service on a device, letting a single IP address handle many simultaneous network con…

What is the Transport Layer (OSI Layer 4)?

The Transport layer is OSI Layer 4 — it manages end-to-end communication between applications on two hosts, using port numbers to distinguish processes and pro…

What is TCP Flow Control and How Does It Work?

TCP flow control prevents a fast sender from overwhelming a slower receiver by having the receiver advertise how much buffer space it currently has left, via t…

What is TCP Congestion Control?

TCP congestion control is the set of sender-side algorithms that limit how much data is put into the network at once, using a congestion window (cwnd) that gro…

What is TCP Slow Start?

TCP slow start is the initial phase of congestion control where a new (or recovering) connection begins sending with a small congestion window and roughly doub…

What is TCP Window Scaling?

TCP window scaling is a negotiated option (RFC 7323) that lets both endpoints multiply the 16-bit window size field by a power of two, expanding the effectivel…

What is the Nagle Algorithm and When Should You Disable It?

Nagle’s algorithm is a TCP send-side optimization that buffers small outgoing segments and coalesces them into one larger segment instead of firing off many ti…

What is TCP Fast Retransmit?

TCP fast retransmit is a loss-recovery mechanism where a sender resends a segment as soon as it receives three duplicate ACKs for it, instead of waiting for th…

What is the TCP FIN Handshake (Connection Teardown)?

The TCP FIN handshake is the four-step process used to gracefully close a connection: each side independently sends a FIN to signal it has no more data, and th…

What is TCP Keepalive and How Does It Work?

TCP keepalive is an optional mechanism where an idle connection periodically sends a small probe segment to check whether the peer is still reachable and the c…

What is a SYN Flood Attack?

A SYN flood is a denial-of-service attack that sends a large number of TCP SYN segments, often with spoofed source addresses, to exhaust a server's connection…

TCP vs SCTP: What Is the Difference?

TCP is a single-stream, byte-oriented, reliable transport protocol, while SCTP (Stream Control Transmission Protocol) is a message-oriented transport that supp…

What Is HTTP/3 and QUIC?

HTTP/3 is the third major version of HTTP that runs over QUIC, a transport protocol built on UDP, instead of TCP — this eliminates TCP-level head-of-line block…

What is a Load Balancer in Networking?

A load balancer is a device or service that sits in front of a pool of backend servers and distributes incoming client requests across them using a chosen algo…

What is a Network Socket vs a Port?

A port is just a 16-bit number (0-65535) identifying an application or service on a host, while a socket is the full combination of protocol, source IP, source…

What Are Ephemeral Ports?

Ephemeral ports are short-lived, dynamically assigned source port numbers, typically drawn from the range 49152-65535 (or 32768-60999 on Linux), that an operat…

What Are Well-Known Ports?

Well-known ports are the reserved TCP/UDP port numbers from 0 to 1023, assigned by IANA to specific standard services, such as 80 for HTTP, 443 for HTTPS, 22 f…

What is the TCP State Machine?

The TCP state machine is the finite set of connection states, such as CLOSED, LISTEN, SYN_SENT, SYN_RECEIVED, ESTABLISHED, FIN_WAIT_1/2, CLOSE_WAIT, LAST_ACK,…

How Does TCP Connection Teardown Work?

TCP connection teardown normally uses a four-step FIN/ACK exchange: the side closing first sends a FIN, the peer acknowledges it and later sends its own FIN on…