TCP

HTTP/2 uses multiplexing technology to allow concurrent transmission of multiple requests over a single TCP connection, while HTTP/3 switches the transport layer from TCP to the QUIC protocol.

Socket provides two main communication modes: TCP (connection-oriented, reliable transmission) and UDP (connectionless, low latency)

QUIC supports multiplexing, where packet loss on a single stream does not block other streams, solving TCP's head-of-line blocking problem.

SYN Flood攻击滥用了TCP三次握手机制

Stacking abstraction layers is a common pattern in software engineering: HTTP sits on top of TCP, REST sits on top of HTTP, and various SDKs sit on top of REST, with each layer not eliminating the layer below.

In loopback testing, TCP sent 450 packets and received 450 packets with no packet loss, UDP sent 1194 and received 1194 with no packet loss, and both supported jumbo frames (sending and receiving 3695 bytes).

Building on an existing open-source gigabit Ethernet project that already had IP layer and UDP functionality, this project separated the ICMP function from the IP core and added a complete TCP client module.

The core logic of the TCP client, state machine code, demonstration slides, and instructional documents were primarily completed with the assistance of AI tools such as Cursor.

TCP sequence numbers increment in units of bytes rather than packets; sending 4 bytes increases the sequence number by 4 regardless of how many packets it is split into.

The TCP client implementation covers mechanisms including slow start, advertised window, MSS option negotiation, timeout retransmission (SYN timeout of 1 second, data timeout of 200 milliseconds), retransmission from the unacknowledged pointer, fast retransmission triggered by three duplicate ACKs, zero-window probing, and keepalive.

Using a network debugging assistant directly for TCP speed testing yields only approximately 31 Mbps, because the debugging assistant does not reply with ACKs fast enough.

After having an AI build a lightweight test APP that only replies with ACKs without storing data, the TCP speed test rate approached full speed.

QUIC runs on top of UDP, resolves TCP's head-of-line blocking problem, and reduces the number of round trips for an initial connection from 2–3 RTTs to 1 RTT, with 0-RTT resumption possible for known servers.

Homa adopts a connectionless design, avoiding the overhead of TCP's connection-state maintenance.

RDMA has extremely high requirements for a lossless (zero packet-loss) network environment, necessitating mechanisms such as Priority Flow Control (PFC), resulting in higher operational complexity than TCP.

TCP's greatest advantage lies in its ubiquitous ecosystem, including OS kernels, NIC hardware offloading, load balancers, and monitoring toolchains.

TCP's ordered byte-stream semantics cause head-of-line blocking—the loss of a single packet blocks the delivery of all subsequent data.

RTMP runs on TCP port 1935 by default, relying on TCP's reliable transmission to ensure audio and video data arrives in order.

Transport-layer network jitter (such as TCP timeouts or connection resets) and server-side rate-limiting responses (such as HTTP 429) behave similarly but have different causes; the former recovers with a brief wait, while the latter is what actually requires a long back-off.

When the traffic carried inside a VPN tunnel is also TCP, TCP meltdown occurs (TCP retransmission stacking), severely degrading transmission efficiency.