A listening TCP socket separates incomplete handshakes from established connections waiting for accept(). The real setting is tcp_max_syn_backlog; this article retains its historical URL spelling. It concerns remembered incomplete requests, whereas the listen() backlog concerns the accept queue. Diagnose which stage is under pressure before choosing a remedy. ...
A Linux network namespace separates networking resources such as interfaces, routes, neighbor tables, socket ports, and packet-filter rules. It shares the kernel with other namespaces; it is not a separate operating system. A process normally inherits its parent’s network namespace, and tools can execute a process in another one. The resulting isolation covers networking resources, not every aspect of process identity or filesystem access. ...
An AAAA resource record contains one 128-bit IPv6 address. An A record contains an IPv4 address. A name may have either type, both types, or several addresses within each type. These are separate RRsets, so A and AAAA can have different TTLs. Publishing AAAA makes an address discoverable through DNS; it does not create an interface, route, listener, or working application. ...
Slow start grows a TCP sender’s congestion window while it learns how much outstanding data the path can support. With enough data and suitable acknowledgments, the classic behavior is approximately exponential growth across round trips. “Doubles every RTT” is a useful simplified pattern, not an unconditional timer rule. The window changes in response to transport feedback and the implementation’s growth conditions. ...
On Linux TCP sockets, the listen() backlog concerns established connections waiting for the application to accept them. The incomplete-handshake queue is a separate concept. Calling accept() removes a pending connection and returns a connected socket for application use. That accepted connection no longer occupies the listener’s accept queue, even if it remains open and busy for a long time. ...
An IPv6 router does not fragment a packet while forwarding it toward its destination. If the packet is too large for the next link, the router discards it and sends ICMPv6 Packet Too Big feedback. The source can then adjust its packet size or, where appropriate, send fragments using the IPv6 Fragment header. Reassembly of those fragments takes place at the destination. ...
TCP keepalive asks whether the other TCP endpoint still responds after a quiet period. It does not ask whether an HTTP handler, database query, or worker is making progress. A peer’s kernel can acknowledge traffic while its application is stalled. Treat transport reachability and useful application responses as different observations. ...
An IPv4 default route is the prefix 0.0.0.0/0: it matches every IPv4 destination, with the least possible specificity. In a selected routing table, a longer matching prefix normally takes precedence. The default is not a procedure that retries whenever a more specific route fails. Routing policy selects relevant tables, and the chosen route describes a forwarding decision rather than promising that the entire round trip will succeed. ...