주제: networking
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롤백 경로를 갖춘 DNS 레코드 변경: TTL 낮추기, 전환, 검증
DNS 변경은 캐시에 남아 있는 기존 TTL이 만료되는 속도로만 사용자에게 전파되므로, 변경 전에 기존 TTL 한 주기만큼 미리 TTL을 낮추고, 새 대상이 모든 곳에서 확인될 때까지 기존 대상이 계속 응답하도록 유지해야 합니다. 또한 RFC 8767이 허용하는 것처럼, 권한 있는 서버에 연결할 수 없을 때 리졸버가 만료된 데이터를 계속 응답할 수 있다는 점도 감안해야 합니다.
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Edge-triggered epoll: drain nonblocking work before waiting for another edge
Avoid a stalled connection by separating readiness notifications from complete application messages.
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Configuring network interfaces with netplan on Ubuntu, and testing changes without losing the connection
Netplan renders YAML under /etc/netplan into networkd or NetworkManager configuration; `netplan try` applies a change and automatically reverts it if nobody confirms within a timeout, which is the safe way to change network settings on a remote host. Debian's ifupdown /etc/network/interfaces is the older, still-supported contrast.
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Client prediction and reconciliation with an authoritative server
Predict local input immediately, reconcile against the matching authoritative command, and replay unacknowledged input while keeping visual correction separate.
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Inspecting and changing macOS network settings from Terminal: networksetup, scutil and DNS cache
networksetup and scutil read and change the active network service, DNS servers, proxies and computer name; dscacheutil and mDNSResponder clear a stale resolver cache after a DNS change so a re-test does not see the old answer.
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The TLS 1.3 handshake in outline
TLS 1.3 negotiates keys in one round trip: the ClientHello already carries a key share, the ServerHello answers with its own, and everything after it, including the certificate, is encrypted. Resumption uses pre-shared keys from session tickets; 0-RTT early data is optional and replayable.
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Client-server clock synchronization: estimate time without hiding uncertainty
Use timestamp exchanges to estimate server-time offset, account for asymmetric delay and drift, and keep clock corrections distinct from simulation and presentation policies.
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Administering DNS Server zones and records from PowerShell, then verifying with Resolve-DnsName
Get-DnsServerZone, adding A and CNAME records, listing records with Get-DnsServerResourceRecord, the scavenging/aging settings that expire stale records, and clearing the resolver cache — with every write checked from the client side, not just the server's own view.
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Setting a static IPv4 address with nmcli without locking yourself out
nmcli can show, modify and activate NetworkManager connections from a script, but changing the address you are connected through can drop the session before the new settings apply. Cloning the profile first and validating before removing the old one keeps the change reversible.
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Server rewind for lag-compensated hit testing
Evaluate eligible attacks against bounded historical target state, validate timing on the server, and make the fairness and world-state policy explicit.
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MTU, fragmentation and path MTU discovery
Ethernet carries 1500-byte IP packets, tunnels and PPPoE carry less, and IPv6 routers never fragment. Path MTU discovery depends on ICMP Packet Too Big messages; when those are filtered, large packets vanish silently while small ones pass, the classic black hole that MSS clamping or packetization-layer probing works around.
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Rollback netcode: deterministic replay and controlled side effects
Predict missing input, restore earlier state when predictions fail, and resimulate within explicit memory and CPU budgets while keeping effects consistent.
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Network configuration tools compared: nmcli, netplan, systemd-networkd and their Windows and macOS equivalents
Reading the current network configuration, setting a static address, and setting DNS servers — the same three tasks across NetworkManager's nmcli, Ubuntu's netplan, systemd-networkd, Windows PowerShell's networking cmdlets, and macOS's networksetup.
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DNS records a web service depends on
A, AAAA and CNAME map names to addresses, MX routes mail, TXT carries verifications and policies, CAA restricts certificate issuers, NS delegates zones; check authoritative answers, not only a cached resolver, before and after changes.
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Proxy environment variables across curl, requests, Go, Java, Node and wget
HTTP_PROXY's uppercase form is deliberately rejected by curl for CGI-injection reasons but accepted by Python requests outside CGI, a NO_PROXY leading dot narrows the match to subdomains in Go's httpproxy while curl ignores the dot and also matches the bare domain, and Node's fetch ignores proxy variables unless NODE_USE_ENV_PROXY or a ProxyAgent is set up.
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Measuring home internet throughput repeatably: a fixed-path, fixed-schedule protocol
A proposed protocol for a household throughput and latency series: hold the device, the wired or wireless path, the test tool and the server constant, run three consecutive tests in three fixed daily slots for two weeks, log connection count and household activity with each run, and read RFC 6349's bandwidth-delay product and single-versus-multiple-connection points as reasons why tool settings change the number; nothing is claimed about any provider.
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curl's exit codes: telling a DNS failure from a TLS failure from --fail
curl returns a distinct numeric code for each class of transport failure (name resolution, connection, TLS, timeout) plus a separate code, 22, that only appears when --fail or --fail-with-body is requested for HTTP error statuses. An agent that greps curl's exit code instead of its text can route retries correctly without parsing output.
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HTTP/1.1, HTTP/2 and HTTP/3: the differences an operator notices
HTTP/1.1 sends one request at a time per TCP connection in text framing; HTTP/2 multiplexes binary streams over one TLS connection with HPACK compression but still stalls on TCP loss; HTTP/3 runs over QUIC on UDP, removes transport head-of-line blocking and is discovered through Alt-Svc or HTTPS DNS records.
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Managing the DHCP Server role from PowerShell: scopes, reservations, authorization, and backup
Get-DhcpServerv4Scope and leases, reserving an address with Add-DhcpServerv4Reservation, authorizing a server in AD with Add-DhcpServerInDC, a failover overview, and backing up the configuration with Backup-DhcpServer before a risky change.
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Configuring network interfaces and addresses on Solaris 11.4 with dladm and ipadm
dladm inventories data links, ipadm creates IP interfaces and static or DHCP addresses, and the ipadm create subcommands take a -t flag to decide whether a change is temporary (until reboot) or persistent. DNS resolution is configured through the network/dns/client SMF service, not by editing resolv.conf directly.
기계 판독 가능: JSON