Articles & Guides
Useful resources for web developers and system administrators
Found 39 · Networking · Reset
Networking
What Is MTU: Fragmentation and How to Fix Issues
What MTU and MSS are, typical values (1500, 1492, jumbo 9000), Path MTU Discovery and black holes. How to measure MTU with ping and set it on your OS.
Networking
SMTP Port 25 vs 465 vs 587: Which to Use and How to Test It
Port 25 relays mail between servers; 587 (STARTTLS) and 465 (implicit TLS) are for clients. Gmail settings, TCP vs UDP, common errors and test commands.
Networking
How to Read Traceroute: Hops, Asterisks, RTT and Who's at Fault
How to read traceroute and tracert output: hop columns, RTT, * asterisks and !H flags, plus how to tell if the fault is on your side, your ISP's or the site's.
Networking
High Ping and Packet Loss: Causes and Fixes
Why ping is high and packets drop, what values are normal, how to measure with ping and traceroute, and how to isolate the problem — your network, ISP, or the server.
Networking
Fix ERR_CONNECTION_CLOSED: Causes and Solutions
ERR_CONNECTION_CLOSED in Chrome means the server dropped the connection. Causes: TCP RST, antivirus, proxy, MTU, TLS. Fix it as a user and on the server.
Networking
Fix ERR_QUIC_PROTOCOL_ERROR: QUIC / HTTP3 Error Guide
What ERR_QUIC_PROTOCOL_ERROR means in Chrome, why QUIC/HTTP3 fails, and how to fix it: disable the QUIC flag, check UDP/443, the Alt-Svc header and server bugs.
Networking
Your Site Is Blocked in Russia: Owner's Guide
How a site owner can check a block in Russia, tell it from a hosting or DNS failure, find the grounds in the EAIS register, and file an unblocking appeal to Roskomnadzor.
Networking
Fix ERR_EMPTY_RESPONSE: Server Returned No Data
ERR_EMPTY_RESPONSE means the server closed the connection with no reply. Learn the causes — backend crash, proxy timeout, WAF — and fix it via nginx and php-fpm logs.
Networking
TSPU, DPI and Traffic Throttling: How It Works
How TSPU and DPI work, how throttling differs from a full block and an outage, the signs that reveal it, and how to run external availability diagnostics.
Networking
How Roskomnadzor Blocks Websites: EAIS, TSPU, DPI
How Roskomnadzor blocks websites: the EAIS register, TSPU under Law 90-FZ, DPI filtering, and the difference between IP, DNS and DPI blocking.