// Topic collection
23 entries in this category
// Fast route
If you are exploring materials on this topic, the next step can be the topics catalog, the homepage with work areas, or the service pages directly.
2026-10-07
ECH (Encrypted Client Hello) — a TLS 1.3 extension that encrypts the first handshake message, ClientHello. The main thing it hides is the site name in the SNI field. Without ECH any node between you and the server can …
Read more2026-10-05
Under the phrase “TLS type” people usually mean different things: protocol version (1.2 or 1.3), cipher suite, certificate type (DV, OV, EV) or a scheme where the client also presents a certificate (mTLS). In this part — …
Read more2026-10-02
HTTPS — this is HTTP transmitted inside a TLS (Transport Layer Security) connection. TLS solves three problems: it encrypts data so they cannot be read in transit; it verifies integrity so they cannot be altered; and it …
Read more2026-09-30
HTTP has three versions in active use: HTTP/1.1, HTTP/2, and HTTP/3. Methods, headers, and status codes are the same across them, so an application usually doesn’t care which version a request arrived with. The …
Read more2026-09-28
Headers are the metadata of an HTTP message: lines like Name: value between the start-line and the body. From them the server understands which site is requested, in what format and language to return the response, who …
Read more2026-09-25
HTTP (HyperText Transfer Protocol) — an application-layer protocol by which a browser, mobile app, or script requests a resource from a server and receives a response. A resource can be an HTML page, an image, JSON from …
Read more2026-09-22
Simple utilities from previous parts each answer their own question: ping — is there connectivity, traceroute — which path packets take, nc — is the port open. The three tools in this part give a more complete picture: …
Read more2026-09-22
An IP address identifies a host, and a port identifies a specific service on it. A web server usually accepts connections on port 80 (HTTP) and 443 (HTTPS), SSH on 22, databases and mail on their respective ports. A …
Read more2026-09-22
It happens: the computer has an address, the router responds, ping 8.8.8.8 works, but websites in the browser do not open. Most often the cause is DNS — the system that translates domain names into IP addresses. If a …
Read more2026-09-22
When “the internet is not working”, it’s convenient to check from the bottom up: first your own computer and local network, then connectivity to external nodes, then DNS, ports and applications. This …
Read more