A default port lets a client omit a number when a protocol or configuration already supplies it. HTTP commonly uses TCP 80, HTTPS TCP 443, and SSH TCP 22. These assignments reduce configuration, but they do not inspect a listener’s bytes or establish its identity. An endpoint includes an address and transport as well as a port, and its application protocol still has to match the caller. ...
A retry is another unit of work, not an automatic improvement in reliability. It can recover from a transient failure, but can also repeat an unsafe operation or add demand to an overloaded dependency. Decide whether the operation is eligible, how much total effort is allowed, and when that effort should happen before choosing a delay formula. ...
A server’s bind address selects which local destination addresses its socket can accept. Binding an IPv4 listener to 127.0.0.1 differs from binding it to 0.0.0.0, the wildcard address. Neither setting alone describes the complete access policy. Routing, network namespaces, packet filtering, port publication, proxies, and application authentication determine how a request reaches the listener and what it may do afterward. ...
An SRV record describes a service target using priority, weight, port, and a target hostname. Its owner normally combines a service label, transport label, and domain, such as _echo._tcp.lab.test. A client that understands that service can query SRV, obtain target addresses through A or AAAA, and connect to the advertised port. Ordinary hostname lookup does not automatically perform this application-specific discovery sequence. ...
The selector turns the Service from a fixed Endpoint into a live view: refresh happens in the background, and a client never edits its config when pods restart. Declared, then given an address A Service turns the constant churn of pods into a stable name. You declare a selector (which pods), a port, and a protocol, and the control plane assigns a virtual IP (cluster IP) and a DNS name that stay fixed while everything behind them keeps changing. The stable name is the contract for every other resource: a Deployment, an Ingress, or another pod can address a service by name without caring which concrete pod exists right now. That indirection is what lets the runtime rearrange the membership without a client ever noticing. ...
Multiplexing shares the transport and keeps ordering within each stream, which is why long-lived pushes fit this model better than request-reply websockets. One connection, many streams HTTP/2 multiplexes many logical streams over a single TCP connection, and gRPC makes each call a stream, so a chatty microservice stops reopening sockets per request. That one shared connection means connection setup, TLS handshake, and idle bookkeeping happen once instead of per call. Streams are independent in ordering and cancellation, so a slow, long-lived stream does not block a short one on the same pipe. The practical effect is a low army of connection state, with per-call overhead shrinking to a frame header. ...
A useful name gives people and software a reference they can carry across an address change. That reference needs a defined scope and owner. A machine’s local hostname, a service’s DNS name, and an instance identifier may intentionally differ. Naming them clearly helps operators understand logs and deployments without pretending that one label automatically establishes every other identity in the system. ...
An IPv6 address contains 128 bits, usually written as eight hexadecimal groups. Text may omit leading zeros and replace one consecutive run of zero groups with ::. These rules preserve the address while shortening its spelling. RFC 4291 defines valid forms; RFC 5952 recommends a consistent representation for display and exchange. Valid syntax and the preferred spelling are related but different questions. ...