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voip

VoIP telephony / PBX

Asterisk, FreeSWITCH

SystemTechniques · 15Primitives · 64 voip Deterministic simulation testingdistributed · medium: Run the whole system in one thread under a seeded scheduler with simulated network, disk and clock, so every failure replays from its seed.›Primary-backup replicationdistributed · medium: One node orders all writes and ships them to standbys; the acknowledgement rule (none, one, all) sets what a crash loses, and an external arbiter decides who takes over.›Acoustic echo cancellationmedia · medium: Adaptive filter (NLMS/frequency-domain) removing far-end echo from the microphone signalJitter buffermedia · medium: A receiver-side buffer holds packets just long enough, a delay tracked from recent arrivals, to reorder them and hand out media at a steady rate.›NAT traversal (STUN, ICE, TURN)media · medium: Learn your public address with STUN, swap candidate addresses over signalling, test pairs with ICE checks, and fall back to a TURN relay if no direct path works.›Packet loss concealmentmedia · medium: Synthesize missing audio frames from prior signal (pitch repetition, neural PLC)Coverage-guided fuzzingsecurity · medium: Mutate inputs, run an instrumented target, and keep any input that reaches a new code edge; feedback turns blind guessing into incremental search.›RTP and RTCPmedia · low: RTP stamps each media packet with sequence number, media-clock timestamp and source ID; RTCP reports loss, jitter, round trip and clock mapping within a bandwidth cap.›Sdp offer answermedia · low: SDP session descriptions and offer/answer negotiationHdr histogramdata-structures · low: Log-linear bucketed histograms with bounded relative error for latency percentilesProcess supervisionhardware-os · low: A parent process starts services, reaps their exits and restarts them under a delay and burst-limit policy, then stops them with SIGTERM before SIGKILL.›Voice activity detectionmachine-learning · low: Per-frame speech/non-speech decision with smoothing, from an energy threshold over a tracked noise floor up to small neural nets.›Audio mixingmedia · low: Summing many streams with gain, clipping control and per-listener minus-one mixesMu law a law compandingmedia · low: G.711 logarithmic companding of 8 kHz speech samplesSip signalingmedia · low: SIP call setup, dialogs, SDP offer/answer and registrar/proxy routingSRTPmedia · low: Per-packet encryption, authentication and replay protection for RTP and RTCP that keeps the headers readable, with the packet index derived from the 16-bit sequence number.›epoll event loopnetworking · low: One thread waits on thousands of non-blocking sockets with epoll_wait and handles only ready ones; the core of nginx, Redis and tokio.›Longest prefix matchnetworking · low: IP prefix lookup structures (DIR-24-8, Poptrie, LC-trie) for routes, ACLs and geo-IPMutual TLSsecurity · low: TLS where the client also proves a certificate key, so every connection carries a verified, rotatable machine identity.›Graceful drainingsystems · low: On a termination signal, stop taking new work, finish in-flight work until a deadline, tell clients to reconnect elsewhere, then exit; clients resume from a token.›Hierarchical timing wheelsystems · low: Timers bucketed by expiry into wheels of slots, coarser wheels for far deadlines: O(1) insert and cancel for millions of timeouts.›Cooperative schedulingconcurrency · low: Green threads/coroutines yielding at await points on a user-space schedulerRecord replaydistributed · low: Record every nondeterministic input (time, randomness, I/O, model and tool outputs, per-tick player input) and re-execute deterministically for debugging, replays and state rebuild+ 8 more techniques+ 48 more primitives

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