Ladder Diagrams » History » Revision 4
Revision 3 (laforge, 03/03/2022 08:51 PM) → Revision 4/8 (laforge, 03/03/2022 08:59 PM)
h1. Ladder Diagrams h2. Initial connection setup Note: we might want to do something for DoS mitigation at the very initial step? {{mscgen_link() msc { hscale=2; client [label="Client"], server [label="Server (main port)"], worker [label="Server (worker port)"], hlr [label="HLR (database)"]; |||; --- [label="Initial connection attempt from client to well-known server/port"]; |||; client => server [label="HELLO_REQ (user_id)"]; server <=> hlr [label="Obtain auth vectors"]; client <= server [label="AUTH_REQ (rand, autn)"]; client => server [label="AUTH_RESP (res)"]; server box server [label="Verify res == xres?"]; server => worker [label="Create worker socket"]; server note server [label="Server accepts client + redirects to worker IP+Port"]; client <= server [label="HELLO_ACK (worker IP:Port, token)"]; ...; client => worker [label="HELLO_REQ (user_id, token)"]; worker box worker [label="Verify user_id + token"]; client <= worker [label="HELLO_ACK"]; ...; client <=> worker [label="TDMoIP"]; ...; } }} Both sides operate timeouts, if those occur, the entire procedure is aborted. h2. subsequent re-authentication {{mscgen_link() msc { hscale=2; client [label="Client"], server [label="Server (main port)"], worker [label="Server (worker port)"], hlr [label="HLR (database)"]; |||; --- [label="At any later point in time, whenever the server wants"]; worker <=> hlr [label="Obtain auth vectors"]; client <= worker [label="AUTH_REQ (rand, autn)"]; client => worker [label="AUTH_RESP (res)"]; worker box worker [label="Verify res == xres?"]; } }} If there is no response to the AUTH_REQ within a timeout, up to three re-transmissions are attempted, before declaring the link as dead. h2. dead peer detection Procedure operates on on both sides: * Every time a packet is received, a timer is re-started. If the timer expires, the link is declared dead, and no further TDMoIP packets are transmitted. ** On the server side, a dead link means the worker port is closed. ** On the client side, a dead link means the client needs to start like in an initial connection attempt by contacting the well-known server port with a HELLO_REQ.