@startuml !theme C4_united from https://raw.githubusercontent.com/plantuml-stdlib/C4-PlantUML/master/themes !include https://raw.githubusercontent.com/plantuml-stdlib/C4-PlantUML/master/C4_Sequence.puml Person(Alice, "Alice") Person(Bob, "Bob") activate Bob Rel(Alice, Bob, "Authentication Request") alt successful case Rel(Bob, Alice, "Authentication Accepted") else some kind of failure loop 1000 times Rel(Alice, Bob, "DNS Attack") end end ref over Alice, Bob : init Rel(Alice, Bob, "hello") ref over Bob This can be on several lines end ref == Initialization == Rel(Alice, Bob, "Authentication Request") Rel(Bob, Alice, "Authentication Response") == Repetition == Rel(Alice, Bob, "Another authentication Request") Rel(Bob, Alice, "another authentication Response") ... 5 minutes later ... Rel(Alice, Bob, "calls via phone") SHOW_LEGEND() @enduml Submit amiga aws-orange black-knight bluegray blueprint cerulean-outline cerulean crt-amber crt-green cyborg-outline cyborg hacker lightgray mars materia-outline materia metal mimeograph minty plain reddress-darkblue reddress-darkgreen reddress-darkorange reddress-darkred reddress-lightblue reddress-lightgreen reddress-lightorange reddress-lightred sandstone silver sketchy-outline sketchy spacelab spacelab-white superhero-outline superhero toy united vibrant       🎉 Discover the future PlantUML Web Editor! 🚀  PNG  SVG  ASCII Art