blockdiag { span_width = 30 User <-> Apache; Proxy <-> AAA; group { Apache <-> Proxy; group { orientation = portrait Apache <-> SSSD; } } User [numbered = 1, shape = actor, width = 60] Apache [numbered = 2, label = "Apache\nAuthenticates user"] SSSD [numbered = 3, label = "SSSD\nProvides user info"] Proxy [numbered = 4, label = "Proxy Transport\nRequest + Metadata"] AAA [numbered = 5, label = "App Server\nAAA"] }