msc {
  hscale="2";
  ms[label="MS"],cell1[label="Cell 1 (BTS+BSC)"],cell0[label="Cell 0 (BTS+BSC)"],__msc[label="MSC"];

  ms rbox __msc [label="Call Re-Establishment"];
  ms note __msc [label="Ongoing voice call: MM is established"];

  ...;

  ms -x cell0 [label="radio link fails"];
  ms x- cell0;

  __msc abox __msc [label="Keep MM until timeout"];

  ms => cell1 [label="Channel Required"];
  ms <= cell1 [label="Immediate Assignment"];
  ms => cell1 [label="Complete Layer3"];
  cell1 => __msc [label="Complete Layer3:\nCM Re-Establishment Request"];

  cell0 <= __msc [label="Clear Command"];
  cell0 => __msc [label="Clear Complete"];

  cell1 <= __msc [label="Authentication Request"];
  cell1 => __msc [label="Authentication Response"];

  cell1 <= __msc [label="Cipher Mode Commad"];
  cell1 => __msc [label="Cipher Mode Complete"];

  cell1 <= __msc [label="Assignment Request\nthis Assignment ACKs the CM Re-Establishment"];
  ms <= cell1 [label="RR Assignment Command"];
  ms => cell1 [label="RR Assignment Complete"];
  cell1 => __msc [label="Assignment Complete"];
}