CC licensed SS7 ISUP Call Flow Diagram

I needed a simple diagram showing the ISUP messages during a call for a visual aid for an analysis. Google images didn't turn up any diagrams permissively licensed, so I created one. Hopefully it can save someone else time not reinventing the wheel (or in this case redrawing it...)

The telephone icon is from AIGA Symbol Signs by AIGA License: Public Domain
The switch icon is from Typicons by Stephen Hutchings  License: Creative Commons (Attribution-Share Alike 3.0 Unported)
Both are untouched.

Image: Author: Andrew Coleman License: Creative Commons Attribution 4.0 Unported (CC BY 4.0)
Hopefully Google Image will pick up the license since it is in the comment section of the png...