<svg width="5cm" height="3cm" viewBox="0 0 500 300" version="1.1">
     <desc>Example animMotion01 - demonstrate motion animation computations</desc>
     <rect x="1" y="1" width="498" height="298" fill="none" stroke="blue" stroke-width="2"/>
     <path id="path1" d="M100,250 C 100,50 400,50 400,250" fill="none" stroke="blue" stroke-width="7.06"/>
     <circle cx="100" cy="250" r="17.64" fill="blue"/>
     <circle cx="250" cy="100" r="17.64" fill="blue"/>
     <circle cx="400" cy="250" r="17.64" fill="blue"/>
     <path d="M-25,-12.5 L25,-12.5 L 0,-87.5 z" fill="yellow" stroke="red" stroke-width="7.06">
          <animateMotion dur="6s" repeatCount="indefinite" rotate="auto">
               <mpath xlink:href="#path1"/>
          </animateMotion>
     </path>
</svg>
Original SVG source