239.255.255.250

tcpdumpを眺めていると、頻繁に上記のipに向けたパケットが放たれているようなのですが、どのソフトからのもので、どうすればやめさせられるのか皆目見当が付きません。
ちなみにこんな感じです。WindowsのPnpなんたらという話は聞いたことがありますが。Macでのこれはなんなんでしょう。気色悪いです。
00:57:44.976236 192.168.1.3.1900 > 239.255.255.250.1900: udp 325 (DF)
00:57:44.976361 192.168.1.3.1900 > 239.255.255.250.1900: udp 329 (DF)
00:57:44.976500 192.168.1.3.1900 > 239.255.255.250.1900: udp 251 (DF)
00:57:44.976680 192.168.1.3.1900 > 239.255.255.250.1900: udp 341 (DF)
00:57:44.976829 192.168.1.3.1900 > 239.255.255.250.1900: udp 309 (DF)
00:57:44.976972 192.168.1.3.1900 > 239.255.255.250.1900: udp 251 (DF)
00:57:44.977145 192.168.1.3.1900 > 239.255.255.250.1900: udp 325 (DF)
00:57:44.977310 192.168.1.3.1900 > 239.255.255.250.1900: udp 333 (DF)
00:57:44.977448 192.168.1.3.1900 > 239.255.255.250.1900: udp 251 (DF)
00:57:44.977600 192.168.1.3.1900 > 239.255.255.250.1900: udp 261 (DF)
00:57:45.486334 192.168.1.3.1900 > 239.255.255.250.1900: udp 325 (DF)
00:57:45.486466 192.168.1.3.1900 > 239.255.255.250.1900: udp 329 (DF)
00:57:45.486605 192.168.1.3.1900 > 239.255.255.250.1900: udp 251 (DF)
00:57:45.486784 192.168.1.3.1900 > 239.255.255.250.1900: udp 341 (DF)
00:57:45.486936 192.168.1.3.1900 > 239.255.255.250.1900: udp 309 (DF)
00:57:45.487079 192.168.1.3.1900 > 239.255.255.250.1900: udp 251 (DF)
00:57:45.487250 192.168.1.3.1900 > 239.255.255.250.1900: udp 325 (DF)
00:57:45.487414 192.168.1.3.1900 > 239.255.255.250.1900: udp 333 (DF)
00:57:45.487557 192.168.1.3.1900 > 239.255.255.250.1900: udp 251 (DF)
00:57:45.487713 192.168.1.3.1900 > 239.255.255.250.1900: udp 261 (DF)
00:58:15.497960 192.168.1.3.1900 > 239.255.255.250.1900: udp 325 (DF)
00:58:15.498096 192.168.1.3.1900 > 239.255.255.250.1900: udp 329 (DF)
00:58:15.498224 192.168.1.3.1900 > 239.255.255.250.1900: udp 251 (DF)
00:58:15.498399 192.168.1.3.1900 > 239.255.255.250.1900: udp 341 (DF)
00:58:15.498548 192.168.1.3.1900 > 239.255.255.250.1900: udp 309 (DF)
00:58:15.498689 192.168.1.3.1900 > 239.255.255.250.1900: udp 251 (DF)
00:58:15.498862 192.168.1.3.1900 > 239.255.255.250.1900: udp 325 (DF)
00:58:15.499026 192.168.1.3.1900 > 239.255.255.250.1900: udp 333 (DF)
00:58:15.499165 192.168.1.3.1900 > 239.255.255.250.1900: udp 251 (DF)
00:58:15.499319 192.168.1.3.1900 > 239.255.255.250.1900: udp 261 (DF)
00:58:16.008022 192.168.1.3.1900 > 239.255.255.250.1900: udp 325 (DF)
00:58:16.008186 192.168.1.3.1900 > 239.255.255.250.1900: udp 329 (DF)
00:58:16.008248 192.168.1.3.1900 > 239.255.255.250.1900: udp 251 (DF)
00:58:16.008421 192.168.1.3.1900 > 239.255.255.250.1900: udp 341 (DF)
00:58:16.008574 192.168.1.3.1900 > 239.255.255.250.1900: udp 309 (DF)
00:58:16.008712 192.168.1.3.1900 > 239.255.255.250.1900: udp 251 (DF)
00:58:16.008890 192.168.1.3.1900 > 239.255.255.250.1900: udp 325 (DF)
00:58:16.009048 192.168.1.3.1900 > 239.255.255.250.1900: udp 333 (DF)
00:58:16.009181 192.168.1.3.1900 > 239.255.255.250.1900: udp 251 (DF)
00:58:16.009338 192.168.1.3.1900 > 239.255.255.250.1900: udp 261 (DF)
00:58:46.019537 192.168.1.3.1900 > 239.255.255.250.1900: udp 325 (DF)
00:58:46.019664 192.168.1.3.1900 > 239.255.255.250.1900: udp 329 (DF)
00:58:46.019799 192.168.1.3.1900 > 239.255.255.250.1900: udp 251 (DF)
00:58:46.019980 192.168.1.3.1900 > 239.255.255.250.1900: udp 341 (DF)
00:58:46.020136 192.168.1.3.1900 > 239.255.255.250.1900: udp 309 (DF)
00:58:46.020279 192.168.1.3.1900 > 239.255.255.250.1900: udp 251 (DF)
00:58:46.020452 192.168.1.3.1900 > 239.255.255.250.1900: udp 325 (DF)
00:58:46.020614 192.168.1.3.1900 > 239.255.255.250.1900: udp 333 (DF)
00:58:46.020755 192.168.1.3.1900 > 239.255.255.250.1900: udp 251 (DF)
00:58:46.020911 192.168.1.3.1900 > 239.255.255.250.1900: udp 261 (DF)
00:58:46.529607 192.168.1.3.1900 > 239.255.255.250.1900: udp 325 (DF)
00:58:46.529731 192.168.1.3.1900 > 239.255.255.250.1900: udp 329 (DF)
00:58:46.529872 192.16