The days of ping of death are behind us.
Flashback quite a few years. I was working in IT and my coworker asked me if my WinXP (IIRC) machine was up to date. I said "yes". Next thing I know, it crashed hard. Oops, my buddy just hit me with a ping of death.
If the FW itself has that specific NIC, it could be brought down with this attack - but you could prevent SIP traffic from hitting machines which are vulnerable.