The time is 10:00 AM, and the network just went down -- and so did the IP phones. You're the IT manager and you're sweating bullets. The network bounces up again and the phones start to acquire an IP address and you're hoping for a good spot in line for the TFTP server before everyone else's phone starts hogging the TFTP. There are 100 people in line before you and it's going to be a long wait for your phone to boot up. Fifteen minutes later, most of the phones have booted up but not all of them, and the CEO is starting to breath down your neck. If this sounds like a bad nightmare, it isn't! It is exactly what can happen to some IP phones on a large, poorly designed IP network that has a tendency to go down due to a myriad of issues.>
even say "but my phones are on a different VLAN", but that just doesn't cut it because you shouldn't be relying on the same layer 3 routing infrastructure to route your IP traffic along with your data. It's conceivable that the Web server on your phone will fall victim to the next great worm from your data network because you have no firewall between them. As for the long boot times of TFTP dependent IP phones, I wasn't exaggerating about the 20 minute boot times. As a matter of fact, I've seen situations where it can take 2 hours for all the IP phones on a large campus to boot up whenever a security update needs to be applied to the IP Call Control Server. That's if you're lucky it didn't get infected by Nimda first. Those updates might happen once a month if that VoIP server is running on a general purpose operating system rather than a purpose-built embedded OS. Even when a single IP phone is booting up on its own, without any contention, it could still take 5 minutes. When I ask the manufacturer why the long boot times, the typical response is that they're all like that and it's really not so bad since it's "only" the initial wait time. My response is "tell it to my boss" when he's wondering why his phone is still booting after 30 minutes. If my Windows XP PC can boot up in 30 seconds,my phone should boot in under half that time.
I'm actually very pro IP telephony and IP phones, as long as they don't need TFTP to boot. Plenty of manufacturers produce IP phones that don't rely on the primitive TFTP protocol to boot, and they can use FTP. It is indeed possible to build a well-designed and extremely stable network that separates voice and data by a firewall, and it is an investment that should be made. There is no denying that IP telephony is the future, so long as you are aware of the pitfalls and know how to avoid them.