Time for my favorite rant -- pardon me for a moment: The more important point for putting Public Safety on IP networks (of any sort) is that the IP link has MONITORING built in.
Most (even so-called "Public Safety ready") IP linking systems DO NOT have ANY way to notify the dispatcher that their transmissions are NOT going out over the air, or that the link coming in from the field radio units is down. VoIP/RoIP is "cheap" but you get what you pay for. Engineering it properly and MONITORING the links is essential, since lives are on the line. I helped some folks test the very early EF Johnson Ethernet ports on the back of their repeaters, and custom "dispatch" software that tied a headset on the sound card on a PC to the repeater(s). The system used Multicast IP (mistake number one), UDP (maybe mistake number two), and when I said, "Unplug the Ethernet jack from the repeater" while the dispatch console was "transmitting"... there was ZERO alarm indication ANYWHERE to tell either the dispatcher, the officers in the field, or the technicians -- THAT THE SYSTEM WAS DOWN. This problem is by no means limited to EFJ, it's just the one I saw in person on a test bench with my own two eyes. RoIP engineers need to pull their heads out of their you-know-what's, and start THINKING again. RF links had a continuous tone on them in most systems for a REASON -- the link was DESIGNED to be continuously monitored by a dry-alarm contact at both ends. Whether or not the system engineer actually took the time/money/effort to USE those dry-contacts and alarms in their system plan, is a whole different story. But most RoIP implementations DON'T EVEN HAVE THEM. Avoid any that don't. Engineering done properly will pay off later. Just because government agencies can't be sued for liability (who's bright idea was THAT?), doesn't mean the system engineer should do anything less than the best job possible for the officers in the field attempting to contact someone for help. RoIP/VoIP is "gee whiz" technology when it provides a link that would otherwise be cost-prohibitive or impossible due to terrain. It's "oh shit!" technology when it fails and no one in the dispatch center knows it's down. "Hero to zero" in one second flat. BUILD NETWORK MONITORING INTO YOUR VOIP/ROIP APPLICATIONS PLEASE. Done with my rant... if it doesn't apply to the technology you've chosen, ignore. If there are those reading along who just had an "oh shit!" moment thinking about their VoIP/RoIP network that's already deployed... go write up that budget request for monitoring and FIX IT... now. Before your bouncing IP link someday kills someone. -- Nate Duehr, WY0X [email protected]
