Switching to VoIP

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Chapter 13: Network Infrastructure for VoIP

and, if configured for a VoIP network, attempts to register with a VoIP server. It

doesn’t care where the VoIP server is. It could be in the next room over, or it could

be in Manitoba, Canada. Such is the nature of TCP/IP. The point here is that you can

set the behavior of the IP hardphone to be identical no matter from where it con-

nects. In theory, if you provide for a consistent registration path from any spot on the

Internet, the phone will behave consistently regardless of where it’s sitting. (This is

what Vonage and BroadVoice have done.)

Like your corporate web site, which can be viewed by mobile users anywhere in the

world, it’s possible for you to allow your telephony users to access your voice ser-

vices from anywhere in the world.

But there are a few gotchas to this Utopian road warrior’s dream:

• There ought to be firewall(s) between the road warrior and his VoIP network.

Depending on your network’s requirements, you may need to allow TFTP, RTP,

IAX, SIP, H.323, SCCP, and the host of VoIP-related traffic (port numbers and

protocols can be referenced in Chapter 10).

• Don’t bet on hotels and other road warrior hotspots offering inline power. Make

sure the road warrior carries an AC power adapter for his hardphone.

• In order