You Can Provide IP Phone Services via a Dialup Connection
Internet
Router
3524 Switch
Network Printer
Server
Server
This is an IP Security (IPSec) site-to-site Virtual Private Network (VPN), such
that each set of devices on each network appears to just be another device on a
larger network.These devices are able to communicate together, use the same
resources, and place IP phone calls between the two sites. One user on one network
would have no idea that the data is carried between the two sites by way
of secured communications across the public Internet, but that’s exactly what is
happening here.
An inescapable issue with this type of arrangement is the possible loss of connectivity
between the two sites should any manner of problem arise with either
www.syngress.com
Figure 10.6 You Can Provide IP Phone Services via a Dialup Connection
Internet
Router
3524 Switch
Network Printer
Server
Server
IP Phone
IP Phone
VLAN
Routing
Voice VLAN
Data VLAN
Telco
PBX
PRI Circuit
Dialup
Server
Site B
Router
346 Chapter 10 • Designing and Implementing Single Site Solutions
site’s router, connection to the public Internet, or the VPN itself.Worse yet, many
small sites do not have a properly sized Internet circuit capable of carrying not
only the VPN traffic but traffic destined for the public Internet. Sites that are on
a VPN connection back to their head office typically use at least a 256 Kbps or
faster circuit, but may be limited to as low as 64 Kbps, such as ISDN.
When these lower-speed capacities are present, connecting two sites together
for the purpose of VoIP or other AVVID solutions becomes very challenging. If
these slower connection speeds cannot be increased, then running AVVID solutions
between the sites will not be possible. In these days of x Digital Subscriber
Line (xDSL), even the slowest IDSL speed of 144 Kbps is capable of supporting
just the VoIP portion of the AVVID portfolio.You can also bond a pair of v.90
modem dialups into a 112 Kbps channel between a pair of Cisco 2600 class
routers that use asynchronous modems.