Step 3 – plan your configuration
Suggested Deployment
A typical 4200 installation uses an
external router, xDSL or cable modem to
terminate the WAN link. The 4200 is
then connected directly to the WAN
termination device to provide critical
functions for enterprise voice and data
traffic. The LAN port of the 4200 is
connected to the enterprise ethernet
local area network (typically a layer 2
switch).
10/100 Ethernet
Switch
WAN IP
65.93.xxx.xxx
4200
IP Phones
PC’s
Default Gateway
65.93.110.1
Public Address Pool
For Servers
67.52.xxx.xx1
67.52.xxx.xx2
67.52.xxx.xx3
67.52.xxx.xx4
Client Adaptor
Analog Phone
WAN Termination
(eg. xDSL Modem)
Softswitch
TFTP Server
Internet
In this example a single public IP address
is used to proxy for all of the IP phones
and to route to multiple PC’s installed on
the LAN. Additionally, a static NAT is
used to route to the publicly addressable
servers.
The 4200 provides the following services:
• WAN/LAN IP routing
• NAT/PAT translation for IP phones
and PC’s. This allows a single
public IP address to be used on
the WAN link to represent all of
the private IP addresses assigned
to the LAN IP phones and PC’s.
• Static NAT entries. This enables the customer to use a WAN public IP address
for data servers (web, mail, ftp, etc.) connected behind the 4200. These
servers can then be configured with private IP addresses for additional
security.
• A “VoIP” aware firewall. A full layer 7 gateway for voice traffic and a stateful
packet inspection firewall for data traffic.
• Traffic shaping and priority queuing to guarantee the quality of VoIP traffic.
These mechanisms protect voice and data traffic from contending for the
same network resources to guarantee low latency and the highest call quality
possible for VoIP traffic. At the same time they ensure the best utilization of
WAN bandwidth by enabling data traffic to burst up to full line rate in the
absence of voice calls. Precedence is given to traffic for the range of
addresses reserved for the IP phones.
• Call Admission Control (CAC). CAC uses a deterministic algorithm to decide
when there are insufficient network resources available to adequately support
new calls and then return the equivalent of a “fast busy” to new call requests.