User manual

4200 User Manual Edgewater Networks, Inc.
Version 2.2 11
The installation of an 4200 on the station side of an enterprise IP PBX is very similar
to the IP Centrex application above. The branch office is connected to the corporate
network using VPNs or private T1 links terminated by a WAN router. The 4200is
then connected directly to the WAN router and the LAN port of the 4200is connected
to the enterprise ethernet local area network (typically a layer 2 switch). The IP PBX
in the corporate headquarters location performs VoIP signaling and the 4200 acts as
a proxy for the voice devices installed at the branch office. The 4200 can perform the
following functions in this application:
 WAN/LAN IP routing.
 Traffic shaping and priority queuing to guarantee high quality voice 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.
 NAT/PAT translation for IP phones and PC’s. This allows a single 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.
 A “VoIP” aware firewall. A full layer 7 gateway for voice traffic and a stateful
packet inspection firewall for data traffic.
 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.
 DHCP server and TFTP relay. These features are used to simplify and
expedite the IP configuration of phones and PC’s. This also includes VoIP
signaling gateway information (MGCP, SIP, H.323 and SCCP).
 Call quality monitoring and test tools.