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Network design
reduce administrative overhead provides a powerful incentive. Most important, by helping
integrate voice and data communication, multimedia messaging, supplier and customer
relationship management, corporate data stores, and other technologies and resources,
converged networks promise to become a key enabler for eBusiness initiatives.
NAT
IP Telephony does not work well with networks that use NAT (Network Address Translation)
because most NAT implementations do not support H.323 protocols. The destination IP address
is encapsulated in more than one header, including the Q.931, H.225, and IP headers. NAT
changes only the address in the IP header, which results in a mismatch that prohibits the control
of calls. Avaya suggests using a firewall to guard against intruders, but the firewall should not
provide NAT functions for IP Telephony packets unless it is Avaya Q.931 friendly.
Telephony without NAT
selective NAT. With Avaya Communication Manager 1.3 and later, products work seamlessly
with many static NAT applications, even if they are not H.323 aware.
Figure 81: IP Telephony without NAT
310 Avaya Application Solutions IP Telephony Deployment Guide
shows an approved sample implementation of a firewall that uses
Figure 81: IP
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