Linksys ATA Administration Guide
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3
Network Address Translation (NAT) and Voice over IP (VoIP)
Configuring Your System for ITSP Interoperability
Configuring Your System for ITSP
Interoperability
This chapter provides configuration details for the purpose of helping you to ensure that your
infrastructure properly supports voice services.
•
”Network Address Translation (NAT) and Voice over IP (VoIP),” on page 38
•
”Firewalls and SIP,” on page 42
•
”Configuring SIP Timer Values,” on page 43
Network Address Translation (NAT) and Voice over IP
(VoIP)
NAT is a function that allows multiple devices to share the same public, routable, IP address to
establish connections over the Internet. NAT is present in many broadband access devices to
translate public and private IP addresses. To enable VoIP to co-exist with NAT, some form of NAT
traversal is required.
Some ITSPs provide NAT traversal, but some do not. If your ITSP does not provide NAT traversal,
you have several options.
•
”NAT Mapping with Session Border Controller,” on page 38
•
”NAT Mapping with SIP-ALG Router,” on page 38
•
”Configuring NAT Mapping with a Static IP Address,” on page 39
•
”Configuring NAT Mapping with STUN,” on page 40
NAT Mapping with Session Border Controller
It is strongly recommended that you choose an ITSP that supports NAT mapping through a
Session Border Controller. With NAT mapping provided by the ITSP, you have more choices in
selecting a router.
NAT Mapping with SIP-ALG Router
If the ITSP network does not provide a Session Border Controller functionality, you can achieve
NAT mapping by using a router that has a SIP ALG (Application Layer Gateway). The Linksys
WRV200 router is recommended for this purpose, although any router with a SIP-ALG can be
used. By using a SIP-ALG router, you have more choices in selecting an ITSP.