Matrix SETU VFX88L System Manual page 168

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incoming request must go through a translation process that also
offers the opportunity to qualify or authenticate the request or
match it to a previous request.
• NAT also conserves on the number of global IP addresses that a
company needs and it lets the company use a single IP address in
its communication with the world.
STUN: (RFC 3489)
Note:
STUN is used if there is a NAT router between VFX88L/VFX44L and
SIP Server (from ITSP).
• STUN stands for Simple Traversal of UDP over NAT. It is a
protocol, which enables the gateway to detect the presence and
type of NAT behind which the gateway is placed. The gateway that
supports STUN can intelligently modify the private IP address and
port in its SIP/SDP message by using the NAT mapped public IP
address and port through a series of STUN queries against a STUN
server located on the public Internet.
• This will allow SIP signaling and RTP media to successfully
traverse a NAT without requiring any configuration changes on the
NAT. STUN presents a working solution for most NATs that are not
symmetric NAT, e.g., most of the SOHO routers have non-
symmetric NAT and in this case, it is OK to use STUN. However,
STUN does NOT work with symmetric NAT and if your routers have
built-in symmetric NAT, do not use STUN.
• A STUN server can help facilitate traversing through most NATs,
except for symmetric NATs.
Outbound Proxy
VoIP service provider can host a SIP outbound proxy server to handle
all of the gateway VoIP traffic. User has to enable this feature if VoIP
service provider has a SIP outbound server to handle voice calls. This
allows the gateway to work with any type of NAT router and eliminates
the need of STUN.
Important Voice Parameters:
Jitter Buffer:
• The clarity of voice heard from the called party is also distorted due
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System Manual
SETU VFX88L/VFX44L V1