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P2000W V2 Troubleshooting Guide
and will soon run out. Thus NAT is very commonly used. Unfortunately from field
test many vendor’s NAT are not SIP friendly.
Fortunately, there are already ways to workaround the NAT for SIP. The most
ommonly used way is listed below. c
SIP pass-through support on NAT router (require router vendor implement it).
STUN.
Outbound Proxy.
There are advantage and disadvantage of each technology.
requires router vendor
plementation. From carrier point of view this does not seem feasible as not every
datagram protocol. It helps to traverse UDP
rough NAT. STUN allows applications to discover the presence and type of NATs
one or
oftware, to use the proxy for all SIP sessions, just like when you configure your Web
For example SIP pass-through on NAT router this
im
NAT router vendor implement this on their router and they do not have control of
which router their customer is using.
STUN is a simple traversal of user
th
between the host and public Internet. It also provides the ability for application to
determine the public IP allocated to the host by NAT. STUN works with many
Existing NATs, and does not require special handling from NAT router. As a result it
can make SIP pass-through NAT. Please refer to RFC 3489 for more details.
The outbound proxy is a normal SIP proxy. You configure your client, the ph
s
browser to use a Web proxy for all Web transactions. In some cases, the outbound
proxy is placed alongside the firewall and is the only way to let SIP traffic pass from
the internal network to the Internet. For more detail you can refer to RFC 3261 for
details.
All contents copyright (c) 2005 ZyXEL Communications Corporation.