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Joined: January 26 2005
Location: United States
Posts: 1666
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| Posted: April 26 2005 at 2:15pm | IP Logged
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Hi Chav,
William just called us and we had a discussion regarding NAT traversal and STUN protocol.
NAT traversal is the single most difficult problem to overcome when deploying VOIP applications and systems.
There are basically 4 "classes" of NAT that are deployed in today's network environments. They are: Full Clone, Restricted Clone, Port Restricted Clone and Symmetric NAT. Note: Any network element that causes network address translation and/or port translation causes the network to be hostile to VOIP applications. This problem is not specific to the SIP and RTP protocols. Other peer-to-peer technologies also face similar issues.
The VOIP Media Engine does not contain any protocol specific capabilities for traversing NATs. This is because all of the standard proposals (STUN, TURN and ICE for example) do not work for all deployments. Symmetric NATs that are generally deployed in commercial environments cause the most problems.
The surest way to deploy VOIP where it will work for all network variations is to deploy VOIP applications (like soft phones) in conjunction with one or more SIP proxies (most often containing registrar support utilizing a common user database) and RTP Media Proxies (often called RTP relays). This is how we most often deploy VOIP Media Engine based applications or servers.
If you properly deploy an RTP media proxy solution, you will have no need for all the purposed NAT traversal protocols. This is what we do for most cases.
In the near term, we suggest you become familiar with IPTEL’s SIP Express router and the two RTP media proxy solutions that are available open source. Another alternative is to deploy session boundary controllers from Jasomi or similar vendors.
LanScape will be offering our scalable SIP proxy and RTP Media proxy solution in the next few months that removes the need to have other special NAT traversal solutions (expensive boundary controllers) or other protocols. Our scalable Centrex SIP proxies and VOIP media proxies will allow end users to deploy VOIP systems as easy as deploying today’s email servers.
LanScape Customer Support.
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LanScape Support Forum -> LanScape VOIP Media Engine™ - Technical Support
Topic: what protocal engine uses to get through the firewall
