Administrator’s Guide for SIP-T5 Series Smart Media Phones
78
Network Address Translation (NAT)
Network Address Translation (NAT) is essentially a translation table that maps public IP address
and port combinations to private ones. This reduces the need for a large number of public IP
addresses. NAT ensures security since each outgoing or incoming request must first go through
a translation process.
NAT Types
Symmetrical NAT
In symmetrical NAT, the NAT router stores the address and port where the packet was sent. Only
packets coming from this address and port are forwarded back to the private address.
Full Cone NAT
In full cone NAT, all packets from a private address (e.g., iAddr: port1) to public network will be
sent through a public address (e.g., eAddr: port2). Packets coming from the address of any
server to eAddr: port2 will be forwarded back to the private address (e.g., iAddr: port1).
Address Restricted Cone NAT
Restricted cone NAT works similar like full cone NAT. A public host (hAddr: any) can send
packets to iAddr: port1 through eAddr: port2 only if iAddr: port1 has previously sent a packet to
hAddr: any. "Any" means the port number doesn't matter.
Port Restricted Cone NAT
Port restricted cone NAT works similar like full cone NAT. A public host (hAddr: hPort) can send
packets to iAddr: port1 through eAddr: port2 only if iAddr: port1 has previously sent a packet to
hAddr: hPort.
NAT Traversal
In the VoIP environment, NAT breaks end-to-end connectivity.
To Next Page
Loading...
Need help?
General
