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Appendix L SIP
NN47923-501
SIP ALG
Some NAT routers can include a SIP Application Layer Gateway (ALG). A SIP
ALG allows VoIP calls to pass through NAT by examining and translating IP
addresses embedded in the data stream. When a VoIP device (SIP client) behind
the SIP ALG registers with the SIP register server, the SIP ALG translates the
device’s private IP address inside the SIP data stream to a public IP address. You
do not need to use STUN if your VoIP device is behind the SIP ALG.
STUN
Using STUN (Simple Traversal of User Datagram Protocol (UDP) through
Network Address Translators), the VoIP device can the presence and types of
NAT routers, firewalls, or both between it and the public Internet. With STUN,
the VoIP device can also find the public IP address that NAT assigned, so the
VoIP device can embed it in the SIP data stream. See “
STUN - Simple Traversal
of User Datagram Protocol (UDP) Through Network Address Translators
(NATs)
” (RFC 3489) for details on STUN.
Business Secure Router SIP ALG
•
SIP clients must be connected to the LAN. A SIP server must be on the WAN.
•
You can make and receive calls between the LAN and the WAN. You cannot
make a call between the LAN and the LAN.
•
The SIP ALG forwards UDP packets with a port 5060 destination to pass
through.
•
The Business Secure Router forwards SIP audio connections.
Summary of Contents for 252
Page 14: ...14 Contents NN47923 501 ...
Page 20: ...20 Figures NN47923 501 ...
Page 24: ...24 Tables NN47923 501 ...
Page 30: ...30 Preface NN47923 501 ...
Page 42: ...42 Chapter 1 Getting to know your Nortel Business Secure Router 252 NN47923 501 ...
Page 48: ...48 Chapter 2 Introducing the SMT NN47923 501 SMT menus at a glance Figure 6 SMT overview ...
Page 72: ...72 Chapter 3 WAN and Dial Backup Setup NN47923 501 ...
Page 80: ...80 Chapter 4 LAN setup NN47923 501 ...
Page 84: ...84 Chapter 5 Internet access NN47923 501 ...
Page 98: ...98 Chapter 6 Remote Node setup NN47923 501 ...
Page 102: ...102 Chapter 7 IP Static Route Setup NN47923 501 ...
Page 130: ...130 Chapter 9 Network Address Translation NAT NN47923 501 ...
Page 156: ...156 Chapter 12 SNMP Configuration NN47923 501 ...
Page 178: ...178 Chapter 14 System information and diagnosis NN47923 501 ...
Page 198: ...198 Chapter 15 Firmware and configuration file maintenance NN47923 501 ...
Page 212: ...212 Chapter 17 Remote Management NN47923 501 ...
Page 232: ...232 Appendix B Triangle Route NN47923 501 ...
Page 252: ...252 Appendix D PPPoE NN47923 501 ...
Page 256: ...256 Appendix E Hardware specifications NN47923 501 ...
Page 266: ...266 Appendix F IP subnetting NN47923 501 ...
Page 308: ...308 Appendix H NetBIOS filter commands NN47923 501 ...
Page 332: ...332 Appendix K Brute force password guessing protection NN47923 501 ...