
Appendix M SIP
339
Nortel Business Secure Router 222 Configuration — Advanced
SIP Servers
SIP is a client-server protocol. A SIP client is an application program or device
that sends SIP requests. A SIP server responds to the SIP requests.
When you use SIP to make a VoIP call, it originates at a client and terminates at a
server. A SIP client could be a computer or a SIP phone. One device can act as
both a SIP client and a SIP server.
SIP User Agent Server
A SIP user agent server can make and receive VoIP telephone calls. This means
that SIP can be used for peer-to-peer communications even though it is a
client-server protocol. In
Figure 168
, either A or B can act as a SIP user agent
client to initiate a call. A and B can also both act as a SIP user agent server to
receive the call.
Figure 168
SIP User Agent Server
SIP Proxy Server
A SIP proxy server receives requests from clients and forwards them to another
server.
In the following example, client device A calls someone who is using client
device C.
1
The client device (A in the figure) sends a call invitation to the SIP proxy
server (B).
2
The SIP proxy server forwards the call invitation to C.
Summary of Contents for 222
Page 14: ...14 Contents NN47922 501 ...
Page 24: ...24 Tables NN47922 501 ...
Page 30: ...30 Preface NN47922 501 ...
Page 46: ...46 Chapter 2 Introducing the SMT NN47922 501 SMT menus at a glance Figure 6 SMT overview ...
Page 70: ...70 Chapter 3 WAN and Dial Backup Setup NN47922 501 ...
Page 78: ...78 Chapter 4 LAN setup NN47922 501 ...
Page 100: ...100 Chapter 6 Remote Node setup NN47922 501 ...
Page 104: ...104 Chapter 7 IP Static Route Setup NN47922 501 ...
Page 132: ...132 Chapter 9 Network Address Translation NAT NN47922 501 ...
Page 154: ...154 Chapter 11 Filter configuration NN47922 501 ...
Page 158: ...158 Chapter 12 SNMP Configuration NN47922 501 ...
Page 198: ...198 Chapter 15 Firmware and configuration file maintenance NN47922 501 ...
Page 212: ...212 Chapter 17 Remote Management NN47922 501 ...
Page 232: ...232 Appendix B Triangle Route NN47922 501 ...
Page 252: ...252 Appendix D PPPoE NN47922 501 ...
Page 260: ...260 Appendix F Hardware specifications NN47922 501 ...
Page 270: ...270 Appendix G IP subnetting NN47922 501 ...
Page 308: ...308 Appendix H Command Interpreter NN47922 501 ...
Page 312: ...312 Appendix I NetBIOS filter commands NN47922 501 ...
Page 336: ...336 Appendix L Brute force password guessing protection NN47922 501 ...