snom technology AG • 3
Table of Contents
1 Overview ..........................................................5
1.1 Applications ...................................................................... 6
1.2 Features ........................................................................... 6
2 Architecture .....................................................9
2.1 The NAT Filter and SIP ........................................................ 9
2.2 NAT ............................................................................... 10
2.2.1 How does NAT work? ..............................................................................................................................................11
2.2.2 Symmetrical RTP ............................................................................................................................................................11
2.2.3 Signalling SIP .......................................................................................................................................................................11
2.2.4 Media RTP ...................................................................................................................................................................................12
2.2.5 Classification of User Agents ....................................................................................................................12
2.2.6 Probing Media Paths .................................................................................................................................................13
2.2.7 The Role of the NAT Filter ..............................................................................................................................13
2.2.8 Optimizing the Media Path for Symmetrical NAT ..................................................14
2.3 Filter Behaviour ............................................................... 15
2.3.1 Registering without UA Support ..........................................................................................................15
2.3.2 Registering with UA Support .....................................................................................................................16
2.3.3 RTP Relay ....................................................................................................................................................................................18
2.4 Scaling and Redundancy ................................................... 20
2.5 Detecting the right NAT Filter ............................................ 21
2.6 Requirements on User Agents ............................................ 21
2.6.1 Non NAT-Aware User Agents .....................................................................................................................21
2.6.2 STUN/ICE-Aware User Agents ................................................................................................................22
2.7 Defining the Maximum Session Time .................................. 22
3 Installation .....................................................25
3.1 Windows ......................................................................... 25
3.2 Linux ............................................................................. 30
4 Configuration ..................................................33
4.1 Logging In ...................................................................... 33
4.2 Port Binding .................................................................... 33
4.3 System Settings .............................................................. 35
4.3.1 Logging ...........................................................................................................................................................................................35
4.3.2 Preparing Recovery ...................................................................................................................................................36
