Tag: NAT
-
Fixing SIP header addresses – Via headers
•
In part 2, Via headers are put under the microscope. I examine how the address in the Via header is set by each node in the path; how and why it may differ from the source address. I will look at the functions available in OpenSIPS to detect and handle situations where the address in the received Via differs from the source address of the request. I touch on the options available within OpenSIPS to select…
-
Fixing SIP header addresses – Introduction
•
The main theme I explore in these articles is when and how a SIP Proxy should alter (or “fix”) embedded sender address information – IP and port – in a SIP request that it has received. The headers that are most relevant here are Via, Contact and Record-Route
-
Using the Clusterer Module for contact replication
•
Summary In this, the second part of a three-part article about the Clusterer Module, I explain how I got on when testing a pair of OpenSIPS Registrar Proxies configured as a highly available cluster. The design, which uses Pacemaker to assign a floating IP to the currently active server, is described in some detail in part 1 (see Scenario 2 for a complete description of the solution). My tests simulated a typical real-world scenario, using a…
-
How to install Mediaproxy 2.5.2 on CentOS 6 64 bit
•
Mediaproxy 2.5.2 is a Python application from AG-Projects which is available as a free download as well as being available as a commercial product from AG-Projects. It is used in combination with the Mediaproxy module of OpenSIPS. Mediaproxy 2 has several dependencies and can be quite tricky to install. The INSTALL instructions that come with the package are very helpful, but unfortunately they are aimed primarily at installers who either have Debian or Ubuntu Linux distributions.…
-
Installing Mediaproxy 2 on CentOS 5 64bit
•
Mediaproxy 2 is a Python application from AG-Projects which is available as a free download as well as being available as a commercial product from AG-Projects. It is used in combination with the Mediaproxy module of OpenSIPS. Unlike Mediaproxy 1, the new version has a lot of dependencies and it can be quite tricky to install. The INSTALL instructions that come with the package are very helpful, but unfortunately they are aimed primarily at installers who…
-
Asterisk behind NAT
•
Scenarios in which NAT may adversely affect Asterisk SIP connections The Asterisk Server is behind NAT The Asterisk server could be on the LAN (or in a DMZ) with a NAT firewall between it and the Internet. When it communicates with external peers or devices, the network connections have to pass through the local NAT device. The remote device that is connecting to Asterisk is behind NAT Suppose that your Asterisk server is connected directly to…
-
Using SIP Devices behind NAT
•
SIP Devices behind NAT: What solutions are available? When an IP phone is installed behind NAT, problems can be created by the NAT device itself, by the phone’s inability to correctly understand its own networking environment or from a combination of the two. Because it is such a common problem, most IP Phones have built-in facilities designed to help them analyse their own networking environment and to help overcome the problems of NAT traversal. Probably the…
-
SIP and NAT: Why is it a problem?
•
Why is it a problem using SIP Clients behind NAT? What is NAT? To understand why SIP Clients behind NAT are a problem, you need to first have some understanding of what NAT is and what it does. NAT stands for Network Address Translation. Unless you are using One-to-one NAT, then a NAT device may also perform Port Address Translation (PAT). For a detailed explanation of NAT click here. If you want, you can also read…
-
About IP Packet Communications – TCP and UDP
•
Devices communicate data to other devices on the Internet using certain recognised protocols that involve routing and transmission of packets of data to a remote device identified by an IP addresses. The most widely used protocols on the Internet are TCP and UDP. The differences between these two protocols are of a highly technical nature which we do not attempt to explain in detail here. However, there are some important common factors about the way they…
-
What is NAT?
•
What is NAT? NAT stands for Network Address Translation. Many devices sold as Firewalls or Routers are actually combined Firewall, Router and NAT device in one box. NAT is the mechanism that allows you to have many PC’s on your LAN all connected to the Internet through a single external IP address. When one of the PC’s on the private side of the NAT device initiates a connection with a server on the Internet, then it…
