The Session Initiation Protocol (SIP) is a signalling protocol used for initiating, maintaining, modifying and terminating real-time communications sessions between Internet Protocol (IP) devices. It enables voice, messaging, video and other multimedia communications applications and services between two or more endpoints on IP networks. So, it’s essential to realistically simulate and test SIP-based traffic.

Standardised in 1999, the Session Initiation Protocol (SIP) was developed to address the evolving needs of IP-based communications, including native support for mobility, interoperability and multimedia. SIP sessions can include VoIP, video conferencing, IM, online gaming and other forms of multi-channel communications. By and large, it replaced SS7 ISUP as the key protocol for establishing and managing sessions, including mid-session events and supplementary services.

The SIP communications protocol determines five attributes when establishing and terminating multimedia sessions:

• User location
• User availability
• User capabilities
• Session setup
• Session management.

Put simply, it’s an application protocol that is used to carry all forms of signalling for digital media, including voice and video. It became integral to mobile networks as it’s essential for IMS (let’s not forget that that the ‘M’ in IMS means ‘multi-media), for managing sessions, and has been key to fixed networks for even longer (remember softswitches). This importance hasn’t diminished, particularly as IMS remains an important adjunct to 5G networks.

This means that, wherever operators are on their 5G journey (Non-Standalone or Standalone), SIP will continue to be an essential component of the network architecture, and as such it’s essential that operators and equipment manufacturers have the right tools for comprehensively simulating and testing realistic SIP traffic – particularly when we consider a heterogeneous environment, spanning 5G, 4G / VoLTE and IMS.

Emblasoft testing tools to validate SIP-based systems

Emblasoft’s comprehensive testing tools enable simulation of a large number of clients using different protocols to validate scalability, performance, and characteristics of MaaP, RCS, RBM, or IMS systems at the network- or node-level. Our testing tools can verify SIP- and MSRP-based systems, including load and functional testing of MaaP, RCS, RBM, IMS, and NG9-1-1.

Emblasoft’s testing tools enable full-stack simulation for SIP, MSRP, RTP, HTTP, and Diameter, as well as more specialised protocols. By simulating user behaviour at the application protocol level, our testing tools provide simulated realistic traffic in the network layer. We can simulate traffic from a User Agent Server (UAS) or User Agent Client (UAC), as well as traffic from a SIP server node and SIP-Trunks.

With our SIP capabilities, it’s possible to test end-points (UE), and simulate the server making it easy to build test cases for different traffic flows – at real scale. Simulations can be performed at the system level (for example, using Gm and Ic interfaces) or at the node level – to allow signalling testing of a specific IMS node. Emblasoft’s tools also support specialised tests, such as SIP forking.

Generate realistic SIP call flows

As mentioned, our SIP capabilities can be used to simulate a UAS or a UAC. Combining the Emblasoft-provided SIP operations into test cases, allows different call flows to be created and tested, simulating different real-world traffic and behaviour. Some operations can generate several SIP requests, but most simply send a SIP request and wait for the SIP response.

The following examples provide an introduction into how operations can be grouped in order to generate typical SIP call flows:

1. At the beginning, common properties are initiated for the SIP stack that are then used by all coming SIP operations. Finally, all the resources used by the SIP stack are released.
2. Register – to simulate a simple SIP-client register call flow, a simple test case is used:
   
3. Basic Session Establishment

Simulating basic SIP session establishment (“Alice to Bob”) is a bit more complicated as it requires simulation of two users – Alice acting as the UAC and Bob acting as the UAS. This can be simulated within a single test case, where both are simulated or, to separate the two sides, a “Call” parameter can be used.

It’s also possible to initiate and simulate a Shared SIP Stack – the same incoming (server) connection (IP and port) is valid until it’s closed once the test case has been executed.

Typically, the used port is allocated dynamically using a short-lived ephemeral port. This means that if test cases are executed by multiple threads one connection will be used per thread and test case.

To simulate SIP server nodes (not an UA) use a fixed port and then share the connection. To allow this you can specify a port and select a “Shared Stack”. When closing a shared SIP stack, it will only close outgoing connections created by the SIP operations within the test case. The incoming server connection will be left open until a test has completed.

There are two parameters controlling the use of a “shared Stack”:

• Shared SIP Stack – where a shared SIP stack is used by all test cases.
• Shared Stack User – which is used when incoming SIP messages for a certain user should be handled by a specific scenario.

Simulate, test and automate SIP Tasks with Emblasoft

Emblasoft provides comprehensive simulation and testing of SIP-based scenarios and traffic. Example files are part of the sw package and are found in our extensions/test/sip directory, which includes:

• Configuration
• Register
• Basic Call.

Of course, all Emblasoft tests can be automated, and re-used to build new test cases, so you’re not always starting from scratch with each new test. Our comprehensive testing systems and solutions provide multiple automated test cases, including functional session verification, performance, scalability and stability verification with different traffic load scenarios, as well as Quality of Service enforcements across multiple nodes.

Emblasoft provides a single platform for function and performance testing that supports advanced automation, as well as integration with CI/CD/CT (DevOps) processes through REST APIs, and enables testing with different load types and formats with control and user plane separation.

So, since SIP is going to be around for a long time to come, we can help you ensure the smooth delivery and performance of key SIP-based services. To find out more, contact us today.