As the telecom world moves closer and closer to software- based infrastructure, many questions are being asked about scalability of these software-based infrastructure solutions. After all, when there are hardware cards full of Digital Signal Processors (DSPs) you could simply plug in more boards or add more systems (at greater cost) to get to the scalability desired. In the software world, when using a single machine, the scalability is directly related to the power of the processor used in the box.

Blog395-MediaServersOne model to obtain higher scalability with software would be to use software-based infrastructure software to start, and then use DSP assist to get higher scalability. But this defeats the purpose of going with software in the first place. First of all it’s no longer software running on Commercial off-the-shelf (COTS) hardware, so expensive hardware will need to be deployed. Using COTS servers with software running on them, whether on premise or in cloud, costs less than specialized hardware solutions. And employing virtualization even on the same server means even more efficiency because multiple software programs can share the same COTS environment. These are core tenets of the move to Network Function Virtualization (NFV). Additionally, time to innovation is much faster with software. New features and enhancements can be added to a software-based solution more easily via a software upgrade as opposed to trying to upgrade a piece of hardware.

What is the alternative though? There are software mechanisms for scaling that have been tried and true with many software programs in the past. As an ex UNIX System product manager (yes, a long, long time ago) I am very familiar with software-based clustering techniques. Bringing these techniques to software-based communications network infrastructure enables these programs to scale as well.

One such network infrastructure that can scale in this way is the media server. Historically chock full of DSPs because of the intense media resource requirements, such as voice and video transcoding and video transrating/transizing, huge inroads have been made with software-based media servers over the past few years that allow them to run in service provider environments. For one, Moore’s Law has now enabled 2,000 channels of voice to run comfortably on a single machine. That will continue to contribute going forward. But those kinds of densities are not good enough for the movement to software-based infrastructure and cloud-based infrastructure.

The media server in the Internet Protocol Multimedia Subsystem (IMS) network is referred to as a Media Resource Function (MRF). The MRF spec calls out an element called the Media Resource Broker (MRB), which is a media resource controller and software load balancer that provides scalability, resiliency and redundancy of media services in the network. The MRB is described in Internet Engineering Task Force (IETF) RFC 6917 as well as the 3GPP specification for IP Multimedia session handling (TS 23.218).

The MRB essentially controls multiple media servers at one time and in this way scalability is achieved. Additionally, the presence of the MRB in the network ensures that media service requests are handled in the most efficient manner possible. The MRB has visibility into both the capabilities (e.g., codec support) and availability of each media server in the network, and routes media service requests to the most appropriate media server accordingly. As such, the current Dialogic MRB can control up to 30,000 sessions at a time. We know how to get higher sessions as well and continue to work on that.

Another benefit is high availability since the MRB can be used to manage multiple media servers in different locations. A software MRB can be deployed in a standalone configuration or as a redundant pair for high availability/scalability scenarios.

When large numbers of media sessions are required, software-based media servers can meet your needs. The era of the hardware-based media server is over.

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More on Dialogic’s PowerMedia XMS Media Server



What is MSRP? What are the advantages?

Message Session Relay Protocol (MSRP) is a protocol for text or multimedia instant messaging (SMS), which exchanges a series of related instant messages across an IP Network in the context of a session. There are many ways to do messaging, but MSRP offers some unique advantages like:

  • Transmission of text messages of any length
  • Add video or pictures in the same message
  • Can be included in the same session as real-time audio/video call
  • End-to-end message reliability
  • Authentication and message integrity
  • Low message delay


Figure1. Illustration of MSRP and PowerMedia XMS for video voicemail application.

How do you establish a session and flow in MSRP?

Now that you know the advantages of the MSRP protocol, we can look at establishing a session and what the flow looks like. We establish a session connection on the PowerMedia XMS (media server) by:

  1. SIP Invite that includes SDP media type (m=message)
  2. TCP port negotiated through exchange (similar to RTP)
  3. XMS Negotiates TCP port with MSRP Server
  4. MSRP message session is established

So, what is happening within the message session? Within the session, the media exchange is handled as well as the file (message) by chunking. Each chunk is then acknowledged by the endpoint and handles retransmission as well. Reports are then run to verify that the complete message has been successful. Connection termination does not happen until the SIP session has ended. The media session will remain active until it explicitly ended. A SIP BYE will terminate the message session. See Diagram below.


Which PowerMedia XMS APIs support MSRP?

The PowerMedia XMS RESTful API and MSML API both support the MSRP protocol, each one with its own distinctive capabilities for each specific application environment.   For RESTful API, there is support for file, text and binary messaging. This includes MSRP peer-to-peer, text messaging, photo sharing and chat services. The MSML API supports file transfer as defined in the MSRP protocol, but with support for sending in only one direction, similar to store and forward architecture.

The more you know about MSRP, the better you’ll begin to understand how it works with PowerMedia XMS for video and voicemail applications. We’re happy to provide you with the latest information as this technology continues to evolve. You can stay ahead of the curve by checking our blogs periodically to find out the latest developments in this space. You can also find tutorial videos, A Journey to Media Server Enlightenment, on our YouTube channel.

Follow us on Twitter @Dialogic for the latest videos and updates.

Check out Dialogic’s PowerMedia XMS Media Server Software and Download Your FREE Trail Licenses Today!


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