5. Example Scenario

Routing Scenario Walkthrough

To help bring all the previous chapters together, this section provides a simple walkthrough using a real-world scenario.

Scenario

This example assumes that VSM is configured to use HOME Native Routing, with HOME’s Splice service coordinating the connection between the selected source and destination.

An operator presses a button on a router control panel to route a source to a destination. Even though there are no physical cross-points being switched, a clear sequence of events takes place.

Step 1 - Operator Issues a Command

The operator selects a source and destination using:

• A VSM hardware control panel
• A VSM web-based UI (software)

The panel sends a message to VSM, which uses its panel engine to interpret the button press. This may, or may not, trigger additional actions in the logic/routing engine of VSM, a key feature which allows VSM to perform complex actions based on a simple button press. Once any additional trigger actions have been completed, VSM then sends a control request to HOME via the HOME API (NATS). At this stage, no media has moved yet—this is only a control instruction.

Step 2 - HOME Processes the Request

HOME:

• Verifies the requested route
• Confirms the devices are registered and available
• Determines the selected source (TX) and destination (RX)

The routing decision is translated into structured control data/instructions. Internally, HOME redistributes this instruction using its messaging system (NATS), ensuring the correct device receives the command in real-time. 

Step 3 - The Receiver Is Instructed to Subscribe

For an ST 2110 stream, routing is achieved by instructing the RX device to subscribe to a specific multicast stream. HOME (via its API and messaging system):

• Sends the connection details via API calls, including the stream information required by the receiver
• Instructs the RX device to join the multicast group
• Updates the system state information

The RX device then signals its multicast membership to the Streaming Media networks

Step 4 - The Network Delivers the Stream

The Streaming Media network:

• Uses IGMP membership information to identify receivers interested in the multicast stream.
• Uses IGMP snooping to control multicast forwarding within the local Layer 2 network.
• Uses multicast routing protocols such as PIM-SM to establish forwarding paths when the stream must traverse routed Layer 3 boundaries.
• Forwards the RTP packets towards the receiving device using the established multicast forwarding state.

If the Streaming Media network operates with ST 2022-7 redundancy:

• The receiver subscribes to corresponding media streams across the independent RED and BLUE networks.
• The receiver uses Seamless Protection Switching (SPS) to reconstruct the media stream from packets received across both paths.
• Provided at least one valid copy of each required packet arrives within the receiver’s supported timing window, media reception can continue without interruption following a failure affecting one network path.

Step 5 - The Signal Appears at the Destination

The RX device:

• Uses its PTP-synchronised media clock to correctly time the received media
• Reconstructs the essence(s)
• Outputs video, audio or other media as required

From the operator's perspective, the result feels identical to switching an SDI router. Behind the scenes, however, the process was:

• API driven
• Software-coordinated
• Multicast-based
• Time-aligned via PTP
• Potentially redundant across two independent networks 

The Important Distinction

This example demonstrates an important principle:

The Broadcast Control network in conjunction with HOME and VSM provides:

• The inventory (which devices exist)
• The control logic (what should connect)
• The messaging layer (how instructions are delivered)
• The system awareness (what devices and streams are currently active)

The Streaming Media network forwards packets according to the multicast forwarding state established through protocols such as IGMP and PIM, independently of the broadcast control system’s routing decisions. For engineers coming from baseband, this is the key conceptual shift:

When properly designed, the operational experience remains familiar, but the flexibility and scalability are significantly greater. 

From Routing to Workflow Orchestration

The previous example demonstrated how a single route is established between a source and destination. In practice, broadcast productions often require multiple coordinated actions to occur from a single operator command. This is where systems such as VSM provide significant value beyond basic signal routing capabilities of HOME. Consider a live production environment.

An operator presses a button on a VSM control panel to make a studio camera available to the production switcher. At a routing level, this action may result in:

• The camera video stream being routed to an input on the production switcher
• The same camera stream being routed to a multiviewer for monitoring
• The camera signal being routed to a processing stage for proxy generation or signal processing
• A proxy or processed version of the signal being routed to a HOME App Multiviewer instance

From the operator’s perspective, only a single button was pressed. Behind the scenes, VSM may coordinate multiple routing actions simultaneously using Signal Paths and the same routing mechanisms described earlier.

Taking the Camera to Air

Later in the production, an operator selects the camera on the production switcher and takes it to air. Unlike the previous routing example, this action may not require any new ST 2110 stream subscriptions. The switch occurs internally within the production switcher itself. However, the wider system may still react to the event. For example:

• Tally information is sent to the camera, illuminating its tally light
• Tally status is distributed to multiviewers so operators can immediately identify the active source
• An “On Air” indicator outside the studio is activated
• Monitoring and status systems are updated
• Production-specific workflows may be triggered automatically

Depending on the facility design, additional actions could include:

• Automatic fading of programme music
• Activation of studio lighting states
• Triggering automation systems
• Updating teleprompter monitoring displays
• Logging operational events for compliance or auditing

No new stream patching may occur because the required streams are already available to the production switcher. Although these actions may involve many different systems, they can all be triggered from a single operator action through the orchestration capabilities of VSM.

The Role of VSM

This illustrates the difference between signal routing and workflow orchestration. Routing determines where media streams are sent. Workflow orchestration determines how the wider production environment responds to operational events. HOME provides the infrastructure services required to register devices, manage resources and establish media connections. VSM builds on that foundation by coordinating multiple systems and devices, allowing a single operator action to trigger a complete production workflow. From an operator’s perspective, the system behaves as a single integrated environment. Behind the scenes, HOME, VSM and the underlying IP infrastructure work together to coordinate routing, control, monitoring and operational logic across the facility.

Epilogue

The transition from legacy baseband infrastructure to IP-based broadcasting represents one of the most significant technological shifts the industry has experienced. While the underlying principles of television engineering remain the same — transporting, processing and controlling media reliably — the methods used to achieve this have changed dramatically. Dedicated physical signal paths have been replaced by software-defined workflows, multicast networking and distributed system control. At first, this transition can appear complex. Terms such as multicast, PTP, SDP, NMOS and APIs introduce concepts that are unfamiliar to engineers whose experience has been rooted primarily in SDI environments. However, as this guide has demonstrated, many of the operational goals remain fundamentally unchanged:

• Signals still need to be routed
• Devices still need to be controlled
• Timing still needs to remain accurate
• Systems still need to be resilient and operationally simple

What changes is the architecture used to achieve those goals.

Modern IP broadcast systems rely on the coordination between network infrastructure, timing systems, control protocols and orchestration platforms such as HOME and VSM. Understanding how these layers interact is essential for designing, commissioning and maintaining reliable ST 2110 facilities. Importantly, IP infrastructure should not be viewed purely as a replacement for SDI. When properly implemented, it provides significant advantages in:

• Scalability
• Flexibility
• Resource sharing
• Redundancy
• System visibility
• Workflow integration

The industry is still evolving, and no two facilities are designed in exactly the same way. However, the core concepts covered throughout this guide form the foundation upon which modern IP broadcast environments are built. For engineers transitioning into IP, the objective is not simply to learn new protocols or terminology, but to develop a new way of thinking about media infrastructure — one where routing, control and processing are increasingly software-defined and network-aware. The concepts introduced throughout this guide provide the foundation for more advanced topics such as spine-leaf network design, effectively scaling networks for multicast applications, system design for software-defined media processing and cloud-based production workflows. While those subjects are beyond the scope of this introduction, understanding the principles covered here provides a strong starting point for working confidently within modern IP broadcast environments. Although the technologies may continue to evolve, the engineering principles of reliability, clarity, resilience and operational simplicity remain unchanged.