NMOS IS-04: Discovery & Registration

What is NMOS IS-04?

NMOS IS-04 is the Discovery and Registration specification from the Advanced Media Workflow Association (AMWA). It allows all ST 2110 devices (senders, receivers, and other nodes) to automatically announce their presence and capabilities on the network.

Without IS-04, operators would need to manually configure IP addresses, SDP files, and multicast groups — making large systems nearly unmanageable.

How IS-04 Works

Enabling NMOS IS-04 on Devices

1. Enable IS-04 Service — In the device web interface or configuration menu, turn on “NMOS IS-04” or “Discovery”.
2. Set Registry Address — Most systems use mDNS (zero-configuration) or a static Registry URL (e.g., http://registry.example.com/x-nmos/registry/).
3. Choose Mode —
   • mDNS

     mDNS (Multicast DNS) in NMOS & ST 2110

     mDNS is a zero-configuration networking protocol that allows devices to automatically discover each other on a local network without needing a central DNS server or manual IP configuration.

     What is mDNS?

     Also known as Bonjour (Apple) or Avahi (Linux), mDNS enables devices to advertise and discover services using simple, human-readable names like _nmos-query._tcp.local or _nmos-registration._tcp.local.

     How mDNS Works in NMOS / ST 2110

     When you enable NMOS IS-04 on a device, it can use mDNS in two main ways:

     1. Service Discovery — Devices announce themselves and their NMOS capabilities using multicast packets.
     
     2. Registry Discovery — Devices can automatically find the NMOS Registry on the network without you entering its IP address or URL.

     Key mDNS Service Types in NMOS

     _nmos-query._tcp.local     →   NMOS Query API (IS-04)
     _nmos-registration._tcp.local →   NMOS Registration API
     _nmos-node._tcp.local        →   Individual NMOS Nodes

     Advantages of mDNS

     • Truly zero-configuration — just plug in the device and it works
     • Ideal for small to medium facilities
     • No need to maintain a central Registry server
     • Fast and simple for testing and temporary setups

     Limitations of mDNS

     • Limited to a single subnet (does not cross routers)
     • Not scalable for very large facilities (hundreds of devices)
     • Less reliable on busy or poorly configured networks
     • No built-in redundancy compared to a dedicated Registry

     When to use mDNS vs Registry Mode:
     
     Use mDNS for small studios, mobile trucks, or quick test setups.
     Use a central Registry for large permanent broadcast facilities where scalability, redundancy, and centralized control are required.

     In modern ST 2110 systems, many devices support both mDNS (for simplicity) and Registry mode (for production scale).
     
     You can often choose the mode in the device’s NMOS configuration settings.

     Close Window
      (recommended for small/simple systems) — No central registry needed.
   • Registry Mode (recommended for production facilities) — All devices register to one or more central registries.
4. Apply & Reboot — Many devices require a restart after enabling IS-04.

Friendly Names in NMOS Setup

Every NMOS node, device, sender, and receiver can have a Friendly Name. This is a human-readable label that appears in control systems instead of cryptic IP addresses or UUIDs.

Friendly names are set in the device’s NMOS configuration page and are advertised in the IS-04 registry. They make routing, troubleshooting, and daily operation much easier.

Common NMOS IS-04 Setup Issues & Tips

• Network Segmentation — IS-04 traffic must be allowed on the control VLAN (usually multicast 224.0.0.251 for mDNS or unicast to the registry).
• Multiple Registries — In large systems, use redundant registries and ensure devices are configured to register to all of them.
• Firewall / ACLs — Port 80/443 and mDNS (5353) must be open between devices and the registry.
• Version Mismatch — Ensure all devices support the same IS-04 version (v1.3+ is common in 2026).
• DNS Resolution — When using static registry URLs, reliable DNS is critical.
• Node Restart Order — Bring up the Registry first, then senders/receivers.
• Friendly Name Duplicates — Avoid identical friendly names across the facility to prevent confusion in control UIs.
• Security — In production environments, consider IS-04 with TLS (HTTPS) and proper authentication.