Network Requirements

Each Scout console requires a minimum of either one or two Ethernet connections. If using the Hardware Media Workstation, two Ethernet connections are required, one for the console PC and one for the media workstation. If using the Software Media Workstation, only one for the console PC is required. More are required when implementing redundant networks. Each VPGate requires one Ethernet port. Outpost requires only one Ethernet port even though it supports two audio connections.

Bandwidth

Avtec recommends that Scout be installed on a 100 Base-T (or faster) network infrastructure.

The commonly used G.711 codec uses approximately 84 kbps for each active conversation. Scout supports other audio codecs (G.723, G.726, and G729) which can use between 8 and 40 kbps.

A typical Outpost to VPGate network connection for one radio operates at 30 kbps to 86 kbps for audio transmission during activity when the radio is squelched. This endpoint traffic is unicast, to reduce multicast traffic on a WAN. Control and keepalive messages add only about 1% - 3% additional overhead.

For efficiency on a LAN, VPGate forwards the unicast packets from Outpost using multicast to the Scout consoles. Audio is automatically forwarded whenever an endpoint is active and transmitting to VPGate, whether 1 or 50 consoles have that endpoint selected or monitored.

Jitter and Latency

For WAN configurations, the delay should be less than 100 ms. Scout Outpost and Media Workstation typically use 20 ms packets and allow jitter ranging from 60 ms to 2.5 seconds. Both Outpost and Media Workstation let you adjust their jitter buffer to optimize performance.

Network latency can affect the flow of conversation by introducing longer than expected delays between talkers. Ideally, overall latency should be less than 150 ms to prevent unwanted delays during conversations. For half-duplex radios, under 300 ms is generally acceptable.

Quality of Service

VPGate supports separate Differentiated Services (DiffServ) values for audio and control packets from VPGate to the endpoint. This allows VPGate to set a higher priority for VoIP packets over control packets to ensure that the audio is transmitted through the network without unwanted delays.