How Live Connects
HireVue has a large number of “Live Media Servers” that handle Audio/Visual streams for each Live session. In order for a Live call to happen, all the users participating in that call have to connect to the same Media Server. To facilitate global video calls, there are pools of these servers strategically located around the globe.
Live 3.0
When a session starts, a Media Server is chosen based on a Team-level configuration if one exists. If this is not defined, then one is chosen based on where your account is hosted. In the EU environment, the “eu-west” AWS region is used. In the US, the “us-east” AWS region is used. All other users that subsequently join the session must connect to that server too. For more information about configuration in your account, contact your CSD or support@HireVue.com.
Connection Methods
HireVue Live uses WebRTC with ICE (Interactive Connectivity Establishment) to provide multiple methods of connecting to a media server. The most frequently used methods are Direct UDP and Relay which are both depicted below. Relay connections are only used when the client is unable to establish a Direct UDP connection due to client network rules.
Direct connect to UDP port 3478 is preferred.
Relay connect to TCP port 443 has high network overhead. The connection is with a TURN server instead of a Media Server.
The ideal connection method in terms of performance is the Direct UDP method. Most personal internet users running on home networks have access to this connection path by default, so they tend to connect to a Live interview this way. However, many corporate firewalls do not have UDP port 3478 open by default. As a result, the interviewers using Live will often end up connecting to Live Media Servers through a Relay path over TCP port 443, which is often already open. Although the Relay connection type is more flexible, audio and video performance will be compromised.
Why does UDP Perform Better?
Internet Protocol (IP) uses either TCP or UDP protocols for Transport of data packets over a network. The Transmission Control Protocol (TCP) is what most internet traffic uses because it is a very reliable way to transmit data over a persistent connection. This is accomplished with an array of error-checking and retransmission features built into it. The price of this reliability is a larger packet size and increased latency. The size of TCP packets increases to include header elements for the error-checking scheme that validates a complete data payload arrived at the destination intact. This is not what has the most impact on speed, however. The major cost is incurred when fragmented, altered, or out-of-sequence packets are detected and the recipient requests the sender to retransmit the failed data. That behavior creates a lot of back-and-forth dialogue to maintain a persistent and reliable connection. All of this adds up to latency, especially over a Wide Area Network which is typically a medium for Live video calls.
By contrast, User Datagram Protocol (UDP) was designed for transmitting data without a persistent connection or the reliability implied by TCP’s confirmed delivery mechanisms. Since the extra header data needed for confirmed delivery is not needed, the data packets of UDP are smaller than TCP. Further, latency is greatly reduced because the back-and-forth handshaking of TCP’s persistent connection is non-existent. By comparison, UDP behaves more like a “one-way rapid transit”. In UDP, not all data is guaranteed, which works well for Audio/Video applications that can handle some minor loss of data and still present high-quality video and sound.
How to Check
HireVue has an online test page that will check how your browser connects to Live Media Servers.
https://app.hirevue.com/ui/live/#info/connection-test/
...click “Run All Tests”. The details tab has deep diagnostic information that can be interpreted by HireVue’s Support team. If you are having connection problems, please include these results in your support request.