Hardware resource allocation rules

A number of different types of connections to Transcoding Conferencing Nodes are required for a conference to take place, or for a gateway call to be made.

A connection can be a call or presentation from an endpoint to a Virtual Meeting Room or Virtual Auditorium, a backplane between Transcoding Conferencing Nodes, or a call into or out of the Infinity Gateway. In this context, a connection is analogous to a port. Note that a Skype for Business client may require two connections (one for the video call, and one for presentation content).

When a connection is proxied via a Proxying Edge Node, the proxying node also consumes connection resources in order to forward the media streams on to a Transcoding Conferencing Node. A transcoding node always consumes the same amount of connection resources regardless of whether it has a direct connection to an endpoint, or it is receiving the media streams via a proxying node.

Each connection to a Transcoding Conferencing Node requires a certain amount of resource, or capacity.

In general, when compared to a single high definition HD 720p call:

  • a Full HD 1080p call uses twice the resource
  • an SD standard definition call uses half the resource
  • an audio-only call uses one sixteenth of the resource.

However, note that:

  • A WebRTC call using the VP8 codec uses the same amount of resource as H.264, and the VP9 codec uses around 25% more resource. Therefore:
    • VP9 at 720p uses the equivalent of 1.25 HD resources
    • VP9 at 1080p uses the equivalent of 2.5 HD resources
    • the maximum number of calls a Conferencing Node can support will be fewer for VP9 calls, for example a node that supports 39 H.264/VP8 SD calls will support 31 VP9 SD calls.

    Note that within the same conference some participants may use VP9 (if they are connected to a Conferencing Node using the AVX2 or later instruction set) while other participants may use VP8 (if they are connected to a Conferencing Node on older hardware).

  • Conferences or gateway calls that use the Adaptive Composition layout, and Teams conferences that use the Teams-like layout, consume additional Conferencing Node resources. The actual amount of additional resource depends on many factors, but as a guide, it uses an additional 1 HD of resource per conference, for up to 3 other video participants, plus approximately another 0.5 HD for each additional (4th, 5th etc.) video participant that is on stage. This is regardless of the call quality / resolution of the conference itself and each individual participant's connection (codec, bandwidth and so on).
  • H.323 audio-only calls are treated the same as video calls for resource usage purposes.
  • Connections to a Media Playback Service use 1.2 times as much resource as a connection to a VMR.
  • When transferring a participant, the transferee can temporarily take two sets of resources while in the process of being transferred. This should not normally last more than a few seconds.

If you want to limit video calls to specific resolutions (and limit the transcoding node resources that are reserved for calls), you should use the Maximum call quality setting (see Setting and limiting call quality for more information).

The following rules determine how hardware resources are allocated and consumed by conference and gateway calls in a Pexip Infinity deployment. They are measured in terms of HD resources, and assume that the Maximum call quality of the conference is set to HD (more or less resources are used for Full HD and SD respectively, as described above):

  • Standards-based endpoints (SIP or H.323) participants:

    • Each participant uses 1 HD resource.
    • Extra resources are consumed when sending main video and presentation content to the endpoint, than when compared to only sending main video. The amount of additional resource depends on many factors, including the resolution and frame rate of both sets of content, and the available bandwidth (plus the general maximum settings for call quality, bandwidth and presentation bandwidth ratio). Thus, if for example, a Conferencing Node is using 1 HD of resource to send just main video, and it then starts also sending presentation content, it may typically use a total of 1 HD of resource for presentation plus 0.5 HD for main video. However, in other circumstances (in particular, the bandwidth configured for the call), it could use 1 HD for content plus 1 HD for video, or potentially just 0.5 HD for content and 0.5 HD for video.
    • When sending two video streams to a dual-screen endpoint, the call bandwidth is always split 50-50 between video and presentation content (and cannot be changed), and it uses twice the resource as when only sending main video.
    • No additional resource is consumed when receiving presentation content from the endpoint.
  • WebRTC VP8/VP9 participants:

    • VP8 participants use 1 HD resource and VP9 participants use 1.25 HD resources for main video.
    • Extra resources are consumed when sending main video and presentation content to the WebRTC endpoint, in the same manner as described above for standards-based endpoints.
    • No additional resource is consumed when receiving presentation content from the endpoint.
  • Skype for Business / Lync participants:

    • Each participant uses 1 HD resource.
    • They each require 1 additional HD resource when sending or receiving presentation.
  • If an endpoint is restricted due to bandwidth limitations to a lower resolution than the conference's maximum call quality, the transcoding node will use the appropriate lower level of resource for that endpoint's connection. For example, if it is limited to an SD connection it will use 0.5 HD resources.
  • Each conference instance on each Transcoding Conferencing Node reserves a backplane connection at a resource level corresponding to the conference's Maximum call quality setting, to allow the conference to become geographically distributed if required. The exceptions to this are:

    • Deployments with a single Conferencing Node. In such cases, no backplanes will ever be required, so capacity is not reserved.
    • Conferences that are audio-only (in other words, where the conference has its Conference capabilities set to Audio-only). In such cases, capacity equivalent to one audio connection is reserved for the backplane.
  • Only one backplane connection is used for each conference on each Transcoding Conferencing Node, regardless of the number of other transcoding nodes that are involved in the conference. Note that on the Administrator interface, backplanes are displayed as unidirectional, so a single link between two nodes is shown with two backplanes, one in each direction. Likewise, a conference between three nodes is shown with six backplanes. However, for resource allocation purposes each node would require just one backplane connection.
  • Pexip Infinity always tries to optimize gateway calls:

    • A gateway call does not reserve resource for a backplane, but will use one if required (for example, if the participants are connected via different Transcoding Conferencing Nodes).
    • For a gateway call to Google Meet, the connection to Google Meet always uses 1 HD resource (it uses VP8) for main video. The resources required for the VTC leg of the connection depend upon the type of endpoint and the Maximum call quality setting. If the VTC endpoint starts to present content then an extra 1 HD resource is used for the connection from Pexip Infinity to Google Meet. However, no additional resources are required on the Google Meet leg if presentation content is sent from Google Meet, but 0.5 HD of additional resource would typically be required for each endpoint receiving presentation.
    • For a gateway call to a Microsoft Teams meeting, the connection to Teams uses 1.5 HD of resource if Maximum call quality is SD or HD, otherwise it uses 1.5 Full HD resources. The resources required for the VTC leg of the connection depend upon the Maximum call quality setting. If any participant presents content, additional resources (typically 0.5 HD) would be required, either on the Teams backplane (when an endpoint presents) or on the node handling the endpoint's media connection (when a Teams client presents). The exact amount of resource used depends on the codec, resolution and frame rate of the presentation stream.
  • If an API participant is the first participant to join a conference, it will reserve a backplane for the conference.

Proxying Edge Node resource requirements

When a connection is proxied via a Proxying Edge Node, the proxying node also consumes connection resources in order to forward the media streams on to a Transcoding Conferencing Node.

A proxying node uses approximately the equivalent of 3 audio-only resources to proxy a video call (of any resolution), and 1 audio-only resource to proxy an audio call.

Extra information

See Pexip Infinity license installation and usage for full information about how call licenses are consumed.

We have provided some resource allocation examples to help illustrate these rules in practice.