Specifications

RAVENNA ASIO & Core Audio Guide
RAVENNA ASIO & Core Audio : Introduction to RAVENNA Technology
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Streaming
Unicast
Unicast (one-to-one) is used in application scenarios such as an individual stream between two devices (e.g. a
multi-channel stream between a console and a recorder/DAW). This uses a point-to-point connection between
the sender and receiver. Since each additional receiver adds its own individual connection network traffic
increases with every additional unicast stream.
Multicast
Multicast (one-to-many) streaming is used in scenarios where a single source is to be distributed to many poten-
tial recipients (e.g. program stream to journalists' desktops). At the sending end this only requires one connection
per stream. Network switches are aware which participants (receivers) should receive any particular multicast and
forward packets only to registered nodes. In multicast set-ups the network traffic only increases on the last (closest
to receiver node) segment(s) of the network path.
Infrastructure
The network infrastructure must be able to transport IP packets and must support a number of standard operat-
ing protocols, e.g. RTP/RTPC for streaming since this is used widely and supports a wide variety of standard pay-
load formats. Some of these formats are mandatory for all RAVENNA devices, others are optional. For example this
protocol offers the possibility of standard media player applications subscribing to RAVENNA streams. Synchroni-
zation across all nodes is achieved via the IEEE1588-2008 (PTPv2 Precision Time Protocol). This is another standard
protocol which can be used on IP. PTPv2 provides a means for synchronizing local clocks to a precision as defined
in AES-11. Accurate synchronization can even be achieved across WAN connections when GPS is used as a com-
mon time domain.
Quality of Service
For the QoS (Quality of Service) protocol DiffServ has been chosen since it is widely supported by most modern
managed switches. Since other traffic can co-exist with RAVENNA on the same network, RAVENNA traffic must be
on the fast track. RAVENNA packets are assigned a high priority classification to ensure expedited transport across
the network, while other packets with lower priority are treated as best-effort traffic. Even within RAVENNA there
are different priorities assigned to different classes of traffic. Synchronization is assigned the highest priority,
immediately followed by any real-time media traffic, while control and configuration traffic will be on a lower pri-
ority level. Any non-RAVENNA traffic would receive the lowest (standard) priority and be treated as best-effort traf-
fic. Performance and capacity scale with the capabilities of the underlying network architecture.