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A set of IEEE standards that aim at providing time-synchronized
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low-latency streaming services through IEEE 802 networks. The currently
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in use AVB technology is called (here) *Gen1* and consists of the
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following IEEE standards (or standard amendments): 802.1AS, 802.1Qat,
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802.1Qav and 802.1BA. However, ever increasing need and requirement for
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low-latency time-synchronized communication resulted in on-going works
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on *Gen2* of AVB. The requirements for *Gen2* are no longer shaped only
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by audio-video industry but also by others (e.g. automotive).
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It seems that AVB *Gen2* and White Rabbit have some commonalties. This
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page is meant to compare next generation of Audio Video Bridging (AVBg2,
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or AVB Gen2) with White Rabbit, both in terms of requirements and
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proposed solutions. Firstly, short introduction to the current AVB (Gen
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1) is provided. Then requirements and proposed solutions for AVBg2 are
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summarized. In a similar form to AVB and AVBg2 descriptions, WR
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description is provided. Finally, AVBg2 and WR are compared. The
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comparison is based on the author's view of AVB and AVBg2 described
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below (which is not thorough).
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following IEEE standards (or standard amendments): **802.1AS**,
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*802.1Qat**, **802.1Qav** and **802.1BA**. However, ever increasing
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need and requirement for low-latency time-synchronized communication
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resulted in an on-going works on *Gen2* of AVB. The requirements for
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*Gen2* are no longer shaped only by audio-video industry but also by
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others (e.g. automotive).
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It seems that AVB *Gen2* and White Rabbit have some commonalties (in
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terms of synchronization, low-latency, determinism, reliability). This
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page is meant to compare the next generation of Audio Video Bridging
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(AVBg2, or AVB Gen2) standard with White Rabbit, both in terms of
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requirements and proposed solutions. Firstly, short introduction to the
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current AVB (Gen 1) is provided. Then requirements and proposed
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solutions for AVBg2 are summarized. In a similar form to AVB and AVBg2
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descriptions, WR description is provided. Finally, AVBg2 and WR are
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compared. The comparison is based on the author's view of AVB and AVBg2
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described below (which is not thorough).
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## **AVB *Gen1***
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The Audio Video Bridging (*Gen1*) technology defines mechanisms (**IEEE
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802.1BA**) which allow to recognizes all the AVB-compatible devices in
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802.1BA**) which allows to recognizes all the AVB-compatible devices in
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the network. Basically, AVB works only within a domain of directly
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connected AVB-compatible network devices (i.e. bridges or endpoints).
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These devices support precise synchronization (**IEEE 802.1AS**) and
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establish stream reservations (register stream and reserve
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resources) across a bridged network between two end stations (talker
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and listener)
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- talkers (source) initiates by sending an SRP *talker advertise*
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message which include:
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- Talkers (source) initiates stream by sending an SRP *talker
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advertise* message which include:
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- Stream ID (source MAC, talker-specific unique ID and
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destination MAC)
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- QoS requirements (e.g., AVB traffic class and data rate
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information),
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- accumulated worst case latency (recalculated at each bridge)
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- listener (destination) acknowledges by replaying with *listener
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- Listener (destination) acknowledges by replaying with *listener
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ready* message
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- the signaling protocols:
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- Multiple MAC Registration Protocol (MMRP) is optionally used to
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control the propagation of Talker registrations throughout the
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bridged network (clause 10.9 of \[1\])
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control the propagation of the Talker's registrations throughout
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the bridged network (clause 10.9 of \[1\])
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- Multiple VLAN Registratin Protocol (MVRP) - used by end stations
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and Bridges to declare membership in a VLAN where a Stream is
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and bridges to declare membership in a VLAN where a stream is
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being sourced (clause 11 of \[1\])
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- Multiple Stream Registration Protocol (MSRP) - a signaling
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Service), between end stations (clause 35.1 of \[1\])
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-
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- stream can be de-registered by either talker or listener
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- stream can be de-registered by either Talker or Listener
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- references
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[1](http://standards.ieee.org/findstds/standard/802.1Qat-2010.html)
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- specifies the default configuration of AVB devices in a network
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- for Ethernet, the method specified by 802.1BA to determine if its
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peer is AVB capable is a combination of 802.3 link capabilities
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peer is AVB-capable is a combination of 802.3 link capabilities
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(determined during Ethernet link establishment) and the link delay
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measurements done by IEEE 802.1AS
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