... | @@ -312,8 +312,8 @@ The enhancements to current IEEE 802.1AS include |
... | @@ -312,8 +312,8 @@ The enhancements to current IEEE 802.1AS include |
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- Synchronization:
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- Synchronization:
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- accuracy: sub-nanosecond in the entire network
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- accuracy: sub-nanosecond in the entire network
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- precision: order of picoseconds in the entire network
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- precision: order of picoseconds in the entire network
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- Reliability seamless redundancy (synchronization-wise and critical
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- Reliability: seamless redundancy (synchronization-wise and critical
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data-wise)
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data-wise) which should ensure high availability
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### Timing and Synchronization
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### Timing and Synchronization
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... | @@ -387,13 +387,31 @@ reconfiguration seem to be inline in WR and AVB. (**ToFinish**) |
... | @@ -387,13 +387,31 @@ reconfiguration seem to be inline in WR and AVB. (**ToFinish**) |
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### Critical-data-wise
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### Critical-data-wise
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WR does not foresee dynamic stream reservation -- it is assumed that
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WR does not foresee dynamic stream reservation -- it is assumed that
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there are two kinds of (1) critical data (so called Control Messages,
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there are two kinds of data: (1) critical (so called Control Messages,
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CMs) and (2) non-critical data (Best-effort, BE). All critical data is
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CMs) and (2) non-critical (Best-effort, BE). All critical data is
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treated equally and share the same resources which are allocated to it.
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treated equally and share the same resources which are allocated to it
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The characteristics distribution of the CMs in WR is also different then
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(a very limited number of CM streams is foreseen). The distribution
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in the distribution of streams in AVB. In WR the critical data stream is
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characteristics of the CMs in WR is also different then streams in AVB.
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supposed to be broadcast within VLAN, thus a stream is propagated to all
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In WR, the critical data stream is supposed to be broadcast within VLAN,
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the end stations within a VLAN: a particular case of such solution is to
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thus a stream is propagated to all the end stations within a VLAN: a
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define VLAN for a stream between two end stations. Still, separate
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particular case of such solution is to define VLAN for a stream between
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VLAN-streams do not have separate resources.
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two end stations. Still, separate VLAN-streams do not have separate
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resources.
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In WR, the critical data is encoded using Forward Error Correction to
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prevent loss of data critical due to data corruption (bit error
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rate/switch malfunction) and to allow dynamic network redundancy while
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providing undisturbed critical data stream. In AVBg2 simplicity
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prevails:
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- if a network can allow dynamic network reconfiguration (e.g.
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requirement of reconfiguration time \< 100ms, [Toyota,
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page 6](http://www.ieee802.org/1/files/public/docs2011/new-avb-KimNakamura-automotive-network-requirements-0311.pdf)),
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then end applications can accept some data loss. Therefore, the some
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data loss due to data corruption is also acceptable.
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- if seamless redundancy is required, static network redundancy
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(independent paths) is used.
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Using FEC has a negative effect on the data delivery latency (probably
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not acceptable by the most stringent AVBg2 requirements). However,
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