... | ... | @@ -388,7 +388,7 @@ defined by VLAN. WR adds sophisticated Forward Error Correction (FEC), |
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at a cost of latency deterioration, to spare network components
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(switches) and still provide undisturbed critical data stream in case of
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component failure (seamless redundancy over dynamically redundant
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network). This is because WR it is foreseen for large scale networks.
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network). This is because WR is foreseen for large scale networks.
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WR does not foresee dynamic stream reservation -- it is assumed that
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there are two kinds of data: (1) critical (so called Control Messages,
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... | ... | @@ -406,10 +406,9 @@ critical data one-to-many stream seems to be a corner case of AVB |
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stream.
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In WR, the critical data is encoded using Forward Error Correction to
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prevent loss of critical data 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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prevent losses due to data corruption (bit error rate/switch
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malfunction) and to allow dynamic network redundancy while providing
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undisturbed critical data stream. In AVBg2 simplicity 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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... | ... | @@ -417,7 +416,7 @@ prevails: |
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it means that the end applications can accept some data loss.
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Therefore, some data loss due to data corruption is acceptable.
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- if seamless redundancy is required, static network redundancy
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(independent paths) is needed.
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(independent paths) is needed. Therefore FEC is not needed.
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WR takes advantage of assumed one-to-many characteristics of the
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critical data in :
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... | ... | @@ -432,13 +431,14 @@ critical data in : |
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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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- in the idea where enhanced STP and FEC are used to provide seamless
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critical data stream over dynamically redundant network - FEC and
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eSTP are decoupled
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- the idea where enhanced LA and FEC are used (LA and FEC are not
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decoupled). However, the enhancement to LA is very similar to static
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redundancy (many different ways proposed: SPB, VLANs). Therefore,
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instead of eLA AVBg2's idea could be used and FEC on top of this.
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- in the idea where enhanced STP (eSTP) and FEC are used to provide
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seamless critical data stream over dynamically redundant network -
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FEC and eSTP are decoupled
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- the idea where enhanced LA (eLA) and FEC are used (LA and FEC are
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not decoupled) -- the enhancement to LA is very similar to static
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redundancy provided by AVBg2 (many different ways proposed: SPB,
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VLANs). Therefore, instead of eLA, AVBg2's idea could be used and
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FEC on top of this.
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The idea of Time Aware Shaper (both at end stations and WR switches) is
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worth considering for WR, especially to meet GSI's requirements.
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