... | ... | @@ -31,32 +31,46 @@ achieved. |
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- very tightly-constrained subset of PTP (which, except for Ethernet,
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supports wireless and Coordinated Shared Networks)
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- it is based on, and includes a profile of, PTP (i.e. IEEE 1588-2008)
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- topology/network-functionality-wise: an IEEE 802.1AS bridge acts
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as an PTP boundary clock, and an IEEE 802.1AS end station acts
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as an ordinary clock \[1\]
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- synchronization-wise: the manner in which an IEEE 802.1AS bridge
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transports synchronization is very similar (mathematically
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equivalent) to the manner in which an PTP peer-to-peer
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transparent clock (TC) transports synchronization \[1\]
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- Each bridge measures frequency offset relative to its
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- *topology/network-functionality-wise: an IEEE 802.1AS bridge
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acts as an PTP boundary clock, and an IEEE 802.1AS end station
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acts as an ordinary clock* \[1\]
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- *synchronization-wise: the manner in which an IEEE 802.1AS
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bridge transports synchronization is very similar
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(mathematically equivalent) to the manner in which an PTP
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peer-to-peer transparent clock (TC) transports synchronization*
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\[1\]
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- *each bridge measures frequency offset relative to its
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neighbors; the accumulated frequency offset relative to the
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GM and the time difference between the arrival of a Sync
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message on the slave port and the sending of a subsequent
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Sync message on a master port are used to construct the
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synchronized time placed in a Follow\_Up message
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- propagation delays between neighboring bridges and/or end
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stations are measured using the peer delay mechanism.
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- The bridge is not required to filter phase as part of
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synchronized time placed in a Follow\_Up message* \[1\]
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- *propagation delays between neighboring bridges and/or end
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stations are measured using the peer delay mechanism* \[1\]
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- *the bridge is not required to filter phase as part of
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transporting synchronization; all phase filtering occurs at
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endpoints (end stations or bridges that have service
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interfaces to applications)
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interfaces to applications)* \[1\]
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- modified BMC (but similar to original)
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- IEEE 802.1AS defines TLV which is attached to Follow\_UP
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message, this TLV conveys frequency offset, relative to the
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grandmaster, it is accumulated (added to by each bridge on
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the way)
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- IEEE 802.1AS devices are *logically syntonized* (time-aware
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Bridgaes can correct time interval measurements using the
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grandmaster frequency ratio \[p22 of 2\]). Optional features
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\[1\]: IEEE 802.1AS bridges and end stations are not be
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required to physically syntonize (using frequency ratio)
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their frequency to the GM frequency (though they are be
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allowed to do this).
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<!-- end list -->
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- time synchronization requirement: -/+500ns with reference to
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network's grandmaster
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- references:
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[1](http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=4659212&tag=1)
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[1](http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=4659212&tag=1),
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\[2:http://standards.ieee.org/findstds/standard/802.1AS-2011.html\]
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### IEEE 802.1Qat: Stream Reservation Protocol (SRP),
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... | ... | |