–Professional A/V studios –Homes with provider 1588 service October 12, 2005 Precise Timing in a Residential Ethernet Environment 17 Changes needed in existingChanges needed in existing productsproducts • Endpoint device needs – Timer – Streaming traffic transmit FIFO(s) • (streaming receive use existing FIFO) – Best to have dedicated ports for streaming data • MPEG-TS, I2S, etc., like existing 1394 links • Bridges – ResE MACs – Streaming routing/filtering • similar to asynch logic – Admission control firmware • similar to 802.1 multicast and VLAN management – Timing propagation Timing SynchronizationTiming Synchronization in ResEin ResE October 12, 2005 Precise Timing in a Residential Ethernet Environment 19 House reference clockHouse reference clock 802.11e Ethernet 802.11e 1394 1394 Room #1 Room #2 Ethernet October 12, 2005 Precise Timing in a Residential Ethernet Environment 20 Legend: clock master clock slave Cascaded TOD synchronizationCascaded TOD synchronization bridge[0] bridge[1] bridge[2] Physical topology constraints October 12, 2005 Precise Timing in a Residential Ethernet Environment 21 Cascaded TOD synchronizationCascaded TOD synchronization bridge[0] bridge[1] bridge[2] Wall-clock distribution model October 12, 2005 Precise Timing in a Residential Ethernet Environment 22 Cascaded TOD synchronizationCascaded TOD synchronization bridge[0] bridge[1] bridge[2] Cascaded adjacent-synchronization hierarchy October 12, 2005 Precise Timing in a Residential Ethernet Environment 23 local offset add global Adjacent-stationAdjacent-station synchronizationsynchronization aTx[n] local offset add global aRx[n] bRx[n] bTx[n] Station A Station B Timing snapshots October 12, 2005 Precise Timing in a Residential Ethernet Environment 24 local offset add global Adjacent-stationAdjacent-station synchronizationsynchronization aTx[n-1] local offset add global aRx[n-1] bRx[n] bTx[n-2] (aTx,aRx,bTx) StationA StationB Snapshot value distribution (information for stationB is time A sent previous snapshot, time A received B’s previous snapshot, and time B sent snapshot before that) Transmit timings are always for previous snapshot because they are recorded when the snapshot was sent, and are not available while the packet is in the process of being sent October 12, 2005 Precise Timing in a Residential Ethernet Environment 25 local offset add global Adjacent-stationAdjacent-station synchronizationsynchronization • rxDelta = (bRx[n-1] – aTx[n-1]); • txDelta = (bTx[n-1] – aRx[n-1]); • clockDelta = (rxDelta – txDelta) / 2; • cableDelay = (rxDelta + txDelta) / 2; • offsetB = offsetA – clockDelta; aTx local offset add global aRx bRx bTx Station A Station B StationB offset adjustments October 12, 2005 Precise Timing in a Residential Ethernet Environment 26 local offset add global Adjacent stationAdjacent station synchronizationsynchronization local offset add global Station A Station B 1kHz/100Hz synch interval … 1ms - 10ms … clockSync October 12, 2005 Precise Timing in a Residential Ethernet Environment 27 • Could add to 802.3 PHY specs: (from IEEE 1588-2002, subclause D.1.1, page 127) • But realistically, more likely to get “when first data symbol of frame is transmitted to or received from PHY” –Less precise … but ResE has frequent clock updat