Residential Ethernet (access control considerations)

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Beatrice Bridges
5 years ago
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1 Residential Ethernet (access control considerations) Alexei Beliaev George Claseman Thomas Dineen David V James Michael Johas Teener Gibson Micrel Dineen Consulting JGG Plumblinks 1

2 Vocabulary possibilities conversation talker listeners 2

3 Categories of work Device discovery (out of scope) Identify/control talkers and their available plugs Admission control (802.1 oriented) Establish conversation between talker and listener(s) Reject unless: linkbandwidth < linkcapacity Clock synchronization Synchronous reception, forwarding, and presentation Transmission gating Talkers and 100Mb bridge ports must be gated Formats Frame formats and content (channel number, time stamps) Time aware service interfaces 3

4 Admission control (some possibilities) 4

5 First access request conversation talker listeners 5

6 First access response conversation talker listeners 6

7 Second access request conversation talker listeners 7

8 Second access response conversation talker listeners 8

9 Established conversations conversation talker listeners 9

10 Delay-matching listener FIFOs talker fifo fifo 10

11 Heartbeat timeouts GARP defines timeout features Tolerates single-frame losses Multiple frame losses are not within its scope Timeouts use to: Release of flooded (very rare) speculative resources Removal of one or more listeners Removal of the talker Etc. More flexible than traffic monitors Monitors place restriction on synchronous flows Support of prioritized asynchronous may be desired 11

12 Isochronous addressing? Frame destinationaddress sourceaddress type/length sourceaddress plugid plugid static assignments vs dynamic otherinfo FCS 12

13 Are bridge changes necessary? End-station throttling (assuming highest priority) With 1Gb/s switches, this may be sufficient Source device spreads transmissions evenly Bunching may be tolerable within the home (needs study) Must ensure that nothing else uses the highest priority But, some access control changes needed anyway Bridges are naturally encountered along the path Central topology database is thus unnecessary 13

14 Summary We need a GARP-like lower level protocol Restrict N-to-N multicast, for 1-to-N traffic Simultaneous bandwidth allocation required Should track/influence in-progress revision (MRP/p802.1ak) The IP admission control alternative Out of scope Layering violations (non-ip synchronous traffic?) Not generally supported by residential bridges Multiple components (and synchronized use) required: A multicast address server? IGMP/snooping for multicast setup? RSVP/snooping for bandwidth negotiation? 14

15 Backup slides (from previous presentations) 15

16 Synchronized time-of of-day clocks (a Residential Ethernet SG presentation) 16

17 Synchronized time-of of-day clocks What? 17

18 House reference clock e e Ethernet Ethernet Room #1 Room #2 18

19 Cascaded TOD synchronization Physical topology constraints bridge[1] bridge[0] Legend: clock master clock slave bridge[2] 19

20 Cascaded TOD synchronization Wall-clock distribution model bridge[1] bridge[0] bridge[2] 20

21 Cascaded TOD synchronization Cascaded adjacent-synchronization hierarchy bridge[1] bridge[0] bridge[2] 21

22 Time-of of-day format options seconds fractions >150 years <250 ps OR seconds nanoseconds OR ticks OR ( ) 16 ns 22

23 Time-of of-day rate adjustments rate carry56 add6 add26 seconds fractions rate delayed carry 23

24 Time-of of-day precedence sp systemid stationid (MAC-48) pp portnumb smaller STP precedence (IEEE Std 802.3D-1998) preferred stationid (byte swapped EUI-64) larger 1394 precedence 24

25 Synchronized time-of of-day clocks Why? 25

26 Bursting causes jitter rx0 1 khz rx1 1 khz rx2 1 khz rx3 8 khz tx4 delay time 26

27 Bunching causes jitter rx0 time rx1 rx2 rx3 time time time tx4 delay time 27

28 Bridge re-clocking contains jitter bridge (etc.) cycle-stamp receive isochronous asynchronous cyclecount gate high low transmit 28

29 Synchronized reception/presentation clocka clockb clockc No long-term drift: clocka, clockb, clockc Clock jitter: sub nanosecond (after PLL) 29

30 Synchronized time-of of-day clocks How? 30

31 Adjacent-station synchronization Timing snapshots Station A local offset add (t1) Station B local offset (t3) add global (t4) (t2) global 31

32 Adjacent-station synchronization Snapshot value distribution Station A local offset add (t1) global (t4) (t1, t4-t2) (t2, t3-t1) local offset (t3) add (t2) Station B global 32

33 Adjacent-station synchronization Offset value adjustments Station A local offset add (t1) global (t4) (t1, t4-t2) (t2, t3-t1) local offset (t3) add (t2) Station B global clockdelta = ((t3 t1) (t4 t2))/ 2; cabledelay = ((t3 t1) + (t4 t2)) / 2; offsetb = offseta clockdelta; 33

34 Adjacent station synchronization local Station A offset clocksync Station B local offset add global 8 khz 125µs add global 34

35 In summary Time-of-day synchronization (house clock) Global synchronization is required Implemented as cascaded adjacent synchronizations Time synchronization formats Binary time is accurate with simple add/subtract Clock-master voting: 48+ or 64+ selection priorities Time-of-day applications Synchronous reception and presentation, within applications Synchronous re-clocking within bridges Time-of-day distribution Pipelined sampling for highest accuracies Cable delays can be derived, based on the same information 35

36 Synchronized time-of of-day clocks Questions? 36

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