DetNet Bounded Latency-04 drafu-fjnn-detnet-bounded-latency-04 - - PowerPoint PPT Presentation

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DetNet Bounded Latency-04 drafu-fjnn-detnet-bounded-latency-04 - - PowerPoint PPT Presentation

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DetNet Bounded Latency-04 drafu-fjnn-detnet-bounded-latency-04 Norman Finn, Jean-Yves Le Boudec, Ehsan Mohammadpour, Huawei EPFL EPFL Jiayi Zhang, Jnos Farkas, Balzs Varga Huawei

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SLIDE 1

DetNet Bounded Latency-04

drafu-fjnn-detnet-bounded-latency-04 Norman Finn, Jean-Yves Le Boudec, Ehsan Mohammadpour, Huawei EPFL EPFL Jiayi Zhang, János Farkas, Balázs Varga

Huawei Ericsson Ericsson

IETF 105 DetNet WG Montréal, 22 July, 2019

7/16/2018 1

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A reminder to new attendees …

  • DetNet is about an upper bound on end-to-end latency – not low

average latency.

  • Bounded latency leads to the ability to compute exactly how many

bufgers are required to achieve zero congestjon loss (and vice versa).

  • Feedback that slows down fmows to avoid congestjon is not an optjon

for the applicatjon space of interest to DetNet.

  • Mathematjcally sound assurances can be given on latency and

congestjon loss.

7/16/2018 2

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SLIDE 3

Major changes from -03 to -04

  • Sectjon 3 reorganized—the “reserve before use” paradigm applies to

both the statjc and the dynamic latency computatjon problems.

  • All of the various supported queuing techniques have been made

subsectjons of sectjon 6, “Queuing techniques”.

  • The difgerent queuing techniques have been given more equal

atuentjon, some enhanced, some shortened.

  • Sectjon 8, “Parameters for the bounded latency model”, has been

deleted.

7/16/2018 3

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Clause 3

Flows are created by:

  • 1. Confjgure the network.
  • 2. Characterize the fmow.
  • 3. Establish the path the fmow is to take.
  • 4. Compute the ability of the network to handle the fmow and the suitability

to the fmow’s requirements of the QoS ofgered, e.g. compute latency.

  • The Statjc latency computatjon: Recompute every fmow’s latency whenever any fmow

is added or removed.

  • The Dynamic latency computatjon: Compute absolute worst-case latency once,

when fmow is created.

  • 5. If satjsfactory results, reserve the resources and give the sender

permission to start.

7/16/2018 4

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Clause 6: Queuing techniques

6.2 Preemptjon: The transmission of exactly one Ethernet frame can be suspended many tjmes, with critjcal frames transmitued in each gap. 6.3 Time-scheduled queuing: Each output queue is gated by a synchronized, rotatjng schedule set by management. 6.4 Asynchronous Traffjc Shaping: Hierarchical per-fmow and per-class shaping, with fewer than one queue per fmow. 6.5 IntServ: Hierarchical per-fmow and per-class shaping, without one queue per fmow. 6.6 Cyclic Queuing and Forwarding: Double- or triple- bufgering for each class on each port, with bufgers cycled in synchrony across network.

7/16/2018 5

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SLIDE 6

6.6 Cyclic Queuing and Forwarding

  • Two-bufger version: Two bufgers per port. Input and output

bufgers swap at the same moment, once every cycle, period

  • TC. Small guard band to allow for transit and forwarding tjme.

All relay nodes are synchronized and swap bufgers at the same moment. Cycle tjme TC > transit tjme + forwarding tjme + clock inaccuracy + max data transmit tjme.

7/16/2018 6

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6.6 Cyclic Queuing and Forwarding

  • Two-bufger version: Two bufgers per port. Input and output

bufgers swap at the same moment, once every cycle, period

  • TC. Small guard band to allow for transit and forwarding tjme.

All relay nodes are synchronized and swap bufgers at the same moment. Cycle tjme TC > transit tjme + forwarding tjme + clock inaccuracy + max data transmit tjme.

7/16/2018 7

TICK!

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SLIDE 8

6.6 Cyclic Queuing and Forwarding

  • Two-bufger version: Two bufgers per port. Input and output

bufgers swap at the same moment, once every cycle, period

  • TC. Small guard band to allow for transit and forwarding tjme.

All relay nodes are synchronized and swap bufgers at the same moment. Cycle tjme TC > transit tjme + forwarding tjme + clock inaccuracy + max data transmit tjme.

7/16/2018 8

TICK!

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SLIDE 9

6.6 Cyclic Queuing and Forwarding

  • Three-bufger version: Three bufgers per port. Same as two-

bufger version, but input bufger swap is out-of-phase with

  • utput bufger swap to allow for arbitrary link delay.

7/16/2018 9 7/16/2018 9

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6.6 Cyclic Queuing and Forwarding

  • Three-bufger version: Three bufgers per port. Same as two-

bufger version, but input bufger swap is out-of-phase with

  • utput bufger swap to allow for arbitrary link delay.

7/16/2018 10 7/16/2018 10

TICK!

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6.6 Cyclic Queuing and Forwarding

  • Three-bufger version: Three bufgers per port. Same as two-

bufger version, but input bufger swap is out-of-phase with

  • utput bufger swap to allow for arbitrary link delay.

7/16/2018 11 7/16/2018 11

TICK!

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SLIDE 12

6.6 Cyclic Queuing and Forwarding

  • Three-bufger version: Three bufgers per port. Same as two-

bufger version, but input bufger swap is out-of-phase with

  • utput bufger swap to allow for arbitrary link delay.

7/16/2018 12 7/16/2018 12

TICK!

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SLIDE 13

6.6 Cyclic Queuing and Forwarding

  • Three-bufger version: Three bufgers per port. Same as two-

bufger version, but input bufger swap is out-of-phase with

  • utput bufger swap to allow for arbitrary link delay.

7/16/2018 13 7/16/2018 13

TICK!

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SLIDE 14

6.6 Cyclic Queuing and Forwarding

  • Three-bufger version: Three bufgers per port. Same as two-

bufger version, but input bufger swap is out-of-phase with

  • utput bufger swap to allow for arbitrary link delay.

7/16/2018 14 7/16/2018 14

TICK!

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SLIDE 15

6.6 Cyclic Queuing and Forwarding

  • Three-bufger version: Three bufgers per port. Same as two-

bufger version, but input bufger swap is out-of-phase with

  • utput bufger swap to allow for arbitrary link delay.

7/16/2018 15 7/16/2018 15

TICK!

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6.6 Cyclic Queuing and Forwarding

  • Time-based CQF is defjned in IEEE 802.1 standards.
  • Packet-marker based CQF is suggested in private DetNet drafus.
  • CQF can be operated at multjple frequencies on one port to serve

more than one Class of Service (bandwidth/latency range):

7/16/2018 16

Slow Medium Fast

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Summary*

Technique Latency computatjon Overprovisioning necessary Handles predictably bursty fmows State required per-hop Time sync required 6.3 Time- scheduled Statjc NP hard Small Yes Per class schedule Yes 6.4 IntServ Statjc (recompute all fmows on any change) Small No Per-fmow state, per-fmow queue No 6.5 Time-Aware Shaping Statjc (recompute all fmows on any change) Small No Per-fmow state, per-port-pair queue No 6.6 Cyclic Queuing & Forwarding Dynamic (trivial additjon) More No None Yes * This table is a generalizatjon. There are many factors that can mitjgate the difgerences. Other queuing schemes have been proposed that make other trade-ofgs.

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Final steps…

  • Refjning the terminology to conform DetNet.
  • Using DetNet terminology and terms.
  • Formal delay analysis of CQF.
  • Per-node bufger size calculatjon.
  • Consistency check with the other WG drafus.

18 24/07/2019

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QUESTION

  • Are we ready for adoptjon?

7/16/2018 19

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7/16/2018 20

Thank you