Comments for P802.1Qdq/D0.0

Jie Xiao, Min Zha, Li Xu{xiaojie23, zhamin, innon.xu}@huawei.com
Huawei Technology Co., LtdComments #1• Current text

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‘data block’ can be replaced by ‘frame cluster’

Weakness: there are multiple words or phrases to express a burst, which are confusing.

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Comments #2• Current text

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Queue Length
A Block Data splits into multiple frames; i.e., Frame Cluster

Revision choice (1)Data Size
Talker’s Queue

Data size should bereduced linearlyrather than verticallyTimeRevision choice (2)Queue Length

A Block Data splits into multiple frames; i.e., Frame Cluster
Frame Number

Talker’s QueueTime

Like the above curve,similar problem also exists.

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Comments #3• Current text

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DeliveryTime defines the time from the first bit sent from atalker to the last bit received at a listener.
deliveryTime
Input of Listener𝑛accumulatedLatency σ𝑘=1 𝑓𝑟𝑎𝑚𝑒𝐿𝑒𝑛𝑔𝑡ℎ(𝑘)𝑠ℎ𝑎𝑝𝑖𝑛𝑔𝑅𝑎𝑡𝑒Time

Accordingly, the formulas (Y-2) & (Y-3) should be modified
𝑑𝑒𝑙𝑖𝑣𝑒𝑟𝑦𝑇𝑖𝑚𝑒 𝑖 =σ𝑛𝑘=1 𝑓𝑟𝑎𝑚𝑒𝐿𝑒𝑛𝑔𝑡ℎ(𝑘)+ 𝑎𝑐𝑐𝑢𝑚𝑢𝑙𝑎𝑡𝑒𝑑𝐿𝑎𝑡𝑒𝑛𝑐𝑦𝑠ℎ𝑎𝑝𝑖𝑛𝑔𝑅𝑎𝑡𝑒

𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑑𝑀𝑖𝑛𝑖𝑚𝑢𝑚𝑆ℎ𝑎𝑝𝑖𝑛𝑔𝑅𝑎𝑡𝑒 =σ𝑛𝑘=1 𝑓𝑟𝑎𝑚𝑒𝐿𝑒𝑛𝑔𝑡ℎ(𝑘)𝑑𝑎𝑡𝑎𝑆𝑖𝑧𝑒=𝑡𝑎𝑟𝑔𝑒𝑡𝐿𝑎𝑡𝑒𝑛𝑐𝑦
𝑡𝑎𝑟𝑔𝑒𝑛𝑡𝐿𝑎𝑡𝑒𝑛𝑐𝑦

𝑌− 2(𝑌 − 3)4Comments #4• Current text

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X.3.1 Accumulated Latency
Per-hop latency imposed by a bridged network against a single frame is discussed in Clause 35and Annex L. Latency between Talker and Listener (hereinafter referred to as Network Latency)
is derived from the sum of per hop latency along the path between them. In bridged networks
controlled by SRP, the value portTcMaxLatency and AccumulatedLatency
𝑎𝑐𝑐𝑢𝑚𝑢𝑙𝑎𝑡𝑒𝑑𝐿𝑎𝑡𝑒𝑛𝑐𝑦 can be obtained from the system, while it can be manually evaluated by
the same way in networks without SRP.

The value AccumulatedLatency 𝑎𝑐𝑐𝑢𝑚𝑢𝑙𝑎𝑡𝑒𝑑𝐿𝑎𝑡𝑒𝑛𝑐𝑦 is used as one of inputs of thecalculating procedure for shaper parameter settings 4 defined in Y.4.

Weakness:① The parameter ‘portTcMaxLatency’ is not used in the whole article, so it canbe deleted?
② Consistent issues: the parameter ‘AccumulatedLatency’ should be𝑎𝑐𝑐𝑢𝑚𝑢𝑙𝑎𝑡𝑒𝑑𝐿𝑎𝑡𝑒𝑛𝑐𝑦, the same as in (X-5). Other parameters, such as
Data Size (𝑑𝑎𝑡𝑎𝑆𝑖𝑧𝑒), Bounded Latency (𝑏𝑜𝑢𝑛𝑑𝑒𝑑𝐿𝑎𝑡𝑒𝑛𝑐𝑦) should also
follow a consistent style.
③ Add description. (see right)

As the calculation of 𝑎𝑐𝑐𝑢𝑚𝑢𝑙𝑎𝑡𝑒𝑑𝐿𝑎𝑡𝑒𝑛𝑐𝑦 (in Equation (V-6) in Annex V of IEEE Std 802.1Qcr,
2020) is highly related to other streams in the system, when the system load changes (especiallynew higher-class streams are added), 𝑎𝑐𝑐𝑢𝑚𝑢𝑙𝑎𝑡𝑒𝑑𝐿𝑎𝑡𝑒𝑛𝑐𝑦 should be recalculated.
Correspondingly, the SRP may also need to be re-executed.

Equation (V-6) in Annex V of IEEE Std 802.1Qcr:

Higher traffic classSame traffic class

Lower traffic class5Comments #5• Current text

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Should include the last frame?

boundedLatency

The figure title is not complete.

Figure X-6—Frame propagation within bounded latency while minimizing over-provision of
bandwidth reservation

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Comments #6• Current text

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Add formula index.

All formulas’ indicesin the new draft arelost, but they arestill cited in the text.

(X-3)

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Explanation

An example:𝒇𝒓𝒂𝒎𝒆𝑺𝒊𝒛𝒆∗ 𝑵−𝟏
𝒄𝒓𝒆𝒅𝒊𝒕_𝑵 = 𝒐𝒖𝒕𝒈𝒐𝒊𝒏𝒈𝑹𝒂𝒕𝒆 ∙ 𝒊𝒅𝒍𝒆𝑺𝒍𝒐𝒑𝒆_𝑵,

Class 1Credit_1

Class 2Credit_2…

which can be larger than one frame size.

Cluster arrives concurrently

Class N
Low priority

Credit_N

Scheduler

During transmitting the first (N-1) higher-class clusters,

High priority

outgoingRate

The ATS scheduler should also works for the case in which the CommittedBurstSize is greater thanMaximum SDU Size. It does not affect other traffic for which the long-term averaged shaping rate.
However, a small value of the CommittedBurstSize is desirable because the transient data rate, which ishigher than the required minimum shaping rate, may be suppressed. This transient manner can be caused by
the arrival of a new frame cluster at the shaper that has already accumulated large number of tokens causing
some frames to be forwarded instantly. Such token-bucket state can occur when no frames arrive at theshaper for a period of time between clusters.
Similar issue also exists in the CBS scheduler. For example, when there are N classes of frame clusters
arrive concurrently in the system, during the scheduling of the higher-class clusters, credits of the lowestclass cluster will be accumulated, which may results in consistent transmission of its frames. To alleviate
this issue, we should also limit the credit upper-bound to the maximum SDU size.

1) As shown in the example, there is a possibility that the number ofcredit/token can be larger then one frame size2) Once the above happen, the assumption (frames are equally spaced) inthe draft may not hold.
3) So we must limit the credit/token upper bounded by one frame size.

8Conclusion and Proposal
Conclusion:• The project will play a great role for the parameter setting of shapers and make TSN easy to work.
• The current draft is good and the comments are trying to make it better/perfect.
Proposal:• It is proposed that these comments are taken into consideration or as input for the further drafting of thecurrent draft.