Re: [Lsr] LSR WG Adoption Poll for "Flexible Algorithms: Bandwidth, Delay, Metrics and Constraints" - draft-hegde-lsr-flex-algo-bw-con-02

[Tony Li <[e-mail]>]

Hi Greg,

That’s a very fair question and not one that has been discussed.

Do we have that kind of accuracy from any of our measurement tools? Is that even on the horizon?  I haven’t seen that…

If it is time for nanosecond level measurement, then is it time to shift to floating point to give us more range?

Tony

> On May 23, 2021, at 1:04 PM, Greg Mirsky <[e-mail]> wrote:
> 
> Hi Shraddha, Authors, et al.,
> I apologize if my question has already been discussed. The unit for the maximum link delay in the draft is a microsecond. There is a group of services that require a highly accurate bounded delay. Have you considered using a nanosecond as the unit for the link delay?
> 
> Regards,
> Greg
> 
> On Wed, May 19, 2021 at 9:17 PM Shraddha Hegde <shraddha=[e-mail] <mailto:[e-mail]>> wrote:
> Hi Pengshaofu,
> 
>  
> 
> Pls see inline..
> 
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> 
>  
> 
> Juniper Business Use Only
> From: [e-mail] <mailto:[e-mail]> <[e-mail] <mailto:[e-mail]>> 
> Sent: Thursday, May 20, 2021 7:26 AM
> To: Shraddha Hegde <[e-mail] <mailto:[e-mail]>>
> Cc: acee=[e-mail] <mailto:[e-mail]>; [e-mail] <mailto:[e-mail]>; [e-mail] <mailto:[e-mail]>
> Subject: Re:[Lsr] LSR WG Adoption Poll for "Flexible Algorithms: Bandwidth, Delay, Metrics and Constraints" - draft-hegde-lsr-flex-algo-bw-con-02
> 
>  
> 
> [External Email. Be cautious of content]
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> 
> Hi Shraddha,
> 
>  
> 
> Thanks. Actually, I don't really want to define other metric types.
> 
> Let's go back to the bandwidth-metric related to bandwidth capability. My worry is that bandwidth-metric (whether it is automatically calculated or manually configured) is not cumulative in nature,
> 
> <Shraddha> Yes that is correct.
> 
> which is different from IGP default metric/TE metric/delay metric,
> 
>  
> 
> so that SPF based on bandwidth-metric may get an unexpected path (see the example of the original mail).
> 
> Can more text be added in the draft to describe why this can work ?
> 
> <Shraddha> Knowing that metric derived inversely from the link bandwidth is not additive in nature, should set the expectation right. I can add some text in this regard.
> 
>  
> 
> Regards,
> 
> PSF
> 
>  
> 
>  
> 
> 原始邮件
> 
> 发件人：ShraddhaHegde
> 
> 收件人：彭少富10053815;
> 
> 抄送人：acee=[e-mail];[e-mail];[e-mail] <mailto:acee=[e-mail];[e-mail];[e-mail]>;
> 
> 日 期 ：2021年05月18日 13:01
> 
> 主 题 ：RE: Re:[Lsr] LSR WG Adoption Poll for "Flexible Algorithms: Bandwidth, Delay, Metrics and Constraints" - draft-hegde-lsr-flex-algo-bw-con-02
> 
> Hi Pengshaofu,
> 
>  
> 
> If an operator wants to configure any other metric type draft provides a mechanism with generic metric.
> 
> Generic metric allows any standard or user-defined type metric to be configured.
> 
> The draft allows for any computing application such as Flex-algo, CSPF etc to make use of the
> 
> Metric. The intention of the draft is that for a particular computation same metric-type is used
> 
> throughout the network. If that is not clear, I’ll add some text in the draft.
> 
>  
> 
> Using a combination of different metrics for a single computation would need significant change to SPF algorithm and it is not in the scope of the draft "Flexible Algorithms: Bandwidth, Delay, Metrics and Constraints".
> 
>  
> 
> Hope that clarifies.
> 
>  
> 
> Rgds
> 
> Shraddha
> 
>  
> 
>  
> 
> Juniper Business Use Only
> From: [e-mail] <mailto:[e-mail]> <[e-mail] <mailto:[e-mail]>> 
> Sent: Monday, May 17, 2021 12:49 PM
> To: Shraddha Hegde <[e-mail] <mailto:[e-mail]>>
> Cc: acee=[e-mail] <mailto:acee=[e-mail]>; [e-mail] <mailto:[e-mail]>; [e-mail] <mailto:[e-mail]>
> Subject: Re:[Lsr] LSR WG Adoption Poll for "Flexible Algorithms: Bandwidth, Delay, Metrics and Constraints" - draft-hegde-lsr-flex-algo-bw-con-02
> 
>  
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> [External Email. Be cautious of content]
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> 
> Hi Shraddha,
> 
>  
> 
> The two methods of automatic generation of BW-metric introduced in the draft are also likely to be the method of manual configuration of BW-metric by operators. Operators can certainly manually configure any  BW-metric he wants to configure.
> 
> However, the manually configured BW-metric cannot deviate from the actual bandwidth capacity of the link, otherwise it could be any other names such as BX-metric.
> 
> For manual assignment, the problem may still exist We can find an example that  the accumulated bandwidth-metric on the path may offset the manually increased bandwidth-metric of links on the path.
> 
> Combination of bandwidth attribute of link and other metric that is cumulative may be another co-exist way to completely address this issue.
> 
>  
> 
> Regards,
> 
> PSF
> 
>  
> 
>  
> 
>  
> 
>  
> 
> 原始邮件
> 
> 发件人：ShraddhaHegde
> 
> 收件人：彭少富10053815;
> 
> 抄送人：acee=[e-mail];[e-mail];[e-mail] <mailto:acee=[e-mail];[e-mail];[e-mail]>;
> 
> 日 期 ：2021年05月17日 12:15
> 
> 主 题 ：RE: Re:[Lsr] LSR WG Adoption Poll for "Flexible Algorithms: Bandwidth, Delay, Metrics and Constraints" - draft-hegde-lsr-flex-algo-bw-con-02
> 
> Hi Pengshaofu,
> 
>  
> 
> I was suggesting to manually assign bandwidth metric which will override the automatic metric calculation
> 
> as described in the draft section 5. Physically adding more fiber/capacity is not a feasible solution.
> 
>  
> 
> Rgds
> 
> Shraddha
> 
>  
> 
>  
> 
> Juniper Business Use Only
> From: [e-mail] <mailto:[e-mail]> <[e-mail] <mailto:[e-mail]>> 
> Sent: Monday, May 17, 2021 7:40 AM
> To: Shraddha Hegde <[e-mail] <mailto:[e-mail]>>
> Cc: acee=[e-mail] <mailto:acee=[e-mail]>; [e-mail] <mailto:[e-mail]>; [e-mail] <mailto:[e-mail]>
> Subject: Re:[Lsr] LSR WG Adoption Poll for "Flexible Algorithms: Bandwidth, Delay, Metrics and Constraints" - draft-hegde-lsr-flex-algo-bw-con-02
> 
>  
> 
> [External Email. Be cautious of content]
> 
>  
> 
>  
> 
> Hi Shraddha,
> 
>  
> 
> Thanks for your rely.
> 
> So it seems that the scheme may lead to the selection of links with less bandwidth. To address this point, the method as you described to assign more bandwidth to high bandwidth links seems not always possible, e.g, adding more fiber ?
> 
> Can this point can be addressed by combination of bandwidth attribute of link and other metric that is cumulative ? IMO, bandwidth is not cumulative.
> 
>  
> 
> Regards
> 
> PSF
> 
>  
> 
> 原始邮件
> 
> 发件人：ShraddhaHegde
> 
> 收件人：彭少富10053815;
> 
> 抄送人：acee=[e-mail];[e-mail];[e-mail] <mailto:acee=[e-mail];[e-mail];[e-mail]>;
> 
> 日 期 ：2021年05月13日 21:01
> 
> 主 题 ：RE: Re:[Lsr] LSR WG Adoption Poll for "Flexible Algorithms: Bandwidth, Delay, Metrics and Constraints" - draft-hegde-lsr-flex-algo-bw-con-02
> 
> Hi Peng shaofu,
> 
>  
> 
> As per the draft, if automatic metric calculation with reference bandwidth method is used to calculate the metric
> 
> Then as per your example s->D path will be chosen since metric is 10.
> 
> Lets say operator wants to choose S->X1->X2-àX10->D path then operator can manually assign higher bandwidth
> 
> Metric on S->D link which will ensure S->D path is not the least cost path.
> 
>  
> 
> Rgds
> 
> Shraddha
> 
>  
> 
>  
> 
> Juniper Business Use Only
> From: [e-mail] <mailto:[e-mail]> <[e-mail] <mailto:[e-mail]>> 
> Sent: Thursday, May 13, 2021 1:05 PM
> To: [e-mail] <mailto:[e-mail]>
> Cc: acee=[e-mail] <mailto:acee=[e-mail]>; [e-mail] <mailto:[e-mail]>; [e-mail] <mailto:[e-mail]>
> Subject: Re:[Lsr] LSR WG Adoption Poll for "Flexible Algorithms: Bandwidth, Delay, Metrics and Constraints" - draft-hegde-lsr-flex-algo-bw-con-02
> 
>  
> 
> [External Email. Be cautious of content]
> 
>  
> 
>  
> 
> Sorry for spelling mistakens in the previous email.
> 
> updated text:
> 
>  
> 
>  
> 
> Hi WG,
> 
>  
> 
> I have a little doubt about the scheme described in this document.
> 
> See the following example:
> 
>  
> 
> S ---- X1 ----- X2 ---- ... ... ----- X10 ----- D
> 
>     \----------------------------------------------/
> 
>  
> 
> Suppose the links in S---X1---X2...---D have the same bandwidth  10G, and the link S-D has bandwidth 1G.
> 
> Suppose that we select "reference bandwidth = 100G", then, 
> 
> each link  in S---X1---X2...---D will have the same bandwidth-metric  10 (i.e., 100/10)
> 
> link S-D will have a bandwidth-metric 100 (i.e., 100/1)
> 
>  
> 
> So flex-algo path from S to D based on bandwidth-metric will be S-D, not S---X1---X2...---D, because the later has a large cumulative bandwitdh-metric (i.e., 11*10).
> 
> But our expect path should not be S-D, but S---X1---X2...---D, as it has large bandwidth.
> 
> Do I misunderstand anything ?
> 
>  
> 
> Regards,
> 
> PSF
> 
>  
> 
>  
> 
>  
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>  
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> 发件人：AceeLindem(acee)
> 
> 收件人：[e-mail] <mailto:[e-mail]>;
> 
> 抄送人：[e-mail] <mailto:[e-mail]>;
> 
> 日 期 ：2021年05月13日 05:49
> 
> 主 题 ：[Lsr] LSR WG Adoption Poll for "Flexible Algorithms: Bandwidth, Delay, Metrics and Constraints" - draft-hegde-lsr-flex-algo-bw-con-02
> 
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> Esteemed Members of the LSR WG,
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>  
> 
> This begins a 2 week WG adoption call for the following draft:
> 
>  
> 
>      https://datatracker.ietf.org/doc/draft-hegde-lsr-flex-algo-bw-con/ <https://urldefense.com/v3/__https:/datatracker.ietf.org/doc/draft-hegde-lsr-flex-algo-bw-con/__;!!NEt6yMaO-gk!TGikk55jVo2FINSWYcGBMe1xnCiMVRlVaOhe77F76PCVbDj893SQ5uuqsET5yKGD$>    
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> Please indicate your support or objection by May 27th, 2021.
> 
>  
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> Authors, please respond to the list indicating whether you are aware of any IPR that applies to this draft.
> 
>  
> 
> Thanks,
> 
> Chris and Acee
> 
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