Hi, Tony:

 

From: [email protected] <[email protected]> On Behalf Of Tony Li
Sent: Wednesday, May 26, 2021 12:31 AM
To: Aijun Wang <[email protected]>
Cc: lsr <[email protected]>; Ketan Jivan Talaulikar <[email protected]>; Acee Lindem 
(acee) <[email protected]>; 
[email protected]
Subject: Re: [Lsr] LSR WG Adoption Poll for "Flexible Algorithms: Bandwidth, 
Delay, Metrics and Constraints" - draft-hegde-lsr-flex-algo-bw-con-02

 

 

Hi Aijun,

 

My suggestion is still not introduce such non-cumulative metric to cumulative 
based SPF calculation process.

 

Again, what we’re proposing is cumulative.

 

[WAJ] My arguments is that your cumulative proposal (section 4.1.1.1 or 
4.1.1.2) can get unexpected result, that is, if there is no manual 
intervention, the E2E sub-optimal path will be selected. You have also 
confirmed this in 
https://mailarchive.ietf.org/arch/msg/lsr/wWoGgwf-Nch0_VxjczZBpLFXyos/, said as 
below:

 

“Override the metric on B-E-D to be even higher.

 

The point of the bandwidth metric (at least in this incarnation) is not to make 
hop count irrelevant. It is    to set the metrics relative to the bandwidth so 
that traffic skews towards higher bandwidths. Hops are still relevant. An 
operator can adjust the reference bandwidth and add manual metrics to achieve 
different effects, depending on their precise needs.”

 

The operator must investigate their topology carefully to add necessary manual 
metric to avoid the unexpected sub-optimal path.  Is it nightmare?

 

 

Best Regards

 

Aijun Wang

China Telecom

 

 

 

 

 

Tony

 

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