[spring] Re: Re: Ask SPRING WG for review draft-liu-spring-sr-policy-flexible-path-selection

Yisong Liu <liuyisong@chinamobile.com> Wed, 11 December 2024 06:23 UTC

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Date: Wed, 11 Dec 2024 14:23:03 +0800
From: Yisong Liu <liuyisong@chinamobile.com>
To: Joel Halpern <jmh@joelhalpern.com>, spring <spring@ietf.org>
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Subject: [spring] Re: Re: Ask SPRING WG for review draft-liu-spring-sr-policy-flexible-path-selection
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Hi Joel,

Thank you for your comments. I want to provide some clarity regarding the purpose and scope of this draft . This draft tackles the scenario where multiple paths are available, and the need arises to switch paths based on their quality metrics. It is not intended to replace the controller's role in global optimization but rather to complement it by allowing for local, quality-driven responses to link degradation.

The draft specifically addresses the ability to switch to alternative paths within a strategy when the current path fails to meet specified link quality criteria such as bandwidth, delay, or packet loss. In cases where a controller issues an SR Policy that encompasses multiple paths, if a path's link quality does not meet the set requirements, it will switch to a backup path for forwarding.

Essentially, this draft resolves the forwarding status of SR Policy paths, facilitating a switch based on link quality. It is important to note that the overall path optimization remains under the purview of the controller, which continues to make global decisions. This draft addresses the selection issue of multiple paths under an SR Policy, ensuring that the network can adapt to local conditions without overriding the controller's broader strategies.

I'm not sure if I've explained everything clearly. If you have any further questions, please feel free to continue the discussion.  



Best Regards

Yisong








 



发件人: Joel Halpern

时间: 2024/12/09(星期一)11:45

收件人: Yisong Liu;spring;

抄送人: draft-liu-spring-sr-policy-flexible-path-selection;

主题: Re: [spring] Ask SPRING WG for review draft-liu-spring-sr-policy-flexible-path-selection                    

Looking at this draft, there seem to be two related aspects, one       of which makes sense, and one of which needs work.     

As a participant, I can understand the general goal.  And       adjusting the path selection when component link issues reduce the       overall available bandwidth, increase the end-to-end delay, or       increase the expected jitter is understandable.  I leave whether       this is the right approach to that problem to those who have       worked more closely with SR policies.     

However, if I read section 4.1 properly, it wants to change the       path selection in response to observed parameters such as observed       packet loss (frequently in practice caused by congestion.)  On       fortunately, distributed dynamic path selection based on       parameters that are sensitive to traffic load has well-known       problems with various responders adjusting resulting in simply       moving the problem.  If you have recognized this problem and I       missed it, please cite RFC 2386 early in the document, and point       to the resolution.  If you have not addressed this problem, please       either do so or restrict the applicability of this proposal.        Delaying response is not sufficient.
          

Yours,     

Joel
          

On 12/8/2024 9:37 PM, Yisong Liu wrote:
                        

         

Dear WG members,         


                  


                      

With               the rise of AI models, new intelligent computing services               require enhanced network reliability, especially in               quality-sensitive scenarios like storage-compute               separation and real-time inference. The               draft-liu-spring-sr-policy-flexible-path-selection offers               flexible path switching for quality degradation, crucial               for maintaining network performance.                    


                      

           

This                 draft proposed a                 new mechanism to specify multiple candidate paths for SR                 policies, allowing for more sophisticated traffic                 engineering. It supports                 dynamic path adjustments based on real-time network                 conditions, optimizing resource utilization and ensuring                 high service quality. This draft aims to provide network                 operators with greater flexibility and control over                 traffic routing in SR networks.           


                          

We                 have just posted a new version. Please see the draft in                 the following link:           

https://datatracker.ietf.org/doc/draft-liu-spring-sr-policy-flexible-path-selection/                  


                    

I               hope you can review this draft and share your feedback.               Welcome any questions and comments.                    


                      

Best Regards         

Yisong on behalf of co-authors              

       
              

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