Hi Ron, Zafar, all, Following the discussion, I'd like to raise three points that I believe are critical.
1. Where is the actual deployment case? PCPPS assumes networks have "excess capacity" that can be powered down. But in real carrier networks, that excess is usually design redundancy for failures. Can the authors point to a specific production network topology where shutting down redundant paths still satisfies the operator's redundancy policy? 2. Wake-up latency and dead while asleep consideration A Power Group can represent an interface, a line card, etc., wake-up latency varies from milliseconds to minutes. If PCPPS puts a line-card-level group to sleep and later needs it for fast recovery, the minutes level wake-up may break the service lossless requirement. More critically, how does the network know the sleeping component is still healthy? When PCPPS later tries to wake it up for recovery, what if it discovers the link is dead, does the current design have any mechanism to verify the health of sleeping Power Groups without fully waking them? 3. Static power values vs. vendor-specific wake-up thresholds The draft recommends static power values to avoid LSDB churn. But real hardware power consumption is load-dependent, and different vendors may have implemented power saving with step functions, not linear curves. A device may consume X watts at 20% load, but when load exceeds 40%, the internal controller wakes up a second component, and power jumps to X+Y W instantly. That threshold is vendor-proprietary and not advertised. Now consider PCPPS, let’s say it moves traffic from path B to path A based on static values (A = 100W, B = 100W), letting B sleep (save 100W). The increased load on A crosses the 40% threshold — A wakes up extra components and jumps to 300W. Net result: path B saves 100W, path A spends +200W — negative energy savings. Thanks, Gen Chen From: Bonica, Ron <[email protected]> Sent: 2026年7月22日 16:08 To: Zafar Ali (zali) <[email protected]>; lsr <[email protected]> Subject: [Lsr] Re: IS-IS Support for PCPPS Inline.... ________________________________ From: Zafar Ali (zali) <[email protected]<mailto:[email protected]>> Sent: Tuesday, July 21, 2026 11:38 PM To: Bonica, Ron <[email protected]<mailto:[email protected]>>; lsr <[email protected]<mailto:[email protected]>> Cc: Zafar Ali (zali) <[email protected]<mailto:[email protected]>> Subject: Re: IS-IS Support for PCPPS Hi Ron What I highlighted is: how come someone who claims to have implemented this did not realize that the sleeping power is non-zero? [RB] Is this a technical question or an ad hominem attack? [RB] Recall that in many hardware architectures, sleeping power is zero. If I draw a dotted line, how does one ensure that the power-saving estimate for a given “power group” is accurate? [RB] Generally, hardware vendors publish this information. The questions Robert asked are valid and related. [RB] And answered in draft-many-teas-power-steering. What is the right data model? We need to ask the Green WG. [RB] The value of a data model is its descriptive efficiency. In this case, if a data model can describe any hardware architecture that you need to describe, it is good enough. [RB] Can you describe a hardware architecture that the data model cannot? If not, there is no valid criticism. Also, operators perform many capacity planning exercises to design the network. The operators need to consider what the implications are for shutting a “power group” What considerations must be in place before shutting down the "power groups"? Is this a good idea, or will it create more pain for network operations? [RB] In Section 3.3.4 of the draft, you will notice a power-sleep-capable bit. This bit is set only of the operator configures the interface to be power-sleep-capable. [RB] There are many reasons why an operator may determine that an interface is or is not power-save-capable. This is beyond the scope of this document. Thanks Regards … Zafar From: Bonica, Ron <[email protected]<mailto:[email protected]>> Date: Monday, July 20, 2026 at 3:55 AM To: lsr <[email protected]<mailto:[email protected]>>; Zafar Ali (zali) <[email protected]<mailto:[email protected]>> Subject: IS-IS Support for PCPPS Zafar, If I understood your comment during the IETF 126 session correctly, you said that the Power Group model may not support some existing hardware architectures. Can you describe such an architecture? Ron
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