---------- Forwarded message ---------- From: Shankar Raman <[email protected]> Date: Thu, Feb 7, 2013 at 1:59 PM Subject: Re: Power aware networks : Comments requested from routing community To: "Eric Osborne (eosborne)" <[email protected]>, [email protected] Cc: Gaurav Raina <[email protected]>, Balaji Venkat Venkataswami < [email protected]>, [email protected]
Hi Eric/Curtis, Since I am not a part of RTGWG, I have been following only half of these emails. Therefore as an observer of few of these emails, I believe there are some critical point that have been missed, which needs clarification. 1. We are not looking at shutting down links. This is left up to the service provider. Probably some ISP may not be able to shut off links, too. 2. The overall idea we are trying to convey is : the data packets are not routed today based on power information but on other criteria (hops, QoS metric etc.). We simply say that we must consider power as another criteria while taking a routing decision. In this way, overall our traffic pattern will incrementally start using low-power consuming devices and finally will force more installation of low-power devices in the Internet. 3. The approach looks at collaborative reduction in power consumption of entities in the Internet, not just at a device level or at the technology point of view (optical or copper etc.). We agree that the idea looks theoretical at present. At least, from the simulations which we tried on various network topologies, we find that there is huge opportunity in power savings using the protocol based approach, depending on the power distribution of the entities. The questions we answer through the methods are: 1. Even when the devices consume low-power, do we have strategies to route data through those devices? 2. Don't we need a overall coordination between these devices to achieve power reduction? Since you have more experience than us in handling the devices and working with the ISPs, we were working R&D for device manufacturers, you have an idea about the ISP device level issues related to cost and power. Please note that our work does not DENY any of these facts. If needed, we are open to collaboration and see how best we can integrate the device power reduction strategies, along with those facilities offered by the routing protocols today to get the best power reduction possible, which is the goal of our research and which is why we are approaching IETF. If you still believe that protocol level methods have no practical significance in power reduction, then we will have to keep this idea to a journal - (as Curtis has mentioned and has agreed to review). We are positive that his advice will add value to our paper and will definitely seek it. Hope this clarifies any confusion. Thanks Shankar -----Original Message----- From: Balaji Venkat Sent: Thursday, February 07, 2013 2:36 AM To: Eric Osborne (eosborne) Cc: [email protected] ; Shankar Raman M J ; [email protected] Subject: Re: Power aware networks : Comments requested from routing community Dear Eric, Comments inline... Sent from my iPad On 07-Feb-2013, at 1:50 AM, "Eric Osborne (eosborne)" <[email protected]> wrote: You aim to optimize core networks through traffic engineering such that > some links can be shut down when not in use, or switched to lower power. > Actually the answer is a No. We do not advocate this approach. The main idea in bgp power path draft has a survey section on previous literature that we quote for reference and state that such approaches cause expensive equipment to be kept unused. You have quoted the survey section of the paper in the above sentence. > Have you done studies in core networks with real equipment that show the > actual amount of money you could save with this approach? Let's walk > through a quick hypothetical network, you tell me where I got it wrong. > > draft-mjsraman-panet-bgp-**power-path says > " Power consumption can be > reduced by trading off performance related measures like latency. For > example, power savings while switching from 1 Gbps to 100 Mbps is > approximately 4 W and from 100 Mbps to 10 Mbps around 0.1 Watts." > Again this is a survey section of the paper surveying the existing approaches. > but provides no documentation to back these costs up nor itemization of > where the power is consumed (amortized across the router? linecard optics? > DWDM gear?) > Our main intent is to allow traffic to follow low power paths through ASs (either through pce like entities or through modifying the bgp path selection algorithm) which consume the least power and possess the required bandwidth. By graphing the topology of a set ASs in the immediate neighbourhood using as-path-info strands typically for a provider manning multiple ASs within the providers own control this mechanism will let large chunks of traffic belonging to a macro FEC traverse such low power ASs through an inter-as te MPLS lsp computed by a pce like entity and setup by RSVP-te. The use of the metric, the way the pwr metric is arrived at , the computation of the topology of ASs, consequent CSPF and then mapping the traffic to the constructed LSP is the main focus if this paper. For dampening fluctuations in the metric which are frequent heuristics algorithms are suggested. By no means are we advocating shutting off links. This scheme facilitates even the follow the moon strategy naturally. > Let's assume that this is true and that it is linear, so that you burn 4W > per Gb. (side note: I suspect this is inaccurate and that scaling is > sublinear, but let's go with it because if it's sub-linear you have even > less of a use case. I also think the real world is far more complex, as > you have all the optical transport gear to worry about. But let's go with > it for now.) > > Running a 100Gb link thus draws 400W. > > Let's say you have a backbone with (300) 100Gb links. Total power > consumption is thus (300*400) == 120 kW > > Running all these links for 24 hours thus draws 120*24 == 2,880 kWh == > 2.8mWh > Power costs are maybe $0.10/kWh in the US. Double that to cover the cost > of cooling, so $0.20/kWh. > Thus, running the entire backbone costs $0.2 * 2,880 = $576/day. > $210,000/year. > Let's say your approach can save one third of the power cost, which means > about $70,000. > > An operator with 300 100Gb links in a network has hundreds of millions of > dollars worth of gear and millions or tens of millions in payroll alone. If > you cut $70k from their opex they probably wouldn't even notice. That's one > or two salaries, or 0.002% of what Time Warner spent on advertising in 2006 > (see: > http://gaia.adage.com/images/**random/FactPack06.pdf<http://gaia.adage.com/images/random/FactPack06.pdf>). > It is a drop in the bucket, if that. And your proposal comes with > significant work attached to it, and significant risk. If your 40 years of > experience in the network industry don't help you understand the risks > you're asking an operator to take then you're missing a crucial part of any > potential real world solution. I do not think your work should be > presented at the IETF unless it makes a much stronger argument that its > benefits outweigh its costs. > Again we are not asking the operator to shut off the equipment. He needs to keep it running as long as he has traffic to carry except that the pce makes a computation every time a large FEC of traffic needs to be carried through his ASs through a path that consumes the least power with the links therein having the required bandwidth. The ratio of consumed power to the available bandwidth is the metric that is used. Consumed power relates to a weighted average of the power consumed within the AS including the edge and core devices while the available bw relates to the links ingressing into the AS at the ASBRs that are the inter connectors between the ASes. So in summary, we do not advocate shutting off links at all. In fact we disagree with that approach. The scheme we advocate tries to optimise the power consumption using the metric based approach with some heuristics. Hope this helps. Thanks and regards, Balaji venkat > > These sorts of power optimizations all seem to be "here's how you reshape > the problem so that you can throw a linear problem solver at it". For > example, [ http://www.cs.berkeley.edu/~**suchara/publications/** > GreenNetsBundles.pdf<http://www.cs.berkeley.edu/~suchara/publications/GreenNetsBundles.pdf>]. > I've never seen anything which shows how much more work it will be for a > network operator or which quantifies the actual savings. > > If you can demonstrate significant savings in real networks at little or > no cost to operators, you have an idea worth pursuing. If your idea will > cause more operational angst (e.g. not knowing whether your unused capacity > will be there when you need it because you shut a third of it off all the > time, increased risk of equipment failure from constant power-cycling, > operational tools and training and expertise required to manage, deploy and > troubleshoot variable-power links and the centralized NMS required to run > them, etc etc etc) then it will find little traction. Green-TE and > power-aware BGP have been floating around for a while and have seen no real > uptake in the WGs as far as I can see. Is that not to be taken as an > indication that there may be no real-world interest in them? If not, what > would it take to convince you? > > > > eric > >
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