Dear all, Adding the rtgwg alias again since the message size was exceeded.
thanks and regards, balaji venkat ---------- Forwarded message ---------- From: Balaji venkat Venkataswami <[email protected]> Date: Thu, Feb 7, 2013 at 3:24 PM Subject: Fwd: Power aware networks : Comments requested from routing community To: [email protected], "Eric Osborne (eosborne)" <[email protected]>, Curtis Villamizar <[email protected]> Adding the rtgwg alias since some of us dont have access to sending mails on it. thanks and regards, balaji venkat ---------- Forwarded message ---------- From: Shankar Raman <[email protected]> Date: Thu, Feb 7, 2013 at 3:17 PM Subject: Re: Power aware networks : Comments requested from routing community To: Balaji Venkat <[email protected]>, "Eric Osborne (eosborne)" < [email protected]> Cc: [email protected], [email protected] Dear Eric, Looks like we have not been clear in conveying our idea. We abstract the power consumed by every router/switch, use it as the power rating. We then assign it to the link as a metric characteristic to get algorithms like SPF and CSPF to choose the lowest power paths or any metric based routing algorithm. So the link metric is a combination of power consumed including the physical link and router components. In effect the link metric is not just the physical link’s metric alone (but the cost of the power consumed by the router/switch on which it connects to the neighbor). Just like routing protocols consider delay, hops as metric we consider this power consumption as yet another metric. 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). 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 ]. 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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