From a source's point, distribution makes sense when cost of geographically-diverse server presence (incremental admin/hw, content distribution) is less than the cost of serving everything from a centralized point. Once that happens... if a substantial
SS> Date: Thu, 14 Nov 2002 13:32:55 -0600 SS> From: Stephen Sprunk SS> Incorrect. Cheap longhaul favors a few centralized SS> exchanges. If there is no economic value in keeping traffic SS> local, it is in carriers' interests to minimize the number of SS> peering points. True. However, cheap longhaul / expensive local means providers _will_ try to reduce loop costs, favoring "carrier hotels". SS> Most vendor-neutral colos have cheap zero-mile loops. Correct. In my original post... are we discussing #1 or #2? It seems as if #2. Where are we drawing the line between "carrier hotel" and "exchange"? I believe Paul was being perhaps more nebulous than today's definition of "exchange" when he referenced 1500 sq-ft in-bottom-of-bank-building facilities. SS> What is the cost of running N loops across town, vs. the cost SS> of pushing that traffic to a remote peering location and SS> back? Be sure to include equipment, maintenance, and SS> administrative costs, not just circuits. "It depends." SS> None of these applications require local exchanges. There is SS> a slight increase in end-to-end latency when you must use a SS> remote exchange, but very few applications care about SS> absolute latency -- they only care about bandwidth and SS> jitter. With bounded latency and "acceptable" typical throughput, one seeks to minimize jitter and cost. Jitter is caused by variable queue time, which is due to buffering, which is a side-effect of statmuxed traffic w/o strict { realtime delivery constraints | QoS | TDM-ish architecture }... yes. And N^2 makes full-mesh irresponsible when attempting to maximize bandwidth... yes. (I think buying full transit from 10 providers is well beyond the point of diminishing return; no offense to INAP.) Again... if loop is expensive, and providers are concentrated in "carrier hotels" with reasonably-priced xconns... when does it become an "exchange"? Note that some exchanges do not provide a switch fabric, but rather run xconns. Sure, one must factor in all the costs. The breakeven point varies, if it exists at all. SS> Distributed content assumes the source is topologically close SS> to the sink. The most cost-efficient way to do this is put SS> sources at high fan-out areas, as this gets them the lowest SS> _average_ distance to their sinks. This doesn't necessarily SS> mean that putting a CNN mirror in 100,000 local exchanges is SS> going to reduce CNN's costs. It depends. Akamai certainly is overkill for smaller sites, and perhaps not cost-effective for others. However, high fan-out can be a _bad_ thing too: Assuming one has substantial traffic flow to various regions, why source everything from NYC? Why not replicate in London, AMS, SJO, IAD, CHI, DFW, LAX, SEA, KSCY? portion of Internet traffic were sourced from one local point, sinks would gravitate toward said point. Of course, I may well be stuck in distance-sensitive mode. If local loop is the primary expense... we're back to what you said about "few, centralized exchanges" and "many carrier hotels"? So, where's the dividing line? Eddy -- Brotsman & Dreger, Inc. - EverQuick Internet Division Bandwidth, consulting, e-commerce, hosting, and network building Phone: +1 (785) 865-5885 Lawrence and [inter]national Phone: +1 (316) 794-8922 Wichita ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Date: Mon, 21 May 2001 11:23:58 +0000 (GMT) From: A Trap <blacklist@brics.com> To: blacklist@brics.com Subject: Please ignore this portion of my mail signature. These last few lines are a trap for address-harvesting spambots. Do NOT send mail to <blacklist@brics.com>, or you are likely to be blocked.