I'd like to mention there could be other good benefits for caching.
For example, It can be beneficial to cache sites that are geographically far
away.
The farther a site is away the more latency it has, and there fore the speed
per session diminishes, based on the formula like window size = bandwidth *
delay.
.
TCP throughput vs. window size for RTT=70ms Window Size Theoretical max
throughput Realistic throughput
8KB 0.9Mb/s 0.8Mb/s
16KB 1.9Mb/s 1.8Mb/s
32KB 3.7Mb/s 2-3.5Mb/s
64KB 7.5Mb/s 3-7Mb/s
128KB 15.0Mb/s 6-14Mb/s
256KB 30.0Mb/s 10-25Mb/s
512KB 59.9Mb/s 20-40Mb/s
1MB 119.8Mb/s 30-60Mb/s
2MB 239.7Mb/s 60-100Mb/s
What often occurs is that Window Size is fixed at the customer PC. So even
if someone has a 100mbps connection, and can test 100mbps to their server
across town 5 ms away, there speed is still severally limited to far away
high latency sites. Many PCs by default, don't enable window sizes above
64k. (Although most newer XP/VISTA machines are now comming Registry
optimized for automatic tuning of larger windows szies, so this isn;t a
problem.)
So its not just about cost of long haul bandwdith, but also desire to
deliver full speed to the consumer. By caching data locally, it enables the
customer to access it at the full broadband connection speed.
But my point being, customers can get a much better perception of
performance if the most common files to download were cached locally for
retrieval.
What I'd be interested in learning more on is how to setup a caching server
to selectively select what to cache based on latency to the content, or most
common data, apposed to just caching everything. In otherwords, how to
optimize the chance that the benefit of caching will outweigh the chances of
getting troubles from caching.
Tom DeReggi
RapidDSL & Wireless, Inc
IntAirNet- Fixed Wireless Broadband
----- Original Message -----
From: "Bo Ring" <[EMAIL PROTECTED]>
To: "WISPA General List" <[email protected]>
Sent: Thursday, July 10, 2008 3:07 PM
Subject: Re: [WISPA] Any thoughts on a decent cache server
> When I was an ISP, that 1% got me in real trouble. They scream loudly.
>
> On Jul 10, 2008, at 3:03 PM, David E. Smith wrote:
>
>> Patrick Nix Jr. wrote:
>>> So is it safer/better to avoid caching servers altogether?
>>
>> About 99% of your users won't notice, or know, or care, that you've
>> got
>> anything like that in your network. The savings in bandwidth (and,
>> to a
>> lesser extent, money not spent on bandwidth) can help you out of a
>> tight
>> spot. Just be aware that the last 1% of customers can get you into
>> trouble.
>>
>> David Smith
>> MVN.net
>>
>>
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>
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Account Manager
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fax: 773.326.4641
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