On 21/05/2010, at 6:43 AM, Paul Tinson wrote:
I don't recall how many connections a browser makes to a singe host but you are right it's a common thing that is done. There is more than one product in the market place that uses this 'trick' to try and accelerate web sites.
Also, modern browsers are now engages in DNS prefetching - Chrome and Firefox 3.5 and above - as another trick. Even before prefetching though most browsers used parallel threads for DNS lookups or an async DNS library.
I would be very interested in any for of investigation around how much of a difference does this really make and would be willing to participate in such an investigation.
+1. We can contribute expertise.
However I think there is also value in understanding what impact a DNS cache hierarchy within NZ would have for NZ as a whole, I am somewhat of an idealistic person so perhaps it has no value and it just of interests me.
+1. I wonder how much the network design of DSL services constrains us? In other words, if I ran an ISP based in Wellington and had customers in Dunedin on Telecom DSL then do I only see their traffic when it arrives at a Wellington POP? So is it actually impossible for me as an ISP with this type of customers, to place DNS servers down in Dunedin to improve the DNS performance for those customers?
I would also be interested in understanding what other providers get in terms of cache hit vs recursion and overall requests vs infrastructure deployed. I know this is somewhat treasured and possibly not publicly available information. If there is any interest from other parties to share this I will approach the people here and see what can be done around some form of disclosure.
We are willing to receive such data individually, anonymise it and then redistribute. Obviously this data is very useful to us too. cheers Jay
Just my thoughts at 6:30 am...
Regards
Paul Tinson
-----Original Message----- From: nznog-bounces(a)list.waikato.ac.nz [mailto:nznog-bounces(a)list.waikato.ac.nz] On Behalf Of Nathan Ward Sent: Friday, 21 May 2010 1:49 a.m. To: NZNOG List Subject: Re: [nznog] Broadband experience and DNS resolution speeds
On 21/05/2010, at 1:42 AM, Joe Abley wrote:
On 2010-05-20, at 09:22, Nathan Ward wrote:
Who on produced this report? Can they come to the next NZNOG meeting for a flogging?
There are grains of truth in the idea that increased latency between clients and resolvers can lead to decreased performance for web applications. Many of the newfangled javascript-riddled sites that the kids seem to like these days use deliberately-randomised URIs and similar techniques deliberately to defeat caching, since caching for some interactive web $buzzword.$excitement apps leads to user pain and suffering.
Vixie presented some data at the recent DNS-OARC meeting in Prague which described a trend for decreasing DNS cache hits, and at least in some cases found that random-looking URIs were contributing to the effect (see https://www.dns-oarc.net/files/workshop-201005/vixie-oarc-Prague.pdf).
If an application like Facebook can generate a few hundred HTTP sessions per page load, it seems possible that cache misses (both in DNS and HTTP caches, remote and local) give a greater effect that you would imagine, and perhaps the cumulative effect of Dunedin-Auckland DNS latency has some noticeable effect. But I agree it seems like a stretch (every cache miss in Auckland probably requires a trip to an authority-only server across an ocean).
It's quite common to use random hostnames to encourage web browsers to parallelize sessions, as (from memory) most browsers will not open more than 4 connections to a single hostname/port.
Some actual science might be nice to see, maybe.
Yep.
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