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F5 Friday: Domain Sharding On-Demand

Domain sharding is a well-known practice to improve application performance – and you can implement automatically without modifying your applications today.

If you’re a web developer, especially one that deals with AJAX or is responsible for page optimization (aka “Make It Faster or Else”), then you’re likely familiar with the technique of domain sharding, if not the specific terminology.

For those who aren’t familiar with the technique (or the term), domain sharding is a well-known practice used to trick browsers into opening many more connections with a server than is allowed by default. This is important for improving page load times in the face of a page containing many objects. Given that the number of objects comprising a page has more than tripled in the past 8 years, now averaging nearly 85 objects per page, this technique is not only useful, it’s often a requirement. Modern browsers like to limit browsers to 8 connections per host, which means just to load one page a browser has to not only make 85 requests over 8 connections, but it must also receive those requests over those same, limited 8 connections. Consider, too, that the browser only downloads 2-6 objects over a single connection at a time, making this process somewhat fraught with peril when it comes to performance. This is generally why bandwidth isn’t a bottleneck for web applications but rather it’s TCP related issues such as round trip time (latency).

Here are the two main points that need to be understood when discussing Bandwidth vs. RTT in regards to page load times:

1.) The average web page has over 50 objects that will need to be downloaded (reference: http://www.websiteoptimization.com/speed/tweak/average-web-page/) to complete page rendering of a single page.

2.) Browsers cannot (generally speaking) request all 50 objects at once. They will request between 2-6 (again, generally speaking) objects at a time, depending on browser configuration.

This means that to receive the objects necessary for an average web page you will have to wait for around 25 Round Trips to occur, maybe even more. Assuming a reasonably low 150ms average RTT, that’s a full 3.75 seconds of page loading time not counting the time to download a single file. That’s just the time it takes for the network communication to happen to and from the server. Here’s where the bandwidth vs. RTT discussion takes a turn decidedly in the favor of RTT.

-- RTT (Round Trip Time): Aka – Why bandwidth doesn’t matter

So the way this is generally addressed is to “shard” the domain – create many imaginary hosts that the browser views as being separate and thus eligible for their own set of connections. This spreads out the object requests and responses over more connections simultaneously, allowing what is effectively parallelization of page loading functions to improve performance.

Obviously this requires some coordination, because every host name needs a DNS entry and then you have to … yeah, modify the application to use those “new” hosts to improve performance. The downside is that you have to modify the application, of course, but also that this results in a static mapping. On the one hand, this can be the perfect time to perform some architectural overhauls and combine domain sharding with creating scalability domains to improve not only performance but scalability (and thus availability). You’ll still be stuck with the problem of tightly-coupled hosts to content, but hey – you’re getting somewhere which is better than nowhere.

Or the better way (this is an F5 Friday so you knew that was coming) would be to leverage a solution capable of automatically sharding domains for you. No mess, no fuss, no modifying the application. All the benefits at one-tenth the work.  

What BIG-IP WebAccelerator does, automatically, is shard domains by adding a prefix to the FQDN (Fully Qualified Domain Name). The user would initiate a request for “www.example.com” and WebAccelerator would go about its business of requesting it (or pulling objects from the cache, as per its configuration). Before returning the content to the user, however, WebAccelerator then shards the domain, adding prefixes to objects. The browser then does its normal processing and opens the appropriate number of connections to each of the hosts, requesting each of the individual objects. As WebAccelerator receives those requests, it knows to deshard (unshard?) the hosts and make the proper requests to the web or application server, thus insuring that the application understands the requests. This means no changes to the actual application. The only changes necessary are to DNS to ensure the additional hosts are recognized appropriately and to WebAccelerator, to configure domain sharding on-demand.

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what is the best quality lens for a nikon f5?

Aug 30, 2007 by ...M... | Posted in Photography

I'm looking to get a new lens for my Nikon F5 camera and was wondering which high powered zoom (300mm+) lens you would recommend for the highest quality, meaning clarity and color definiton, landscape shots from my camera thanks!
please go here to see my style of photography and then make a recommendation thanks!
http://www.flickr.com/photos/mourphoto/

Well, first of all landscapes are shot with wide angle lenses (18mm or so).

Nikon is really your only choice when it comes to the "highest quality", clarity and color definition.

High powered zoom ... 300mm + ? You have the AF-S VR Zoom-Nikkor 200-400mm f/4G IF-ED and AF VR Zoom-Nikkor 80-400mm f/4.5-5.6D ED

Well, the question has to be how fast do you want the lens? If those are too slow, then you are looking for a prime lens like the 400mm f/2.8

How do you make a webpage refresh without having to press F5?

Jan 13, 2008 by julie_ramrattan2003 | Posted in Programming & Design

I play this game and the page usually changes, but you have to refresh the page to see the updates every 5 minutes or so. Is there a way to make the page automatically refresh without my having to press F5 every 5 minutes?

try this

http://downloads.zdnet.com/download.aspx?docid=208787

Its called Auto URL Refresher and it does just what you are looking for

1 more i found... heres a free one
http://www.windowsmarketplace.com/details.aspx?view=info&itemid=19736

Speedometer on my 2006 Arctic Cat F5 is not working properly?

Jan 03, 2009 by mtba_99 | Posted in Maintenance & Repairs

I just bought a 2006 Arctic Cat F5. The speedometer and the odometer do not work, but the RPM gauge is working properly and so is the hour gauge. Has anyone experienced this problem and if so how do I fix it?

The sensor may have come unplugged or is bad. Unplug it by the gearcase and check the ohm reading as the track turns. It should show a pulse which will increase as speed increases.

What is the technical difference between F5 refresh and Right-click and clicking refresh.F5 dont work as good?

Jun 05, 2007 by Stealth | Posted in Other - Hardware

It seems when I make registry changes right-click refresh works to refresh the changes but when I press F5 the screen flickers but doesnt refresh but if I move the cursor around a bit and keep pressing F5 eventually it will refresh almost at a completely random time.But I dont knowcomputers to do nothin at random.There has to be a technical reason for this,Thanks

software vrs hard coding.. The F5 key is a set of codes that make the software react the software has a slightly diff command code that is instant.. it is just computer hardware vers software.. use whatever works best or reinstall windows. sometimes that can repair any bad strings that was messed up from installing stuff or messing with the settings..

What should I do if a F5 tornado is coming and I am in an antique sword shop?

Aug 20, 2007 by jj | Posted in Weather

With a thousand swords, knives, daggers, and axes that are razor sharp.

The shop is one room. And I'm in the middle of nowhere. No basement, bathroom, or hall. And the door is locked. And the windows sealed. What do I do?

Wow... dude, if that were to happen....... you'd be screwed.

I just got a f5 coolster moped that is 50cc. How can i get it to go faster?

Sep 16, 2007 by MIRIAMDOVE | Posted in Maintenance & Repairs

i read on a website that it could go faster by removing the clutch but i don't know where it is located. by removing it the moped should go from 45 to 55 mph.

Remove the clutch and it won't go at all, let alone faster.

I allways have to press Alt+F5 to increase the resolution of the pictures whilst on the internet?

Sep 20, 2007 by Nikolai | Posted in Monitors

What do i have to change so that the pictures are allways top quality on every page?

there is no option for that cause its not in ur control cause it configured to the size u see according to the design of the Site

thanks,

The z key and the 1 key on my keyboard are behaving like an F5 or a hot key. How can I fix this?

Oct 13, 2008 by Karan | Posted in Other - Hardware

I did nothing to configure them this way. Help is appreciated. I have to write numbers with the keypad, cannot write the letter z without wondering if it will get written or if it will refresh a webpage, and forget about the exclamation mark, once again it refreshes. If I use ctrl+z it immediately writes something like a quotation mark. This is really wierd. Help is appreciated.

Has anything been spilt on the keyboard? Maybe there's a short circuit there. Might be worth borrowing someone else's keyboard to see if it still does it. If not try re-installing it.

Is it possible for there to be a huge F5 tornado that surrounds the eye of a catagory 5 hurricane?

Dec 07, 2007 by june c | Posted in Weather

How scary is that? Would the amount of fatalities increse from the tornado?

This may be the making of a new science fiction novel but it does not stand the test of good science. The eye of a typical hurricane is 60 to 300 nautical miles in diameter either of which is clearly beyond scientific possibility. And then there are the dynamics of a tornado most all of which are missing in the core of a hurricane. Tornadoes do form frequently in the periphery of a tropical storm as it moves overland posing another severe weather threat in addition to flooding and strong winds.

How can you survive an F5 tornado if stuck outside without a shelter?

Jul 25, 2008 by cookinghamusa | Posted in Weather

Any tips?

Get away from structures and the road. find a low area and lay on your stomach. DO NOT CROUCH! don't allow any space under you.