what technology expands the normal capabilities of a web browser for a specific webpage This is a topic that many people are looking for. unusual-travel-destinations.com is a channel providing useful information about learning, life, digital marketing and online courses …. it will help you have an overview and solid multi-faceted knowledge . Today, unusual-travel-destinations.com would like to introduce to you What happens when you load a webpage?. Following along are instructions in the video below:
“What i want to do now is try and put together several of the concepts concepts that we ve worked with so far to talk about how what is the process that happens by which a web page ends up displaying something within your browser. So what does that look like when you first open your browser on your computer. What you re doing is you re running a program that exists on your local computer. So the program is something like chrome or firefox.
Safari internet. Explorer. One of many different browser programs that lives on your local machine. So it exists on your hard drive.
When you when you start that program by you know. However you start your program double clicking on the icon or finding it from a menu or something. Like that what happens is your operating system is loading. That program from your hard drive into its working memory and then starting to execute that program locally so at that point no internet resources have been required.
When your browser first starts it will open a window it ll open a window on your local display and your display and the browser are all just locally hosted. It hasn t had to go out to the network. Necessarily now it may have gone out to the network to check to make sure that it had the most recent version maybe. There s some kind of advertising.
That it required from the internet. But basic requirement is did not require the internet at that point. Now you as a user have your browser window open. And you go into the address bar.
And you type in an address for example wwic suc ie d. U. Now when you hit enter in that browser window your browser starts to undertake a number of interactions with the internet in order to get the html file that it needs to render in its browser window from the internet. The first thing that it needs to do is it needs to know where on the internet.
Does it go to find wwic suca edu in order to solve that we have to execute the dns or domain. Name service. Lookup. Protocol.
And so the browser is first going to see within its own program. Hey have i ever seen have i seen this address recently because what i need to do is i need to translate this from dub dub wic sec ided you into an ip address that consists of if it s ipv4 for different sets of numbers. So the first thing that it does at this point is look in its dns cache to see if it has ever translated that recently if it s recently translated it let s say it hasn t so then what it s going to do it s going to ask for that translation from the operating system. The operating system is going to check to see whether in its hosts file depending on your operating system that can be different locations whether there is a manual translation that s been put into your into your computer to translate that domain name into an ip address.
If it s not present then what the operating system is going to do is it s going to look within its dns cache. And say hey has any program on this computer. Recently tried to look up something from dub dub dub dcs. You see ided you because if it has then i have a record of that translation already and i m going to use that so that would be a cache hit in the operating system level.
If that s not present then the operating system will say well i can t answer this query. So i m going to have to go out to the internet to get this query solved. And so it s going to ask the isp to or that for you whoever you re connected to and the internet service provider is going to check to see whether or not through the domain name service system. It s going to check to see whether or not it has seen that request recently not just from your computer.
But from any of the computers. Which it hosts so you can see it each level. We re encompassing a broader and broader group a pool of possible users that could have requested this translation. If your isp cannot find that translation for you then it may then it probably is going to go out and go to the definitive source.
It s going to go to the overarching domain. Name service system. And it will request it from one of the top level domain names. And that requires the process that we looked at in our dns lecture of asking the hot top level.
Who will tell us where edu is hosted or which will tell us where uci is hosted and so if we have to go to the top level. Because all of our caches. Amidst will get back the definitive answer of what the ip address is that will get returned to our internet service provider. Who will say oh ok well i got the definitive at um translation.
I m going to keep that in my cache for a little bit so it puts it into its cache. Then your internet service provider passes. It back to your operating system your operating system. Says thanks isp for that translation.
You know i m going to keep a copy of that translation in case. Someone else asks in a little bit so it adds it to its cache. The operating system then sends it back to the browser. And the browser keeps a copy of it and then the browser uses that translation now it knows we re on the internet.
It can find the information that you re looking for and so now it executes a second request. This request is not for the translation. But this is the request for the actual html document and so with the knowledge of the ip address and with the knowledge of the domain domain name. It sends that request out using the http whatever protocol.
You ve specified in your url typically it s going to be http or https. So it will put that request out on the internet and your isp will pass that request to another computer. Which will pass it to another computer and another computer chain of computers. That s where the internet gets its power from all these computers connected together that are passing requests along one at a time from some source to some destination.
Now there s a whole other set of protocols for how those computers understand which way to pass the data packet that s not relevant for our discussion. Here it s sufficient to know that when our browser puts that request on to the internet. The internet is going to route it to the destination that we ve specified with our ip address. When the computer on the other side of that chain the one that s responsible for handling requests for that ip address receives the request it s going to look at the domain name that was requested and the.
Resource that was requested from it for. Example the indexhtml file or whatever file or resource. You ve requested and a program on the remote website is going to evaluate it that program on the remote website. Is called a webserver typical web servers are programs like apache apache has a web server other web servers include ones by microsoft there s some lightweight servers that are used like engine nginx.
What other web servers php can actually run its own web server as well and there are a lot of little web servers that can be run just in a lot of programs that can be executed. So there s a lot of different programs that can possibly act as a web server just like there are a lot of different programs that can act as a web browser whichever web server it is that s running on that remote client it receives that http request on a particular port for example. Port. 84.
Http or 443 for https and it then goes and tries to resolve that if the request was simply for a file that exists on the hard drive then the web server will go to the web servers hard drive. And it will grab the html document and it will send it back over the internet. If it wasn t just us if if that web server is not designed to just deliver files it may need to construct the html text on the fly. So it may have a program that is going to decide based on who made the request what content should be put into that html document so a company like amazoncom.
For example is going to fill out that html document with an advertisement and some recommended products and maybe. An order history maybe. Some information that you asked for last time you came to this web site. If that s the case.
Then the web server is actually going to use a whole bunch of other computers that it has at its disposal to construct the html that it s going to send back to the browser whatever it does though the web server is going to return an html document that has the tags and the tree structure attributes content. All that stuff it s going to travel back across the internet probably in a path. Very similar to the path that it took. But not necessarily the same and then your web browser who is waiting for your web server to send a response back will receive that text document it will then analyze that text document assuming that it s html and will create a tree structure internally in the browser using that tree structure.
It will begin to render create create a visual representation of the html of what the html demonstrated now we ve seen that there are some tags for example. The image tag that might be in an html document that references other resources on the internet. So an image tag for example often most of the time actually references other files. Which are the image files themselves.
And so just that first html document that s returned may not be all the information. That s necessary for your browser to draw the picture of the webpage in in the window. It may need to go out and get many other resources and so in previous example. We ve seen how some reason.
Some websites require 40 resources or 70 resources or hundreds of resources. Those resources. Include images. They may include information about how to aesthetically draw your your html diagram your html document for example using css stylesheets.
And it waits for the user to interact with the page that it s drawn and until the web until until that happens. It s going to just do nothing other than render. The page as it was delivered so that s basically the end to end story about how the web browser gets content and delivers it back and that puts together many of the different pieces that we ve seen up until this point and in our tutorials thanks for your attention. ” .
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