Application Protocols HTTP and the World Wide Web

pcbuck April 22, 2021 0 Comments



Internet Infrastructure


The Internet backbone is made up of many large networks which interconnectwith each other. These large networks are known as Network Service Providersor NSPs. Some of the large NSPs are UUNet, CerfNet, IBM, BBN Planet,SprintNet, PSINet, as well as others. These networks peer with each other toexchange packet traffic. Each NSP is required to connect to three NetworkAccess Points or NAPs. At the NAPs, packet traffic may jump from one NSP’sbackbone to another NSP’s backbone. NSPs also interconnect at MetropolitanArea Exchanges or MAEs. MAEs serve the same purpose as the NAPs but areprivately owned. NAPs were the original Internet interconnect points. BothNAPs and MAEs are referred to as Internet Exchange Points or IXs. NSPs alsosell bandwidth to smaller networks, such as ISPs and smaller bandwidthproviders. Below is a picture showing this hierarchical infrastructure. — Diagram 4 This is not a true representation of an actual piece of the Internet. Diagram4 is only meant to demonstrate how the NSPs could interconnect with each otherand smaller ISPs. None of the physical network components are shown in Diagram4 as they are in Diagram 3. This is because a single NSP’s backboneinfrastructure is a complex drawing by itself. Most NSPs publish maps of theirnetwork infrastructure on their web sites and can be found easily. To draw anactual map of the Internet would be nearly impossible due to it’s size,complexity, and ever changing structure.

Internet Protocols Revisited


As hinted to earlier in the section about protocol stacks, one may surmisethat there are many protocols that are used on the Internet. This is true;there are many communication protocols required for the Internet to function.These include the TCP and IP protocols, routing protocols, medium accesscontrol protocols, application level protocols, etc. The following sectionsdescribe some of the more important and commonly used protocols on theInternet. Higher level protocols are discussed first, followed by lower levelprotocols.

Application Protocols: HTTP and the World Wide Web


One of the most commonly used services on the Internet is the World Wide Web(WWW). The application protocol that makes the web work is Hypertext TransferProtocol or HTTP. Do not confuse this with the Hypertext Markup Language(HTML). HTML is the language used to write web pages. HTTP is the protocolthat web browsers and web servers use to communicate with each other over theInternet. It is an application level protocol because it sits on top of theTCP layer in the protocol stack and is used by specific applications to talkto one another. In this case the applications are web browsers and webservers.HTTP is a connectionless text based protocol. Clients (web browsers) sendrequests to web servers for web elements such as web pages and images. Afterthe request is serviced by a server, the connection between client and serveracross the Internet is disconnected. A new connection must be made for eachrequest. Most protocols are connection oriented. This means that the twocomputers communicating with each other keep the connection open over theInternet. HTTP does not however. Before an HTTP request can be made by aclient, a new connection must be made to the server.When you type a URL into a web browser, this is what happens: 1. If the URL contains a domain name, the browser first connects to a domain name server and retrieves the corresponding IP address for the web server. 2. The web browser connects to the web server and sends an HTTP request (via the protocol stack) for the desired web page. 3. The web server receives the request and checks for the desired page. If the page exists, the web server sends it. If the server cannot find the requested page, it will send an HTTP 404 error message. (404 means ‘Page Not Found’ as anyone who has surfed the web probably knows.) 4. The web browser receives the page back and the connection is closed. 5. The browser then parses through the page and looks for other page elements it needs to complete the web page. These usually include images, applets, etc. 6. For each element needed, the browser makes additional connections and HTTP requests to the server for each element. 7. When the browser has finished loading all images, applets, etc. the page will be completely loaded in the browser window. Check It Out – Use Your Telnet Client to Retrieve a Web Page Using HTTP — Telnet is a remote terminal service used on the Internet. It’s use hasdeclined lately, but it is a very useful tool to study the Internet. InWindows find the default telnet program. It may be located in the Windowsdirectory named telnet.exe. When opened, pull down the Terminal menu andselect Preferences. In the preferences window, check Local Echo. (This is soyou can see your HTTP request when you type it.) Now pull down the Connectionmenu and select Remote System. Enter www.google.com for the Host Name and 80for the Port. (Web servers usually listen on port 80 by default.) PressConnect. Now typeGET / HTTP/1.0and press Enter twice. This is a simple HTTP request to a web server for it’sroot page. You should see a web page flash by and then a dialog box should popup to tell you the connection was lost. If you’d like to save the retrievedpage, turn on logging in the Telnet program. You may then browse through theweb page and see the HTML that was used to write it. Most Internet protocols are specified by Internet documents known as a RequestFor Comments or RFCs. RFCs may be found at several locations on the Internet.See the Resources section below for appropriate URL’s. HTTP version 1.0 isspecified by RFC 1945.

Internet Protocol


Unlike TCP, IP is an unreliable, connectionless protocol. IP doesn’t carewhether a packet gets to it’s destination or not. Nor does IP know aboutconnections and port numbers. IP’s job is too send and route packets to othercomputers. IP packets are independent entities and may arrive out of order ornot at all. It is TCP’s job to make sure packets arrive and are in the correctorder. About the only thing IP has in common with TCP is the way it receivesdata and adds it’s own IP header information to the TCP data. The IP headerlooks like this: — Diagram 8 Above we see the IP addresses of the sending and receiving computers in the IPheader. Below is what a packet looks like after passing through theapplication layer, TCP layer, and IP layer. The application layer data issegmented in the TCP layer, the TCP header is added, the packet continues tothe IP layer, the IP header is added, and then the packet is transmittedacross the Internet. — Diagram 9

Internet Infrastructure


The Internet backbone is made up of many large networks which interconnectwith each other. These large networks are known as Network Service Providersor NSPs. Some of the large NSPs are UUNet, CerfNet, IBM, BBN Planet,SprintNet, PSINet, as well as others. These networks peer with each other toexchange packet traffic. Each NSP is required to connect to three NetworkAccess Points or NAPs. At the NAPs, packet traffic may jump from one NSP’sbackbone to another NSP’s backbone. NSPs also interconnect at MetropolitanArea Exchanges or MAEs. MAEs serve the same purpose as the NAPs but areprivately owned. NAPs were the original Internet interconnect points. BothNAPs and MAEs are referred to as Internet Exchange Points or IXs. NSPs alsosell bandwidth to smaller networks, such as ISPs and smaller bandwidthproviders. Below is a picture showing this hierarchical infrastructure. — Diagram 4 This is not a true representation of an actual piece of the Internet. Diagram4 is only meant to demonstrate how the NSPs could interconnect with each otherand smaller ISPs. None of the physical network components are shown in Diagram4 as they are in Diagram 3. This is because a single NSP’s backboneinfrastructure is a complex drawing by itself. Most NSPs publish maps of theirnetwork infrastructure on their web sites and can be found easily. To draw anactual map of the Internet would be nearly impossible due to it’s size,complexity, and ever changing structure.

Internet Protocols Revisited


As hinted to earlier in the section about protocol stacks, one may surmisethat there are many protocols that are used on the Internet. This is true;there are many communication protocols required for the Internet to function.These include the TCP and IP protocols, routing protocols, medium accesscontrol protocols, application level protocols, etc. The following sectionsdescribe some of the more important and commonly used protocols on theInternet. Higher level protocols are discussed first, followed by lower levelprotocols.

Application Protocols: HTTP and the World Wide Web


One of the most commonly used services on the Internet is the World Wide Web(WWW). The application protocol that makes the web work is Hypertext TransferProtocol or HTTP. Do not confuse this with the Hypertext Markup Language(HTML). HTML is the language used to write web pages. HTTP is the protocolthat web browsers and web servers use to communicate with each other over theInternet. It is an application level protocol because it sits on top of theTCP layer in the protocol stack and is used by specific applications to talkto one another. In this case the applications are web browsers and webservers.HTTP is a connectionless text based protocol. Clients (web browsers) sendrequests to web servers for web elements such as web pages and images. Afterthe request is serviced by a server, the connection between client and serveracross the Internet is disconnected. A new connection must be made for eachrequest. Most protocols are connection oriented. This means that the twocomputers communicating with each other keep the connection open over theInternet. HTTP does not however. Before an HTTP request can be made by aclient, a new connection must be made to the server.When you type a URL into a web browser, this is what happens: 1. If the URL contains a domain name, the browser first connects to a domain name server and retrieves the corresponding IP address for the web server. 2. The web browser connects to the web server and sends an HTTP request (via the protocol stack) for the desired web page. 3. The web server receives the request and checks for the desired page. If the page exists, the web server sends it. If the server cannot find the requested page, it will send an HTTP 404 error message. (404 means ‘Page Not Found’ as anyone who has surfed the web probably knows.) 4. The web browser receives the page back and the connection is closed. 5. The browser then parses through the page and looks for other page elements it needs to complete the web page. These usually include images, applets, etc. 6. For each element needed, the browser makes additional connections and HTTP requests to the server for each element. 7. When the browser has finished loading all images, applets, etc. the page will be completely loaded in the browser window. Check It Out – Use Your Telnet Client to Retrieve a Web Page Using HTTP — Telnet is a remote terminal service used on the Internet. It’s use hasdeclined lately, but it is a very useful tool to study the Internet. InWindows find the default telnet program. It may be located in the Windowsdirectory named telnet.exe. When opened, pull down the Terminal menu andselect Preferences. In the preferences window, check Local Echo. (This is soyou can see your HTTP request when you type it.) Now pull down the Connectionmenu and select Remote System. Enter www.google.com for the Host Name and 80for the Port. (Web servers usually listen on port 80 by default.) PressConnect. Now typeGET / HTTP/1.0and press Enter twice. This is a simple HTTP request to a web server for it’sroot page. You should see a web page flash by and then a dialog box should popup to tell you the connection was lost. If you’d like to save the retrievedpage, turn on logging in the Telnet program. You may then browse through theweb page and see the HTML that was used to write it. Most Internet protocols are specified by Internet documents known as a RequestFor Comments or RFCs. RFCs may be found at several locations on the Internet.See the Resources section below for appropriate URL’s. HTTP version 1.0 isspecified by RFC 1945.

Internet Protocol


Unlike TCP, IP is an unreliable, connectionless protocol. IP doesn’t carewhether a packet gets to it’s destination or not. Nor does IP know aboutconnections and port numbers. IP’s job is too send and route packets to othercomputers. IP packets are independent entities and may arrive out of order ornot at all. It is TCP’s job to make sure packets arrive and are in the correctorder. About the only thing IP has in common with TCP is the way it receivesdata and adds it’s own IP header information to the TCP data. The IP headerlooks like this: — Diagram 8 Above we see the IP addresses of the sending and receiving computers in the IPheader. Below is what a packet looks like after passing through theapplication layer, TCP layer, and IP layer. The application layer data issegmented in the TCP layer, the TCP header is added, the packet continues tothe IP layer, the IP header is added, and then the packet is transmittedacross the Internet. — Diagram 9

Internet Infrastructure


The Internet backbone is made up of many large networks which interconnectwith each other. These large networks are known as Network Service Providersor NSPs. Some of the large NSPs are UUNet, CerfNet, IBM, BBN Planet,SprintNet, PSINet, as well as others. These networks peer with each other toexchange packet traffic. Each NSP is required to connect to three NetworkAccess Points or NAPs. At the NAPs, packet traffic may jump from one NSP’sbackbone to another NSP’s backbone. NSPs also interconnect at MetropolitanArea Exchanges or MAEs. MAEs serve the same purpose as the NAPs but areprivately owned. NAPs were the original Internet interconnect points. BothNAPs and MAEs are referred to as Internet Exchange Points or IXs. NSPs alsosell bandwidth to smaller networks, such as ISPs and smaller bandwidthproviders. Below is a picture showing this hierarchical infrastructure. — Diagram 4 This is not a true representation of an actual piece of the Internet. Diagram4 is only meant to demonstrate how the NSPs could interconnect with each otherand smaller ISPs. None of the physical network components are shown in Diagram4 as they are in Diagram 3. This is because a single NSP’s backboneinfrastructure is a complex drawing by itself. Most NSPs publish maps of theirnetwork infrastructure on their web sites and can be found easily. To draw anactual map of the Internet would be nearly impossible due to it’s size,complexity, and ever changing structure.

Internet Protocols Revisited


As hinted to earlier in the section about protocol stacks, one may surmisethat there are many protocols that are used on the Internet. This is true;there are many communication protocols required for the Internet to function.These include the TCP and IP protocols, routing protocols, medium accesscontrol protocols, application level protocols, etc. The following sectionsdescribe some of the more important and commonly used protocols on theInternet. Higher level protocols are discussed first, followed by lower levelprotocols.

Application Protocols: HTTP and the World Wide Web


One of the most commonly used services on the Internet is the World Wide Web(WWW). The application protocol that makes the web work is Hypertext TransferProtocol or HTTP. Do not confuse this with the Hypertext Markup Language(HTML). HTML is the language used to write web pages. HTTP is the protocolthat web browsers and web servers use to communicate with each other over theInternet. It is an application level protocol because it sits on top of theTCP layer in the protocol stack and is used by specific applications to talkto one another. In this case the applications are web browsers and webservers.HTTP is a connectionless text based protocol. Clients (web browsers) sendrequests to web servers for web elements such as web pages and images. Afterthe request is serviced by a server, the connection between client and serveracross the Internet is disconnected. A new connection must be made for eachrequest. Most protocols are connection oriented. This means that the twocomputers communicating with each other keep the connection open over theInternet. HTTP does not however. Before an HTTP request can be made by aclient, a new connection must be made to the server.When you type a URL into a web browser, this is what happens: 1. If the URL contains a domain name, the browser first connects to a domain name server and retrieves the corresponding IP address for the web server. 2. The web browser connects to the web server and sends an HTTP request (via the protocol stack) for the desired web page. 3. The web server receives the request and checks for the desired page. If the page exists, the web server sends it. If the server cannot find the requested page, it will send an HTTP 404 error message. (404 means ‘Page Not Found’ as anyone who has surfed the web probably knows.) 4. The web browser receives the page back and the connection is closed. 5. The browser then parses through the page and looks for other page elements it needs to complete the web page. These usually include images, applets, etc. 6. For each element needed, the browser makes additional connections and HTTP requests to the server for each element. 7. When the browser has finished loading all images, applets, etc. the page will be completely loaded in the browser window. Check It Out – Use Your Telnet Client to Retrieve a Web Page Using HTTP — Telnet is a remote terminal service used on the Internet. It’s use hasdeclined lately, but it is a very useful tool to study the Internet. InWindows find the default telnet program. It may be located in the Windowsdirectory named telnet.exe. When opened, pull down the Terminal menu andselect Preferences. In the preferences window, check Local Echo. (This is soyou can see your HTTP request when you type it.) Now pull down the Connectionmenu and select Remote System. Enter www.google.com for the Host Name and 80for the Port. (Web servers usually listen on port 80 by default.) PressConnect. Now typeGET / HTTP/1.0and press Enter twice. This is a simple HTTP request to a web server for it’sroot page. You should see a web page flash by and then a dialog box should popup to tell you the connection was lost. If you’d like to save the retrievedpage, turn on logging in the Telnet program. You may then browse through theweb page and see the HTML that was used to write it. Most Internet protocols are specified by Internet documents known as a RequestFor Comments or RFCs. RFCs may be found at several locations on the Internet.See the Resources section below for appropriate URL’s. HTTP version 1.0 isspecified by RFC 1945.

Internet Protocol


Unlike TCP, IP is an unreliable, connectionless protocol. IP doesn’t carewhether a packet gets to it’s destination or not. Nor does IP know aboutconnections and port numbers. IP’s job is too send and route packets to othercomputers. IP packets are independent entities and may arrive out of order ornot at all. It is TCP’s job to make sure packets arrive and are in the correctorder. About the only thing IP has in common with TCP is the way it receivesdata and adds it’s own IP header information to the TCP data. The IP headerlooks like this: — Diagram 8 Above we see the IP addresses of the sending and receiving computers in the IPheader. Below is what a packet looks like after passing through theapplication layer, TCP layer, and IP layer. The application layer data issegmented in the TCP layer, the TCP header is added, the packet continues tothe IP layer, the IP header is added, and then the packet is transmittedacross the Internet. — Diagram 9

How to ping an IP address or website


Updated: 12/31/2020 by Computer HopePinging an IP address or website helps you determine if your computer cancommunicate over a network with another computer. Below are the steps on howto ping an IP address and website based on your computer operating system.

Changing your home network IP address


To change or specify the IP address of your computer as it appears on your LAN(local area network), follow the steps below. Keep in mind, if you’reconnecting to the Internet with a broadband connection, adjusting your networksettings may cause issues with your broadband connection. Finally, if yourhome network uses a router, it could be assigning your computer dynamic IPaddresses, and specifying a static IP address may cause issues.

ipconfig – Retrieve Basic TCP/IP Network Information


To get basic network information from your computer, type the following in thecommand window then press `Enter`: `ipconfig`The screenshot example below is the ipconfig output of a particular computer.The output of your ipconfig result will differ depending on your network setupand the type of network adapters installed on your computer. In our screenshotexample, it shows the following basic networking information about thecomputer from which ipconfig was ran. * IPv4 address: 192.168.0.98 * Network subnet mask: 255.255.255.0 * Default Gateway: 192.168.0.1Please note that unless your computer is connected directly to the Internet(this is rare), the IP address reported by ipconfig will be your local networkIP, not your public external IP address.While other network details can be retrieved by the ipconfig utility, for mostnetwork troubleshooting, this is what is typically needed.Back to Top* * *

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