Before diving into software coding, you should have a broad architectural plan for your application. Keep in mind that an application’s architecture is distinctly different from the network architecture. From the application developer’s perspective, the network architecture is fixed and provides a specific set of services to applications. The application architecture, on the other hand, is designed by the application developer and dictates how the application is structured over the various end systems. In choosing the application architecture, an application developer will likely draw on one of the two predominant architectural paradigms used in modern network applications: the client-server architecture or the peer-to-peer (P2P) architecture.
In a client-server architecture, there is an always-on host, called the server, which services requests from many other hosts, called clients. The client hosts can be either sometimes-on or always-on. A classic example is the Web application for which an always-on Web server services requests from browsers running on client hosts. When a Web server receives a request for an object from a client host, it responds by sending the requested object to the client host. Note that with the client- server architecture, clients do not directly communicate with each other; for example, in the Web application, two browsers do not directly communicate. Another characteristic of the client-server architecture is that the server has a fixed, well- known address, called an IP address (which we’ll discuss soon). Because the server has a fixed, well-known address, and because the server is always on, a client can always contact the server by sending a packet to the server’s address. Some of the better-known applications with a client-server architecture include the Web, F1′R Telnet, and e-mail.
Often in a client-server application, a single server host is incapable of keeping up with all the requests from its clients. For example, a popular social-networking site can quickly become overwhelmed if it has only one server handling all of its requests. For this reason, a cluster of hosts-sometimes referred to as a server farm-is often used to create a powerful virtual server in client-server architectures. Application services that are based on the client-server architecture are often infrastructure intensive, since they require the service providers to purchase, install, and maintain server farms. Additionally, the service providers must pay recurring interconnection and bandwidth costs for sending an4 receiving data to and from the Internet. Popular services such as search engines (e.g., Google), Internet commerce (e.g., Amazon and e-Bay), Web- based v-mail (e.g, Yahoo Mail), social networking (e.g., MySpace and Facebook), and video sharing (e.g., YouTube) are infrastructure intensive and costly to provide.
In a P2P architecture, there is minimal (or no) reliance on always-on infrastructure servers. Instead the application exploits direct communication between pairs of intermittently connected hosts, called peers. The peers are not owned by the service provider, but are instead desktops and laptops controlled by users, with most of the peers residing in homes, universities, and offices. Because the peers communicate without passing through a dedicated server, the architecture is called peer-to-peer. Many of today’s most popular and traffic-intensiye applications are based on P2P architectures. These applications include file distribution (e.g., BitTorrent), file searching/sharing (e.g., eMule and LimeWire), Intemet telephony (e.g., Skype), and IPTV (e.g., PPLive).
By: Imran Rashid
Posts Tagged ‘Ip Address’
Network Application Architectures
January 22nd, 2010Troubleshooting Two Common Network Card Driver Problems
November 29th, 2009
One, your PC is slowing down after installing network adapter drivers. When you finish the installation of your net card driver and restart the PC, you find the boot up is markedly slower than before. Firstly, ensure that you have set up your compatible driver properly.
Commonly, it is in gear that the startup becomes much slower than before after a single computer experiences a network configuration, for the system will detect the adapter one more time. Surely, if the system freezes up for a long time on start, you should scrutinize the machine for other failures.
Besides, if you haven’t specified an IP address for your net card, your system will search one for it automatically on startup, which will take about 10 seconds. Even though your NIC is not in use at present, you’d better assign an IP address to it, and simply disable this card in the BIOS so as to boost the computer’s boot up.
Network card itself is less likely to have problems. The failures usually come from its drivers or the mismatch of transmission rate between the computer and the adapter, for these you can unload the driver and then readjust the correct network adapter parameter.
Two, your net card driver is broken while cleaning virus or because of shutting down the computer improperly.
If your network adapter programs are damaged and the adapter can not work, the network is unreachable and the net card light is on, go to the Device Manager (Start / Control Panel / System / Hardware / Device Manager) you will find a yellow exclamatory mark beside the Network adapters, which indicates that your net card driver is working irregularly, you need to unload and reinstall it.
By: Molly Smith
How to Connect Multiple Computers to One Broadband Internet Connection
October 9th, 2009
Broadband, or high-speed, Internet connection is what many users currently use in their home. Along with high-speed Internet, many users may also use a router to allow multiple computers to connect to the Internet. This post will describe how a router is used to connect multiple computers. To make it easier to understand, I will use where you live as a comparison to how your computer is connected to the Internet.
What is an IP Address?
IP addresses are a series of numbers in the form: nnn.nnn.nnn.nnn, where nnn is a one to three digit number. An IP address is unique to an individual computer on a network, similar to how your home has a unique address. For an Internet connection, an IP address is supplied by your Internet Service Provider (ISP). In some cases, your ISP may provide you with more than one IP address, which allows you to connect multiple computers. As you will see later, however, you can still connect multiple computers with a single IP address.
Connecting a Single Computer
Connecting a single computer to your high-speed Internet is very simple to do. Simply connect a network cable into your modem, and then into the network card in your computer. Your computer will then be assigned an IP address from your ISP. For example, if your ISP assigned you the IP address of 24.24.50.17, then your computer will have that IP address.
When you make a request to a server, such as for a Web page, the Web server knows which IP address made the request. The information is then sent through the Internet and back to your computer. This is similar to when someone sends you mail to your home. The address on the mail allows it to be delivered to your home and not somewhere else.
Connecting Multiple Computers
How can multiple computers connect if only one address is assigned? When you make a request for a Web page, how does it know which computer requested that page? Let’s take our home analogy one step further. Let’s say instead of living in a house, you live in an apartment. When someone sends you mail, they not only include your address but also an apartment number. This number is internal to your apartment building and every apartment has its own unique number. Similarly, multiple computers can connect to the Internet if they each had there own unique local IP address. This can be handled by a router.
A router is a piece of hardware that connects directly to the modem. Each computer is then connected to the router, instead of the modem. Now instead of your computer having the IP address supplied by your ISP, your router now is assigned that IP address. This is similar to your router acting as the apartment building.
The beauty of a router is that it can assign its own local IP addresses. When you connect a computer to the router it now receives one of the IP addresses assigned by your router, similar to how each apartment has it’s own number. Now when you make a request for a Web page, the request is sent using the same ISP address, but this time it is assigned to the router. When the Web page is returned, the router receives the request, and sends it locally to the computer that requested the page.
The router also has its own local address that is similar to the local IP addresses of the computers. So now the router has two addresses assigned to it: an external one provided by your ISP, and a local one provided by it. This allows the router to connect to both the Internet and the local network.
Note: The 192.168.xxx.xxx address are special IP addresses reserved for Local Area Networks (LANs).
Managing a FTP or Web Server on Your Network
Let’s take a look at this scenario. You have a router connecting multiple computers to the Internet. But now you want to create a FTP or Web server. No problem. You setup the necessary software on a computer on your network, told someone outside your network the local IP address of your FTP server and they try to connect. They then discover that they can’t connect. Why? Its similar to someone mailing something to you by just specifying your apartment number and no address.
The IP address assigned to your computer is local to your network. You can connect to that computer from within your network, but not from the Internet. You will need to use your ISP-assigned IP address (the one assigned to your router) to have someone from the Internet connect to your FTP server. The problem is that your router is assigned that IP and not your computer, and since an IP address must be unique, how can two computers have the same IP? The answer: they can’t, but they don’t need to.
Routers have the ability to forward information on a port to a specific computer. A port is a numbered channel that data can be sent through on a network. You cannot physically see it as it is a virtual channel used extensively in networking for sending/receiving data. For FTP servers the default port is 21; however another port can be used.
Open your router setup and look for the port forwarding option. Specify the internal IP address of your FTP server and the port number and then save that information. Now when a user tries to access your FTP site, they must use the ISP IP address that is assigned to your router. The router will then notice that the data is being sent on port 21 and then forward it automatically to your FTP server. A Web server can be setup the same way, but its default port is usually 80.
Note: By default a router will dynamically assign IP addresses to the computers connected to it. This means that the first computer to connect to the router will get the first available IP address, and the next will get the second, and so on. If you manage an FTP server, it may be easier to assign a static IP address to the computers to ensure that the FTP server always has the same IP address.
This article described how to connect one or more computers to one Internet connection. It is important to remember the following:
If you have one computer connected directly to the modem, then that computer will be assigned the IP address from your ISP. When using a router, the the router will be assigned the IP address from your ISP. Any computers connected to the router will be assigned a local address by the router. A router will have the ISP IP address and a local IP address. This allows it to connect to both the Internet and your network. When setting up a computer as a FTP, Web, or other server to communicate over the Internet, it is important to use the router’s IP address to access your server. You will then need to forward the necessary port to your server.
For more information, please read the Technically Easy blog.
By: Paul Salmon
