ABOUT DOMAIN NAMES
The most common types of domain names are hostnames that provide more memorable names to stand in for numeric IP addresses. They allow for any service to move to a different location in the topology of the Internet (or an intranet), which would then have a different IP address.
By allowing the use of unique alphabetical addresses instead of numeric ones, domain names allow Internet users to more easily find and communicate with web sites and other server-based services. The flexibility of the domain name system allows multiple IP addresses to be assigned to a single domain name, or multiple domain names to be assigned to a single IP address. This means that one server may have multiple roles (such as hosting multiple independent Web sites), or that one role can be spread among many servers. One IP address can also be assigned to several servers, as used in anycast and hijacked IP space.
Hostnames are restricted to the ASCII letters "a" through "z' (case-insensitive), the digits "0" through "9", and the hyphen, with some other restrictions. Registrars restrict the domains to valid hostnames, since, otherwise, they would be useless. The Internationalized domain name (IDN) system has been developed to bypass the restrictions on character allowances in hostnames, making it easier for non-english alphabets to use the Internet. The underscore character is frequently used to ensure that a domain name is not recognized as a hostname, for example with the use of SRV records, although some older systems, such as NetBIOS did allow it. Due to confusion and other reasons, domain names with underscores in them are sometimes used where hostnames are required.
The following example illustrates the difference between a URL (Uniform Resource Locator) and a domain name:
URL: http://www.example.net/index.html
Domain name: www.example.net
Registered domain name: example.net
As a general rule, the IP address and the server name are interchangeable. For most Internet services, the server will not have any way to know which was used. However, the explosion of interest in the Web means that there are far more Web sites than servers. To accommodate this, the hypertext transfer protocol (HTTP) specifies that the client tells the server which name is being used. This way, one server with one IP address can provide different sites for different domain names. This feature goes under the name virtual hosting and is commonly used by Web hosts.
For example, as referenced in RFC 2606 (Reserved Top Level DNS Names), the server at IP address 192.0.34.166 handles all of the following sites:
example.com
www.example.com
example.net
www.example.net
example.org
www.example.org
When a request is made, the data corresponding to the hostname requested is served to the user.
Every domain name ends in a top-level domain (TLD) name, which is always either one of a small list of generic names (three or more characters), or a two characters territory code based on ISO-3166 (there are few exceptions and new codes are integrated case by case). Top-level domains are sometimes also called first-level domains.
The most common types of domain names are hostnames that provide more memorable names to stand in for numeric IP addresses. They allow for any service to move to a different location in the topology of the Internet (or an intranet), which would then have a different IP address.
By allowing the use of unique alphabetical addresses instead of numeric ones, domain names allow Internet users to more easily find and communicate with web sites and other server-based services. The flexibility of the domain name system allows multiple IP addresses to be assigned to a single domain name, or multiple domain names to be assigned to a single IP address. This means that one server may have multiple roles (such as hosting multiple independent Web sites), or that one role can be spread among many servers. One IP address can also be assigned to several servers, as used in anycast and hijacked IP space.
Hostnames are restricted to the ASCII letters "a" through "z' (case-insensitive), the digits "0" through "9", and the hyphen, with some other restrictions. Registrars restrict the domains to valid hostnames, since, otherwise, they would be useless. The Internationalized domain name (IDN) system has been developed to bypass the restrictions on character allowances in hostnames, making it easier for non-english alphabets to use the Internet. The underscore character is frequently used to ensure that a domain name is not recognized as a hostname, for example with the use of SRV records, although some older systems, such as NetBIOS did allow it. Due to confusion and other reasons, domain names with underscores in them are sometimes used where hostnames are required.
The following example illustrates the difference between a URL (Uniform Resource Locator) and a domain name:
URL: http://www.example.net/index.html
Domain name: www.example.net
Registered domain name: example.net
As a general rule, the IP address and the server name are interchangeable. For most Internet services, the server will not have any way to know which was used. However, the explosion of interest in the Web means that there are far more Web sites than servers. To accommodate this, the hypertext transfer protocol (HTTP) specifies that the client tells the server which name is being used. This way, one server with one IP address can provide different sites for different domain names. This feature goes under the name virtual hosting and is commonly used by Web hosts.
For example, as referenced in RFC 2606 (Reserved Top Level DNS Names), the server at IP address 192.0.34.166 handles all of the following sites:
example.com
www.example.com
example.net
www.example.net
example.org
www.example.org
When a request is made, the data corresponding to the hostname requested is served to the user.
Every domain name ends in a top-level domain (TLD) name, which is always either one of a small list of generic names (three or more characters), or a two characters territory code based on ISO-3166 (there are few exceptions and new codes are integrated case by case). Top-level domains are sometimes also called first-level domains.
www.CNTR.net
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CNTR.net
CNTR.net
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CNTR.net
Created since 2002
CNTR undertakes both pure and applied research into the development of the computer networking technologies and multimedia application systems which are fundamental to the future of the information age.
This three year PhD project is in the area of intelligent networked computer software applications. The aim of this research project is to investigate new protocols or methodologies that will allow software applications running in computer networks to adapt intelligently to network conditions between any two or more end stations, in order to ensure that the user's perceived Quality of Service be maintained. The motivation behind this project is the increased usage of the internet, especially for real-time multimedia applications such as audio and video streaming, internet phones etc., and the problems associated with network congestion leading to poor response and long delays.
This project however will not attempt to address the problems of network congestion but rather how to capitalise existing resources in order to provide networked services with reasonable and persistent Quality of Service. One way for applications to cope with changes in network performance that arise as a result of network heterogeneity is to adapt by monitoring and measuring the state of the network and changing their behaviour in response to the measurements. One of the ways in which networked applications could adapt to the network conditions is by choosing the best server, in terms of network responses, from a list of servers mirroring the same content located at different geographical locations. The other technique is by negotiating different content ‘quality’ depending on the network conditions between the client and the server. For example in a video streaming application, different bit rates or image quality would be used accordingly with differing client/server network conditions in order to maintain an acceptable viewing quality regardless of the network connections. In due course it is hoped that other techniques would also be developed and tested.
In order to achieve this adaptation, information regarding network conditions has to be first gathered. Since substantial research in this area has already been conducted by various parties, our initial work was to review those network measurement techniques and adopt a suitable one for use in our subsequent work. Few researchers have been able to define generalized algorithms or frameworks that will help development of network adaptable applications. Our goal is to design methodologies for adapting multimedia applications and subsequently implementing them in an actual prototype application so that further issues or problems in this area can be investigated.
This three year PhD project is in the area of intelligent networked computer software applications. The aim of this research project is to investigate new protocols or methodologies that will allow software applications running in computer networks to adapt intelligently to network conditions between any two or more end stations, in order to ensure that the user's perceived Quality of Service be maintained. The motivation behind this project is the increased usage of the internet, especially for real-time multimedia applications such as audio and video streaming, internet phones etc., and the problems associated with network congestion leading to poor response and long delays.
This project however will not attempt to address the problems of network congestion but rather how to capitalise existing resources in order to provide networked services with reasonable and persistent Quality of Service. One way for applications to cope with changes in network performance that arise as a result of network heterogeneity is to adapt by monitoring and measuring the state of the network and changing their behaviour in response to the measurements. One of the ways in which networked applications could adapt to the network conditions is by choosing the best server, in terms of network responses, from a list of servers mirroring the same content located at different geographical locations. The other technique is by negotiating different content ‘quality’ depending on the network conditions between the client and the server. For example in a video streaming application, different bit rates or image quality would be used accordingly with differing client/server network conditions in order to maintain an acceptable viewing quality regardless of the network connections. In due course it is hoped that other techniques would also be developed and tested.
In order to achieve this adaptation, information regarding network conditions has to be first gathered. Since substantial research in this area has already been conducted by various parties, our initial work was to review those network measurement techniques and adopt a suitable one for use in our subsequent work. Few researchers have been able to define generalized algorithms or frameworks that will help development of network adaptable applications. Our goal is to design methodologies for adapting multimedia applications and subsequently implementing them in an actual prototype application so that further issues or problems in this area can be investigated.
