Network transparency
Encyclopedia
Network transparency in its most general sense refers to the ability of a protocol to transmit data over the network
in a manner which is transparent
(invisible) to those using the applications that are using the protocol.
The term is often applied in the context of the X Window System
, which is able to transmit graphical data over the network and integrate it seamlessly with applications running and displaying locally.
, a second resource needs to be managed in much the same manner: the network
. Preferably, the user should be protected from the network operational details. Then there would be no difference between database applications that would run on the centralized database and those that would run on a distributed one. This kind of transparency is referred to as network transparency or distribution transparency. From a database management system
(DBMS) perspective, distribution transparency requires that users do not have to specify where data is located.
Some have separated distribution transparency into location transparency and naming transparency.
Location transparency in commands used to perform a task is independent both of the locations of the data, and of the system on which an operation is carried out.
Naming transparency means that a unique name is provided for each object in the database.
) or at the application layer
.
Transparency at the IP layer means the client targets the real IP address of the server. If a connection is non-transparent, then the client targets an intermediate host (address), which could be a proxy or a caching server. IP layer transparency could be also defined from the point of server's view. If the connection is transparent, the server sees the real client IP. If it is non-transparent, the server sees the IP of the intermediate host.
Transparency at the application layer means the client application uses the protocol in a different way. An example transparent HTTP request for a server:
An example non-transparent HTTP request for a proxy (cache):
Application layer transparency is symmetric when the same working mode is used on both the sides. The transparency is asymmetric when the firewall (usually a proxy) converts server type requests to proxy type or vice versa.
Transparency at the IP layer does not mean automatically application layer transparency.
Computer network
A computer network, often simply referred to as a network, is a collection of hardware components and computers interconnected by communication channels that allow sharing of resources and information....
in a manner which is transparent
Transparency (computing)
Any change in a computing system, such as new feature or new component, is transparent if the system after change adheres to previous external interface as much as possible while changing its internal behaviour. The purpose is to shield from change all systems on the other end of the interface...
(invisible) to those using the applications that are using the protocol.
The term is often applied in the context of the X Window System
X Window System
The X window system is a computer software system and network protocol that provides a basis for graphical user interfaces and rich input device capability for networked computers...
, which is able to transmit graphical data over the network and integrate it seamlessly with applications running and displaying locally.
Databases
In a centralized database system, the only resource that needs to be shielded from the user is the data (that is, the storage system). In a distributed DBMSDistributed database management system
A distributed database management system is a software system that permits the management of a distributed database and makes the distribution transparent to the users. A distributed database is a collection of multiple, logically interrelated databases distributed over a computer network...
, a second resource needs to be managed in much the same manner: the network
Computer network
A computer network, often simply referred to as a network, is a collection of hardware components and computers interconnected by communication channels that allow sharing of resources and information....
. Preferably, the user should be protected from the network operational details. Then there would be no difference between database applications that would run on the centralized database and those that would run on a distributed one. This kind of transparency is referred to as network transparency or distribution transparency. From a database management system
Database management system
A database management system is a software package with computer programs that control the creation, maintenance, and use of a database. It allows organizations to conveniently develop databases for various applications by database administrators and other specialists. A database is an integrated...
(DBMS) perspective, distribution transparency requires that users do not have to specify where data is located.
Some have separated distribution transparency into location transparency and naming transparency.
Location transparency in commands used to perform a task is independent both of the locations of the data, and of the system on which an operation is carried out.
Naming transparency means that a unique name is provided for each object in the database.
Firewalls
Transparency in firewall technology can be defined at the networking (IP or Internet layerInternet layer
The internet layer or IP layer is a group of internetworking methods in the Internet protocol suite, commonly also called TCP/IP, which is the foundation of the Internet...
) or at the application layer
Internet layer
The internet layer or IP layer is a group of internetworking methods in the Internet protocol suite, commonly also called TCP/IP, which is the foundation of the Internet...
.
Transparency at the IP layer means the client targets the real IP address of the server. If a connection is non-transparent, then the client targets an intermediate host (address), which could be a proxy or a caching server. IP layer transparency could be also defined from the point of server's view. If the connection is transparent, the server sees the real client IP. If it is non-transparent, the server sees the IP of the intermediate host.
Transparency at the application layer means the client application uses the protocol in a different way. An example transparent HTTP request for a server:
GET / HTTP/1.1
Host: example.org
Connection: Keep-Alive
An example non-transparent HTTP request for a proxy (cache):
GET http://foo.bar/ HTTP/1.1
Proxy-Connection: Keep-Alive
Application layer transparency is symmetric when the same working mode is used on both the sides. The transparency is asymmetric when the firewall (usually a proxy) converts server type requests to proxy type or vice versa.
Transparency at the IP layer does not mean automatically application layer transparency.
See also
- Data independenceData independenceData independence is the type of data transparency that matters for a centralized DBMS. It refers to the immunity of user applications to make changes in the definition and organization of data....
- Replication transparency