Transparency in a Architecture Web environments

Architecture Web environments are some examples of how transparency works in distributed systems.

For example, when writing the name of a web page from your browser,the first thing that is done is to translate that name to an IP address,that IP address is where the information that you want to access fromthe Web browser is hosted. There are millions of IPs addresses and maychange frequently needed a large database distributed over severalnodes, which in turn each node is composed of several "machines" thatare able to maintain the data correctly and quickly resolve any domainname to an IP address. This work uses the so-called name server"Domain name system" (DNS).

We can see that the principle of transparency of location would be thesame regardless from where the user search for a web page.

Another example of transparency of replication also occurs when we access a web page that is replicated in a CDN, CDNS are geographicallydistributed servers that are responsible for replicating a web page to beclosest to the end user. How example, when we access a page in whichthe server is in Australia, requests and responses have to travel fromSpain to Australia and from Australia to Spain, which not only makes theloading time of a web page is larger, but that in addition we chargeconsiderably network since data have to make a much bigger journey.

To improve this the CDN (Content Delivery Network) are used, areresponsible for replicating the web in different geographically distributedservers that work as one, and when you request a web page from Spain,the CDN which is closer or less collapsed node will return content to theuser, so that navigation is smoother, getting a better experience for theuser.

Also in the CDN we see the principle of location transparency, since thesame web may be sent or accessed from various geographical pointsand the result of the submitted content will be the same for the enduser, regardless of where the user is the CDN.

We use the principle of transparency of audience, for example, when wemake a purchase via a digital supermarket that has a distributed systemto be able to make purchases online, and access your page, we purchase,and there is no problem because there are several users shopping at thesame store, i.e. programming we can have several "objects" without onemodify the data of another.

In the CDN or environments websites that use multiple servers, we cansee the principle of transparency of decisions, when one of the servers "isfallen" and you may not return the content and another server takesover sending the content to the user as if they were a single entity.

Scaling transparency manifests itself when we incorporate other serversto the network's content without that there is no stop service or noproblem, simply joins other machines that will help to alleviate theworkload of existing servers.

Transparency in a Web or CDN

 Transparency

Transparency is defined as hiding user and programmer of the separation of the components of a distributed system applications, so the system is perceived as a whole, rather than a collection of independent components. Transparency exerts a great influence in the design of system software.

The RM-ODP reference manual [ISO 1996a] identifies eight forms of transparency. They provide a useful overview of the motivation and goals of distributed systems. The transparencies defined are:

Transparency of access: allows access to remote information objects in the same way as a local information objects.

Location transparency: allows access to information without knowledge of their location objects
Transparency of audience: allows multiple processes to operate concurrently using shared information objects and so there is no interference between them.
Replication transparency: allows you to use multiple instances of the objects of information to increase the reliability and performance without having users or application programs by that know the existence of replicas.

Failure transparency: allows users and application programs to complete its tasks despite the occurrence of faults in hardware or in software.

Transparency of migration: allows the movement of information within a system objects without affecting users or application programs.

Transparency of performance. It allows that the system is reconfigured to improve the performance while the various load.

Scaling transparency: allows the expansion of the system and applications without changing the structure of the system or the application algorithms.

The two most important are the transparencies of access and location; its presence or absence affects strongly the use of distributed resources. Often it is called them to both network transparency. Network transparency provides a similar degree of anonymity in resources which is located in centralized systems.