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three tier

srijan sharma
Ranch Hand

Joined: Jan 24, 2001
Posts: 32
hi all,
i wanna know the exact diference about two tiered and three tiered approach.i have asked a lot ppl. but all make the answer round and round. can anybody explain me precisely and any web sites for that..
Frank Carver

Joined: Jan 07, 1999
Posts: 6920
What's the difference between "two tier" and "three tier"? The answer is, of course, "one tier"
In practice it is actually almost as simple as that.
A system may be considered as "two tier" if the system the user uses communicates with another system where important stuff happens (what this stuff is can vary, but is commonly business or application logic, database storage etc.)
A system may be considered as "three tier" if the system the user uses communicates with a second system, which in turn communicates with a third system, and important stuff happens in both the second and third systems. Again, what happens at each tier can vary, but typically the second system (also known as "middle tier", "middleware" etc.) holds temporary values, business logic etc. and the third system stores permanent or long-lived data.
The most important thing to note is that systems which just route or forward traffic from one system to another are not usually considered as "tiers". So if I run a client application in my PC, which talks to a database application on another machine, thats "two tier", even if my client actually talks to a router which talks to a firewall which talks to a load-balancer which talks to the final application.
Finally it's also common to see the term "n tier". This indicates a much more flexible distribution of processing and storage, where important stuff happens on several systems which can all communicate with each other.
Has this helped?

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