What s the difference between Layers and Tiers

Question

What s the difference between  Layers  and  Tiers

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Layers are conceptual entities  and are used to separate the functionality of software system from a logical point of view  when you implement the system you organize these layers using different methods  in this condition we refer to them not as layers but as tiers

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I ve found a definition that says that Layers are a logical separation and tiers are a physical separation

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I like the below description from Microsoft Application Architecture Guide 2     Layers describe the logical groupings of the functionality and components in an application  whereas tiers describe the physical distribution of the functionality and components on separate servers  computers  networks  or remote locations  Although both layers and tiers use the same set of names  presentation  business  services  and data   remember that only tiers imply a physical separation

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Yes my dear friends said correctly  Layer is a logical partition of application whereas tier is physical partition of system  tier partition is depends on layer partition  Just like an application execute on single machine but it follows 3 layered architecture  so we can say that layer architecture could be exist in a tier architecture  In simple term 3 layer architecture can implement in single machine then we can say that its is 1 tier architecture  If we implement each layer on separate machine then its called  3 tier architecture  A layer may also able to run several tier  In layer architecture related component to communicate to each other easily  Just like we follow given below architecture    presentation layer business logic layer data access layer   A client could interact to  presentation layer   but they access public component of below layer s  like business logic layer s public component   to  business logic layer  due to security reason  Q   why we use layer architecture   because if we implement layer architecture then we increase our applications efficiency like      security      manageability      scalability  other need like after developing application we need to change dbms or modify business logic etc  then it is necessary to all   Q   why we use tier architecture    because physically implementation of each layer gives a better efficiency  without layer architecture we can not implement tier architecture  separate machine to implement separate  tier and separate tier is implement one or more layer that s why we use it  it uses for the purposes of fault tolerance     easy to maintain   Simple example  Just like a bank open in a chamber  in which categories the employee    gate keeper  a person for cash a person who is responsible to introduce banking scheme manager   they all are the related components of system   If we going to bank for loan purpose then first a gate keeper open the door with smile  after that we goes to near a person that introduce to all scheme of loan after that  we goes to manager cabin and pass the loan  After that finally we goes to cashier s counter take loan  These are layer architecture of bank   What about tier  A bank s branch open in a town  after that in another town  after that in another  but what is the basic requirement of each branch           gate keeper a person for cash a person who is responsible to introduce banking scheme manager   exactly the same concept of layer and tier

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In plain english  the Tier refers to  quot each in a series of rows or levels of a structure placed one above the other quot  whereas the Layer refers to  quot a sheet  quantity  or thickness of material  typically one of several  covering a surface or body quot    Tier is a physical unit  where the code   process runs  E g   client  application server  database server  Layer is a logical unit  how to organize the code  E g   presentation  view   controller  models  repository  data access   Tiers represent the physical separation of the presentation  business  services  and data functionality of your design across separate computers and systems  Layers are the logical groupings of the software components that make up the application or service  They help to differentiate between the different kinds of tasks performed by the components  making it easier to create a design that supports reusability of components  Each logical layer contains a number of discrete component types grouped into sublayers  with each sublayer performing a specific type of task    The two-tier pattern represents a client and a server  In this scenario  the client and server may exist on the same machine  or may be located on two different machines  Figure below  illustrates a common Web application scenario where the client interacts with a Web server located in the client tier  This tier contains the presentation layer logic and any required business layer logic  The Web application communicates with a separate machine that hosts the database tier  which contains the data layer logic   Advantages of Layers and Tiers   Layering helps you to maximize maintainability of the code  optimize the way that the application works when deployed in different ways  and provide a clear delineation between locations where certain technology or design decisions must be made   Placing your layers on separate physical tiers can help performance by distributing the load across multiple servers  It can also help with security by segregating more sensitive components and layers onto different networks or on the Internet versus an intranet    A 1-Tier application could be a 3-Layer application

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Technically a Tier can be a kind of minimum environment required for the code to run   E g  hypothetically a 3-tier app can be running on    3 physical machines with no OS   1 physical machine with 3 virtual machines with no OS    That was a 3- hardware tier app  1 physical machine with 3 virtual machines with 3 different same OSes   That was a 3- OS tier app  1 physical machine with 1 virtual machine with 1 OS but 3 AppServers   That was a 3- AppServer tier app  1 physical machine with 1 virtual machine with 1 OS with 1 AppServer but 3 DBMS   That was a 3- DBMS tier app  1 physical machine with 1 virtual machine with 1 OS with 1 AppServers and 1 DBMS but 3 Excel workbooks    That was a 3- AppServer tier app    Excel workbook is the minimum required environment for VBA code to run   Those 3 workbooks can sit on a single physical computer or multiple   I have noticed that in practice people mean  OS Tier  when they say  Tier  in the app description context   That is if an app runs on 3 separate OS then its a 3-Tier app    So a pedantically correct way describing an app would be    1-to-3-Tier capable  running on 2 Tiers  app         Layers are just types of code in respect to the functional separation of duties withing the app  e g  Presentation  Data   Security etc

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Layers are logical separation of related-functionality code   within an application  Communication between layers is explicit and loosely coupled   Presentation logic Application logic Data Access logic   Tiers are Physical separation of layers  which get hosted on Individual servers  in an individual computer process      As shown in diagram   1-Tier  amp  3-Layers    App Logic  with out DB access store data in a files  2-Tier  amp  3-Layers    App Logic  amp  DataStorage-box  2-Tier  amp  2-Layers    Browser View php   amp  DataStorage procedures  2-Tier  amp  1-Layers    Browser View php   amp  DataStorage  query sending is common  3-Tier  amp  n-Layer     Browser View php   App Logic jsp   DataStorage   n-Tier advantages  Better Security Scalability   As your organisation grows You can scale up your DB-Tier with DB-Clustering with out touching other tiers  Maintainability   Web designer can change the View-code  with out touching the other layers on the other tiers  Easily Upgrade or Enhance  Ex  You can add Additional Application Code  Upgrade Storage Area  or even add Multiple presentation Layers for Separate devises like mobile  tablet  pc

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Why always trying to use complex words   A layer   a part of your code  if your application is a cake  this is a slice   A tier   a physical machine  a server    A tier hosts one or more layers     Example of layers    Presentation layer   usually all the code related to the User Interface Data Access layer   all the code related to your database access   Tier   Your code is hosted on a server   Your code is hosted on a tier   Your code is hosted on 2 servers   Your code is hosted on 2 tiers   For example  one machine hosting the Web Site itself  the Presentation layer   another machine more secured hosting all the more security sensitive code  real business code - business layer  database access layer  etc       There are so many benefits to implement a layered architecture  This is tricky and properly implementing a layered application takes time  If you have some  have a look at this post from Microsoft  http   msdn microsoft com en-gb library ee658109 aspx

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When you talk about presentation  service  data  network layer  you are talking about layers  When you  deploy them separately   you talk about tiers    Tiers is all about deployment   Take it this way  We have an application which has a frontend created in Angular  it has a backend as MongoDB and a middle layer which interacts between the frontend and the backend  So  when this frontend application  database application  and the middle layer is all deployed separately  we say it s a 3 tier application   Benefit  If we need to scale our backend in the future  we only need to scale the backend independently and there s no need to scale up the frontend

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I use layers to describe the architect or technology stack within a component of my solutions  I use tiers to logically group those components typically when network or interprocess communication is involved

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Layers refer to logical seperation of code  Logical layers help you organise your code better  For example an application can have the following layers   1 Presentation Layer or UI Layer 2 Business Layer or Business Logic Layer 3 Data Access Layer or Data Layer  The aboove three layers reside in their own projects  may be 3 projects or even more  When we compile the projects we get the respective layer DLL  So we have 3 DLL s now   Depending upon how we deploy our application  we may have 1 to 3 tiers  As we now have 3 DLL s  if we deploy all the DLL s on the same machine  then we have only 1 physical tier but 3 logical layers   If we choose to deploy each DLL on a seperate machine  then we have 3 tiers and 3 layers   So  Layers are a logical separation and Tiers are a physical separation  We can also say that  tiers are the physical deployment of layers

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Logical layers are merely a way of   organizing your code  Typical layers   include Presentation  Business and   Data     the same as the traditional   3-tier model  But when we   re talking   about layers  we   re only talking about   logical organization of code  In no   way is it implied that these layers   might run on different computers or in   different processes on a single   computer or even in a single process   on a single computer  All we are doing   is discussing a way of organizing a   code into a set of layers defined by   specific function       Physical tiers however  are only about   where the code runs  Specifically    tiers are places where layers are   deployed and where layers run  In   other words  tiers are the physical   deployment of layers    Source  Rockford Lhotka  Should all apps be n-tier

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Read Scott Hanselman s post on the issue  http   www hanselman com blog AReminderOnThreeMultiTierLayerArchitectureDesignBroughtToYouByMyLateNightFrustrations aspx     Remember though  that in  Scott World   which is hopefully your world also      a  Tier  is a unit of deployment  while a  Layer  is a logical separation of responsibility within code   You may say you have a  3-tier  system  but be running it on one laptop   You may say your have a  3-layer  system  but have only ASP NET pages that talk to a database   There s power in precision  friends

[architecture] What's the difference between "Layers" and "Tiers"?

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