While deploying ACI (Application Centric Infrastructure), implementers face tough task of deciding whether mode of fabric deployment should be Network Centric or Application Centric. The task is more challenging due to the fact that administrators and designers are less familiar with ACI related terms like Bridge domain (BD), Endpoint group (EPG), Contracts and Tenants amongst others. Considering the challenges being faced in embracing ACI architecture, in this article we shall discuss on 2 modes of ACI deployment – (1) Network Centric and (2) Application Centric.
Network Centric approach is considered a soft transition for customers from traditional architecture to ACI architecture. This approach allows existing network architecture and flows to remain the same, henceforth allowing IT resources considerable amount of time to get acclimatized with the new terminologies of ACI fabric. On the other hand, Application Centric approach is comparatively a new approach model where application tiers are defined by EPGs . In this setup, Application Profiles are created for each application with EPGs based on the application architecture tiers.The notion is to give the network administrator a view of the application, its connectivity & security requirement from the ACI fabric.
While Network Centric mode considers traditional approach of retaining concept of Subnetting and using VLANs and VRFs, in contrast Application Centric approach hides traditional network related terminologies (such as VRFs, VLANs, and subnets). Infact default gateway may or may not reside in ACI fabric when it comes to Network Centric setup, whereas default gateway resides in ACi fabric in most of occasions.
When it comes to mapping,former considers mapping of BD and EPG to VLAN , latter will Map applications with same functions to same EPGs.Network Centric approach is recommended when gradual migration from existing setup to new infrastructure is required, whereas Application Centric approach is preferred when a greenfield Network environment is being setup. Notable to share that key requirement of Application oriented policy modelling is to have the application visibility and its dependency mappings.
Below is the table which enumerates the comparison between both approaches in a structured form –
Hope this article helps clarify differences between Network Centric and Application centric approach in ACI architecture.