East-West and North-South is the traffic pattern of an application in the context of a datacenter.
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Applications residing in the datacenter can be built in many tiers. Three-tier application architecture is well known and commonly deployed by the application developers.
For smaller application deployments, two tier is not uncommon and for static , very small web server deployment, only one tier ( one or more server ) might be serving for web, business logic and database processes.
Figure-1 Three tiers applications
Applications may interact with common services such as Active Directory, DNS, NTP , and also can interact with other applications.
Within or between data centers, if the application talks with other application or within application tiers, or with these common services, the traffic pattern is called as east-west.
Traffic stays in data center and do not travel to the other places in the network such as HQ , Remote Offices and so on.
Figure-2 Three layer topology
If the amount of traffic between the servers are not so much and aggregation layer can handle the access layer traffic and port density, three layer physical network architecture is well known,commonly established model in the data center today as depicted in the Figure-2 If the traffic grows between the servers and aggregation layer cannot handle the load, either additional aggregation layer is deployed to create another POD, or a different physical network architecture which is called as Leaf and Spine or CLOS architecture can be deployed.
Figure-3 Leaf and Spine topology
When web servers talk with the application servers or application servers talks with database servers, these interactions are examples of an east-west traffic pattern.
Applications can be accessed from campus networks, branch offices, the WAN, or the Internet. In this case, applications are considered to be at the South, so the communication is defined as north-south.
Did you deploy Leaf/Spine architecture or 2/3 tier access, distributon/core model ? Share your experience and insights in the comment below.