With a traditional network architecture, the data center manager could load a rack with components that were likely to communicate with each other (say, application servers, and database servers). The advent of server virtualization exacerbated these problems with traditional networking as east-west traffic became even more prevalent because virtualization essentially randomized the locations of the virtual machines (VMs). Any Layer 3 traffic needs to leave the rack and reach the aggregation tier of switches before being routed, even back to the same rack it came from. These multiple hops, frequently across oversubscribed backplanes, can take a very long time – 50 us. However, the problem to understand with this traditional network design is that it’s expensive and not deterministic – east-west communication between racks of gear has traffic traveling to the aggregation layer and frequently to the data center core.

Also, this type of configuration allows for a vast number of ports at the access layer.

If the access switches are 10G, then this communication can have high throughput as well. The good news with this hierarchical model is that traffic between two nodes in the same rack if at Layer 2 of the network stack, is sent with low latency. Access layer switches are frequently located at the top of a rack, so they are also known as top of rack (ToR) switches.įigure 1: data center network infrastructure diagram: The hierarchical model in a data center network switching architecture This traditional network architecture is also known as a three-tier architecture, which Cisco, in turn, calls the “hierarchical inter-networking model.” It consists of core layer switches ($$$), which connect to distribution layer switches ($$, sometimes called aggregation switches), which in turn connect to access layer switches ($). In the 2000s, data center network infrastructure for large companies and large compute farms was built based on a three-layer hierarchical model. This blog answers the question “what is traditional networking?” and touches on innovations in data center networking over the last two decades.

Tor switch meaning