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What is a converged network adapter?
2017-01-17
Network Card NIC

A converged network adapter (CNA) is a single network interface card (NIC) that contains both a Fibre Channel (FC) host bus adapter (HBA) and a TCP/IP Ethernet NIC. It connects servers to FC-based storage area networks (SANs) and Ethernet-based local area networks (LANs).

converged network adapter

What is a converged network adapter?

Converged network adapter (CNA), also called a converged network interface controller (C-NIC), is a computer input/output device that combines the functionality of a host bus adapter (HBA) with a network interface controller (NIC). In other words, it "converges" access to, respectively, a storage area network and a general-purpose computer network.

What is converged network adapter used for?

The CNA connects to the server via a PCI Express (PCIe) interface. The server sends both FC SAN and LAN and traffic to an Ethernet port on a converged switch using the Fibre Channel over Ethernet (FCoE) protocol for the FC SAN data and the Ethernet protocol for LAN data. The converged switch converts the FCoE traffic to FC and sends it to the FC SAN. The Ethernet traffic is sent directly to the LAN. And Converged Network Adapters can be used as stand-alone 10 GE NIC (Network Interface Cards), if storage networking is not immediately required. FCOE & FC SAN functionalities can be added later on.

Advantage of converged network adapter

The main advantage of Converged Network Adapter is the reduction of the number of adapters required on the server, reduction of the amount of cables, reduction in the amount of switch ports, reduction in the number of PCI Express slots (on the server). .Using a single CNA to connect servers to storage and networks reduces costs by requiring fewer adapter cards, cables, switch ports, and PCIe slots. CNAs also reduce the complexity of administration because there is only one connection and cable to manage.


Now you have known the applications and advantages of converged network adapter, so what is the difference between traditional setup and new setup? Don’t worry, we will introduce it now and allow you have a more profound understanding of it. 

Traditional setup VS New setup

In large enterprise companies, main servers have (at least) two adapters – FC HBA (FIber Channel Host Bus Adapter) & Ethernet NIC (Ethernet Network Interface Card) to connect to the storage network (Fiber Channel) and computer network (Ethernet). Converged Network Adapters converge the functionality of both the adapters into one. 

Traditional setup VS New setup
In the above diagram, both the traditional set up with FC HBA + NIC (and) the new set up with CNA/FCOE is represented. As you can see, with the set up in the first diagram, two separate adapters are required on the server to connect to Ethernet based Computer Network and FC based Storage Network respectively.

But the set up in the second diagram requires just one adapter (Converged Network Adapter – CNA) which carries both Ethernet traffic as well as FCOE traffic in a single cable. This cable connects to one of the Ethernet ports in the Converged Switch that has both Ethernet as well as Fiber Channel ports. This Converged Switch converts the FCOE traffic in to Fiber Channel traffic to be sent to the FC SAN over the Fiber Channel Network. The computer network traffic is directly sent to the LAN over the Ethernet Network.

Apart from network adapter, “converged” technology also applied to switches, so we will briefly introduce the definition of converged switch to you. 

What is a converged switch?

The server sends both FC SAN and LAN and traffic to an Ethernet port on a converged switch using the Fibre Channel over Ethernet (FCoE) protocol for the FC SAN data and the Ethernet protocol for LAN data. The converged switch converts the FCoE traffic to FC and sends it to the FC SAN.

Summary

Since most of the Converged Network Adapters support 10 GBEE (10 Gigabit Enhanced Ethernet), the performance of the network carrying both network and storage traffic should be good enough. And since CNA follows the same Ethernet standards, 40 GBEE & 100 GBEE will be supported in future.
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