Fig 1: Data Center

FC SAN provides a high-performance infrastructure for the movement of localized data. Organizations are now looking for ways to transport data over a long distance between their SANs present at multiple geographic locations. One of the best ways to achieve this goal is to interconnect geographically distanced SANs through reliable and high-speed links. This approach consists of transporting the FC block data through the IP infrastructure. FCIP is a tunneling protocol that helps distributed FC SANs to be interconnected over the existing IP-based networks.

FCIP is extensively used in disaster recovery implementations in which data is duplicated to the storage located at a remote site.

FCIP Protocol Stack:

Fig 2: FCIP Protocol Stack

Application layer generate SCSI commands and data, which are processed by various layers of the protocol stack.

The higher layer protocol SCSI includes the SCSI driver program that executes the read-and-write commands. Below the SCSI layer is that the Fibre Channel Protocol(FCP) layer, that is just a Fibre Channel frame whose payload is SCSI. The FCP layer rides on the top of the FC transport layer. This allows the FC frames to run natively inside theSAN environment. Additionally, the FC frames are often encapsulated into an IP packet and sent to a distant SAN over an IP Network.

Fig 3: FCIP Encapsulation

Encapsulation of FC frame into an IP packet could cause the IP packet to be fragmented when the data link cannot support the maximum transmission unit (MTU) size of an IP packet. When the IP packet is fragmented, the required parts of the header must be copied by all fragments. When the TCP packet is segmented, normal TCP operations are used for receiving and re-sequencing the data before passing it to the FC processing portion of the device.

FCIP Topology:

Fig 4: FCIP Topology

In the FCIP environment, we connect FCIP gateway to each fabric with the help of a standard FC connection. The FCIP gateway at one end of an IP network encapsulates the FC frames into IP packets. The gateway at the other end removes the IP wrapper and sends the FC data to the layer 2 fabric. An IP address is assigned to the port on the gateway, which is connected to an IP network. After the IP connectivity is established, the nodes in the two independent fabrics can communicate with each other.

FCIP Performance and Security:

Performance, reliability, and security should always be considered while implementing storage solutions.
Configuring multiple paths between FCIP gateways eliminates single points of failure and provides increased bandwidth. In a scenario of extended distance, the IP network might be a bottleneck if sufficient bandwidth is not available.
Security is also a consideration in an FCIP solution because the data is transmitted over public IP channels. Many security options are available to protect the data based on the router. IPSec is one such security measure that can be used in the FCIP environment.