FIBRE CHANNEL and IP SAN INTEGRATION(7)

The maturity and mission-critical deployment of Fibre Channel (FC) in storage area networks (SANs) creates a unique class of multi-terabit networks with demanding throughput, latency, scalability, robustness, and availability requirements. This paper revie

should have very low latency and sufficient bandwidth to forward commands and payloads, and support a sufficiently large number of sessions to enable storage consolidation (a high end storage array on the FC side shared by a large number of IP based servers). Management of the multi-protocol SAN is a critical part of the deployment success.3.3 FCIPFCIP is a tunneling protocol that transports all FC ISL traffic. Similarly, FCIP uses TCP/IP as the transport protocol and IPSec for security. A FCIP link tunnels all ISL traffic between a pair of FC switches, and may have one or more TCP connections between a pair of IP nodes for the tunnel end points. From the FC fabric view, an FCIP link is an ISL transporting all FC control and data frames between switches, with the IP network and protocols invisible. One can configure one or more ISLs (using FCIP links) between FC switches using FCIP links. Figure 3 shows an example of FCIP links being used as ISLs between FC switches A and B. SERVER FC-4 FC IP FC ISLs over FCIP STORAGESTORAGEFC SWITCH AFC SWITCH BFC-4SERVERFigure 3 FC-FCIP Tunnel A key advantage of the FCIP tunnel approach is transparency to a fabric, as existing fabric tools and services are used. Once a FCIP link is configured, existing fabric operations and management continue. Similarly, fabric initialization, FSPF routing protocol, and name/state change services run transparently over FCIP links. However, since FC fabric-level control protocols run over the FCIP tunnel, IP and TCP connection failures can disrupt the FC fabrics on both sides. Given the speed and bandwidth differences between FC and a typical IP network used to interconnect remote SANs, the design and management of congestion and over-load conditions is important to understand. For the FCIP tunnel, a simple FIFO (first in first out) frame forwarding queue design can result in head-of-line blocking of fabric initialization protocol frames when the tunnel is congested, or the TCP connection is in slow-start recovery mode. Another case to consider is when a SCSI-FCP transaction time out occurs, the entire transaction (such as 1 MB block) might be retransmitted over an FCIP link that is experiencing congestion. In addition, there might be multiple application streams using the same FCIP link, and there is no mechanism to help reduce or avoid network congestion. These are possible107

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