This section describes the key concepts and recommended settings in the MDS. This section includes the following topics:

An FCIP profile defines characteristics of FCIP tunnels that are defined through a particular MDS Gigabit Ethernet interface. Profile characteristics include the:

The MDS enables you to define up to three FCIP profiles per physical MDS Gigabit Ethernet interface. Because a tunnel can be created for each profile, a Cisco MDS switch with two physical Gigabit Ethernet ports can have up to six profiles. Most configurations have only one profile per Gigabit Ethernet interface. Riverbed recommends maximizing the number of profiles configured for each GigE port to increase the total number of TCP connections.

In the profile setting, the default maximum and minimum bandwidth settings per FCIP profile are 1000 Mbps and 500 Mbps, respectively. You can achieve better performance for unoptimized and optimized traffic using 1000 Mbps and 800 Mbps. This is the rate of the LAN-side TCP entering the SteelHead, so that setting it aggressively high does not have any downside, because the SteelHead terminates TCP locally on the LAN side and the MDS can slow down if it tries to go too fast by advertising a smaller TCP window.

Similarly, leave the round-trip setting at its default (1000 ms in the Management Console, 1 ms in the CLI), because the network in this context is effectively the LAN connection between the MDS and the SteelHead.

If you are doing unoptimized runs, configure the bandwidth and latency settings in the MDS to reflect the actual network conditions of the WAN link. These settings improve performance in terms of enabling the MDS to fill-the-pipe with unoptimized runs in the presence of latency.

An FCIP tunnel configuration is attached to a profile and defines the IP address and TCP port number of a far-side MDS to which an FCIP connection is established. You can keep the tunnel configuration default settings, with the following key exceptions:

FCIP settings allow you to specify the number of TCP connections associated with each FCIP tunnel. By default, this setting is 2: one for Control traffic, and one for the Data traffic. Do not change the default value. The single-TCP mode only exists to maintain compatibility with older FCIP implementations. Separating the Control and Data traffic has performance implications because FC is highly jitter sensitive.

You can set whether the MDS compresses the FCIP data within the FCIP tunnel configuration. You must disable it when the SteelHead is optimizing. On the MDS the default setting is off. The best practices of common SAN replication vendors (for example, EMC) recommend turning on this setting when there are no WAN optimization controller (WOC) systems present. However, when adding SteelHeads to an existing environment, it should be disabled.

The following example shows a Cisco MDS FCIP gateway configuration. Cisco-style configurations typically do not show the default values (for example, compression is off by default, and is not present in this configuration dump). Also, this configuration does not show any non-FCIP elements (such as the FC ports that connect to the SAN storage array and VSANs). This example shows a standard and basic topology that includes an MDS FCIP gateway at each end of a WAN link, MDS1, and MDS2.

Riverbed recommends the following best practices regarding a Cisco MDS FCIP configuration:

The following table summarizes the CLI commands RiOS v5.5.3 or later with Cisco MDS FCIP.

If you increase the number of FCIP profiles, you must also create separate in-path rules to disable Nagle for other TCP ports (for example, 3226 and 3227).

Similarly, if you decide to set QoS rules to focus on port 3225 to drive traffic into a particular class, you must create rules for both ports 3226 and 3227.