Cisco Systems OL-12518-01 manual Cisco, Round Trip Time, IPS Module

Chapter 4 FCIP over IP/MPLS Core

Using FCIP Tape Acceleration

The min-available-bwparameter provides the necessary control. Even in the presence of drops, the sender tries aggressively to reach the value configured for this parameter. Even if the congestion window is decreased because of drops, it is increased again on every send so that it is not less than the configured minimum bandwidth.

Round Trip Time

RTT is a measure of the latency or delay back and forth over the FCIP tunnel. RTT is typically twice the end-to-end or one-way delay. Note that IP packets can take different paths each way through a network, so the unidirectional delays are not always equal.

You must configure an appropriate estimate for the RTT. An underconfigured RTT may cripple FCIP throughput. In SAN-OS 1.3 and later releases, the RTT is automatically adjusted from its initial setting.

The configured RTT value is used to calculate the initial TCP MWS and the appropriate TCP window scaling factor. Based on the dynamic RTT, the actual TCP MWS is adjusted dynamically within the bounds of the initially chosen TCP scaling factor.

Customer Premises Equipment (CPE)—Cisco 9216/9216i and Cisco 7200

Cisco 9216

The Cisco MDS 9216 Multilayer Fabric Switch brings new functionality and investment protection to the fabric switch market. Sharing a consistent architecture with the Cisco MDS 9500 Series, the Cisco MDS 9216 combines multilayer intelligence with a modular chassis, making it the most intelligent and flexible fabric switch in the industry. Starting with 16 2/1-Gbps auto-sensing Fibre Channel ports, the MDS 9216 expansion slot allows for the addition of any Cisco MDS 9000 Family modules for up to 48 total ports.

The modular design of the Cisco MDS 9216 allows it to support any Cisco MDS 9000 Family switching or storage services module. The available modules include the following:

•16-port and 32-port 2/1-Gbps auto-sensing Fibre Channel switching modules

•IP Storage Services Module supporting iSCSI and FCIP over eight ports of 1-Gbps Ethernet

•Advanced Services Module providing in-band storage virtualization and switching services

•Caching Services Module supporting fabric-based storage virtualization with integrated data caching

Optionally configurable, these modules give the Cisco MDS 9216 Multilayer Fabric Switch unparalleled functionality and versatility.

IPS Module

The IP Storage (IPS) Services Module is the heart of FCIP service. The flexible IP storage services (4-port and 8-port configurations) deliver both FCIP and iSCSI IP storage services. The iSCSI functionality is software configurable on a port-by-port basis.

The IPS module offers the following:

•Simplified business continuance and storage consolidation—Uses widely known IP to cost-effectively connect to more servers and more locations over greater distances than previously possible.

	Data Center High Availability Clusters Design Guide
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