McDATA 4314 Installation Guide download pdf (Page 24)

McDATA 4314 Fibre Channel Switch Module Installation Guide

2-4

Performance

The switch module supports class 2 and class 3 Fibre Channel service with a

maximum frame size of 2148 bytes at transmission rates of 1-Gbps or 2-Gbps.

An external port adapts its transmission speed to match that of the device to

which it is connected prior to login when the connected device powers up.

Related performance characteristics include the following:

• Distance

• Bandwidth

• Latency

Distance

Consider the physical distribution of devices and switches in the fabric.

Choose SFP transceivers that are compatible with the cable type, distance,

Fibre Channel revision level, and the device host bus adapter. Refer to

Specifications for more information about cable types and transceivers.

Each Fibre Channel port is supported by a data buffer with a 16 credit

capacity; that is, 16 maximum sized frames. For fibre optic cables, this enables

full bandwidth over the following approximate distances:

• 26 kilometers at 1-Gbps (0.6 credits/Km)

• 13 kilometers at 2-Gbps (1.2 credits/Km)

Beyond these distances, however, there is some loss of efficiency because the

transmitting port must wait for an acknowledgement before sending the next

frame.

Longer distances can be spanned at full bandwidth by extending credits to

G_Ports, F_Ports, and E_Ports. Each port can donate 15 credits to a pool from

which a recipient port can borrow. The recipient port also loses a credit in the

process. For example, you can configure a recipient port to borrow 15 credits

from one donor port for a total of 30 credits (15+15=30). This will support

communication over the following approximate distances:

• 50 Km at 1-Gbps (30÷0.6)

• 25 Km at 2-Gbps (30÷1.2)

You can configure recipient and donor ports using the EFCM BASIC

application or the Set Config command. Refer to the McDATA 4314 Command

Line Interface Guide for information about the Set Config command.

Bandwidth

Bandwidth is a measure of the volume of data that can be transmitted at a

given transmission rate. A Fibre Channel port can transmit or receive at

nominal rates of 1-Gbps or 2-Gbps depending on the device to which it is

connected. This corresponds to actual bandwidth values of 106 MB and 212

MB. Multiple source ports can transmit to the same destination port if the

destination bandwidth is greater than or equal to the combined source

bandwidth. For example, two 1-Gbps source ports can transmit to one 2-Gbps

destination port. Similarly, one source port can feed multiple destination

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McDATA 4314 Installation Guide Page 24

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