Q-Logic 59226-00 B Manuel D’Utilisation

5 – Managing Ports

Using the Extended Credits Wizard

59226-00 B

5-15

A

Each port is supported by a data-buffer with a 8-credit capacity; that is, 8 
maximum sized frames. For fiber optic cables, this enables full bandwidth service 
over a distance of 13 kilometers at 1 Gbps (0.6 credits per Km) or 6 kilometers at 
2 Gbps (1.2 credits per Km). Longer distances can be spanned at full bandwidth 
by borrowing credits from designated donor ports thus pooling the buffer 
capacities. This is called credit extension. Each donor port contributes 7 credits to 
the pool from which the recipient ports can draw. The recipient port also loses one 
credit in the process. For example, one donor port contributes 7 credits to the pool 
from which a recipient draws for a total of 14 credits (7+7). This provides 
approximately 23 Km at 1 Gbps (14÷0.6) or 11 Km at 2 Gbps (14÷1.2).

To extend credits, open the Wizards menu and select Ext Credit Wizard. The 
Extended Credit Wizard leads you through the following process to extend credits 
based on transmission distance requirements:

1.

Extended Distance: Explains the concepts and principles of extending port 
credits. Click the Next button.

2.

Extended Distance Requirements: Specify speed and distance requirements 
for each port then click Next.

3.

Designate Donor Ports: Select available ports and click >> to move the port 
into the Selected Donor Port column shown in 

. Match the number 

of ports needed with the number of designated donor ports. Click the Next 
button.