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5 – Managing Ports
Using the Extended Credits Wizard
59226-00 B 5-15
A
5.3
Using the Extended Credits Wizard
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 Figure 5-3. Match the number
of ports needed with the number of designated donor ports. Click the Next
button.
Figure 5-3. Designate Donor Ports