5 – Managing Ports
Using the Extended Credits Wizard
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5.3
Using the Extended Credits Wizard
Each port is supported by a data-buffer with a 12-credit capacity; that is, 12
maximum sized frames. For fiber optic cables, this enables full bandwidth service
over a distance of 20 kilometers at 1-Gbps (0.6 credits per Km), or 10 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. For example, one donor port
contributes 11 credits to the pool from which a recipient draws 11 for a total of 23
credits (12+11). This provides approximately 38 Km at 1-Gbps (23÷0.6) or 19 Km
at 2-Gbps (23÷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 the Next button.
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
