5 – Managing Ports
Using the Extended Credits Wizard
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5.3
Using the Extended Credits Wizard
Each 1/2/4-Gbps port is supported by a data-buffer with a 16-credit capacity; that
is, 16 maximum sized frames. For fiber optic cables, this enables full bandwidth
service over the following distances:
26 kilometers at 1-Gbps (0.6 credits per Km)
13 kilometers at 2-Gbps (1.2 credits per Km)
6 kilometers at 4-Gbps (2.4 credits/km)
Longer distances can be spanned at full bandwidth by borrowing credits from
designated 1/2/4-Gbps donor ports thus pooling the buffer capacities. This is
called credit extension. Each donor port contributes 15 credits to the pool from
which the recipient ports can draw. The recipient port also loses one credit in the
process. For example, you can configure a 1/2/4-Gbps 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)’
12 km at 4-Gbps (30÷2.4)
Only 1/2/4-Gbps ports can donate or borrow credits. 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.
