5 – Managing PortsUsing the Extended Credits Wizard59097-02 B 5-15A5.3Using the Extended Credits WizardEach 1/2/4-Gbps port is supported by a data-buffer with a 16-credit capacity; thatis, 16 maximum sized frames. For fiber optic cables, this enables full bandwidthservice 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 fromdesignated 1/2/4-Gbps donor ports thus pooling the buffer capacities. This iscalled credit extension. Each donor port contributes 15 credits to the pool fromwhich the recipient ports can draw. The recipient port also loses one credit in theprocess. For example, you can configure a 1/2/4-Gbps recipient port to borrow 15credits from one donor port for a total of 30 credits (15+15=30). This will supportcommunication 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 theWizards menu and select Ext Credit Wizard. The Extended Credit Wizard leadsyou through the following process to extend credits based on transmissiondistance requirements:1. Extended Distance: Explains the concepts and principles of extending portcredits. Click the Next button.2. Extended Distance Requirements: Specify speed and distance requirementsfor each port then click Next.3. Designate Donor Ports: Select available ports and click >> to move the portinto the Selected Donor Port column shown in Figure 5-3. Match the numberof ports needed with the number of designated donor ports. Click the Nextbutton.
