This Tip discusses the use of Binding and Insistent Domain IDs for FICON Directors
Binding and Insistent Domain IDs
Insistent Domain IDs prohibits the use of dynamic Domain IDs in order to ensure that predictable Domain IDs are being enforced within the fabric. For example, if a switch has this feature enabled and a new switch is connected to it (via an ISL) without the preferred Domain ID, then the new switch is segmented into a separate fabric and user data will not flow. The Insistent Domain IDs feature also ensures that duplicate Domain IDs are not being used within a fabric.
Binding is a method used in the switch to prevent devices and/or other switches from attaching to the switch, based on WWNs that are defined to a membership list.
World-Wide Names (WWN)
Nodes and ports have unique 64-bit addresses that are used to identify them in an FC topology. These addresses are assigned by the manufacturer, with a vendor-specific portion defined by the IEEE standards committee. These addresses (in the FC standard) are called Node_Names and Port_Names, and when they are world-wide unique, they are referred to as:
World-Wide Node_Name (WWNN)
World-Wide Port_Name (WWPN)
A WWN (any WWNN or WWPN) is usually written in sets of two hex digits, separated by colons (for example, 08:45:12:56:43:00:D5:A0).
There are three levels of binding, depending on the degree of security/integrity desired:
A port membership list is defined in the switch with the WWPN of a port on that particular switch and the WWPN of the port of the authorized switch or device. This method is port-dependent, which means the fiber connection cannot be moved from one port to another on the switch without changes to the port membership list.
A switch membership list is defined to the switch with the WWNNs of the switches and/or devices that are authorized to attach to it. This method is port-independent, which means the fiber connection can be attached to any port on the switch.
A fabric membership list is defined with WWNNs and Domain IDs of the switches that are authorized to attach to it. This method is port-independent, which means the fiber connection can be attached to any port on the switch.
These binding types and Insistent Domain IDs are configured in the switch and are known as the High Integrity feature; they are independent of one another and can overlap.
The following figure illustrates the concept of a high integrity fabric. In this example, FC Switch 1 allows the devices (4 and 5) and switches (7, 8, and 9) to attach as follows:
Device 4 using switch binding can be attached via any port.
Device 5 using port binding can only be attached through WWPN 16 via WWPN 51.
FC Switch 7 using port binding can only be attached through WWPN 11 via WWPN 71.
FC Switch 8 using switch binding can be attached via any port.
FC Switch 9 using fabric binding (WWNN 9 and Domain ID 9) can be attached via any port.
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