Now, I know the an Avaya switch product "ERS 5510-24T", how can I find the Object identifier for the product without using sysObjectID? Because before use snmpget to get the OID, we need have static list that use to map the OID, and then we know what the product is.
The vendors usually have a MIB that identifies its products. For Avaya I found the G3-AVAYA-MIB with some product OIDs, and the Nortel S5-REG-MIB which seems to be more appropriate. If you want to support a vendor, you'll have to search for the OIDs, or ask them.