The Network or Domain UserId is your most used Id. There is no set standard for generation of the UserId except that it should be unique. The discussion here applies to any IT system which has an Authentication and/ Authorization module. In many cases the Active Directory/ Azure Id is used for authentication and authorization to various systems.
UserID generation algorithm options
1. Use FirstName and LastName combination with an optional special character. e.g. Aaron.Nichols. When the 2nd person with same First, last name joins you append a sequential number (Aaron.Nichols1). This works fine till one of the Aaron's is terminated at which point you have the option of reusing the Id for the next person or just generating a new one. Reusing lets you keep the number lower with time as churn happens. But, you lose out on transaction tracking over all employments of an individual.
2. Use the initials of first and last name and add a sequential number at the end. This gives you buckets of Ids, ideally 26P2 (Combinations). These buckets will not be evenly used.
