Domains, Trees, Forests

Domains, Trees & Forests
Every Domain is part of a Tree, is part of a Forest (even a single domain)
Domains which share the parent domain name belong to the same tree
Trust Relationships connect domains
Forest Root (Root Domain) - First domain, cannot change
Enterprise admins control entire forest
Domain admins control their domain
Trees later merged via forest trust will share resources but not schema
Global catalogue is replicated across the whole forest
Trusts
Trust Relationships can have a
Two-way transitive trust (follows through to sub-domains)
One-way directional trust
Shortcut trust (can be either of the above) (two or one way)
Forest trust - between two forests (unlike below) (two or one way) 
Realm trust - Unix/Linux Realm (Kerberos)
Setup via Active Directory Domains and Trusts
Configure DNS to ensure they can communicate (conditional forwarders)
KCC
Knowledge consistency checker - all D.Cs have it
Creates a circular ring of trust between D.Cs in close proximity (latency) within the same site (intrasite replication)
Updates based on D.C. Availbility, checks every 15 minutes
Separation of sites frees up bandwidth.
KCC Creates new rings within each site and appoints one D.C. as a Bridge Head (every 180 minutes) (can be altered) (Inter-Site Replication)
Site Links
Redundant site links are setup, each have a cost (default 100)
Adjust cost based on primary and secondary links
IP Addresses are set such that devices interact with their local D.C. (Subnets)
Site link bridging can be setup based on a hierarcy (default all on)
May wish to disable site link bridging where a site has multiple sub-sites
Configured and Managed via AD DS > Sites