When to create a shortcut trust
Shortcut trusts are one-way or two-way, transitive trusts that administrators can use to optimize the authentication process.
Authentication requests must first travel a trust path between domain trees. In a complex forest this can take time, which you can reduce with shortcut trusts. A trust path is the series of domain trust relationships that authentication requests must traverse between any two domains. Shortcut trusts effectively shorten the path that authentication requests travel between domains that are located in two separate domain trees. For more information about trust paths, see Understanding Trust Direction.
Shortcut trusts are necessary when many users in a domain regularly log on to other domains in a forest. Using the following illustration as an example, you can form a shortcut trust between domain B and domain D, between domain A and domain 1, and so on.
For more information about how to create a shortcut trust, see Create a Shortcut Trust.
Using one-way trusts
A one-way, shortcut trust that is established between two domains in separate domain trees can reduce the time that is necessary to fulfill authentication requests—but in only one direction. For example, when a one-way, shortcut trust is established between domain A and domain B, authentication requests that are made in domain A to domain B can use the new one-way trust path. However, authentication requests that are made in domain B to domain A must still travel the longer trust path.
Using two-way trusts
A two-way, shortcut trust that is established between two domains in separate domain trees reduces the time that is necessary to fulfill authentication requests that originate in either domain. For example, when a two-way trust is established between domain A and domain B, authentication requests that are made from either domain to the other domain can use the new, two-way trust path.