Kerberos cluster application reference architecture

The Kerberos cluster Access Gateway architecture represents a set of components required for Kerberos based authentication and authorization using Access Gateway and a redundant Kerberos cluster. This architecture represents an environment providing fault tolerance for both Access Gateway and Kerberos.

This architecture is designed to meet the following requirements:

  • Protect a Kerberos (Windows IIS) based service.
  • Meets basic fault tolerance and high availability needs for Access Gateway
  • Meet basic fault tolerance and high availability for the Kerberos domain and Key Distribution Center (KDC).

Benefits and drawbacks

Benefits Drawbacks
  • Can be used to replace VPN.
  • Provides basic fault tolerance and capacity support.
  • Can be expanded with additional workers as required to add capacity.
  • Load balanced.
  • Admin instance is accessed behind the firewall.
  • Kerberos domain and KDC are both fault tolerant and redundant.
  • Complex Access Gateway domain.
  • More complex Kerberos domain.
  • Pre Access Gateway DMZ based load balancer must support session affinity (sticky sessions).

Architecture

Components

Location

 Component Description
External internet Web clients

Traditional client browser accessing Access Gateway using known as [appN|consumer-app1].example.com URLs.
consumer-app1.example.com URLs not shown URL representing the application an external web client would enter to access one of the applications secured by Access Gateway. Typically all URLs of this nature are served by, and resolve to, the Access Gateway instance.
Okta org

Your Okta org, providing identity services.
Okta org Universal Directory

Okta Universal Directory, housed in an Okta org, containing users outside other LDAP or Active Directory implementations. Typically these include other customer accounts, partner accounts, and more.
Firewall External internet to DMZ Traditional firewall between the external internet and the DMZ hosting Access Gateway.
DMZ Pre Access Gateway load balancer. Pre load balancer Balances load between clients and the cluster. Positioned between clients and the cluster.
Access Gateway Access Gateway cluster, located in the DMZ is used to provide access to applications used by external internet clients.
Contains a Kerberos service and a keytab.
See Create keytab for details of creating a keytab.
See Add Kerberos service for details of defining a Access Gateway Kerberos service.
Typically hosted in a virtual environment such as Amazon Web Services, MS Azure, Oracle OCI or something similar. See Manage Access Gateway deployment.
Firewall DMZ to internal firewall Traditional firewall between DMZ and the internal network.
Internal network Service/Protected application The set of protected web resources, in this case Microsoft Services, accessed using the consumer-app1.internal-example.com URLs.

Supported versions:

  • Microsoft IIS IWA: IIS 7 or later
  • Microsoft OWA IWA: IIS 7 or later
Pre internal Kerberos domain load balance Load balancer for the Kerberos domain service cluster.
Microsoft domain service cluster with Key Distribution Center Domain service cluster containing a Key Distribution Center (KDC) .
In this architecture the Domain service/KDC represents multiple instances acting as a cluster.

Other considerations

DNS is typically split between external and internal domains. All external URLs, such as [appN|consumer-app1].example.com, would be served externally and point to the Access Gateway instance. Internal URLs, used by Access Gateway such as [protd-N|consumer-app1].internal-example.com, would be served by internal DNS.

Most architectures forward log events to an external syslog component. Okta strongly recommends that a logging server be configured for all Access Gateway environments. See Configure log forwarders.


Additionally, Access Gateway itself is typically managed via internal access only. That is, administrators typically access Access Gateway itself from behind the firewall. This is shown in other architectures.