Storing leases in LDAP

[Victoria Risk]

I really would like to know why KEA was started. If there is a problem
> / bad programing in ISCs DHCP why not upgrading that one? Maybe it's
> more work but definitely less work than starting from scratch -
> especially if you don't go new ways like implementing LDAP / DB
> support from scratch.

It is reasonable to think of Kea as the re-write of ISC DHCP.  The decision was made several years ago that the only way to address the drawbacks of ISC DHCP was by ‘starting from scratch.'

Kea was developed to address three main problems:

- ISC DHCP is very mature, and difficult to maintain.  It isn’t modular, and was not designed for unit testing. This makes it very difficult to add new features, or make any major changes without destabilizing it.  

- The biggest complaint people have about ISC DHCP is having to restart it after changing the address pools.  We have extended the remote OMAPI interface on ISC DHCP as far as we think we can to eliminate most of the need to restart, but we can’t eliminate that completely. Kea is designed to be updated without restarting.

- The second complaint, or missed opportunity, has to do with making lease information available in a database. Kea was designed for this. We built in MySQL and have already had a second database (PostGres) contributed, and someone could certainly add an LDAP database backend.  

In addition to not requiring a restart, and having an optional database back end, Kea is also designed to be easily extensible with callouts.   It is much better documented and we are already seeing that external contributors can more successfully extend Kea than ISC DHCP.  

As far as the status of Kea, it is in early deployment. We know of some successful deployments, but they are in fairly homogenous environments, with simple applications, like datacenter networking and free wi-fi services, that require few features.  As we add features we expect that Kea will be useful in more complex environments.   We welcome contributions to Kea, and are hosting it on GitHub to facilitate that.