Version Numbering

Each software release from ISC has a version code that identifies it. The version code contains the architecture number, the major release number, and the minor release number.

For example, BIND 9.10.1 is:

  • BIND 9
  • Major Release 10
  • Minor Release 1

Minor releases fall into 2 categories:

Security Releases

Generally consist of the absolute minimum necessary change from the previous release, making it easier for users to upgrade quickly, as security releases are usually time critical.

Roll-up Bugfix Releases

Include whatever bugfixes have accumulated since the last release, and can include a large number of changes. Most of these changes are usually relatively small, but the volume of new code in a roll-up bugfix release is generally much larger than in a security release. We also reserve the right to include some minor features in point releases (e.g. 9.9.5 for BIND or 4.3.1 for DHCP).


Many organizations that use ISC code have internal rules about how often they can upgrade to new releases from vendors, so unscheduled releases are problematic. To avoid unscheduled releases, ISC calls security releases “patch” versions. Version numbers for patched releases include the conventional three-part version number with an appended patch number. Thus, the first security patch to DHCP 4.2.1 is numbered DHCP 4.2.1-P1.

Security patches are made available both as patches and also as integrated release packages. Security patches will generally be the minimal change necessary to fix the security problem, so that users whose code vetting process requires them to read every new or changed line of code will be able to incorporate security-related bugfixes quickly.

Roll-up bugfix releases are issued periodically as numbered minor releases. Such releases include any security patches since the previous full release. For example, BIND 9.10.1 would include whatever patches were in BIND 9.10.0-P1.

ISC also has Extended Support Version (ESV) versions of software, for companies who need longer change management time frames than our standard release schedule offers.

Other abbreviations used at ISC:

  • Release Candidate (rc)
  • Beta (b)
  • Alpha (a)
  • Windows Specific (w)
  • Subscription Releases (access limited to subscribers)  (S)

Explanation of Version Status

Status Meaning
Development Software is under active development, pre-production alphas, betas and release candidates. Recommended for Testing Environments only.
ESV Extended Supported Version. Use the software for Production Environments needing infrequent upgrades and no new features.
Current-Stable The software is current and its use is recommended for Production
Maintenance Bug and security fixes will be issued when appropriate, soon to be EOL
EOL End of life: critical security fixes may be issued if recently EOL’d
Deprecated The software is not supported by ISC. Do not use this version.

Last modified: October 2, 2014 at 2:24 pm