For details on some of the features found in specific IOS 12 platform builds, go to www.cisco.com/warp/customer/732/120/808-pp.htm. For an outline of the naming conventions used with the actual IOS binary, see www.cisco.com/warp/customer/432/7.html (note that this site is somewhat outdated, but still useful). For lists of features included in particular IOS 12 builds (but not address platform details), check out www.cisco.com/univercd/cc/td/doc/product/software/ios120/120newft/index.htm. And for a general overview of versioning methodology, go to www.cisco.com/warp/customer/732/general/537-pp.htm.

· How To Understand Versioning Basic IOS versioning is as follows: w.x.(y)z (for example, 12.0.(2)T). The "w" and "x" provide versioning information on the major release level, while "y" refers to the maintenance release of that version. For example, 11.3(1) is the first maintenance release of the 11.3 major release. Cisco also uses the term "interim builds" to incorporate bug fixes between maintenance releases, for example, 11.3(1.5).

Cisco has yet to thoroughly document the "z" space, which is for letters assigned to the Early Deployment (ED) builds. Aside from ED, the vendor has two other phases to its IOS life cycle: Limited Deployment (LD) and General Deployment (GD). ED releases denote new technology and features; LD releases serve as intermediary steps between ED and GD releases; and GD releases are considered proven, stable builds. Focus on deploying IOS builds in the GD (General Deployment) phase. The ED builds include a letter that signifies the type of included technology. This nomenclature is somewhat confusing: a "T" build is for "Technology," "D" stands for DSL and "X" appears to be for what Cisco calls "a one-time only" release.

We hope Cisco will release a definitive guide to these naming conventions soon, though we do admire its commitment to consistent versioning; we wish Microsoft and Sun would take notice.