One important point to realize is that although early versions of SSL VPN products offered greatly varied feature sets, today's leading offerings have relatively similar features. This is especially true when comparing features on paper (that is, as listed in marketing materials).
Part of the maturation process of each individual product is for its vendor to give it the ability to deliver the capabilities that the market demands, which often entails duplicating the functionality of competing offerings. As a result, the definition of what a product must offer to be considered an 'SSL VPN' is becoming increasingly clear and standardized with the passage of time.
Nonetheless, as was alluded to in earlier chapters, the underlying technology implementing the various features differs greatly from product to product. Such differences may affect the ease and speed at which a vendor can introduce desired features into its offering. As a result, as time passes, it is growing...