• Why do these programs replace IAS in Windows and FreeRADIUS in Linux?

TekRADIUS lot more features and more flexible than the competition.
TekRADIUS obvious possibilities and different than IAS can point to:
Quick and Easy deploy and installation, Limit simultaneous-use for users, Bandwidth Limitation for each user, Daily, Weekly and Monthly Usage, Time Limitation, Basic UI for basic users, Daily Connecting, Build-in DHCP server for best management user, Install to all version of Microsoft Windows (Windows XP, Vista, Windows 7, Windows 8, 8.* and Windows 200*/2008 server) and SQL Support for best centralized management.
The facilities mentioned above are just some of the great features TekRADIUS than IAS and IAS will not ever be able to provide top facilities and best management option for WPA-ENTERPRISE (802.*X) and PPOE VPNs.
One of the main features TekRADIUS use SQL to store user data that BACKUP features affordable as well as being much easier to manage users in future.
One of the important feature of TekRADIUS against other radius tool and FreeRADIUS (in LINUX) is Active Directory integration. Because the Active Directory system is solely under Windows is absolutely better manage Active Directory users in the software under the Windows operating system.
You can use ‘Tunnel-tag’ to select specify VLAN for each user or group. This is really useful in enterprise and big network for manage different groups.
Most of the important option in TekRadius is easy Deb***ing with Log files.
Since it supports such a wide range of authentication methods, this is one of the most secure free servers that you can use for Windows. TekRADIUS supports PAP, CHAP, MS-CHAP v*, MS-CHAP v2, EAP-MD5, EAP-MS-CHAP v2, EAP-TLS and PEAP (PEAPv0-EAP-MS-CHAP v2) authentication methods.
TekRADIUS also supports RFC 2868 - RADIUS Attributes for Tunnel Protocol Support and RFC *07* - Deriving Keys for use with Microsoft Point-to-Point Encryption (MPPE). You can authenticate and authorize PPTP/L2TP connections using TekRADIUS.
Commercial editions of TekRADIUS provide a unique feature; assignment of IP addresses to Wired/Wireless clients authenticated using EAP authentication. TekRADIUS can send Packet of Disconnect (PoD) or execute user defined session kill command when a user consumes all his or her ****** (SP Edition only).
You can specify how much time user account will be valid after the first logon (Time-Limit) and you can specify allowed logon days and hours (Login-Time).
TekRADIUS can working for long time without any problem and error. This is an experience of members and ********s.