Overview:
Application Request Routing v2.5 improves the performance and the scalability of ARR in its disk caching scenarios.   In addition to fully incorporating the enhancements described in KB 2406763, it includes additional optimizations to balance the use of memory and disk caching.   The use of this release is especially recommended to those who are extensively using the disk caching features in ARR.

Download ARRv2.5 from:
ARRv2.5 is available only via Web Platform Installer (WebPI). Download ARRv2.5 via WebPI here.
The download pages for ARRv2.5 can be found at:

  • Microsoft Application Request Routing Version 2.5 (x86) here.
  • Microsoft Application Request Routing Version 2.5 (x64) here.

Features:
ARRv2.5 is mostly a performance and scalability focused release, so there is little functional difference between ARRv2.1 and ARRv2.5.   However, when it comes to disk caching performance and scalability, including latency improvements, there are significant differences between ARRv2.1 and ARRv2.5.
One functional change that is worth mentioning is the ability to set the client affinity cookie on the main domain name.   This particularly interesting if the site has multiple sub-domains, such as images.contoso.com, members.contoso.com and so on.   On such sites, in order to maintain client affinity across sub-domains, the client affinity can be set on the main domain, .contoso.com.

Support:
ARRv2.5 is a fully release version and therefore the support is provided via Microsoft Support.   In addition, the ARR forum is a great place to connect with the community, including the ARR product team.