Proxy-State  AVP ( 33 )

This Attribute is available to be sent by a proxy server to another server and MUST be returned unmodified in the Access-Accept, Access-Reject, Access-Challenge or Accounting message. When the proxy server receives the response to its request, it MUST remove its own Proxy-State (the last Proxy-State in the packet) before forwarding the response.

Reference: RFC 2865   View