dual-streaming interim accounting for high volume

[Tariq Rashid]

hi, 

under high load, we are familiar with the usual problem of dropped accounting packets. this leads to retires and timeouts and possible "marked dead", either by the NAS or intermediate radius proxies.

this problem is particularly pronounced when a proxy used to sent traffic to multiple home servers, one of which is slow/unresponsive. this can lead to that proxy as being seen as "dead" by many NASes.

a solution would be to split the accounting radius flow, such that the proxy or other freeradius server replies immediately with an acknowledgement to the NAS, and then forwards the packet onto the target home server, not necessariy waiting for a response. a more intelligent approach may fast reply with cached replies such that rejects can be effective.

illustrated:

1.  [NAS] ---> acct ---> [proxy]

2.  [NAS] <--- acct <--- [proxy] ----> acct ---> [target radius server]

is this possible, or likely to be possible with freeradius?

i know about a mechanism which uses a second process to tail the radius accounting log files, but this is fragile and prone to inconsistencies.

tariq