Tracking request / response packets

[Alan DeKok]

On Jul 7, 2025, at 7:16 AM, tach yon <tachyon at live.co.uk> wrote:
> Wondering please, does FreeRADIUS use only the packet identifier number to match request / response packets together?

  Yes.  That is mandated by RFC 2865, with updates in RFC 5080:

https://datatracker.ietf.org/doc/html/rfc5080#section-2.2.2

> Or a combination of things - to further decrease the likelihood of mixing up two packets with matching identifier numbers?

  The server can't use a "combination of things", because the client only uses the packet Code and ID.

> If the server is busy, 256 concurrent packets doesn't feel like a lot. I wondered if it might use a combo of packet code + identifier, or something like that, to help keep track of which client a request came from.

  If the client needs to send more than 256 packets to a server, it is supposed to open more source ports.  See https://datatracker.ietf.org/doc/html/rfc2865#section-2.5

  Alan DeKok.