Am Mon, 10 Apr 2017 10:26:14 +0200 schrieb Lennart Poettering <lenn...@poettering.net>:
> On Sun, 09.04.17 19:22, Paul Freeman (p...@coredev.org.uk) wrote: > > > Hi, > > We are seeing high latency (>100ms) when resolving local names via > > LLMNR. > > Queries and responses in LLMNR are supposed to be delayed by a random > time up to 100ms according to the RFC. See: > > https://tools.ietf.org/html/rfc4795 section 2.7, and section 7. > > If you add up the delay for the query and the response you'll get a > delay up to 200ms for a full transaction. Well it seems a bit more complicated: The random delays are a combined value of jitter and timeout. And it depends on whether you're currently the sender or responder: Responders have shorter timeouts (only jitter), according to section 2.7. It also says SHOULD wait (so it is a good idea), and it says the jitter MAY be ignored if the responder knows the name is unique. Only the sender MUST wait for timeout+jitter. This is where the 200ms come from, but it may even be 1000+100ms if you are connected to none-IEEE 802.* media, e.g. VPN or PPP interfaces and LLMNR is configured to listen on these, as far as I understand section 7. According to RFC2119, the terminology SHOULD suggests that systemd could maybe make this configurable? Maybe taking the proper warnings for this configuration into account for administrators... Still you would see delays of at least 100ms then because the sender MUST wait. -- Regards, Kai Replies to list-only preferred. _______________________________________________ systemd-devel mailing list systemd-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/systemd-devel
