Re: pinger

On 1 Feb 2001, at 20:59, Henrik Nordstrom <hno@hem.passagen.se> wrote:

> I agree fully. Never liked the ICMP probing.
>
> The only issue is that TCP measurements are slightly more dependent on
> the server load, and cannot easily be done in parallell with the fetch
> without perhaps making people even more upset..

 I don't think this is a problem. We build up a cache of RTT's per hosts.
 if we have 1 request to a host, then we can serve first one from source.
 It is not worse than sending pings all over the place.
 Peer RTT data is most probably always fresh, no need to "reping" them.
 And source hosts typically have several accesses in a row, so for a
 second request we already have some data about source RTT.
 I'd also think that higher dependanse from server load is a feature, not
 a bug. If we have many IP's per urlhost, we can sort of loadbalance
 between them, avoiding loaded hosts.

> Andres Kroonmaa wrote:
> >
> > We use pinger, to determine 2 things: RTT to the server, and hop-count.
> >
> > Hop-count has quite little meaning for nearly anything. Mostly people
> > want to use RTT for peer selection, but this RTT has also some problems.
> > quite often sites are blocking icmp ping, and may get frustrated if squid
> > caches allover the world are pinging their server too often. icmp gets
> > usually higher handling priority in OS'es than normal traffic.
> >
> > Do we really need pinger? Why can't we just measure time it takes to
> > tcp-connect to the target server, (or time to first reply data from peer)
> > and remember that as sort of RTT metric?
> >
> > We could pick neighbors by that metric, and we would be less prone to
> > pick peers that are in reality overloaded, and we could also use that
> > metric for decisions whether to cache replies from given server or not.
> >
> > just thought...
> >
> > ------------------------------------
> > Andres Kroonmaa <andre@online.ee>
> > Delfi Online
> > Tel: 6501 731, Fax: 6501 708
> > Pärnu mnt. 158, Tallinn,
> > 11317 Estonia
>

------------------------------------
 Andres Kroonmaa <andre@online.ee>
 Delfi Online
 Tel: 6501 731, Fax: 6501 708
 Pärnu mnt. 158, Tallinn,
 11317 Estonia
Received on Thu Feb 01 2001 - 13:18:46 MST