[BBLISA] slow wan link

[Edward Ned Harvey]

> From: bblisa-bounces at bblisa.org [mailto:bblisa-bounces at bblisa.org] On
> Behalf Of Daniel Feenberg
> 
> We have maxed out our WAN link, and users are complaining of slow access
> to websites and x-windows interaction. Yet when I ping sites on the
> internet I see no lost packets, and ping times for relatively close hosts
> are consistently 20 - 30 milliseconds. Large packets are about the same.
> Ping times to our ISP's router at their POP are 2-4 milliseconds. I see no
> dropped pings to real hosts. Sometimes the ISP router drops a ping but I
> understand that may be due to ICMP limiting.
> 
> I have difficulty reconciling these facts. If pings are fast and packets
> are not dropped, why do users see problems? I can confirm things seem
> slow. Is this the dreaded "buffer bloat" problem so recently hyped? Is
> there anything I can do here to aleviate it while waiting for more
> bandwidth?

You should never drop pings, or any other traffic.  If you are dropping any
type of traffic, you have a much more serious problem.  So looking for
dropped packets is not a good test.  Er ... It's something you should test,
but you should always expect 0% loss, even on the most heavily overloaded
connection.

Looking at the roundtrip delay (20-30ms) is a good test, to measure
round-trip latency.  This metric is important for gui interactive things
(and any type of traffic that has a lot of small round-trip packets, such as
samba).  I would normally consider 20-30ms to be perfectly acceptable.
However, you specifically mentioned X.  This is bad, because X is
notoriously heavy in the round-trip packets, which is to say, should not be
used on WANs even if your WAN is really good.  Also, X will die and all of
its processes will die if there's a network glitch or the client reboots,
which is another "should not be used on WAN ever" situation.  Instead, I
would recommend you look into VNC, RDP, Exceed OnDemand, or NX.  These all
greatly improve your WAN gui performance, as well as reliability.  VNC and
RDP are free (but for linux / X systems in general, RDP isn't greatly
available).  NX is only free for a single machine.

On some networks, different types of traffic will be prioritized
differently.  But http is never given high priority, and ICMP is never given
high priority either.  So I don't recommend increasing the http priority,
and you can safely assume you're not seeing skewed results caused by
over-priority of your ICMP traffic.  Long story short, prioritization is a
subject worth mention, but it seems to be just tangential to the present
topic.