home network monitoring and shaping

Wed Feb 13 00:46:50 UTC 2013

I've had great luck with Cisco's fair-queue option (and similar
techniques).  Using RED, small queues (think on the order of 10-20
packets), and creating a choke point in and out of the network, I've
implemented similar behavior on plenty of DSL lines on the CPE-side.  My
most successful was sharing one 7mbps line with 120 technical employees -
before the implementation of improved queuing, web pages took 60 seconds or
more to load during peak usage.  After implementation, people didn't know
they were on a shared DSL unless they tried streaming video (fortunately
not a business requirement) or a bulk download (it worked fine, it just
would be slow if there were several others going on at the same time).  I
suspect I could have even made a VoIP call across the line with a MOS in
the high 3's easily.

A second issue is poor wireless retransmission and buffering
implementations in consumer wireless.  For my home, to make VoIP work with
low-end gear, I had to break most HTTP sessions and switch to a delay-based
congestion control algorithm inside my network - due to the 5+ second
buffers on the wifi gear.  That would probably have been enough, but
turning on WMM really took the rest of the pain out of wifi-VoIP.

I don't know how to fix the home wifi problems (WMM helps with some
applications, certainly, but it's not a full solution if you still have 5
second buffers in the default traffic class).  But for the other problems,
it would be nice if my provider didn't give me huge buffers and no RED on
the output queue (I have no idea if they are doing the best they can with
the gear they have or not, so there may not be any option here).  But, even
without that, home routers can do better than they do now.  My router knows
what speed it's connected at.  It can create an internal bottleneck
slightly slower, prioritize small packets, implement RED, and use
reasonably-sized buffers (fast downloads should not increase ping times by
hundreds of ms).  I shouldn't need to hang a Linux box between it and my
home network.

Large buffers have broken the average home internet.  I can't tell you how
many people are astonished when I say "one of your family members
downloading a huge Microsoft ISO image (via TCP or other congestion-aware
algorithm) shouldn't even be noticed by another family member doing web
browsing.  If it is noticed, the network is broke.  Even if it's at the end
of a slow DSL line."