I suspect that my Xfinity Flex box has too small an internal buffer and is
starving when fed by my cake-enabled OpenWrt router.
For the last few weeks, I've been streaming Amazon Prime Video shows and
movies and the box tends to go to black screen after 5-10 minutes of
viewing, followed by a jump to the Flex main menu (which selects which
streaming service to view). I thought perhaps the box was overheating or
that there was a bug in the Amazon app that caused it to crash to the home
screen. This week the same thing happened when I watched a show on HBO Max.
On a hunch, I disabled SQM on the router and was able to watch an hour of
TV with no interruption, using a different service on successive nights. My
next test will be to re-enable SQM and try viewing to see if I get a black
screen and crash to home screen again.
Sometimes instead of a black screen I get a "problem with connection"
message. So my theory is that the Flex box has too little buffer to handle
hiccups in the feed, and is depending on a deep buffer in the Xfinity
modem. Except that I have the modem set to bridge mode so I can disable its
DHCP server and let my LAN server handle DHCP and DNS and other services.
My SQM config follows:
config queue 'eth1'
option itarget 'auto'
option etarget 'auto'
option linklayer 'none'
option interface 'eth1.2'
option debug_logging '0'
option verbosity '5'
option qdisc 'cake'
option qdisc_advanced '1'
option squash_dscp '1'
option squash_ingress '1'
option qdisc_really_really_advanced '1'
option script 'layer_cake.qos'
option iqdisc_opts 'docsis wash besteffort nat ingress'
option eqdisc_opts 'docsis ack-filter nat'
option ingress_ecn 'NOECN'
option egress_ecn 'NOECN'
option download '170000'
option upload '9000'
option enabled '1'
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