Hi all,
is there any way to tune latency for customers connected to casa c100g cmts via docsis 3?
There is around 20ms latency what is quite a lot (someone say that is normal) but i want to know if there isnt any way to tune the latency to reach 4-5ms stable?
Sometime i can see pings around 4-7 ms but most pings are in 15ms - 22ms range.
Thankx a lot
Here is a confiig of my upstream interface:
spectrum-rule 1
frequency 53800000
channel-width 6400000
power-adjustment continue 6
map-advance dynamic 400
no rate-limit
ingress-cancellation 100
pre-equalization extended-taps
logical-channel 0 profile 3 secondary-profile 102,101
logical-channel 0 minislot 2
logical-channel 0 pre-equalization auto-reset
no logical-channel 0 shutdown
logical-channel 1 channel-width 800000
logical-channel 1 profile 101
logical-channel 1 minislot 8
no logical-channel 1 shutdown
no shutdown
spectrum rule 1
cm-hop
channel-width 6400000 800000
action modulation channel-width
back-hop-limit 3 2
correctable-fec threshold 15
uncorrectable-fec threshold 2
profile 3 snr-threshold 330
profile 101 snr-threshold 260
modulation-profile 101
request atdma qpsk off 64 0 16 338 0 16 fixed on 1 1536 qpsk0
initial atdma qpsk off 640 5 34 338 0 48 fixed on 1 1536 qpsk0
station atdma qpsk off 384 5 34 338 0 48 fixed on 1 1536 qpsk0
a-short atdma qpsk off 84 6 75 338 13 16 shortened on 1 1536 qpsk0
a-long atdma qpsk off 96 8 220 338 0 16 shortened on 1 1536 qpsk0
modulation-profile 102
request atdma qpsk off 64 0 16 338 0 16 fixed on 1 1536 qpsk0
initial atdma qpsk off 640 5 34 338 0 48 fixed on 1 1536 qpsk0
station atdma qpsk off 384 5 34 338 0 48 fixed on 1 1536 qpsk0
a-short atdma 16qam off 104 12 75 338 6 16 shortened on 1 1536 qpsk1
a-long atdma 16qam off 104 16 220 338 0 16 shortened on 1 1536 qpsk1
changing map-advance dynamic 400 to 200 or to stacit havent changed anything on latancy.
An effective way to reduce latency is by modifying the interleave of downstream carriers.
Hi ...
would ask if you could fix this issue with latency in past ?
I have the same "problem" but i am on eurodocsis so can't change interleave ...
On BSR64000 the latency is between 4-7 ms and C100G 11-25 ms (only two modems online now in lab at c100g)
thanks in advance
Marek
What software version?
If it is 8.6+ or greater you can turn on Low Latency Docsis.
The easiest win is to turn on AQM (Active Queue Management)
this is done on a per Service Class basis, either in modem config or via service class in CMTS config.
e.g.
cable service-class 1
name ds-PIE-AQM
max-traffic-rate 100000000
min-packet-size 0
tos-overwrite 0xFF 0x0
downstream
app-id 0
aqm-enable 1
aqm-algorithm 1
cable service-class 2
name us-PIE-AQM
max-traffic-rate 100000000
min-packet-size 0
tos-overwrite 0xFF 0x0
upstream
app-id 0
aqm-enable 1
aqm-algorithm 1
If that does not get you where you want you can use ASF (Aggregate Service Flow) on both US/DS Service Flows again via modem config or service class config.
there a few other levers but they get increasingly complex from here.
Hi .. thank you very much ...
The Software is 7.2.6 (SMM 2x10 / DS 8x96 / US 16x8)
i tested it but it´s not really better ... sometimes there are ping about 300ms ...
cmts have nothing todo ;) only 2 modems and ping directly from cmts / CPU usage at 2%
How can i check it at cli if AQM is working proberly ?
are there some other things i can check ?
thanks in advance
Marek