Re: [Telrad] QCI levels and latency

Thu, 02 Feb 2017 14:03:51 -0800

When I had it set to 256k both ways for GBR and MBR, I would see anywhere from 500-700kbps on iperf on the dedicated bearer.
So I created global service profile at 100m x 30m, and set the dedicated bearer to 1m x1m GBR and 6m x 2m MBR. 


Now I see big numbers in speedtest.net, but I only get 6.3 x 2.8 on 
iPerf.



It must not police the traffic to that exact amount....otherwise I think 
it must be working.

-Adam



------ Original Message ------
From: "Adam Moffett" <[email protected]>
To: "[email protected]" <[email protected]>
Sent: 2/2/2017 11:45:12 AM
Subject: Re: [Telrad] QCI levels and latency


My list too
I'm having the same confusion for the exact same reason.


------ Original Message ------
From: "Nathan Anderson" <[email protected]>

To: "'Adam Moffett'" <[email protected]>; "[email protected]" 
<[email protected]>

Sent: 2/2/2017 3:55:24 AM
Subject: RE: [Telrad] QCI levels and latency


I used GBR 100k / MBR 256k, same as the example documentation on the 
Telrad Zendesk KB article.  For a single VoIP channel, should be fine.





...however, I am afraid that either what I wrote earlier is wrong and 
misleading, or it is right and should be working but isn't working.  I 
realized that having uplink traffic sent on the dedicated bearer with 
MBR 256k should mean iperfs done from UEs would show max. 256k upload. 
 However I'm not seeing this.  Now, maybe they thought through this 
issue enough to exempt iperf traffic originated from the UE itself 
from getting marked with the MGMT DSCP value (although I have reason 
to believe this is not the case...it actually looks like none of the 
traffic originating from the UE is getting marked!), but even if that 
were the case, I tried having a MikroTik that was behind a UE 
indiscrimiately mark all outgoing traffic with the DSCP I'm using for 
my dedicated bearer, and did an upload test with MikroTik 
bandwidth-test, and it is only getting limited by the UL AMBR, and not 
by the dedicated bearer's UL MBR.  (And I did verify through a packet 
sniff that the bandwidth-test packets received on the other side of 
our PDN router had the expected DSCP value set in the IP header.)





So either something isn't working correctly here when it comes to 
getting the UE to use the right bearer for this traffic, or I am 
missing a step somewhere.  So strange though because I could swear I 
tested this earlier and found that it was working as expected.  
Perhaps I only exhaustively tested the downlink stuff (which is 
definitely working as expected: TCP sessions get capped at 256k if I 
mark downward packets with the right DSCP value).





I guess this is just yet another question to throw on my ever-growing 
pile of "things I need to ask Telrad about."




-- Nathan




From:[email protected] [mailto:[email protected]] On 
Behalf Of Adam Moffett

Sent: Wednesday, February 01, 2017 8:07 AM
To:[email protected]
Subject: Re: [Telrad] QCI levels and latency




Ok thanks.  Great info.  How large did you make your dedicated 
management bearer?  I did 256k, but now I'm thinking it's not big 
enough.





I still can't say anything authoritative about what would happen with 
QCI 6 vs QCI 7, but presumably if the system couldn't fit a packet 
into the delay budget it would have to drop it.  We could make some 
guesses about the ramifications of that, but I think you'll have to 
test to know for sure.  If I'm guessing, then I'd guess the only time 
you can't hit the PDB is when there's congestion, so most of the time 
you wouldn't see a difference.  When there is congestion I think you'd 
see less throughput on individual TCP connections....though maybe you 
would see lower RTT as well, and total system throughput might not be 
affected.  I am literally making that up, so take it for what it's 
worth LOL.








------ Original Message ------

From: "Nathan Anderson" <[email protected]>


To: "[email protected]" <[email protected]>; "Adam Moffett" 
<[email protected]>


Sent: 1/31/2017 6:19:43 PM

Subject: RE: [Telrad] QCI levels and latency




Yes, that should be enough for specifically prioritizing management 
traffic itself on the uplink (like accessing the UE web interface, 
ping responses from the CPE, presumably also things like SNMP and 
TR-069 responses, etc.).





If you need to prioritize certain customer upload traffic then you 
will also need to either 1) check the DATA box (which is, I believe, 
the default) on the DSCP page (7000) and then put the dedicated 
bearer's DSCP value in there as well (which will prioritize ALL 
traffic, and which likely isn't what you want unless this is a 
special customer and the UL MBR and UL GBR specified on the default 
bearer is sufficient for the use of that connection), or 2) UNcheck 
the DATA checkbox (because if it is checked, it will override the 
DSCP in the IP header of ALL user traffic, even if the value is set 
to 0), which will allow IP packets originating from the user to 
proceed through the UE with the DSCP mark untouched.





At this time, unfortunately the CPE8000 cannot have its management 
uplink traffic prioritized without also unilaterally steamrolling the 
DSCP mark on user-generated traffic (MGMT and DATA DSCP override 
cannot be enabled and disabled independently!).  I have brought this 
to Telrad's attention, so hopefully that will be addressed in a 
future firmware version.




-- Nathan

________________________________________


From: [email protected] <[email protected]> on behalf 
of Adam Moffett <[email protected]>


Sent: Tuesday, January 31, 2017 1:13 PM

To: [email protected]

Subject: Re: [Telrad] QCI levels and latency



  I don't have an answer to the question on QCI 7 vs QCI 6.



I was curious how you configure the UE to classify upload traffic.  I

noticed the default config on both 7000 and 8000 is set to use DSCP 6

for management, so I made my dedicated bearer use DSCP 6.  Is that

enough, or is there more to it?



I could probably read the manual and figure this out, but I was just

stabbing at it in my spare time :)





------ Original Message ------

From: "Nathan Anderson" <[email protected]>

To: "[email protected]" <[email protected]>

Sent: 1/31/2017 3:20:34 PM

Subject: [Telrad] QCI levels and latency




All,




We recently implemented iPCRF on our EPC to great effect.  We added 
a


QCI 1 profile that we apply to our dedicated bearer, and are

prioritizing our VoIP service using that.  So that we can easily see


and verify the effectiveness of this, we also started sending ICMP 
over



the same dedicated bearer.  Average latency and jitter to CPEs 
dropped


like a rock right after we did that, so it is clearly working.




When our ENBs start to become moderately busy, we still notice that 
RTT



for traffic on the default bearer can become both exceptionally 
latent


and jittery.  This is easy to see if we run a constant ping to a CPE


and then stop prioritizing ICMP to that CPE in the middle of the 
ping



test.  Ping jitter goes up significantly almost immediately.  When 
we


prioritize ICMP, all we end up doing is masking that problem.




Unfortunately, release 6.6 only allows for one dedicated bearer, so 
we



can't classify different types of traffic across multiple QCI levels 
in



order to try to help deal with this better.  But after looking at 
the


various QCI levels that are defined in the LTE spec


(https://en.wikipedia.org/wiki/QoS_Class_Identifier), I am wondering 
if


there isn't a short-term answer to this problem while we wait for


multiple dedicated bearer support.  Specifically, I see that each 
level



also has a defined "packet delay budget".  QCI 6, the default pick 
for



the default bearer, has a PDB of 300ms.  What would happen if we 
were


to, say, switch to using QCI 7, which has a PDB of 100ms, for our


default bearer?  Would we actually see an overall improvement in 
RTT?


And if so, would it be at the expense of anything/what would be the

downside(s)?  (For example, would overall throughput end up taking a


hit because it is trying to service UEs less efficiently so that it 
can


make good on the latency budget?)



I'm curious to know if anyone has tried this.



Thanks,



--

Nathan Anderson

First Step Internet, LLC

[email protected]



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