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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