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Upstream Speeds in Docsis 3

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Upstream Speeds in Docsis 3

Has anyone done a package with upstream speeds at 25megs or 45megs, and if so, how are your upstreams and cm configs set up? I've got 2 bonded 64qam 6.4mhz wide upstreams, and I'm finding it more difficult to get the upstreams to actually run at the provisioned speeds, more than 18mbs. I can get it closer by setting the SfMaxTrafficBurst up higher, but that surely I don't want that number to be ridiculously high?

Have you tried setting the

Have you tried setting the minislot-size to 2 (rather than the default 1)

Yea, I've tinkered with the

Yea, I've tinkered with the minislot size, and it didn't change anything, tried 2 and 4, I also dropped the interleave from 32 to 16.
fragmentation and concatenation are on by default, but when I run the show cable modem mac, it says No on both? I know the concat setting in the modem config is set to 0, which according to packetace, means unlimited.

I've attached my lab cmts config and modem config file.

When I first fired this up a couple years ago, i think I got the upstream to go 90-100mbs with 4 upstreams, but I did that by using a ridiculously large burst number, and that profile had performance issues in voice/gaming applications - I want to avoid that. Most of our production packages only go to 10mbs so it hasn't been an issue - but now I've got a couple that need more than that...

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try this :

try this :

! tweak cmts

int cable 1/0
cable default-phy-burst 0

! tweak config file

UpstreamServiceFlow =
SfReference = 11
SfQosSetType = 7
SfTrafficPriority = 1
SfMaxTrafficRate = 25600000
SfMaxTrafficBurst = 3044 <== change to 10000
SfMaxConcatBurst = 0 <== change to 10000


caps at 10mb/s


So I've been tinkering with this some more this morning. No variation of configuration I've tried in the CMTS seems to have any affect one way or another on the upstream speed. Only changing the upstream burst speed in the modem config seems to have any effect.

My main concern is if this will have a negative effect on voice traffic?

The other thing that bothers me, is that even though fragmentation and concatenation are enabled by default on the upstreams, in the cmts, when I run the command show cable modem mac, It says No on both? That should be Yes, right?

Try with max concat burst

Have you already try using 11000 in max concat burst and 11000 in max burst at UPSTREAM parameters in the config file? Using 0 in max concat burst isn't means unlimited for >D1.X purposes.

DOCSIS 3.0 does not use

DOCSIS 3.0 does not use traditional fragmentation and concatenation.

Instead it uses a new/enhanced variation called Continuous Concatenation and Fragmentation (CCF).

So when you do a show cable modem mac you should see
ver D2.0 has Frag yes and Conc yes
ver D3.0 has Frag no and Conc no

1) You said your normal

1) You said your normal packages limit people to 10Mbps. And then you say your testing is capping at 10Mbps also? This sounds a bit suspicious. Are you sure your test modems are loading the correct config file?

2) When I look at your testing config file I see this :

Upstream flow 2 = 64K, Prio 7
Upstream flow 11 = 25M, Prio 1
Upstream classifier steering UDP port 2727 into flow 2

Downstream flow 21 = 25M, Prio 1
Downstream flow 102 = 64K, Prio 7
Upstream classifier steering UDP port 2727 into flow 102

What is the UDP 2727. Is that voice trying to match voice traffic? When troubleshooting, you should remove any config that isnt absolutely necessary.

Now, any traffic that doesn't have a matching classifier goes to the first (lowest numbered) flow. So in your case I reckon that no traffic will be hitting 25Mbps upstream flow 11 ?

3) remove the rate-adapt command from the cmts

4) login to Arris modem web page and see if all 4 upstreams are incrementing their octet counters evenly

5) post a show cable modem xxxx.xxxx.xxxx

qos verbose
wide channel


I did remove all the old voice flows from the file, And I have tried removing the rate-adapt command. The arris modem page doesn't show upstream octet counters? Those particular settings you gave me earlier produced 10mbs/up.

I managed to get 25mb/s out of it by setting the max traffic to 29mb and the burst to 30000, concat to 3044. Also, at the moment, I have changed the rate-adapt command, replacing "local" with "rate 0" .... But I don't think I should have to overprovision to get the speed. Even wide open best I can get out of the test bench is 40-something.

I will get those show cable modem screens and post them later today or tomorrow morning, as I'm not going to get any testing time this morning most likely.

I have been working on this with IBBS on our live CMTS also (2 bonded upstreams, same cmts config otherwise), and a wide-open package there...

# SfId = 341 -- assigned by CMTS, correlates to PcSfId
SfClassName = ""
SfQosSetType = 7
SfTrafficPriority = 5
SfMaxTrafficRate = 104857600
SfMaxTrafficBurst = 4194303
SfMinReservedRate = 0
SfMinReservedRatePktsize = 0
SfActiveQosTimeout = 0
SfAdmittedQosTimeout = 0
SfMaxConcatBurst = 65535
SfSchedulingType = 2

It only gets 23mbs/up or so.. They don't seem to think at that point that it would be a configuration issue, and they were wanting me to try a Motorola modem (which I don't have since we only use Arris modems now..) I do have a couple Cisco modems laying around I might try this week though. Always seems like I never get enough time to sit and work on this, although, I guess if I didn't have 40 things to do at once, I'd probably get bored, LOL.

Here it is

The show commands, and at the end is a fresh show run of the cmts, and the current cmconfig file.

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