Only getting 250ish Mbps with 343Mbps Modem why ??

Discussion in 'Networking & Security' started by Subzerok11, Apr 14, 2019.

  1. Subzerok11

    Subzerok11 Gawd

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    I have a Arris SB6141 which is rated at 343Mbps. This is happening with and without the router by the way. The ethernet cable is a Cat5e that's 6 foot long. My router is a ASUS RT-N66U Gigabit Router, both of the these items are only 2-3 years old. The only thing that changed was my Spectrum internet plan went from 100/10 to 400/20. I know I shouldn't expect 400Mbps with the modem but I should at least get in the low 300's right ?
     
  2. BlueLineSwinger

    BlueLineSwinger Gawd

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    Depends on how the ISP has set things up. The SB6141 is fairly old, and limited to 8 down and 4 up channels. Spectrum may require more down channels in order to reach the 400 Mb/s your connection is rated for.

    If you can find a SB6183 for cheap, that might get you up to full (skip the SB6190 and other with the apparently problematic Intel chipset). If cost is less of an issue and you want something that'll probably be useful for longer, consider a DOCSIS 3.1 unit.
     
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  3. Ehren8879

    Ehren8879 [H]ardness Supreme

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    Nope, though the 6141 bonds eight channels, you also share those channels with your neighbors.

    Time to upgrade that modem to a 6183 or preferable an 8200
     
  4. Dead Parrot

    Dead Parrot 2[H]4U

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    Connect via cable direct to the modem and do your speed tests. Also try a different cable. Cat 5e should work but possible that cable is out of spec or has suffered pet/foot damage. I have always felt pretty good about getting 80% speed compared to the marketed speed for a gizmo. You aren't far off that.
     
  5. Krispy Kritter

    Krispy Kritter Gawd

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    You can get a modem for free (ie: price is already included in the price) from Charter. I'm surprised they upgraded your account without a new modem and without a truck roll.
     
    Last edited: Apr 26, 2019
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  6. harbingerofdoom

    harbingerofdoom Gawd

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    do this.

    dont forget that when you're testing with a computer - you cant get 100% accurate results. you also have overhead up to 20% considered to be still healthy and between the two and just on the math that would put you around 275 assuming 343 with 20% overhead - you toss in local variances in your LAN and PC thats running the test and there ya go 250 is totally in that area.

    i have a feeling that the 6141 is locked into a speed profile lower than that of the max throughput it can handle by spectrum. they DO handle older docsis 3.0 hardware in that way in my area which i was told was because they become unstable above 250-300. personally i call B.S. on that and i do think its so they have a way to push their higher speeds... but if they are doing that and you're only hitting say 10-15% overhead.... you would still only see about 250ish.
     
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  7. djoye

    djoye 2[H]4U

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    You can connect directly to the modem and try, that might get you more speed, but some of the numbers you see appear to be 'theoretical'. I had an older modem that should have been good for 343Mbps but it wasn't so I had to upgrade all of my equipment.

    Over time as Comcast has increased its speeds here, I've learned that a 1Gbps router/switch might not be able to provide a quarter of that speed even while wired. When I went to the 300Mbps package, I needed to buy a new router and modem (SB6190). I think I initially bought the SB6190, then found my last router to be the weak link.

    A good resource is https://www.smallnetbuilder.com/

    They run tests on consumer-grade network equipment and then provide real numbers for what speeds you can expect wired and wireless.
     
  8. Vengance_01

    Vengance_01 [H]ardness Supreme

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    Spectrum enforces certain modems requirements at different service levels. The 6141 is limited to the 100mbit teir. You will need a 16/4 modem or even a 32/4or8 channel bonding.
     
  9. newls1

    newls1 2[H]4U

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    def need an upgraded modem. when i was on a comcast plan of 150m/bit my xb3 modem bonded to 24ch down 4 up... you 100% need a new modem.
     
  10. Spartacus09

    Spartacus09 Gawd

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    So 250/383 sounds about right after their limit and processing through a router.

    Most ISPs will only run the modem up to about 75% of it's maximum to reduce stress on their rental equipment, ie) the SB6183 is rated for 686Mbps but is generally capped for 500Mb even if you had the higher tier.

    The SB6190 ( and several other 32x8 modems) is plagued by the intel puma 6 chipset latency issue thats why you had a poor experience likely.
    I'm not sure if they've finally got the issues ironed out or not, as of mid 2018 they are back on most ISP's approved modem list so I'd like to give them the benefit of a doubt.

    Or just avoid it all and snag the SB6183 (about 70$) or the SB8200 (about 165$), both of those have the broadcom chips that are solid, the SB8200 being the newer model.
     
  11. djoye

    djoye 2[H]4U

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    I may not have typed that clearly, but I've actually not had problems with the SB6190, it was the past modem and router combo (Zoom 5341J "343 Mbps", maybe an older Netgear router) that couldn't effectively handle 300 Mbps; I think I was stuck around 250-270 Mbps and both devices were incapable as I had tested directly from each. Regarding the 6190, there's a Puma6 test on DSLReports, my results have always been fairly decent but improved greatly as they updated firmware over time, now my results are mostly green with a little yellow and even less orange. My signal levels are a little high, so maybe that's helping me out.

    I've recently upgraded to Comcast 400 Mbps and I hit up to 500 Mbps download without a problem. They always seem to over-provision a little here, at 300 I'd usually get 375 Mbps steady.
     
  12. Spartacus09

    Spartacus09 Gawd

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    Gotcha, that might be why then, you're not utilizing even 50% of the capability, the 6190's are rated for full gig service.
     
  13. bman212121

    bman212121 [H]ard|Gawd

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    So Ehren8879 is correct, but I can elaborate the rest of the answer for those wondering. The 343mbps rating is based upon the theoretical limit using European standards. In Europe channels have 8mhz of bandwidth, but in the US channels are limited to 6mhz. (It's legacy channel spacing from television) It's not that anyone is throttling anything, but it's because the channel width is 75% of what the rating is done at.So estimating 75% is somewhat correct, and the theoretical bandwidth for a 6mhz channel using QAM256 is about 38mbps. I've seen 36mbps out of a SB5100 (Single channel), so it's pretty close to that. Getting one channel with nothing on it is one thing, but it's unlikely you'll be able to get 8 channels with no other traffic on them. So at 3am you might be able to squeeze out 300mbits if you're lucky, but during the day it could be a lot less than that because other modems are using some of that capacity.
     
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  14. Ehren8879

    Ehren8879 [H]ardness Supreme

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