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Author Topic: BCM63168 Modems that Support Baby Jumbo Frames (Bridge Mode)  (Read 30364 times)

johnson

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Re: BCM63168 Modems that Support Baby Jumbo Frames (Bridge Mode)
« Reply #285 on: February 18, 2019, 12:04:56 PM »

Thanks for trying it out bkehoe.

I guess there is some other factor I cant test for that is causing issues.

my NIC supports something called JUMBO FRAMES and its currently disabled, the options are 'DISABLED' or 'xKB MTU' (where 'x' = a value of 2-9) - is it worth using this feature? if so, which MTU KB value?

also you mention 'MTU Path Discovery' - is this a feature that my NIC & router can use to set the LAN MTU? or is it a feature the router & dslam uses to set the WAN MTU..?

Do you have some ethernet card "helper" program or something installed supplied by the manufacturer? Excuse me ignorance, but I have never dealt with such programs, as far as I know and have experienced modern OSs manage all settings themselves to be optimum. If it was me I would select 9k jumbo frames as it should manage smaller MTUs automatically, or just uninstall the extra "settings" program.

As far as I understand pMTU works from endpoint to endpoint, so its your PCs OS negotiating the best MTU possible through to the service you are connecting to.
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Weaver

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Re: BCM63168 Modems that Support Baby Jumbo Frames (Bridge Mode)
« Reply #286 on: February 19, 2019, 04:43:00 PM »

You also have to have an isp that supports MTU 1508, and their wholesale carrier if applicable and the phone line link and DSLAM or FTTC must all support it. There are web-based testing tools that will test the link all the way to / from a test server to discover MTU.
« Last Edit: March 13, 2019, 03:12:39 PM by Weaver »
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MrMike

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Re: BCM63168 Modems that Support Baby Jumbo Frames (Bridge Mode)
« Reply #287 on: February 19, 2019, 09:58:54 PM »

The commands required with unmodified firmware are as follows:

Code: [Select]
ifconfig ptm0 mtu 1508
ifconfig ptm0.1 mtu 1508

Sorry to jump back to this particular post. So in theory I can enter these 2 commands on stock firmware to enable baby jumbo frames without having to install any custom firmware? Of course they'll be the requirement to re-enter these commands on modem reboot / re-sync. My Zyxel is in bridge mode so I'll configure the PPPoE MTU settings over on my main router.
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johnson

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Re: BCM63168 Modems that Support Baby Jumbo Frames (Bridge Mode)
« Reply #288 on: February 19, 2019, 10:39:25 PM »

Unfortunately not. In bridge mode the switch ports on the Zyxel must support > 1500 byte MTU ethernet frames in order to pass PPPoE packets with full 1500 byte payloads. Hence the modification to the drivers Makefile:
Code: [Select]
EXTRA_CFLAGS += -DCONFIG_BCM_ETH_JUMBO_FRAME

As this change is needed when compiling, a modified firmware is a must when in bridge mode.

If you are comfortable with VMs and basic linux usage the process is fairly painless to build your own image. Request the source package from Zyxel (the have a handy form for it) and you can build a firmware with only trust in them.

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Weaver

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Re: BCM63168 Modems that Support Baby Jumbo Frames (Bridge Mode)
« Reply #289 on: February 20, 2019, 07:05:27 AM »

I forgot to say, in my previous post, that when my isp was using BT 20CN as their wholesale carrier, BT did not support MTU 1500+8=1508, so I got a good modem, got everything set up for IP MTU 1500 and then couldnít understand why it didnít work, and was disappointed. And my ISP had failed to point this gotcha out when they were advertising MTU 1500 capabilities.
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meritez

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Re: BCM63168 Modems that Support Baby Jumbo Frames (Bridge Mode)
« Reply #290 on: February 20, 2019, 09:25:03 PM »

Test it here:

http://www.letmecheck.it/mtu-test.php

That site states I have an MTU of 1494..

Using the VMG1312-B10A .16 firmware with the newer xdsl driver and a fix for 1500 MTU here: https://richard.burtons.org/2017/03/12/mtu-1500-for-bt-adsl-with-openwrt/

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johnson

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Re: BCM63168 Modems that Support Baby Jumbo Frames (Bridge Mode)
« Reply #291 on: February 20, 2019, 09:31:20 PM »

That site states I have an MTU of 1494..

Using the VMG1312-B10A .16 firmware with the newer xdsl driver and a fix for 1500 MTU here: https://richard.burtons.org/2017/03/12/mtu-1500-for-bt-adsl-with-openwrt/

What router are you using, a WNDR3700 with openwrt on as in the link?
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meritez

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Re: BCM63168 Modems that Support Baby Jumbo Frames (Bridge Mode)
« Reply #292 on: February 21, 2019, 11:13:40 AM »

What router are you using, a WNDR3700 with openwrt on as in the link?

TP-Link WDR4300 running openwrt 18.06.2
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johnson

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Re: BCM63168 Modems that Support Baby Jumbo Frames (Bridge Mode)
« Reply #293 on: February 21, 2019, 11:52:38 AM »

TP-Link WDR4300 running openwrt 18.06.2

Do 1472 pings work to cloudflare etc?

If not you can try setting the base ethernet adapter on the router (usually eth0) to 1508 as per:
https://forum.kitz.co.uk/index.php/topic,21273.msg390527.html#msg390527

And test again.

In my experience letmecheck.it is accurate.
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Alex Atkin UK

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Re: BCM63168 Modems that Support Baby Jumbo Frames (Bridge Mode)
« Reply #294 on: March 05, 2019, 01:13:05 PM »

Isn't there an "auto" setting for the MTU within BGW?

If you were using a Unix or Linux kernel based system, there would be no need to change the MTU of the system's interface from "auto".

Are you sure about that?  Both my Fedora boxes show MTU 1500 for all interfaces (with no MTU specified in the network configuration) and if I try to ping a larger size between them I get "ping: local error: Message too long, mtu=1500".

I would be quite interested if I can get path MTU working as it would reduce the CPU load when transferring files between them.
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Modems: 2 x VMG3925-B10B V5.13(AAVF.12)C0-jumbo
Router: i5-7200U appliance running pfSense.
ISP: Zen Unlimited Fibre 2 + Plusnet Unlimited Fibre Extra.

burakkucat

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Re: BCM63168 Modems that Support Baby Jumbo Frames (Bridge Mode)
« Reply #295 on: March 05, 2019, 08:43:38 PM »

Well that's Fedora for you.  ;)  Six months is a very long time in Fedora-land.  :D
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Alex Atkin UK

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Re: BCM63168 Modems that Support Baby Jumbo Frames (Bridge Mode)
« Reply #296 on: March 13, 2019, 03:04:38 PM »

Well that's Fedora for you.  ;)  Six months is a very long time in Fedora-land.  :D

Fedora is supposed to be the "bleeding edge" of distros so if they don't have it then surely 99% of distros do not?
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Modems: 2 x VMG3925-B10B V5.13(AAVF.12)C0-jumbo
Router: i5-7200U appliance running pfSense.
ISP: Zen Unlimited Fibre 2 + Plusnet Unlimited Fibre Extra.

Weaver

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Re: BCM63168 Modems that Support Baby Jumbo Frames (Bridge Mode)
« Reply #297 on: March 13, 2019, 03:58:21 PM »

@bkhoe well if letmecheck.it tester says you donít have a big enough IP PDU MTU (only 1492) then some upstream device is limiting your path and you will just have to stick with that smaller MTU unless you can swap out the system that is the bottleneck.

When I was using BT 20CN ADSL and G.992.1 with PPPoEoA I could not get IP MTU 1500 (PPP PDU MTU 1500+8=1508) to work at all. This was even though I had the right modem and had all of the other required bits here. It was because the BT service just refused to handle 1508 byte long PPP frames. So I was just stuck with IP PDU MTU = 1492 like you.

The checklist is router plus modem plus internet link upstream, especially including any internet access carrier service, not forgetting any possible wholesale carrier services such as BT or TalkTalk Wholesale or others, not just your ISP themselves. In fact it will be the wholesale carrier service that matters, if any, not the ISP. Whatever is nearest to you in the chain. See Kitzís articles on internet access in this site.
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Alex Atkin UK

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Re: BCM63168 Modems that Support Baby Jumbo Frames (Bridge Mode)
« Reply #298 on: March 14, 2019, 08:18:52 PM »

A new version of the VMG3925-B10B firmware is now up on:

https://github.com/trejan/VMG3925-B10B

This contains (i) the jumbo frames patch; and (ii) a mechanism to sync the admin user password to supervisor + root.

Do you have a pre-compiled binary for this?
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Modems: 2 x VMG3925-B10B V5.13(AAVF.12)C0-jumbo
Router: i5-7200U appliance running pfSense.
ISP: Zen Unlimited Fibre 2 + Plusnet Unlimited Fibre Extra.

highpriest

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Re: BCM63168 Modems that Support Baby Jumbo Frames (Bridge Mode)
« Reply #299 on: March 15, 2019, 07:30:23 PM »

You also have to have an isp that supports MTU 1508, and their wholesale carrier if applicable and the phone line link and DSLAM or FTTC must all support it. There are web-based testing tools that will test the link all the way to / from a test server to discover MTU.

My ISP (Zen) told me once that RFC4638 is supported on all FTTC connections that use BT's network. Not sure how true that is.
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Zen | Zyxel VMG8324-B10A (with RFC4638 patch) | EdgeRouter PoE | UniFi AP AC Pro + Lite
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