[Mikrotik] VPLS Control Word

Chupaka chupaka at gmail.com
Fri Apr 6 09:06:21 CDT 2012


So, have you increased Ethernet MTU to something more than 1518?..


2012/4/6 <butch-mikrotik at ics-il.net>

> Right. I determined that is why I could only send 1472 in the beginning.
> However, shouldn't I be able to send larger packets when the Control Word
> will fragment and reassemble packets? I can only do 1486 now, which is 1518
> - 28 - 4.
>
> ----- Original Message -----
> From: "Chupaka" <chupaka at gmail.com>
> To: "Mikrotik discussions" <mikrotik at mail.butchevans.com>
> Sent: Friday, April 6, 2012 6:19:50 AM
> Subject: Re: [Mikrotik] VPLS Control Word
>
> In Windows, you set data payload size for ping, and header is 28 bytes
> long. So "ping -l 1472" creates packets with length = 1472 + 28 = 1500
> bytes.
>
> --
> Подпись:
> (добавляется в конце всех исходящих писем)
>
>
>
> 2012/4/6 <butch-mikrotik at ics-il.net>
>
> > As I understood it, VPLS Control Word would fragment an Ethernet packet,
> > then reassemble at the far end of the VPLS tunnel.
> >
> > Without changing any L2MTU settings, when I set ping to do not fragment,
> I
> > can only get 1472 across. I understand the overhead that VPLS has, but I
> > thought using the Control Word would resolve that issue for me.
> >
> > MPLS MTU was set to 1508. I increased it to 1518, which I understand is
> > the MTU of Ubiquiti AirOS 5.3 gear.
> >
> > I increased the L2MTU to 1518 on all interfaces I could. For some reason,
> > on my 493 and 750, I couldn't change the L2MTU, but it was higher than
> 1518.
> >
> > I did try my test again, but it still wouldn't let me pass a ping larger
> > than 1472 without fragmenting. I suspect this is because that's all
> regular
> > Ethernet allows.
> >
> > With L2MTU and MPLS MTUs set to 1518, it looks like I can traffic an MTU
> > of 1486 (using pings set to not fragment).
> >
> > I set my Windows MTU to 1518 and pinged through the MPLS\VPLS cloud.
> >
> > Does this sound right?
> >
> > What happened to control word auto fragmenting and reassembling?
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