Re: Why packets (from my ISP to me) on the WAN VC side of my router are twice the size of packets on the Ethernet (and a corresponding twice as many bytes)
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On Thu, Feb 09, 2017 at 08:00:15AM -0500, rhkramer@gmail.com wrote:
> On Thursday, February 09, 2017 07:21:58 AM Dan Purgert wrote:
> > rhkramer@gmail.com wrote:
> > > I noticed today that those statistics pages do tell me the size of the
> > > MTUs
> > >
> > > On the: MTU is:
> > > WAN VC 1540
> > > Ethernet 1500
> >
> > Yuck. Hate it when people start mucking around with MTUs ...
>
> If somebody was mucking about with MTUs it tweren't me. I'm guessing those
> are set in the modem, and Earthlink provided the modem--maybe they changed
> something. (And maybe they are who I should ask about the twice as many bytes
> issue--but I guess I have to be ready to deal with the support people in
> India--IIRC from last time, I can insist on speaking to a native English
> speaker....)
This is the result of PPPoE or something similar: your packets are being
wrapped in other packets (e.g. PPP) which go between your provider and
your router), and all that goes in Ethernet (which has a payload of
1500 for "normal" frames). Of course, the wrapper's headers (in my example
above PPP) have to go somewhere, and that are the missing 60 bytes.
Needless to say, *if* it's PPPoE this is mostly superfluous these days
and just historical ballast: but I guess the people at your provider's
knowing this and able to do something about it have long been outsourced.
Yah. I'm becoming a cynic.
Cheers, nevertheless :-)
- -- tomás
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