[127197] in North American Network Operators' Group
Re: pls help about mtu setting
daemon@ATHENA.MIT.EDU (Tom Pipes)
Thu Jun 17 16:53:21 2010
X-Barracuda-Envelope-From: tom.pipes@t6mail.com
Date: Thu, 17 Jun 2010 08:39:29 -0500 (CDT)
From: Tom Pipes <tom.pipes@t6mail.com>
To: nanog list <nanog@nanog.org>, Deric Kwok <deric.kwok2000@gmail.com>
In-Reply-To: <AANLkTilPqJNGJP4oiEy1A6Uxz57vTPwBEmkaZwp2hKcF@mail.gmail.com>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
Are you authenticating with PPPoE?=C2=A0 If so, it has a maximum MTU size o=
f=C2=A01492 due to the encapsulation overhead.=20
---=20
Tom Pipes=20
T6 Broadband/=20
Essex Telcom Inc=20
tom.pipes@t6mail.com=20
----- Original Message -----=20
From: "William Herrin" <bill@herrin.us>=20
To: "Deric Kwok" <deric.kwok2000@gmail.com>=20
Cc: "nanog list" <nanog@nanog.org>=20
Sent: Thursday, June 17, 2010 8:36:00 AM=20
Subject: Re: pls help about mtu setting=20
On Thu, Jun 17, 2010 at 8:19 AM, Deric Kwok <deric.kwok2000@gmail.com> wrot=
e:=20
> My DSL company asks me to set the modem 146 2 and my old company used 14 =
92=20
> Why it is not standard 1 500?=20
Because they're wrapping your packet inside another packet that they=20
then transmit on a line with a 1500 byte MTU. The header on their=20
packet needs a few bytes, so you can't have them.=20
Regards,=20
Bill Herrin=20
--=20
William D. Herrin ................ herrin@dirtside.com =C2=A0bill@herrin.us=
=20
3005 Crane Dr. ...................... Web: <http://bill.herrin.us/>=20
Falls Church, VA 22042-3004=20
