I can fetch the header of websites via IPv6 but not the webpage, why?

Templin, Fred L Fred.L.Templin at boeing.com
Tue Jan 21 22:01:20 CET 2014


> -----Original Message-----
> From: ipv6-ops-bounces+fred.l.templin=boeing.com at lists.cluenet.de [mailto:ipv6-ops-
> bounces+fred.l.templin=boeing.com at lists.cluenet.de] On Behalf Of Richard Hartmann
> Sent: Tuesday, January 21, 2014 12:48 PM
> To: Tore Anderson
> Cc: Ez mail; ipv6-ops at lists.cluenet.de
> Subject: Re: I can fetch the header of websites via IPv6 but not the webpage, why?
> On Mon, Jan 20, 2014 at 11:59 AM, Tore Anderson <tore at fud.no> wrote:
> > As Erik mentions, lowering the TCP MSS will likely work around the
> > problem. You can probably do this by having the RAs your router emits to
> > the LAN advertise an MTU of 1452 to match your tunnel (which in turn
> > should make your desktop default to a TCP MSS of 1392), and/or have your
> > router rewrite ("clamp") the MSS value in TCP packets it forwards
> > to/from the tunnel to 1392.
> Unless a party has one single IPv6-enabled machine, clamping MSS on
> the gateway is probably preferable.

If you clamp the MSS to a smaller size but DO NOT advertise a small
MTU on the LAN, hosts that use RFC4821 can at a later time probe for
packet sizes that are larger that the MSS and advance the MSS size
if the probe succeeds. So, clamp the MSS but leave the MTU of the
LAN the same as that of the native link.

Thanks - Fred
fred.l.templin at boeing.com
> > Or, even better, get rid of the tunneling crap and get native IPv6. This
> > is a very common problem for IPv6 tunnels. As a web site operator I
> > would actually prefer it if people stayed IPv4-only until their ISP
> > could provide them with properly supported IPv6 connectivity. Oh well...
> Most people don't have that liberty as of right now; increasing
> adoption is arguably better, especially considering that a lot of
> people developing software need to fix part of the ecosystem.
> Richard

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