IPv4 to IPv6...

[Lennart Sorensen]

On Wed, Oct 06, 2010 at 11:29:33AM -0400, James Knott wrote:
> PPP adds at least 5 bytes, PPPoE adds 8.  6in4 tunnelling adds 20, for a  
> "savings" of 12 bytes in favour of PPPoE.  However, the minimum MTU for  
> IPv6 is 1280 bytes, IIRC.  In that context, there's not much of a  
> difference.

6in4 tunneling adds 20 bytes on top of what IPv4 PPPoE already needed.
The 6in4 still runs on top of PPPoE after all, so it is in addition,
not instead of.

> That is precisely what PPPoE does.  It routes your connection to the  
> ISP, independent of the underlying ethernet network, just like tunneling  
> with UDP, IP protocol 41, GRE etc.  In each and every one of these, you  
> take the IP data (v4 or v6) and encapsulate it into an added layer.

Actually PPPoE runs on layer2 ethernet and is not even routeable.  Now the
ATM layer than the ADSL modem adds is routeable as far as I know, which
is how the phone network moves the data to the ISP I believe.

> As I mentioned in another note, PPP is used for some serial connection  
> (I've configured it over T1, ISDN, SHDSL and good ol' dial up modem).   
> ADSL normally used PPPoE.

Well ADSL in this part of the world normally uses Ethernet, and frequently
(for home users at least) uses PPPoE on top of that.  Other parts of
the world often use PPPoA instead skipping the ethernet bit entirely.

-- 
Len Sorensen
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