IPv4 to IPv6...

[James Knott]

Lennart Sorensen wrote:
> There is a difference between running IPv6 over IPv4 over PPP versus
> IPv6 over PPP.
>
> It does save 20 bytes per packet after all, which is not irrelevant.
>    
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.
> If you consider tunnel to mean tunner over IP, then they are right.
> Most people don't consider ppp to be a tunnel since it is point to
> point over a wire.  Tunnels tend to be between end points that are not
> directly connected.  Hence the idea of tunneling through a network.
> PPP doesn't do that.
>    
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.

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.


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