The MPLS WG Archive

[Markus Jork <mjork@avici.com>]

> Kireeti> One could use the 'check first  nibble' hack :-( It would be neater
> Kireeti> to use the L3PID. 
> 
> Eric> Well, I wouldn't want  to have to set up a separate  TE tunnel just to
> Eric> handle the  IPv6 traffic,  so I'd recommend  the "check  first nibble"
> Eric> hack.  
> 
> Actually, there is a real  interoperability issue lurking here which we need
> to get clear on. 
> 
> In  conjunction with  php, "check  first nibble"  could mean  either  of the
> following: 
> 
> 1. The penultimate  node pops the last  label off the stack,  creates a data
>    link layer frame with IPv4 as the protocol type, and transmits the frame.
>    The receiver  of the  frame checks the  first nibble  to see what  the IP
>    version is  and treats  the packet as  IPv4 or  IPv6 depending on  the IP
>    version.
> 
> 2. The penultimate node pops the stack,  checks the first nibble to see what
>    the IP version  is, and creates a data link layer  frame with either IPv4
>    or IPv6  as the protocol type, depending  on the value of  the IP version
>    field. 
> 
> What I meant was 1; I'm not sure which Kireeti meant. 
> 

I certainly would have expected option 2!

Markus