BGP TTL check in 12.3(7)T

Thu Apr 8 20:29:56 UTC 2004

On Thu, 8 Apr 2004, Iljitsch van Beijnum wrote:
> > You have an interesting point WRT the TTL 0.  Perhaps if you receive
> > a packet with a TTL of 0 that is destined for yourself you should just
> > accept it?
> 
> The interesting thing is that packets with a TTL of 0 wouldn't 
> ordinarily be seen in the wild. A router won't forward a packet with a 
> TTL of 1 (as this becomes 0 during the forwarding process) and a host 
> that sends out packets with a TTL 0 can only expect to communicate on 
> the local subnet. (So I guess doing all of this with TTL 0 rather than 
> 255 would have been just as effective.)

Even sending packets with TTL=0 is invalid, so this is a moot point.  
Or were you proposing modifying the sending and receiving 
implementations and the IPv4/6 specifications?

>From hosts requirements for v4, for example:

            A host MUST NOT send a datagram with a Time-to-Live (TTL)
            value of zero.

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings