RINA - scott whaps at the nanog hornets nest :-)

Jack Bates jbates at brightok.net
Sat Nov 6 16:47:35 CDT 2010


On 11/6/2010 4:40 PM, sthaug at nethelp.no wrote:
>  For some value of "works". There are way too many places filtering
>  ICMP for PMTUD to work consistently. PMTUD is *not* the solution,
>  unfortunately.

He was referring to the updated RFC 4821.

" In the absence of ICMP messages, the proper MTU is determined by starting
    with small packets and probing with successively larger packets.  The
    bulk of the algorithm is implemented above IP, in the transport layer
    (e.g., TCP) or other "Packetization Protocol" that is responsible for
    determining packet boundaries."

It is designed to support working without ICMP. It's draw back is the 
ramp time, which makes it useless for small transactions, but it can be 
argued that small transactions don't need larger MTUs.


Jack




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