> > 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
That is also somewhat mitigated in that it operates in two modes. The first mode is what I would call "passive" mode and only comes into play once a black hole is detected. It does not change the operation of TCP until a packet disappears. The second method is the "active" mode where it actively probes with increasing packet sizes until it hits a black hole or gets an ICMP response.
