[131865] in North American Network Operators' Group
RE: RINA - scott whaps at the nanog hornets nest :-)
daemon@ATHENA.MIT.EDU (George Bonser)
Sat Nov 6 17:52:39 2010
Date: Sat, 6 Nov 2010 14:52:26 -0700
In-Reply-To: <4CD5CCF7.8000404@brightok.net>
From: "George Bonser" <gbonser@seven.com>
To: "Jack Bates" <jbates@brightok.net>,
<nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
>=20
> He was referring to the updated RFC 4821.
>=20
> " 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."
>=20
> 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.
>=20
>=20
> 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.
