[149942] in North American Network Operators' Group
Re: Common operational misconceptions
daemon@ATHENA.MIT.EDU (Owen DeLong)
Fri Feb 17 01:46:07 2012
From: Owen DeLong <owen@delong.com>
In-Reply-To: <4F3DF2AA.4040308@necom830.hpcl.titech.ac.jp>
Date: Thu, 16 Feb 2012 22:41:43 -0800
To: Masataka Ohta <mohta@necom830.hpcl.titech.ac.jp>
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
I believe he understands just fine. However, his point (and I agree with =
him) is that
if you are behind NAT, it isn't full end-to-end functionality, even if =
it does allow some
degraded form of end-to-end connectivity with significant limitations =
which are not
present in the absence of NAT.
"I can't use your address" is inherent in the network.
"I can't use whatever port number I want on my side of the connection" =
is not.
Owen
On Feb 16, 2012, at 10:24 PM, Masataka Ohta wrote:
> Valdis.Kletnieks@vt.edu wrote:
>=20
>> No, you said specifcially that it can be restored by end system*S*
>> plural.
>=20
> Yes, end to end connectivity is restored.
>=20
> However, that end to end connectivity is restored does not
> mean your boxes can use 131.112.32.132 nor port 49734.
>=20
>> Yes, I can get one box listening. Now tell me how to get
>> the second and third boxes listening on the same port.
>=20
> Perhaps, you misunderstand how end systems behind NAT
> must interact with UPnP or something like that to be
> able to restore the end to end connectivity.
>=20
> End systems behind UPnP boxes are allocated disjoint
> sets of global port numbers, only among which, end
> systems can use as their global port numbers.
>=20
> End systems can obtain information on port numbers
> they can use through UPnP or something like that.
>=20
> Thus, there is no port number collision at the global
> side of the UPnP box.
>=20
> Similar mechanism is described in draft-ohta-e2e-nat-00.txt
>=20
> Masataka Ohta
