Re: NAT-PMP not honoring requested external port
Re: NAT-PMP not honoring requested external port
- Subject: Re: NAT-PMP not honoring requested external port
- From: james woodyatt <email@hidden>
- Date: Mon, 9 Jun 2008 22:44:52 -0700
On Jun 9, 2008, at 19:35, Jens Alfke wrote:
On 9 Jun '08, at 6:00 PM, james woodyatt wrote:
It sounds like you're trying to establish a hairpinned connection
through the NAT-PMP mapped port.
No; if you re-read my example, the destination peer was outside the
NAT. My question refers to what port number the NAT assigns to an
_outgoing_ connection where the originating internal host/port match
an existing mapping.
I'm sorry to have gotten confused. I think I see what's happening now.
What I expected to happen is that peer sees an incoming connection
from [ABS public address], port PUB. I.e. the ABS does the same
PRIV->PUB port mapping for the outgoing connection.
Instead, the peer sees a random port number. Is that the expected
behavior? (The NAT-PMP spec doesn't seem to address this.)
I think it's fair to describe this as suboptimal behavior on the part
of AirPort. You may be interested to note that there isn't anything
in <http://tools.ietf.org/html/draft-ietf-behave-tcp> about it,
either. That's unfortunate, because the behavior you're describing
goes against the spirit of REQ-2, though it doesn't actually violate
the letter. Simultaneous open still works-- it just doesn't work as
well as it should because there is an unnecessary ambiguity in what
public port is used for the connection.
It seems like the BEHAVE working group is the appropriate place to
discuss your expectations of the general case of NAT behavior. I've
filed an enhancement request for the AirPort firmware to address this
issue, but it would be nice if every NAT had predictable behavior in
this regard. Sadly, they don't.
--
james woodyatt <email@hidden>
member of technical staff, communications engineering
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Macnetworkprog mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden