Dicom and NAT; Does NAT work with Dicom?

Dicom and NAT; Does NAT work with Dicom?

Post by B Smit » Tue, 28 Nov 2000 04:00:00

Is there any internal ip data inside the Dicom exchanges, or is ip data
restricted to the ip envelope?

Any reason NAT will break the Dicom protocol?


Dicom and NAT; Does NAT work with Dicom?

Post by C Kronenwette » Tue, 05 Dec 2000 04:00:00

There are implementations of Dicom such as the Agfa Impax which require an
Oracle database connection to be established through the firewall before
anything will begin to work. Unless the firewall has enabled a protocol to
properly handle such Oracle connections, failure is certain (the workstation
will not even start  running).
If the Dicom implementation attempts to check the attempted association
coming from a system on the other side of a NAT enabled firewall against its
own hosts file it may also fail to allow the connection.  If the
implementation is, on the other hand, fairly braindead as to which
connections it will accept, you may be successful.  Your actual mileage may

Quote:> Is there any internal ip data inside the Dicom exchanges, or is ip data
> restricted to the ip envelope?

> Any reason NAT will break the Dicom protocol?


1. Multiplayer when connected via router with NAT does not work

Hello FS2000 users:
Time ago, someone posted he encountered problems when he try to run
FS200 in multiplaying mode using a local router that use (possibly) NAT
I replayed that due to the method used by a router with NAT, problem can
arise from that. I was not sure on that matter that time.
Now I can reply YES. FS2000 can not run in multiplayer mode if we use a
router to gain acces to internet via an Internet Service Provider that
use a dynamic IP address delivery (dynamic allocation) to his customers.
Even if we demand for an static IP address, problems remain. Static or
dynamic IP allocation is not the matter but the configuration we use in
our local (intranet) network.
I use NAT (Network Address Translation) in my router because I have only
one legal IP address while in my local net (ethernet) I have 4 hosts
with 4 intranet address. My legal IP address is the one used by my
router for each outbound packet sent to internet while it use locals
address for each inbound packet comming from internet. Obviously,
translation address take place in my router (a Linux box) using vector
(address) tables.
So I was unable to reach to multiplayer server or I was unable to
receive data from the multiplayer server (more truly).

To confirm my suspect, I installed a copy of FS200 (sorry Bill Gates) in
another host of my home intranet and...Hellas I can see the other plane.
When configured, I give in both hosts the IP address they have in the
intranet. I see the callsign over each respective plane landed at Meigs
at 25 meters each from the other. Curiouslly each plane (really each
program) see the other plane moving forward and backward even with
parking brake armed???. May be Microsoft can explain this abnormal

NAT does not work well in some circumstances. As I know, programs based
on UDP are not well suited to be used with NAT because are not
connection oriented. Translation address tables are constructed based on

each connection (TCP sockets). So I suspect FS2000 use UDP paradigma.

To play in multiplayer (or to execute multi...something) the best
tecknology is multicast. Does FS2000 use multicast?.
It should be nice to know how FS2000 manage communication to outer
world. It should be nice to know how messages from FS2000 are mapping in
(TCP or UDP?) as well as the port used (ephemeral or well known port?).
All this information and many more must be done by the FS2000
manufacturer as other purchase contract are done in the comercial world.
This information may be included as technical reference manual available
(free or not) for who interested, to make FS2000 more enjoyable an
runable in differents environments (like multiplay from intranet sites).

If someone have some of this information pls to posted here and we will
discuss on it. In meantime I will use an "snifer" to monitor traffic in
my intranet, trying to discover what's going on with IP datagrams. If I
success, it
will be posted here. No permission is needed from Bill Gates. Does it?

    Celestino Okenve

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