14 Jan
2003
14 Jan
'03
3:46 p.m.
Craigh,
the problem unfortunately lives deeper than in SER -- it is
about SIP interaction with NATs. SIP advertises IP addresses
and port numbers in its messages, a technique which does not
work along with NATs. What happens is that SIP messages from
your private network get out to the public Internet, still
carry private IP addresses in it, and attempts of other call
parties to use these private IP addresses will fail.
A preview of the .11 documentation mentions these issues.
(I hope the correct link is www.iptel.org/ser/doc/, I'm offline
now.)
I'm unfortunately not aware of a method that would be able
to traverse Linux-NAT for Messengers. All of the methods
I'm aware of take some kind of NAT-support in end-devices,
SIP-support in NATs or both. They include ALG (i.e., SIP
awareness in NATs,for example intertex NATs do that), STUN
(phones' ability to "fool" NATs, for example k-phone or
snom do it), UPnP (must be supported by both phone and NAT),
manual configuration (one must have "tweakable" phones
and NATs and the ability to actually tweak both), or
"symmetric phones" (like Cisco's ATA).
-Jiri
At 11:28 AM 1/14/2003, Craig Graham wrote:
I have a Linux box at home acting as a masquerading/NAT
gateway for a few
Windows PCs, and have installed SER on there in order to use MS Messenger to
talk to people outside.
SER appears to be working in that I can get Messenger up on two PCs, connect
to SER and set up a voice connection between the two PCs. However, I cannot
connect to people offsite.
Relevant IPChains entries are
target prot opt source destination ports
ACCEPT udp ----l- anywhere anywhere any ->
5060
ACCEPT udp ------ anywhere anywhere any ->
7070:7080
I have made no changes to the default SIP configuration; it is working as
installed by the rpm package ser-0.8.10-1.i386.rpm. A browse through the
mailing list archive and through the admin guide doesn't show anything
obvious. No errors are reported to /etc/messages or /etc/syslog and serctl
moni does not show anything that looks relevant.
Does anyone have any suggestions?
--
Dr. Craig Graham, Software Engineer
Advanced Analysis and Integration Limited, UK. http://www.aail.co.uk/
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--
Jiri Kuthan http://iptel.org/~jiri/