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Re: [SCTP-Discussion] RE: INIT from private IP address to public IP address never received


Chronological Thread 
  • From: Michael Tüxen <Michael.Tuexen AT micmac.franken.de>
  • To: "Eng Se-Hsieng" <g0202512 AT nus.edu.sg>
  • Cc: "La Monte Henry Piggy Yarroll" <piggy AT baqaqi.chi.il.us>, <sctp_impl AT external.cisco.com>, <discussion AT sctp.de>
  • Subject: Re: [SCTP-Discussion] RE: INIT from private IP address to public IP address never received
  • Date: Sat May 3 22:32:00 2003
  • List-id: SCTP Discussions <discussion.sctp.de>
Are you using the hostname parameters? Which machine is the source of the
ICMP packets.

I do not believe that the NAT engine handles the SCTP packets...

Best regards
Michael

On Friday, May 2, 2003, at 16:31 Europe/Berlin, Eng Se-Hsieng wrote:

Dear all,

I have tried the following scenario using the Reference Implementation
with actual existing networks. Host A is on a GPRS network and Host B is
on a university network and is assigned a fixed IP.

Results using the University of Essen's implementatino were very
similar.

Host A (private IP 172.18.56.36) towards Host B (fixed IP
137.132.165.205)

That means you are using NAT. The NAT firewall almost certainly
does NOT support SCTP. I don't know of ANY SCTP NAT firewalls
available yet.

The following is the tcpdump output from the operator, although it's probably not the NAT machine. Two surprising things occured.

1. DNS queries of the source machine hostname (CYRILLE) with variations CYRILLE.nus.edu.sg and CYRILLE

2. for every SCTP packet sent, we noticed one corresponding ICMP packet on Ethereal, from the operator's network, with the Destination Unreachable (3) code and Host Unreachable subcode (1). Surprisingly, the Protocol Unreachable subcode wasn't received.

Would you happen to have any ideas on what these ICMP packets are for or why the DNS queries are carried out? Path MTU discovery?

Also, what are the chances of UDP encapsulation being supported on actual NATs today? We are thinking of trying that out.

Thank you.

Regards,
Se-Hsieng

14:30:39.826588 I 172.22.83.100 > 137.132.165.146: ip-proto-132 48
14:30:39.947056 I 172.22.83.100 > 137.132.165.146: ip-proto-132 48
14:30:45.826561 I 172.22.83.100 > 137.132.165.146: ip-proto-132 48
14:30:57.126663 I 172.22.83.100 > 137.132.165.146: ip-proto-132 48
14:31:21.266795 I 172.22.83.100 > 137.132.165.146: ip-proto-132 48
14:32:12.178799 I 172.22.83.100 > 137.132.165.146: ip-proto-132 48
14:33:04.639663 I 172.22.83.100.32770 > 137.132.123.4.53: 53768+ A? CYRILLE.nus.edu.sg. (36) (DF)
14:33:04.659178 O 137.132.123.4.53 > 172.22.83.100.32770: 53768 NXDomain* 0/1/0 (83)
14:33:05.719556 I 172.22.83.100.32770 > 137.132.123.4.53: 53769+ A? CYRILLE. (25) (DF)
14:33:05.724976 O 137.132.123.4.53 > 172.22.83.100.32770: 53769 Refused 0/0/0 (25)
14:33:06.399734 I 172.22.83.100.32770 > 137.132.5.2.53: 53769+ A? CYRILLE. (25) (DF)
14:33:06.405689 O 137.132.5.2.53 > 172.22.83.100.32770: 53769 Refused 0/0/0 (25)
14:33:07.279830 I 172.22.83.100.32770 > 137.132.123.4.53: 53769+ A? CYRILLE. (25) (DF)
14:33:07.285648 O 137.132.123.4.53 > 172.22.83.100.32770: 53769 Refused 0/0/0 (25)
14:33:07.999634 I 172.22.83.100.32770 > 137.132.5.2.53: 53769+ A? CYRILLE. (25) (DF)
14:33:08.859617 I 172.22.83.100 > 137.132.165.146: ip-proto-132 48



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