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


Chronological Thread 
  • From: "Eng Se-Hsieng" <g0202512 AT nus.edu.sg>
  • To: "La Monte Henry Piggy Yarroll" <piggy AT baqaqi.chi.il.us>
  • Cc: <sctp_impl AT external.cisco.com>, <discussion AT sctp.de>
  • Subject: [SCTP-Discussion] RE: INIT from private IP address to public IP address never received
  • Date: Fri May 2 16:32:01 2003
  • List-id: SCTP Discussions <discussion.sctp.de>
>> 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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