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Re: [SCTP-Discussion] questions on sctplib1.3.1, addip, NAT


Chronological Thread 
  • From: Michael Tuexen <Michael.Tuexen AT micmac.franken.de>
  • To: Ilknur Aydin <aydin AT mail.eecis.udel.edu>
  • Cc: discussion AT sctp.de, Andreas Jungmaier <andreas.jungmaier AT web.de>, Chien-chung Shen <cshen AT mail.eecis.udel.edu>
  • Subject: Re: [SCTP-Discussion] questions on sctplib1.3.1, addip, NAT
  • Date: Tue Apr 5 23:22:02 2005
  • List-id: SCTP Discussions <discussion.sctp.de>
Hi Ilknur,

see my comments in-line.

Best regards
Michael

On Apr 5, 2005, at 22:49 Uhr, Ilknur Aydin wrote:


Hi Andreas,

I have checked the source code for sctplib1.3.1. (Please see the attached .pdf file).

My understanding is that:

1- sctpd opens a raw socket and listens for incoming IP packets with protocol number 132 (SCTP) and hands them to the correct sctp instance.
That should be correct.

2- client_socket and unix_socket are two unix sockets opened on arbitrary ports for communication between sctpd and sctp instance.
That should be correct.

could you verify 1 and 2 ?

I am wondering if stplib1.3.1 works with NATs? Consider the case
The SCTP/NAT issue is not related to any particular SCTP implementation.
There will show up internet drafts covering SCTP over NAT within the next
days.

echo_server runs on a linux machine with one interface and global ip address.
terminal (client) runs on a linux redhat 9, behind a NAT, with one interface and ip address.

I tried this configuration, it did not work. Should I somehow config NAT (to work with port 132) or sctplib ?
132 is not a port number, but the protocol id in the IP header. Normally you can run
SCTP through currently available NATs only if you configure the host running SCTP
as an exposed host. Of course this works only with single homed associations and
without ADDIP.

Finally, as far as I see, sctpd opens a routing socket and hence whenever there is a change in the routing table (route/path added/deleted) sctpd is informed by the kernel with netlink/rtnetlink of this change. And this is the way to trigger sending asconf(add/delete-ip) chunks ??
That should be correct. Using this mechanism the sctpd can process all interface
reconfigurations and it does not matter if they are initiated through manual ifconfig,
automatic DHCP (re)configuration or whatever mechanism.

Thanks,

Ilknur Aydin
DEGAS Networking Group
Dept. of Computer and Information Sciences
University of Delaware
http://www.cis.udel.edu/~aydin<port.q.to.andreas.pdf>



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