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Re: [SCTP-Discussion] Heartbeat


Chronological Thread 
  • From: Andreas Jungmaier <ajung AT exp-math.uni-essen.de>
  • To: discussion AT sctp.de
  • Subject: Re: [SCTP-Discussion] Heartbeat
  • Date: Tue Aug 28 15:52:01 2001
  • List-id: SCTP Discussions <discussion.sctp.de>
  • Organization: University of Essen, Germany

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Dear all, dear Sebastien,


> When I make a ping on 172.16.1.213 the client answer to the server (it is
> OK)
> But when I plug out the cable on 213 and I do the same ping, I have an
> answer from 212 (it is not OK)

That depends on the OS, as Michael said... if the IP addresses are in
the same subnet, the interface might accept the packet and the computer
have it analyzed by its IP stack. Which would accept it, since it *is* for
this endpoint, the second interface of which however is not connected.

> My problem with SCTP is that when the server do a RequestHeartbeat on
> 172.16.1.213 and the cable is disconnect, I receive a Heartbeat ACK on the
> server (see on the network), the answer may come from 172.16.1.212)

Yes, however the server will encode the interface to which the HB
is sent in the heartbeat chunk. Thus, no matter from which interface
the HB ACK comes, the server will recognize to which interface the
HB has been sent, and account for the correct one.

> I think, that in the client (in intern) there is a link between Eth0 and
> Eth1 that do this (with the ping and with Heartbeat !).

Yes, that is the way the OS seems to work.


> When you work with SCTP what kind of network do you have (I don’t have yet
> a real network to test sctp library). When you have two IP addresses, are
> they on different network (e.g. 172.16.1.212 and 130.12.4.13)

We use two machines with two interfaces, that are coupled back to back
in the most simple case (since NICs are really cheap, that should be
trivial to put up).
I.e.

+-------------+ +-------------+
| Host A | | Host B |
| | crossover | |
| 192.168.1.1 |---------------| 192.168.1.2 |
| | | |
| | | |
| | | |
| | | |
| | crossover | |
| 192.169.2.1 |---------------| 192.169.2.2 |
| | | |
+-------------+ +-------------+

If you

> What do you think about my problem ?

I do not understand why it is a problem !

As mentioned before there is a number of surprising effects
that may occur with multihoming...you may also have a look
at the latest discussion of the IETF transport area working
group mailing list...


Best regards,
Andreas

- --

- ------------------------------------------------------------------------
Dipl.-Ing. Andreas Jungmaier | _
Computer Networking Technology Group | ASCII ribbon campaign ( )
University of Essen | - against HTML email X
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