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Hi Raja,

you simply found a bug in the sctplib. I can confirm that
handling of unordered segmented data simply does not work.
Even with 2 segements (tested on MacOS X).

Andreas, can you loog at this? I guess it is a problem in the
stream engine...

See further comments in-line.

Best regards
Michael

On Jun 24, 2004, at 8:11 AM, RAJAKUMAR wrote:

Hi,

I tried out winsctplib-1-0-1 in WINDOWS XP following the
instructions given in the "Readme" file. I build the application with
Microsoft Visual Studio .NET and the application is compiled
successfully.

According to the suggestion of Mr. Michael Tuexen I am executing
echo tool as a client as well as server in two different machines. Now I

Can see through the network analyzer that association is established
between
Client and server, and also I can see one packet being reflected between
the server and the client all the time.

Using the echotool application I tested the ordered and
unordered delivery for fragmented case.

For ordered delivery from the client side I sent 4000 bytes (it
was fragmented into three DATA chunks), it was received at the server
side and the 4000 bytes is echoed back (only after re-ordering). For
ordered delivery it was working fine.

But for unordered delivery from the client side I sent 4000 bytes
(it was fragmented into three DATA chunks); it was received at the
server side. But it was not echoing back the 4000 bytes. Can you tell me
the reason behind this?

One more doubt I want to clarify with you about handling the
unordered fragmented DATA chunk.

See the scenario (for unordered delivery, fragmented) below,

1. Let us assume that two user messages each containing same
contents
"HI HELLO HOW ARE YOU"
2. From the client side, first user message was fragmented into
five chunks, for example,

"HI" contains TSN 1, SSN 0, SID 0,
unordered
"HELLO" contains TSN 2, SSN 0, SID 0,
unordered
"HOW" contains TSN 3, SSN 0, SID 0,
unordered
"ARE" contains TSN 4, SSN 0, SID 0,
unordered
"YOU" contains TSN 5, SSN 0, SID 0,
unordered

3. Now send these fragmented message to the server.

4. Let us assume that the TSN 5(lost) not reached the server
"YOU" contains TSN 5, SSN 0, SID 0, unordered

5. Now from the client side, Second user message was fragmented
into five chunks, for example,

"HI" contains TSN 6, SSN 0, SID 0,
unordered
"HELLO" contains TSN 7, SSN 0, SID 0,
unordered
"HOW" contains TSN 8, SSN 0, SID 0,
unordered
"ARE" contains TSN 9, SSN 0, SID 0,
unordered
"YOU" contains TSN 10, SSN 0, SID 0,
unordered


6. Now send these fragmented message to the server.

7. Let us assume that the TSN 6 to TSN 9 (lost) not reached the
server.


My doubt regarding this scenario is as follows, As per
the scenario the server receives TSN 1, TSN 2, TSN 3, TSN 4, TSN 10.

TSN 1 (B bit set to 1, E bit set to 0) is the first fragmented
segment of the first user message.
TSN 2 (B bit set to 0, E bit set to 0) is the middle fragmented
segment of the first user message.
TSN 3 (B bit set to 0, E bit set to 0) is the middle fragmented
segment of the first user message.
TSN 4 (B bit set to 0, E bit set to 0) is the middle fragmented
segment of the first user message.
TSN 5 (not received waiting for that ..........)

Now TSN 10 is received,,,,,,,,

TSN 10 (B bit set to 0, E bit set to 1) is the last fragmented
segment of the second user message.

How TSN 10 will be handled on the server side?.

It will just be stored. The receiver has to wait for TSN 5 to know that
the first user message is complete and can be delivered to the user.

with best regards,
Raja Kumar.



Today's Topics:

1. Re: help on winsctplib (Michael Tuexen)

--__--__--

Message: 1
Cc:
<discussion AT sctp.de>
From: Michael Tuexen
<Michael.Tuexen AT micmac.franken.de>
Subject: Re: [SCTP-Discussion] help on winsctplib
Date: Sun, 30 May 2004 23:16:46 +0200
To:
<rajakumar AT acmet.com>

You can use the echotool as a server and a client.

To run the server execute on one machine
echo_tool -V
To run the client on another machine
echo_tool -V -n 1 -d <destination_address>

Using this setup you should see one packet being reflected
between the server and the client all the time.

Best regards
Michael




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---

• [SCTP-Discussion] Doubt on handling unordered fragmented DATA chunk, RAJAKUMAR, 06/24/2004
  • Re: [SCTP-Discussion] Doubt on handling unordered fragmented DATA chunk, Michael Tuexen, 06/25/2004
    • Re: [SCTP-Discussion] Doubt on handling unordered fragmented DATA chunk, Andreas Jungmaier, 06/28/2004
      • [SCTP-Discussion] How to use socketapi and sctplib, Le Vinh Dat, 06/28/2004

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