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Re: [SCTP-Discussion] FW: SCTP...


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  • From: Michael Tuexen <Michael.Tuexen AT micmac.franken.de>
  • To: Shetty K Manjunatha-A1465Z <A1465Z AT motorola.com>
  • Cc: discussion AT sctp.de, ajung AT exp-math.uni-essen.de
  • Subject: Re: [SCTP-Discussion] FW: SCTP...
  • Date: Fri Jan 2 21:37:03 2004
  • List-id: SCTP Discussions <discussion.sctp.de>

Manjunatha,

SCTP allows the peer to 'withdraw' an acknowledgement when it is
still above the cumulative ack. From RFC 2960:

iii) If the SACK is missing a TSN that was previously
acknowledged via a Gap Ack Block (e.g., the data receiver
reneged on the data), then mark the corresponding DATA chunk as
available for retransmit: Mark it as missing for fast
retransmit as described in Section 7.2.4 and if no retransmit
timer is running for the destination address to which the DATA
chunk was originally transmitted, then T3-rtx is started for
that destination address.

So there is no chance to do free the memory for GAP acked chunks when you
want to be compliant with RFC 2960.

The only think I can suggest if memory is a problem is that you write
a memory management for the sctplib and delete all calls to malloc by using
some sort of pools (mbufs or whatever...)

Best regards
Michael


On 2. Jan 2004, at 20:58 Uhr, Shetty K Manjunatha-A1465Z wrote:

Micheal,
We are using the VxWorks and we don't have unlimited buffers. Please let me know if you have any other alternatives.
Is it not a good idea to drop the messages acked by the peer even though one of the lower TSN is not yet acked?

Pls advise

Manjunatha Shetty K
Phone: 1-847-632-2503



-----Original Message-----
From: Michael Tuexen
[mailto:Michael.Tuexen AT micmac.franken.de]
Sent: Friday, January 02, 2004 12:56 PM
To: Shetty K Manjunatha-A1465Z
Cc:
discussion AT sctp.de;

ajung AT exp-math.uni-essen.de
Subject: Re: [SCTP-Discussion] FW: SCTP...


Manjunatha,

from the chargen_server.c:

SCTP_getAssocDefaults(sctpInstance, &instanceParameters);
instanceParameters.maxSendQueue = SEND_QUEUE_SIZE;
SCTP_setAssocDefaults(sctpInstance, &instanceParameters);

This shows how you limit the sendqueue. If you do not do this, the
sendqueue
is unlimited. It is the same as setting it to 0, the default.

The implementation works as follows:
The sctplib always uses malloc if it needs memory. Using this strategy no send call will ever block. To provide this feature (needed for the
chargen
server, for example) we introduced the sendqueue limit. It is only a
counter
which supervises the number of chunks queued. But it is no real memory
management.

I hope this clarifies things a bit
Michael

On 2. Jan 2004, at 18:08 Uhr, Shetty K Manjunatha-A1465Z wrote:

Micheal,
Thanks for the reply.
What is this option "sctplib without any limits"? Could you please
provide me more information on this? You mean we need to increase the
size of the stack? Or some thing else?
Please advise.

Manjunatha Shetty K
Phone: 1-847-632-2503



-----Original Message-----
From: Michael Tuexen
[mailto:Michael.Tuexen AT micmac.franken.de]
Sent: Thursday, January 01, 2004 12:04 PM
To: Shetty K Manjunatha-A1465Z
Cc:
ajung AT exp-math.uni-essen.de;

discussion AT sctp.de
Subject: Re: [SCTP-Discussion] FW: SCTP...


Using the limited queues we are limiting the resources the sctplib is
using. Since all chunks have to be stored until the cumulative TSN
acks passes the TSN of the chunk we have to store TSN10 to TSN100.
This behaviour is required by SCTP.

You can use the sctplib without any limits. Then you can send as much
as you like (and memory is available at the host).

Best regards
Michael

On 1. Jan 2004, at 1:43 Uhr, Shetty K Manjunatha-A1465Z wrote:

All,
Any body can help in answer the question below?

Manjunatha Shetty K
Motorola Inc
Phone: 1-847-632-2503



-----Original Message-----
From: Shetty K Manjunatha-A1465Z
Sent: Wednesday, December 31, 2003 5:18 PM
To: 'Michael Tüxen'
Cc: Shetty K Manjunatha-A1465Z
Subject: RE: SCTP...


Micheal,

I have a quick question on SCTP stack. Quick response would really
helpful. If I am transmitting data from TSN 1 to TSN 200. But I am
getting SACK or ACK for all the frames other than say TSN 10. I am
pumping the data at the higher rate. Will my SEND Q will store all
the msgs with TSN value above 10 till I get ACK for this msg or it
will clear off all the msgs from the SEND Q which got ACK from the
PEER.

Scenario:
SCTP LOCAL SCTP PEER

Msg(TSN1) ==================>ACKED back Msg(TSN2)===================>
ACKED back .......................... .....
Msg(TSN10) ===================> NOT RECEIVED (Say Dropped) so no ACK.
..... Re transmission Msg(TSN10)====================> Dropped, no ACK
..... Msg(TSN99)====================> ACKED
Msg(TSN100)===================>ACKED
Retransmission Msg(TSN10)===============> ACKED Now!!!!!

Now the question is what happens to SEND Q? Will store all the
msgs(TSN 11 to TSN 100) in the SEND Q till it gets the ACK for TSN 10
or not? Please clarify me.

In the heavy traffic condition we are seeing that Send Q is getting
full! Your explanation on handling of SEND Q would be very helpful.

Manjunatha Shetty K
Phone: 1-847-632-2503



-----Original Message-----
From: Michael Tüxen
[mailto:Michael.Tuexen AT micmac.franken.de]
Sent: Tuesday, September 09, 2003 2:17 PM
To: Manjunatha Shetty
Subject: Re: SCTP...


Hi,

I can not remember that Bug. We are currently testing 1.0.0 of the
sctplib for release and I will test that this works with the released
version. You report is very good, we can reproduce the scenario.

Do you have any further problems?

Best regards
Michael

On Tuesday, Sep 9, 2003, at 15:53 Europe/Berlin, Manjunatha Shetty
wrote:

Thanks for the quick response,

We are facing problems with sctp, Problem description is mentioned
below.

Can you please help in this regard. We are using SCTP stack which
has SCTP Freeware..

I could see in some FAQ present in SCTP discussion email list,where
there are some problems in the area of re-transmission.


Problem Sequence:

SCTP Peer SCTP
---- ---------

DATA REQ (TSN 10)
-------------------------------------------> getting dropped
DATA REQ (TSN 11)
------------------------------------------->
SACK (TSN 11, GAP TSN 10)
<------------------------------------------
DATA REQ (TSN 10)
------------------------------------------> Re-Transmission, getting
dropped
DATA REQ (TSN 12)
------------------------------------------>
SACK (TSN 12 GAP TSN 10)
<------------------------------------------
DATA REQ (TSN 13)
------------------------------------------>
SACK (TSN 13, GAP TSN 10)
<------------------------------------------
DATA REQ (TSN 14)
------------------------------------------>
SACK (TSN 14, GAP TSN 10)
<------------------------------------------

After the first retransmission there is no re-transmission, even
though the SACK is indicating that there is a missing TSN 10.

I really appreciate if could help me out in this regard. Whether
this is a known bug or not?

Thanks,
Manju


-----Original Message-----
From: Michael Tüxen
[mailto:Michael.Tuexen AT micmac.franken.de]
Sent: Tuesday, September 09, 2003 6:06 PM
To: Manjunatha Shetty
Subject: Re: SCTP...


Hi Manju,

there is no such repository. Internally we use CVS but it not fix by
fix...

Best regards
Michael

On Tuesday, Sep 9, 2003, at 10:39 Europe/Berlin, Manjunatha Shetty
wrote:

Would like to know is there any repository where all the bug fixes
information are stored?
 
Thanks & Regards,
Manju

-------------------------------------------------
| Manjunatha Shetty K.
| Wipro Technologies,
| Creator 4th Floor,
| International Tech Park,
| Whitefield Road.
| PH: 8411990     Extn: 1003
-------------------------------------------------

 



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