opensand team mailing list archive

[Julien BERNARD <jbernard@xxxxxxxxxxxxxxxxxxx>]

Andrei,
> Today I tried to test GSE but I got another type of errors.
>
> Testbed setup:
> Return - ATM/AAL, Forward - GSE
> GW FIFO size 2180 (see attached file TCP_CW_GSE_1_flow_GW_buff_2180)
> iperf with the option -M 1400
>
>  Log from ST:
>
> /Jul 26 13:15:17 router st: [encap] [Gse.cpp:deencapPacket():658] ERR: 
> [Gse::Context::deencapPacket] GSE deencapsulation failed (Packet is 
> too long for the deencapsulation buffer: PDU dropped), drop packet//
> //Jul 26 13:15:22 router st: [dvb_rcs_tal] 
> [bloc_dvb_rcs_tal.cpp:connectToQoSServer():1138] 
> [Tal][BlocDVBRcsTal::connectToQoSServer] service on TCP/12000 is not 
> available/
>
> Log from GW :
>
> /Jul 26 13:17:37 router gw: [encap] [Atm.cpp:deencapAtm():384] ERR: 
> [Atm::Context::deencapAtm] AAL5 packet is not valid, drop all of the 
> ATM cells in the desencapsulation context//
> //Jul 26 13:17:37 router gw: [encap] [Atm.cpp:deencapsulate():164] 
> ERR: [Atm::Context::deencapsulate] ATM desencapsulation failed, drop 
> packet//
> //Jul 26 13:17:38 router gw: [dvb_rcs] 
> [SatelliteTerminalList.cpp:setList():601] end of simulation file 
> reached, restart at beginning.../
>
> The example of CW with GW FIFO size 2500 is in the file 
> TCP_CW_GSE_1_flow_GW_buff_2500
> When I used iperf without option "-M" (file 
> TCP_CW_GSE_1_flow_GW_def_MSS) I got another errors:
>
> /Jul 26 13:51:06 router st: [encap] [Gse.cpp:deencapPacket():658] ERR: 
> [Gse::Context::deencapPacket] GSE deencapsulation failed (CRC32 
> computed does not match the received one: PDU dropped), drop packet//
> //Jul 26 13:51:06 router st: [dvb_rcs_tal] 
> [bloc_dvb_rcs_tal.cpp:connectToQoSServer():1138] 
> [Tal][BlocDVBRcsTal::connectToQoSServer] service on TCP/12000 is not 
> available/
>
> Is there any way to avoid encapsulation errors? May be you can 
> recommend iperf (or another traffic generator) parameters, OpenSand 
> parameters which were proved to be stable during your experiments 
> (packet size, ST/GW buffers, encapsulation types)?

I think the deencapsulation errors are due to loss of GSE fragments in 
the GW fifo when it is full. Don't you have "FIFO is full: drop packet" 
messages ?
There is several ways to detect these errors in the GSE library this is 
why you can get different logging messages.

When using iperf you cannot avoid these errors with small fifos because 
iperf will send as much as possible until TCP receives NACK.
If you increase the FIFO size, the TCP window may expire before the FIFO 
is full, you won't have loss but TCP will retransmit packets that may be 
still waiting in the FIFO.

I don't have good iperf parameters because I never did advanced TCP 
tests but maybe other contributors can help you on this. I recommend you 
open a new subject if you want to increase your chances to get an answer.
However, I think the parameters may considerably depend on your traffic 
profile.


> Regarding your last question about small ST buffer. When I set up ST 
> buffer equal to 10 I saw the following errors:
>
> /Jul 26 14:12:37 router st: [dvb_rcs] 
> [PhysicStd.cpp:onRcvEncapPacket():84] ERR: FIFO is full: drop packet//
> //Jul 26 14:12:37 router st: [dvb_rcs_tal] 
> [bloc_dvb_rcs_tal.cpp:onEvent():333] ERR: SF#645: frame 2: unable to 
> store received encapsulation packet (see previous errors)//
> //Jul 26 14:12:38 router st: [dvb_rcs_tal] 
> [bloc_dvb_rcs_tal.cpp:connectToQoSServer():1138] 
> [Tal][BlocDVBRcsTal::connectToQoSServer] service on TCP/12000 is not 
> available/

According to the log, the FIFO should not be to small to allow the TCP 
connection.

> What is the preferable way to upgrade OpenSand from version 1.0 to 
> 2.0? I'll need to uninstall all packages of version 1.0 and then 
> install the new ones?

Yes, removing (and purging) the whole packets is preferable because some 
things have changed. You can easily purge every opensand packet with 
"apt-get purge libopensand-* opensand-*"
For the installation of the 2.0.0 version, you can use the repository as 
explained in the installation manual [1].
As we made many modifications for the 2.0.0 version, could you please 
report any difference that could be abnormal or even improvements ?


[1] - 
http://opensand.org/support/wiki/doku.php?id=installation_manual#installation_from_packages

Regards,


--
Julien BERNARD