Fast Retransmission Settings

Fast Retransmission Settings

[Brandon Moreno]

Hi,

I have a general question about lksctp's fast retransmit implementation.


I am currently using lksctp-tools-1.0.6-1.i386.rpm on my server side.
After setting up an sctp connection, I am seeing proper messaging while
we run various messages over the SCTP stream. The issue that I am seeing
is when a packet is lost in the network. Presently, when a TSN is lost
on our client side, it starts transmitting sack messages with gap
reports. The server side is receiving the gap sack messages, however it
is not retransmitting the packet until the rto timer expires. Since the
rto timer increases, eventually the whole sctp association is going down
when too many gap reports are received without a retransmission.

I am curious why we are not seeing fast retransmit after 4 gap reports
are received. Is there some setting that will affect fast retransmit
being on or off?

Thanks,
Brandon Moreno
Ericsson BCAM
(972)684-1791 esn x444-1791

The author works for Telefonaktiebolaget L M Ericsson ("Ericsson"), who
is solely responsible for this email and its contents. All inquiries
regarding this email should be addressed to Ericsson. Nortel has
provided the use of the nortel.com domain to Ericsson in connection with
this email solely for the purpose of connectivity and Nortel Networks
has no liability for the email or its contents. The web site for
Ericsson is www.ericsson.com <http://www.ericsson.com/> ."

Re: Fast Retransmission Settings

[Vlad Yasevich]

Brandon Moreno wrote:
> Hi,
> 
> I have a general question about lksctp's fast retransmit implementation.
> 
> 
> I am currently using lksctp-tools-1.0.6-1.i386.rpm on my server side.
> After setting up an sctp connection, I am seeing proper messaging while
> we run various messages over the SCTP stream. The issue that I am seeing
> is when a packet is lost in the network. Presently, when a TSN is lost
> on our client side, it starts transmitting sack messages with gap
> reports. The server side is receiving the gap sack messages, however it
> is not retransmitting the packet until the rto timer expires. Since the
> rto timer increases, eventually the whole sctp association is going down
> when too many gap reports are received without a retransmission.
> 
> I am curious why we are not seeing fast retransmit after 4 gap reports
> are received. Is there some setting that will affect fast retransmit
> being on or off?

No, but there might be a bug in the kernel you are using.  Which kernel
version are you using on the server?

-vlad

> 
> Thanks,
> Brandon Moreno
> Ericsson BCAM
> (972)684-1791 esn x444-1791
> 
> The author works for Telefonaktiebolaget L M Ericsson ("Ericsson"), who
> is solely responsible for this email and its contents. All inquiries
> regarding this email should be addressed to Ericsson. Nortel has
> provided the use of the nortel.com domain to Ericsson in connection with
> this email solely for the purpose of connectivity and Nortel Networks
> has no liability for the email or its contents. The web site for
> Ericsson is www.ericsson.com <http://www.ericsson.com/> ."
> 
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-sctp" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 

RE: Fast Retransmission Settings

[Brandon Moreno]

 Hi Vlad,

Thanks for the quick reply. The kernel version we are using is
2.6.23.1-42.fc8

Thanks,
Brandon Moreno
Ericsson BCAM
(972)684-1791 esn x444-1791

The author works for Telefonaktiebolaget L M Ericsson ("Ericsson"), who
is solely responsible for this email and its contents. All inquiries
regarding this email should be addressed to Ericsson. Nortel has
provided the use of the nortel.com domain to Ericsson in connection with
this email solely for the purpose of connectivity and Nortel Networks
has no liability for the email or its contents. The web site for
Ericsson is www.ericsson.com."


-----Original Message-----
From: Vlad Yasevich [mailto:vladislav.yasevich@hp.com] 
Sent: Monday, February 22, 2010 1:42 PM
To: Moreno, Brandon ERICSSON (RICH2:MX15)
Cc: linux-sctp@vger.kernel.org
Subject: Re: Fast Retransmission Settings



Brandon Moreno wrote:
> Hi,
> 
> I have a general question about lksctp's fast retransmit
implementation.
> 
> 
> I am currently using lksctp-tools-1.0.6-1.i386.rpm on my server side.
> After setting up an sctp connection, I am seeing proper messaging 
> while we run various messages over the SCTP stream. The issue that I 
> am seeing is when a packet is lost in the network. Presently, when a 
> TSN is lost on our client side, it starts transmitting sack messages 
> with gap reports. The server side is receiving the gap sack messages, 
> however it is not retransmitting the packet until the rto timer 
> expires. Since the rto timer increases, eventually the whole sctp 
> association is going down when too many gap reports are received
without a retransmission.
> 
> I am curious why we are not seeing fast retransmit after 4 gap reports

> are received. Is there some setting that will affect fast retransmit 
> being on or off?

No, but there might be a bug in the kernel you are using.  Which kernel
version are you using on the server?

-vlad

> 
> Thanks,
> Brandon Moreno
> Ericsson BCAM
> (972)684-1791 esn x444-1791
> 
> The author works for Telefonaktiebolaget L M Ericsson ("Ericsson"), 
> who is solely responsible for this email and its contents. All 
> inquiries regarding this email should be addressed to Ericsson. Nortel

> has provided the use of the nortel.com domain to Ericsson in 
> connection with this email solely for the purpose of connectivity and 
> Nortel Networks has no liability for the email or its contents. The 
> web site for Ericsson is www.ericsson.com <http://www.ericsson.com/>
."
> 
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-sctp" 
> in the body of a message to majordomo@vger.kernel.org More majordomo 
> info at  http://vger.kernel.org/majordomo-info.html
>