netdev - Re: SCTP research inquiry

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Message-ID: <CAHJk9CfKKuhUbROZ1mFZLnrpnMpTBSusyY09HmNjErAs7GH4Aw@mail.gmail.com>
Date:	Thu, 4 Sep 2014 09:54:19 +0100
From:	Kostantinos Katsaros <dinos.katsaros@...il.com>
To:	Vlad Yasevich <vyasevich@...il.com>,
	Daniel Borkmann <dborkman@...hat.com>
Cc:	netdev <netdev@...r.kernel.org>
Subject: Re: SCTP research inquiry

Dear Daniel, Vlad,

Thank you for your replies.

@ Daniel
I will have a look in the methods you suggested.
However, DCE comes with net-next-2.6 and a specific version (git tag
fed66381d65a35198639f564365e61a7f256bf79). It is also tested with
linux-stable 3.4.5 but it requires some patching that is not provided
in full. So I would have to see check what are the differences between
those two and possibly apply the changes by hand.

@Vlad
With ns-3/dce you can have either ‘real’ applications like iperf, or
ns-3 applications (traffic generators) running on your nodes.
I would prefer to have iperf but I would need to use a modified
version that supports SCTP.

-- 
Konstantinos Katsaros

On Wednesday, 3 September 2014 at 21:44, Vlad Yasevich wrote:

On 09/03/2014 01:07 PM, Kostantinos Katsaros wrote:

Dear NetDev list,

I am a researcher from Univ. of Surrey. I know that this list is
mainly for developers of linux-kernel but I want to ask for some help
to understand the SCTP implementation and pointers to some aspects.

What I would actually like to do, is to modify the default SCTP
operation with respect to primary/secondary interface selection and
analyse it in simulations with NS-3. However, I haven't found an API
or some other help and I was advised to contact this list. I know that
NS-3 is capable of using linux-kernel implementations through the use
of DCE, but my issue here is in the SCTP implementation.

There a few questions I have in a basic scenario with two nodes
connected via 2 interfaces.

Are you looking for user-space API that provide the information you need?
The reason I ask is that all I've seen of dce requires you to have
an posix-like application to run on top of the protocol you want to use.
I don't know if DCE allows you directly call linux kernel functions.

Based on the above answer, I can point you more resources.

-vlad

- How can I dynamically select which of the two interfaces is primary?
Which method is responsible or should be called to switch?

- I guess that SCTP has some variable holding the estimated RTT on
each path (also used for calculating RTO). Is this accessible and how?
I would like to use this as a triggering mechanism to the switch
method above. In principle select the path with the minimum RTT.

- In a similar way of TCP Westwood (Plus), I would like to estimate
the available bandwidth and use this as trigger.

- Finally, I want to monitor the ratio (packets or bytes sent) on each
of the available paths. How can I implement such mechanism? Do I have
to implement a 'sniffer'?

I would appreciate any help, pointers, code snippets.

Regards,

Kostas
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