Google Summer of Code 2010 ideas

[Harti Brandt]

On Fri, 19 Mar 2010, Atis wrote:

A>On Fri, Mar 19, 2010 at 4:25 PM, Harti Brandt <hartmut.brandt at dlr.de> wrote:
A>> Hi,
A>>
A>> On Fri, 19 Mar 2010, Atis wrote:
A>>
A>> A>2) SCPS, Space Communication Protocol Standards
A>> A>This is probably my first project choice if all goes well. Space
A>> A>protocols - this sounds very cool :) and is related to my research
A>> A>interests (IP protocols over lossy networks). The first question is -
A>> A>do these protocols also have some practical value? This is not-so-new
A>> A>family of protocols, but it seems that very few implementations exist.
A>> A>On the one hand, this could be a good thing, because now there a
A>> A>chance for FreeBSD to be the first OS with open source SCPS
A>> A>implementation. On the other hand - lack of use seems to imply lack of
A>> A>importance and usefulness. The second question - is complete
A>> A>implementation of all the protocols supposed? At first glance it seem
A>> A>that e.g. SCPS Security Protocol simply duplicates the functionality
A>> A>already present in IPSec. Still, support for all protocols may be
A>> A>needed for interoperability and completeness of the implementation.
A>> A>Also, the amount of work required for this project is very unclear at
A>> A>the moment.
A>>
A>> Acctually the definition of these protocols has been taken over by CCSDS
A>> (ccsds.org). I think they are now in some of the green or blue books
A>> (cannot remember the color). There is some heavy push in the satellite
A>> community on moving towards CCSDS protocols so, for sure, there is
A>> practical value in the corresponding communities. I cannot answer the
A>> question to what extend an implementation is required. I know that we have
A>> some activity in the lower layers and that the upper layers are also used
A>> (file transfer, for example). Don't know about networking and security,
A>> though.
A>>
A>> harti
A>>
A>
A>Thanks for the reply. Looks like I will cross this project out from my list.
A>I have found that there is even a reference implementation of SCPS protocols:
A>http://www.openchannelsoftware.com/projects/SCPS.
A>It's usable from FreeBSD too, because they have implemented everything
A>in userspace, probably to achieve portability. I wonder whether it
A>would make sense to rewrite it or some parts of it (TCP "performace
A>enchancing proxy" is the interesting one) for kernel mode.
A>Theoretically, that should mean better latency, and no data copy
A>overheads, right? But then again, satellite link bandwidths probably
A>are too small to make such improvements important.

PEPs are a big issue for the satellite people. With DVB-S2 over a 40MHz 
transponder you can get 60-80MBit/s if you have good whether. With a RTT 
of 600ms or more getting TCP to an acceptable speed gets quite tricky. Of 
course not all people can afford a full transponder, but even a shared 
link DVB-S2 + RCS requires tuning...

I don't know what bitrate you can get in a Docsis system, but I would 
assume that it is comparable.

There are also a lot of commercial users of different VSAT systems, but I 
have no idea what the share of FreeBSD is in these systems.

harti