[Sis-csi] RE: networking details

[Assi Friedman]

I would like to point out that a lot of discussion needs to go into the
physical/link layers of this migration. CCSDS as-is is has its history
significantly influenced from the STDN era. This history does not make it
very conducive to IP in space. Migrating to IP will require us to address
the physical/link layers. As is, CCSDS had the foresight to acknowledge that
there will be a future need to readdress this, but the future is now
present. I try to start at the side closest to the hardware, since protocol
stacks can be reloaded, hardware boxes are much harder to reload.

Assi

 

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 Assi Friedman - Innoflight Inc. 
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  _____  

From: sis-csi-bounces at mailman.ccsds.org
[mailto:sis-csi-bounces at mailman.ccsds.org] On Behalf Of Adrian J. Hooke
Sent: Thursday, February 08, 2007 11:34 AM
To: CCSDS Cislunar Space Internetworking WG
Subject: Re: [Sis-csi] RE: networking details

 

Maybe this is a good time to take stock of where we are. I think that it is
fair to say that there is broad international agreement that:

1. We can see future requirements for the emergence of a more networked
approach to space communications.
2. Accordingly, we need to develop a migration strategy that leads us
towards more capable networking protocols.
3. IP has a role in that migration strategy. 

Beyond those elements of consensus, it's not clear that there is much
agreement on how or when to initiate change. 

At 06:09 AM 2/8/2007, Keith Hogie wrote:



  Moving to spacecraft using Internet protocols a change to the whole space
communication concept.  


No, it's not a change to the space communication *concept*; it's a change to
the space communication *infrastructure*. If we go there in one big bang, it
will certainly change a lot of infrastructure. But is it change for the sake
of change, or change because we simply can't operate another day in space
without an all-IP system?




Now we are changing the space end so that selected Internet technologies and
be used end-to-end.


Why? There are plenty of cases where selected use of Internet technologies
is beneficial *without* using them end-to-end.




If we accept that we want and need a routed infrastructure in space in the
future, why wouldn't we want to start putting it in place with missions
currently being built. 


Well, cost ands risk *might* be among the reasons. Why do the NASA
Exploration vehicles currently being built look so much like Apollo?




If we start launching some of our future systems with no routed IP, is there
a clean path for them to "migrate" and be full participants in the future
network. 


Turn that around. If we start launching *some* of our future systems
exclusively with routed IP, is there a clean path for them to be full
participants in the future international community of missions that see no
need for it?

Nobody's arguing that there won't be an increasing need for portions of the
international space mission support infrastructure to adopt more powerful
routing technologies. When you need IP and IP works, you should use IP. But
does that mean that *everything* has to become IP-based, all at once? And
yes, there's a migration path: it's called international space
standardization in general and in particular it's called a Virtual Channel.
It means that you can run part of your system using existing infrastructure,
in parallel with part of your system using IP-based approaches. Change the
mix of traffic on the VCs and you can migrate with hardly any impact.




Isn't it more beneficial to take this opportunity to deploy a whole fleet of
new systems and start the first systems with the technologies we want to end
up with.


This far out, how do you know where you will end up? Isn't it more
beneficial to take the opportunity to deploy new systems that are based on
the technologies that we use now, which already have the built-in capability
to evolve towards IP or any other future routed approach? 




Starting new missions with IP technologies also means that they can start
benefiting from the greatly increased options for early testing between
various subsystems. Systems don't need to wait until final integration and
test to start doing interoperability tests.  With IP interfaces built in,
systems can start running basic interface and functionality tests while they
are still at their manufacturing locations.  This can be done years earlier
than normal I&T and find
basic problems much earlier when they are easier and cheaper to fix. 


This claim is so sweeping that it deserves its own discussion thread.
Suffice to say that there are many people on this list who strongly doubt
that the impacts on the real world of space mission I&T are anywhere near
that rosy.




I agree that we don't need to pin down all the details now, but we do need
to have some sort of plan on how things will roll out.  


We all agree with that.




We may not need all the network routing capabilities for 10 years but there
seem to be lots of benefits from starting to make use of end-to-end Internet
technologies now.


Of course: that's why we formed this Cislunar Space Internetworking working
group. But as an international standardization working group, it should
develop a pragmatic and consensus strategy for how it proposes to move the
international space community forward. We need a clear picture - agreed by
all partners - that shows why we need to change, when we need to change and
how we need to change.

///adrian



Adrian J. Hooke
Chairman, CCSDS Engineering Steering Group (CESG)

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