[Sis-csi] RE: networking details

[Adrian J. Hooke]

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)
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailman.ccsds.org/pipermail/sis-csi/attachments/20070208/ae6d7a13/attachment.htm