[Sis-csi] Finishing off the architecture book

[Scott Burleigh]

Scott, Keith L. wrote:

>All,
>
>I'd like to skip the telecon today, but we need to get the architecture
>book finished off.  I think the last thing we need is to introduce the
>'phasing' notion as we discussed in Rome, and I had the action to write
>some text to that effect.  Let's discuss over email.  I will also be
>out next week, but back the week after.
>
>
>How about the following as a short section on phasing in capability:
> 
>6	PHASED INTRODUCTION OF CAPABILITIES
>
>Moving from traditional operations to a completely IP-based system in
>one step would be jarring at best.  While the concepts of automated
>data forwarding, routing, and network quality of service are mature and
>have operational experience terrestrially, their applicability to a
>'MANET of networks' composed of orbiting satellites, orbiting relays,
>lunar outposts, and lunar transit vehicles leaves several questions.
>One of the largest open questions is how to structure a dynamic routing
>protocol to handle the changing connectivity among various spacecraft.
>We thus propose developing the protocols to populate the architecture
>presented here in three phases:
>
>1.	Simple spacecraft without in-space routing
>2.	Simplified in-space routing among cooperating spacecraft
>3.	Advanced in-space routing among multiple spacecraft
>
>In the first phase, spacecraft will not be required to use other
>spacecraft as IP routers in order to reach the ground.  This admits the
>use of layer-2 relays such as TDRSS, but greatly simplifies
>network-layer routing.  Because the spacecraft may use different ground
>stations and hence change their points of attachment to the Internet,
>routing from ground-based systems to space-based systems is an issue
>(routing toward the ground-based systems, which do not move within the
>Internet topology, is trivial).  Techniques such as MobileIP would work
>here, as would a more managed approach where GRE tunnels from the
>spacecraft's 'home' location to the correct ground station are
>configured and maintained from a mission operations center.
>  
>
Do we want to say something explicit about static routing here?  I 
suspect someone will bring up the term and wonder why we aren't using it.

>In the second phase, we will consider simple routing among spacecraft
>that are designed to know of each other's existence and where the
>in-space routing does not require a full dynamic routing protocol to
>manage connectivity.  An example of such a situation would be an
>orbiter-lander mission, where the lander could route data via the
>orbiter to reach Earth.  This situation is not much more complex than
>the first phase, since the only thing changing from the point of view
>of the terrestrial routing is the orbiter's point of attachment to the
>ground.
>
>In the third phase we will consider the general case of
>spacecraft-to-spacecraft routing where two spacecraft, A and B, can use
>each other as relays to communicate with the ground, or may communicate
>with the ground directly.  This is more complicated because spacecraft
>A's could be directly attached to the ground (via a DTE/DFE link), in
>which case packets from other locations on the ground to spacecraft A
>should be routed to spacecraft A's home (assuming some form of
>tunneling is used).  Spacecraft A's point of attachment could also be
>via spacecraft B, in which case packets to spacecraft A would need to
>be routed toward spacecraft B's home (again, assuming some form of
>tunneling from spacecraft B's home location to the current ground
>station serving spacecraft B).
>  
>
I think this explains the scenarios well.  Do we also need to say 
something about the technology development/investment that agencies will 
be biting off in order to progress through these phases?

Scott