[Sis-csi] RE: networking details
Edward Greenberg
edward.greenberg at jpl.nasa.gov
Fri Feb 9 16:27:23 EST 2007
Dave, You are correct and this stuff that is flying around is just
religious ferver. I have been trying to get a picture of the in
space networking needs for Constellation for a long time and have yet
to see anything that is operationally blessed. We can talk about
routing desires for ever but what are the real requirements. Are
things going to take random walks in space or are missions and
hardware movements going to scheduled and exhaustively tested before
anything moves. Is automated address management needed, or is it
over kill for the first 30 years of the program? And If the
environment in the later years of the program is centered around the
Moon or Mars, how will the delays effect the operational use of UDP.
Deep space missions have been forced to use store and forward
operations for years, and the protocols supporting those missions are
focus for that environment. So can anyone supply an operational
scenario that requires the advanced networking features that IPv6
brings to the table.
At 2:40 PM -0500 2/9/07, Dave Israel wrote:
>Before another whole thread starts about link layer issues again,
>can somebody explain why the link layer matters are so critical at
>this time that we keep spending time and energy debating them,
>instead of working on the many networking issues that need to be
>resolved? I'd rather see that discussed, than any arguments about
>any link protocols.
>
>It seems to me that the real need is to get missions to start
>evolving to networking based communications first. Once that
>starts, optimization may follow. How much time have we lost in "IP
>versus CCSDS" debates, when in reality there really isn't mutually
>exclusive decision required?
>
>Dave
>
>At 02:20 PM 2/9/2007, Keith Hogie wrote:
>
>>Adrian,
>>
>> A major concern is what you mentioned below about Virtual Channels.
>>Those are a CCSDS data format that was developed 20 years ago and was
>>a fine solution for the time. It sounds like you are proposing that
>>that VC data structure be maintained as the underlying format for civil
>>space programs for the next 20 years. Does it make sense to
>>plan on extending the life of a 20 year old protocol format for
>>20 more years or is it time for an upgrade or replacement of
>>the VC format.
>>
>> During the last 20 years lots of protocols have come and gone and
>>been replaced by new ones that better suit users current needs. The
>>commercial world primarily uses Frame Relay and DVB over thousands
>>of satellite links supporting tens of thousands of users. They have
>>created a very large commercial market of internationally
>>interoperable products with much better layering and function
>>support than the basic CCSDS VCDU.
>>
>> So it seems that a major question is whether the current VC
>>structure is the best structure to use for the future or is it
>>time to upgrade to more current solutions at that level?
>>
>> As far as future IP missions interoperating with future missions
>>that see no need for IP, that's fine but then they don't have any
>>plans to communicate with future IP missions anyway. Ground stations
>>can still support both IP and non-IP formats as many do already.
>>The facilities, antennas, transmitters, and receivers still need
>>to do their jobs just the same. The real question is whether the
>>bits coming off the space link go into a CCSDS specific box that
>>processes VCs or if the bits go into a commercial router. This
>>is not a major change to the infrastructure. Yes, it is a change,
>>but the communication world has changed drastically over the last
>>20 years and we need to decide if it is time for the civil space
>>community to catch up or if it wants to keep doing its own thing.
>>
>>Keith
>>
>>
>>Adrian J. Hooke wrote:
>>
>>>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.
>>>>
>>
>>snip
>>
>>>>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.
>>>
>>
>>----------------------------------------------------------------------
>> Keith Hogie e-mail: Keith.Hogie at gsfc.nasa.gov
>> Computer Sciences Corp. office: 301-794-2999 fax: 301-794-9480
>> 7700 Hubble Dr.
>> Lanham-Seabrook, MD 20706 USA 301-286-3203 @ NASA/Goddard
>>----------------------------------------------------------------------
>>
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>______________________________________________________________
>Dave Israel
>Leader, Advanced Technology Development Group
>Microwave & Communication Systems Branch
>NASA Goddard Space Flight Center Code 567.3
>Greenbelt, MD 20771
>Phone: (301) 286-5294 Fax: (301) 286-1769
>E-mail: dave.israel at nasa.gov
>
>"Without deviation from the norm, progress is not possible." -Frank Zappa
>
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