[Sis-csi] IPv6?
Chris.Taylor at esa.int
Chris.Taylor at esa.int
Mon Jun 11 03:32:02 EDT 2007
Keith, you misunderstand my concerns, I guess I haven't expressed them very
well but some of discussion surrounding IP makes me see red .
I have no problem at all with the ordered introduction of IP to complement
the existing standards. In fact, I've already contributed to it's use on ESA
projects and we too are running pilots using IP for remote integration. My
concern is with the hype surrounding IP and it's proffering as the panacea to
solve all our problems, often to the detriment of the existing
recommendations. The fact is, the existing recommendations provide a rich
set of services that are able to incorporate the use of IP with little impact
and for this they should be complemented, not criticised. When I see moves to
replace the present fixed length framing structure by HDLC just so we can use
a commercial Cisco router, I take issue.
We could introduce IP tomorrow with little impact out existing links (as long
as we use currently preferred options for link multiplexing) but would it
solve all problems - no. We would still have the same issues with our deep
space links where manual store and forward operations are still the order of
the day. We would still have a lack of well defined flight-based X-support
services as with the current Mars programme. In itself, the introduction of
IP essentially brings us a larger address space and use of a commercial
protocol but not much more than that.
My reference to ephemeral commercial standards was not directed at IPv6,
which I believe will remain stable for decades. But as part of the IP hype
and the criticism of CCSDS recommendations it has also been suggested that we
should take existing commercial standards, especially in the area of
wireless. I just want to stress some caution here as the market is changing
so quickly that no one really knows what will be baseline in 10 years, or
even 2 or 3 years for that matter.
In summary, I take the position that CCSDS should be moving towards adoption
of IP along side existing protocols in a controlled and evolutionary manner.
We should be stressing the benefits of IP without hiding the fact that it
does not, in itself, solve all issues. We should also make it clear that the
difficulties we face for future exploration missions are not caused by the
present CCSDS recommendations but are inherent to the scenario of long delays
and time disjoint, often bandwidth constrained, links.
Regards,
//ct
Keith Hogie
<Keith.Hogie at gsfc.
nasa.gov> To
Chris.Taylor at esa.int
11/06/2007 07:16 cc
Lloyd Wood <L.Wood at surrey.ac.uk>,
sis-csi-bounces at mailman.ccsds.org,
Please respond to CCSDS Cislunar Space Internetworking
keith.e.hogie at nasa WG <sis-csi at mailman.ccsds.org>
.gov Subject
Re: [Sis-csi] IPv6?
Chris,
For many years we have had missions begging for ways for their
spacecraft to communicate with each other. The CCSDS addressing
structure doesn't support that. We also have missions that have been
built and tested by using IP connectivity to support basic interface
testing across IP networks long before final mission integration. Using
IP technologies is not just about the operational phase. There are many
benefits starting in the earliest phases of the mission design. There
are also many groups outside the civil space community that are using IP
for their space communication systems because they see it as the faster,
better, and cheaper solution.
Many of us are concerned about where IP will be 15 years from now and
that is why many people are deciding to start their space systems using
IPv6. We know that IPv6 will be around 15 years from now and IPv4 will
be fading.
As far as the number of addresses that will be needed 15 years from
now, I don't really know. But once someone decided that 640 KB of
memory would be plenty for a computer. They quickly learned the error
of their ways. We may not need millions of addresses, but if they were
available it's possible that missions would find ways to make use of
them. History is full of innovative people finding ways to use
technologies in ways that were not initially envisioned.
Is it really proper to say that we currently know everything and have
the perfect solution for space communication and that nothing should
change for the next 15 years?
You mention that IP obscures the real issues that need to be tackled.
Can you be more specific on what you think those issues are?
Thanks,
Keith Hogie
Chris.Taylor at esa.int wrote:
> I am well aware of the emerging initiatives in DTN and the fact that by
> introducing another layer of bundling we could resolve some of the issues
> with IP. I'm also well aware that we can fly a commercial router just for
the
> benefit of sending point to point traffic from a payload to ground.
Something
> we can do anytime with existing software and at zero cost. But this is not
my
> point. I'm asking what we really need in the next 15 year or so period, a
> period in which the commercial terrestrial standards will evolve out of all
> recognition and many (most) of the standards used today will have long
gone,
> as will the commercial support and components needed for long duration
> missions. Just how many IP addresses are we going to need for the flight
> infrastructure in place at the time - 4, 5? Wow. Do we really need a fully
IP
> routed flight architecture to support a few IP cognizant nodes.
>
> I would contend that the recent pushing of IP in the context of exploration
> is essentially hype. Dangerous hype at that, as it obscures the real issues
> that need to be tackled to resolve existing problems and agree an
> evolutionary path forwards. Until I see a realistic configuration (not the
> futuristic, commercially driven nonsense) of what we can expect in 15-20
> years, and set of accompanying comms requirements that justify the need for
> IP, I will continue to doubt the goals, objectives and understanding of the
> IP exponents.
>
> //ct.
>
>
>
> Lloyd Wood
> <L.Wood at surrey.ac.
> uk>
To
> Sent by: Chris.Taylor at esa.int
> sis-csi-bounces at ma
cc
> ilman.ccsds.org CCSDS Cislunar Space
Internetworking
> WG <sis-csi at mailman.ccsds.org>
>
Subject
> 08/06/2007 19:56 RE: [Sis-csi] IPv6?
>
>
>
>
>
>
>
>
>
>
> At Friday 08/06/2007 17:45 +0200, Chris.Taylor at esa.int wrote:
>
>> Just to stir things up a bit, has it really been decided that we will use
IP
>> on our future links. From the discussion it seems like a done deal but our
>> ESA studies and opinion is that IP doesn't bring us much other than a bit
>> more address space that we probably don't need anyway. Rather than
discuss
>> the merits of IPv4 and 6 it may be more productive to critically examine
the
>> application of IP to see how it may be employed or not. I should say that
I
>> have no particular issue with the use of IP its just that I think the
>>
> problem
>
>> is much wider and by concentrating on v4/v6 there is a danger of missing
the
>> real problems - IP doesn't work on links that have disjoint connectivity
>>
>
> Actually, IP works just fine on links with disjoint connectivity, as large
> amounts of delay/disruption tolerant networking work and mobile ad-hoc work
> by many people have shown. For example, we've developed our own
IP/UDP-based
> transport protocol for moving files over disjoint links, and there are
other
> protocols that work over IP in these environments. TCP won't work well, but
> then TCP's operational range is surprisingly limited. TCP is not IP.
>
> See:
> http://www.ee.surrey.ac.uk/Personal/L.Wood/dtn/
> ftp://ftp-eng.cisco.com/lwood/dtn/README.html (IE users: passive ftp must
be
> ON in Tools/Options... Advanced tab)
> - Saratoga: a Delay-Tolerant Networking convergence layer with efficient
link
> utilization, Lloyd Wood, Wesley M. Eddy, Will Ivancic, Jim McKim and Chris
> Jackson, submitted to the Third International Workshop on Satellite and
Space
> Communications (IWSSC '07), September 2007.
> - Saratoga: A Convergence Layer for Delay Tolerant Networking, Lloyd Wood,
> Wesley M. Eddy, Will Ivancic, Jim McKim and Chris Jackson, work in progress
> as an internet draft, version -00 submitted to the IETF, May 2007.
>
> For a detailed discussion of how IP can be used in the disjoint environment
> of intermittent space links, see:
> http://www.ee.surrey.ac.uk/Personal/L.Wood/cleo/
> ftp://ftp-eng.cisco.com/lwood/cleo/README.html (IE users: passive ftp must
be
> ON in Tools/Options... Advanced tab)
> - Using Internet nodes and routers onboard satellites, Lloyd Wood, Will
> Ivancic, Dave Hodgson, Eric Miller, Brett Conner, Scott Lynch, Chris
Jackson,
> Alex da Silva Curiel, Dave Cooke, Dan Shell, Jon Walke and Dave Stewart,
> special issue on Space Networks, International Journal of Satellite
> Communications and Networking, vol. 25 issue 2, pp. 195-216, March/April
2007
> - particularly section 14.
>
> The primary argument for using IP imo is that you can just reuse
> well-developed commercial technologies without reinventing the wheel,
> minimising your overall software development and testing costs.
>
> (How much is esa spending on developing Spacewire? IP already runs well
over
> LVDS HDLC serial links, and is used on them in space.)
>
> regards,
>
> L.
>
>
> <http://www.ee.surrey.ac.uk/Personal/L.Wood/><L.Wood at surrey.ac.uk>
>
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