[e2e] TCP in outer space
Adrian J. Hooke
adrian.j.hooke at jpl.nasa.gov
Tue Apr 10 09:31:05 PDT 2001
At 07:01 AM 04/10/2001 +0900, Fred Baker wrote:
>As to whether another protocol could be used or is in use, yes, there are
>other protocols involved, but not TCP variants. http://www.ccsds.org
>describes the architecture.
Much of the work at http://www.ccsds.org focuses on the wireless data link
connecting a remote spacecraft to a supporting ground station. The CCSDS
space link protocols include a mix of powerful FEC and - for the forward or
"command" path, where absolute reliability is essential - link layer ARQ.
Flowing through the CCSDS space link are the end-to-end protocols that we
use to communicate with remote end systems in space. In short delay
environments - perhaps out to Lunar distance - we can use the native
Internet suite, with suitable tuning as noted by Mark Allman.
Alternatively, CCSDS has extended and adapted the Internet suite to better
match the challenged space environment; these extensions are known as the
"space communications protocol specifications" or "SCPS" and can be found
at http://www.ccsds.org/blue_books.html. The four key documents are CCSDS
713.0-B-1, SCPS Network Protocol; CCSDS 713.5-B-1, SCPS Security Protocol;
CCSDS 714.0-B-1, SCPS Transport Protocol; and CCSDS 717.0-B-1, SCPS File
Protocol. As noted by Eric Travis, splitting the transport connection at
the ground station can realize some fairly spectacular performance gains.
More detailed information is available at http://www.scps.org.
Beyond Lunar distance, chatty protocols give way to more taciturn
communications owing to the large propagation delays. The CCSDS File
Delivery Protocol that is currently under development (CCSDS 727.0-R-4 at
http://www.ccsds.org/red_books.html) is a file-based Application having its
own non-chatty built in reliability mechanisms. We regard it as an early
progenitor of the custodial, store and forward "Bundling" approach that we
are examining with Vint Cerf as part of the Interplanetary Internet
Adrian J. Hooke
Manager, DARPA-NASA InterPlaNetary Internet (IPN) Project
Jet Propulsion Laboratory,
Telecommunications and Mission Operations Directorate
M/S 303-400, 4800 Oak Grove Drive
Pasadena, California 91109-8099, USA
+1.818.354.3063 voice; +1.818.393.3575 fax
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