[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 
architecture, http://www.ipnsig.org.

Best regards
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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