Tim:
The problem with mandating BER is that it drives people towards either
massively over-engineering the link or towards crossing their fingers and
hoping for sunny days. Craig Partridge notes that "we went to a variety of
industry meetings and talked about handling error rate issues and were
told, point blank, by industry reps that the satellite community thought
that was a waste of time because their (near-term) goal was to make
satellite error rates consistent with fiber". It is my suspicion that these
folk are either marketeers or incurable optimists.
The fact of life is that space links *are not* fiber links -- "when they're
good they're very very good, but when they're bad they're horrid". Many of
us feel that a more robust solution would be a local approach which
exploits the fact that we generally have very clear indicators when the
space link is going south. Providing some inter-layer signalling whereby
the space link can tell TCP "hey, that loss wasn't congestion, it was a
fade" may not be a bad idea at all. With such an approach, the TCP
retransmission control becomes an extension of the FEC, not an independent
entity.
Best regards,
Adrian J. Hooke
NASA-JPL
At 12:27 PM 98/03/28 -0500, Tim Bass (IETF) wrote:
>So, I highly suggest that this WG formalize the requirement
>that the TCPSAT group expects a certain BER over a certain
>time period (or a table of these requirements)
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