[e2e] local recovery or not local recovery, was: Re: Satellite networks latency and data corruption

[Detlef Bosau]

Christian Huitema wrote:
> There are pros and cons to hop by hop and end to end control. 
> 
> The nature of loss (weather events) implies that there is generally no
> correlation between the error rates of the multiple hops. In practice,
> only one hop will have a significant error rate, while the others will
> be quasi free of errors.

Could it be feasible then to insert ARQ IS-IS only around the satellite 
link, which suffer from weather events?
> 
> You will also find that a typical hop-by-hop ARQ (e.g. HDLC with
> selective rejects) results in large delays if you assume re-sequencing
> at each node, because all flows must wait for the retransmission of any
> error -- in practice, the offending hop delay becomes three times larger
> than necessary. 

O.k. But I think this must be compared to the delay seen by a pure ES-ES 
approach. If you consider a typical path drain behaviour resulting from 
packet loss, there may be short pause in the flow as well.

> 
> You could opt to not implement re-sequencing, but then you have to deal
> with end to end re-ordering. Given the satellite hop delays, the out of
> sequence packet will arrive about 450 ms after the original packet. In
> all likelihood, TCP will have triggered an end to end retransmission,
> thus negating any bandwidth advantage to hop by hop retransmission.
> 


Could this behaviour be alleviated by TCP spoofing as discussed e.g. in 
Mark Allman´s paper?

DB


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