Re: Delivery Times .... was Re: Bandwidth, was: Re: Free Internet & IPv6

Also allow for "partially reliable" delivery as in SCTP.
On Dec 26, 2012 6:03 PM, "Detlef Bosau" <[email protected]> wrote:

> Am 25.12.2012 04:19, schrieb [email protected]:
>
>>
>> Indeed, bandwidth is now meaningless as a term, just as "broadband" is.
>> Once upon a time, both referred to bounds on the frequency components of
>> the physical layer signal, both in wires (twisted pair, coax, etc) and in
>> RF.   The RF bandwidth of 802.11b DSSS modulation was about 10 MHz, whereas
>> the bitrate achieved was about 2 Mb/sec.  Now we use OFDM modulation in
>> 802.11n, with bandwidths of 40 MHz more or less, but bitrates of >> 40
>> Mb/sec.   (yes, that is mostly because of 64-QAM, which encodes 6 bits on
>> each subcarrier within an OFDM "symbol").
>>
>> What causes the 802.11n MAC protocol to achieve whatever bitrate it
>> achieves is incredibly complex.   Interestingly, in many cases the problem
>> is really bad due to "bufferbloat" in the 802.11n device designs and
>> drivers, which causes extreme buildup of latency, which then causes the TCP
>> control loops to be very slow in adapting to new flows sharing the path.
>>
>>
>>
> And this refers directly to my original question.
>
> May I put it in very simple words.
>
> In mobile networks (let's include wifi there) a packet is either reliably
> delivered - in unpredictable time.
> Or it is unreliably delivered - that is possible in predictable time.
>
> Can we agree upon that?
>
> I still want to write my research proposal. However, I'm tired to get it
> rejected after exactly these two lines.
>
> Detlef
>
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> The nonsense that passes for knowledge around wireless networking,
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> blind leading the blind. (D.P. Reed, 2012/12/25)
> ------------------------------**------------------------------**------
>
>