[e2e] Historical question: Link layer flow control / silent discard

[Detlef Bosau]

Am 24.05.2013 19:16, schrieb John Day:
> The nature of the link layer protocol is mostly determined by the 
> characteristics of the media. In the early networks, it was not 
> uncommon for the link layer to be a protocol that looked something 
> like what we think of HDLC, i.e. ack/retransmission with fixed 
> (usually small) window size.  In these early fixed window protocols, 
> ack and flow control were seen as all part of the window scheme.  The 
> quality of the lines pretty much dictated the use of these sorts of 
> protocols over long distances.  As the data rate increased, the delay 
> imposed by this class of protocols made them inadequate.

However, the delay could be kept quite small - as wee see in TCP flow 
control.
>
> With the advent of LANs, these HDLC-like protocols were not really 
> required. 

At least in CSMA/CD Ethernet, it is implicitly given by the MAC scheme: 
There can only be one packet on the media.
>
> It would be certainly be incorrect to conclude that a decision was 
> made not to use them, especially since the ARPANET was not turned off 
> until 1990 or thereabouts. 

As I said, I would like to understand these decisions, particularly as 
many of them are not self evident and perhaps may be questioned.



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