[e2e] Historical question: Link layer flow control / silent discard
jeanjour at comcast.net
Fri May 24 10:16:07 PDT 2013
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.
With the advent of LANs, these HDLC-like
protocols were not really required. But to say,
they went completely out of use by 1981 would
probably be incorrect. In the US, some of the
longer runs of the ARPANET, such as Illinois to
Utah were relatively error free. At the same
time, short runs like Rome, NY to Cambridge had
much higher rates.
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.
At 5:34 PM +0200 5/24/13, Detlef Bosau wrote:
>O.k., perhaps this is for all readers with grey
>hair (if there is still hair at all....) and
>grey beards ;-)
>When I read the original catenet work by Cerf,
>the Catenet employed link layer flow control.
>To my understanding, this was abandoned when the
>ARPAnet turned into the Internet (in 1981?).
>After this change, the link layer flow control
>was replaced by a "silent discard" of packets
>which cannot be accepted for delivery.
>Is this correct?
>What was the reason for this decision and have
>there been any alternative approaches?
>70565 Stuttgart Tel.: +49 711 5208031
> mobile: +49 172 6819937
> skype: detlef.bosau
> ICQ: 566129673
>detlef.bosau at web.de http://www.detlef-bosau.de
More information about the end2end-interest