🚀 go-pugleaf

In article <1992Apr5.155151.5567@newshost.anu.edu.au>, cmf851@huxley.anu.edu.au (Albert Langer) writes:
|> 
|> Alternatively, instead of running X.25 PLP over TCP,
|> TCP could be treated as a Permanent Virtual Circuit and a single channel
|> CONS provided over that. The TCP "urgent data" pointer could be used to
|> mark the end octet of each DLSDU or NPDU for the "data link" version or
|> similar for a "network layer" version (e.g. using the T.70 "minimal
|> network layer" 2 octet headers plus the TCP acknowledgement status for an 
|> equivalent to the X.25 PVC with full Q bit and D bit facilities).
|> 
As usual, I stick to what I know, ignoring the thornbushes that line
the path.....
I had this idea also (about using the URG pointer for something).
I actually checked it with Jon Postel at the time (1984):
When a recipient is reassembling TCP segments, and finds the sequence


(byte 12 to 72; URG at 73)
(byte 73 to 112; URG at 113)

it is perfectly legal to return to the user bytes 12 to 112, and only signal
the URG at position 113.
So URGs are useless for anything other than their stated purpose: To indicate
to the recipient that there is urgent data somewhere down the data stream.
It gives no help in finding out where the urgent data actually is.

-- 
                   Harald Tveit Alvestrand
Harald.Alvestrand@delab.sintef.no
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