The IP over ATM Mailing List Archive by date

[Jon Crowcroft <J.Crowcroft@cs.ucl.ac.uk>]

we were talking about expierences with IP on ATM and decided we would
like to start some kind of discussion on alternate protocol wrappers
for IP around AAL5

2 examples why we need it

1/ Video on RTP on UDP/IP on AAL5

if we lose a single cell, we lose the whole packet
however, note, early packet discard is NOT appropriate, since many
video encodings are very loss tolerant, and you can also build
recivers that do cell loss concealment extremely well. However, most
AAL5 SAR recevier boards either do the reassemlby on board, and trash
the whole packet if a cell is lost, or they do the reassembly to the
host memory, but still trash the packet, even if they give yu an error
indication (what a waste of all those dma cycles!)

we'd like to propoe peopel think about deliverying partial IP packets,
and think hard about a siognal being propogated thru AAL5, IP and UDP
to say "I know the CRC and UDP checksums fail, but i don't care"

2/ TCP on IP on AAL5 on an ABR service

we'd like an explicit congestion bit (even if ATT don';t let us get
the explicit rate,they'll still pass the congestion signal back sooner
than packet loss in traditional TCP congestion detection) signal from
AAL up thu IP....

this may not be quite the right WG to discuss this, but just sartting
fro mthese two e.g.s i can think of a range of simple signals that
require very modest modificatio nto the code (e.g in BSD or streams
IP, the 2 ideas above are a few lines of code....i can eventhink of an
API for deivering partial packets to an application....)

thoughts?

 jon