The IP over ATM Mailing List Archive by date

[Grenville Armitage <gja@thumper.bellcore.com>]

Jim,
	[..]
>>Not nearly so bad as if you change encapsulations.  We have over a thousand
>>ATM interfaces that we've shipped, and we thought the encapsulation stuff
>>had been put to bed.  It would be unfortunate if vendors that had nothing
>>to lose were not sympathetic to the fact that there *is* an installed base.

I don't understand the comparison. You've got an installed base of
(I presume) 1577/1483 compatible code overlying all those ATM
interfaces. This installed base has nothing to worry about if
your clients never want native multicast support. When they
_do_ want that support, you'll be upgrading the installed base
anyway (to include MARS or proprietory extensions). Unless your
'installed base' of ATM interfaces imposes a kludgy LLC/SNAP
in hardware, there does not appear to be any substance to your
concern. A software upgrade is a software upgrade.

	[..]
>>I don't see any difference in cycles whatsoever between doing at the IP
>>layer or below. 

it would be trivial to include an extended encaps option in every
router that gets a software upgrade to do IPmc over ATM.

Alternatively, if you build the encaps layer in external hardware,
then the answer is that you'll save bus/main-cpu activity by filtering
before passing packets to the IP layer/forwarding engine.

gja