[prev in list] [next in list] [prev in thread] [next in thread] 

List:       ipng
Subject:    (IPng 4976) Re: IPv6 over ATM encapsulation
From:       Paul Koning <pkoning () xedia ! com>
Date:       1997-11-25 14:51:11
[Download RAW message or body]

>>>>> "FFFFDan" == Dan Grossman <dan@dma.isg.mot.com> writes:

 >>  If an excess of complication is added only to appease the "cell
 >> tax" contingent, perhaps I'm saying it's not justified by real
 >> arguments.  Cell tax is either small or non-existent compared with
 >> "4B/5B tax" or "Manchester encoding" tax. Ultimately, one pays for
 >> baud rate, not net bit rate.
 FFFFDan> I don't think it adds a lot of complexity.  The negotiation
 FFFFDan> machinery is part of everybody's portable signalling
 FFFFDan> software, and once it's in place, it's probably just a test
 FFFFDan> and branch in the driver.  I think this little complexity is
 FFFFDan> justified a) by taking an argument away from the ATM haters
 FFFFDan> b) by the fact that I don't think anybody's done for IPV6
 FFFFDan> any analysis along the lines of Ramon Caceres' thesis on the
 FFFFDan> effects of SAR on IPV4. and c) Bryan's interoperability
 FFFFDan> arguments.

The complexity issue isn't in the negotiation or configuration.  It is
in the fact that it introduces a second format in the fastpath.  

Ok, so it's optional, but that's beside the point.  Either it's
useful, in which case I should use it (and take the performance hit in
the fastpath) or it's not useful, in which case it would be preferable
not to have it exist.

The interesting question is: if it's useful to have null
encapsulation, why isn't it the default?  I've never heard of anyone
running anything other than IP over 1483 LLC encapsulation, so that
doesn't seem like the issue.  On the other hand, there is one thing
one does run alongside IP, i.e., ARP.  Which brings up another
question: is the option of null encapsulation actually meaningless
because 1577 doensn't work if you tried to use it?

	paul

--------------------------------------------------------------------
IETF IPng Working Group Mailing List
IPng Home Page:                      http://playground.sun.com/ipng
FTP archive:                      ftp://playground.sun.com/pub/ipng
Direct all administrative requests to majordomo@sunroof.eng.sun.com
--------------------------------------------------------------------

[prev in list] [next in list] [prev in thread] [next in thread]