Hello Justin,
Yes, the links are absolutely asymmetric. This does not lessen the huge
difference in interference and overhead due to multicast. Moreover, it
does not quantify the frequency of occurrence of the matter under
discussion.
Notably, 802.11 is already guaranteed bidirectional at layer-2, so most
of the discussion about bidirectionality has to be assumed oriented
towards other wireless media. Even so bidirectionality is not black &
white because the statistics for lost packets will often be different
(between 0% and 100%) in each direction.
Of course, all wireless media are in addition asymmetric on tiny
timescales beyond the purview of IP, and thus IP mechanisms cannot hope
to cure all such ills.
Did you like my proposal to make the proposed multicast solution into an
optional feature, accompanied by a description of the costs of multicast?
What if a proposal (developed to better assure bidirectionality) causes
a net *loss* in packet delivery ratio? Did you have comments about how
multicast is inherently much more expensive and less reliable than
unicast for 802.11 and other media?
Regards,
Charlie P.
On 6/26/2015 12:38 PM, Justin Dean wrote:
I've have had first hand experience with the flakiness in real radios both 802.11 and other. Multicast vs Unicast is supported differently with different radio models and behavior is also often different. Hell it can be a challenge just to get radios to sync on the same mac ssid and keep them there. I stand by my point that bi-directional checks are a minimum for getting things at least somewhat logically sane. Having another mechanisms for checking connectivity nhdp/dlep/wifidriver would negate the need for the check, and would likely provide better information/routes. The trick would be making this more efficient mode well defined using clearly defined AODVv2 use bi-directional neighbor table (populated with whatever discovery mechanism one wishes)
This paper from 2007 documents the issues of asymmetric link characteristics quite clearly.
http://www.sciencedirect.com/science/article/pii/S1570870505001149
I've made my issues known here and proposed ways to address them. Once the new draft is out I'll be posting comments to the manet list as this is a WG document and if consensus is going to be reached it will have to happen there.
Justin Dean
On Fri, Jun 26, 2015 at 2:19 PM, Victoria Mercieca <vmercieca0@xxxxxxxxx <mailto:vmercieca0@xxxxxxxxx>> wrote:
Hi everyone,
I apologise, I have not found time today to work on this. If
anybody wishes to suggest text for the RREP multicast approach
while I am away, I'll be happy to cut and paste it in on the
Monday before the deadline. Same goes for any text we need to add
for the gateway topic. Failing that, I can look at the RREP stuff
on the Sunday when I get back if I need to.
In case there's any reason you need to generate a draft, I'm
attaching the current version of my working directory with the
pandoc files. Info from
//www.freelists.org/post/aodvv2-discuss/Fwd-manet-ID-Action-draftietfmanetaodvv209txt,1
should
all still apply from the last time I sent the zip file out. Also,
I'll probably still check emails from time to time if you need
anything.
Kind regards,
Vicky.
On Thu, Jun 25, 2015 at 10:04 AM, John Dowdell
<john.dowdell486@xxxxxxxxx <mailto:john.dowdell486@xxxxxxxxx>> wrote:
Good morning all
As you all know, draft submission cut off time is 2359 UTC on
Monday 6 July (= 0059 July 7 in UK). Vicky is on holiday next
week, and Lotte is fast approaching (if not already in) exam
time, which means we need to go firm on two topics currently
under discussion by the time Vicky starts work at 0900 UK time
tomorrow (so that's 0100 Friday for Charlie, 0400 Stan and
1000 Lotte) in order for Vicky to make final substantive
changes. Any remaining scraps can be tidied up on the Monday
6th when Vicky returns from holiday and we can submit.
I believe Working Group Last Call does not mean we can't make
any more changes. You'll have seen (and some of you have
lived) the changes to DLEP as it went through and following
the last call period. We still haven't had a great deal of
feedback from the working group which means they're either
busy, don't have an opinion, or are ok with it, but regardless
we still need to plough on and come to consensus for now.
Details can still be worked on, and indeed I was just
discussing with Vicky the prospect of an author team call
while most of us are at Prague.
So the two topics are gateways and routes to neighbours.
I'm not going to direct the outcome, that wouldn't be fair,
but I need you all to come to a position of "good enough for
now", to arrive at a document that we can all defend at
Prague, and that position needs to be arrived at by the time
mentioned above. This may mean each of you need to concede on
certain points of detail, perhaps against your better
judgement, but it won't be the last time we can change things.
I'm really pleased with the progress, we have come a long way.
Let's work together to get these last points agreed (for now)
and written up.
Thanks and Best Regards
John
