Subject: [Autoconf] BDRP vs. world hunger

From: [email-masked]
Date: Thu, 24 Sep 2009 11:13:40 +0200 (CEST)

Hi Charlie,

I think we people can produce enough food for solving world hunger.
Maybe there are some L8 (political layer) problems to solve. Let's not
tackle this in [Autoconf].

|BRDP is, if you'll pardon my simplification, a souped-up version
|of Router Advertisement.  So, it isn't designed at all for autonomous
|MANETs.

BRDP is on top of RA, that is correct. It could be updated to run on top of
PacketBB messages, but now it is independent of any MANET protocol.

Did you check 5.3.  Support for Autonomous MANETs ?
It is a bit out of context for BRDP. As I see it, assigning globals is the
tough part.

|It is not clear from what you said how BRDP can begin to solve the
|problem that I outlined whereby four nodes cooperate to form a highly
|mobile network.

I assume unique Interface-IDs. I do not reject any proposal for DAD,
although I do prefer IDs that are unique by nature. This because no
overhead and no DoS vulnerability. I say DAD is optional.
If one comes up with a multi-hop 62-bit Duplicate ID Detection, it could
be used for interface-IDs with any address type.

It was less than 3 weeks ago that I saw a complete operational network
down due to DAD. A misbehaving DHCP server responded on ARP probes from
another DHCP server. I hate DAD. For good reasons.

(I also dislike DHCP servers without non-volatile memory, that rely on DAD
for not reassigning the same addresses over and over)

|If I was challenged to make a solution to the problem using BRDP,
|I would do so by nominating a distinguished node to define a routing
|tree for the network.  On average, the pathlengths would be
|reasonable, and the node beaconing BRDP messages would
|be the root of the tree.  Disregard for now the difficulty that
|BRDP is only specified for networks connected to the Internet.

This facility was included in the parent of BRDP. It would help using less
ULA prefixes and help address list compression, as nodes would have a
common prefix. An alternative is listen to already existing ULA prefixes.

|This model of operation is workable, but it suffers from the obvious
|problems of robustness (what if the root wanders away) and selection
|of the distinguished node (what if there are multiple contenders).
|But this is all speculation -- you may not even desire to offer BRDP
|as a solution which might be applicable in the general case.

I set BRDP temporally on hold, as it is solution space.
And I check ROLL every now and then. I'll line up with their solution one
day.

|Clearly, BRDP does _not_ connect all MANETs on the globe,
|if some are disconnected.

The claim was on scalability of the proposed mechanism. This claim is very
true. It is not in my hands connecting all MANETs to the Internet.

|  Plus, it is not a property of BRDP that
|connects a multiplicity of MANETs.  It is a property of the Internet,
|which would be the same whether BRDP or any other gateway
|protocol were to be put into service.

I don't think BRDP is a gateway protocol. I left out the routing part of
earlier versions of the mechanism (Tree Discovery). I clearly state that
the MANET protocol shall provide reachability.
Of course it is easy to recreate the path to the gateway, as there is a
DAG. And some are working on this, see ROLL for details.

The difficulty is selecting the path to the gateway that does not block
packets due to ingress filters. Therefore I suggest BRDP based routing
(again, this is not a routing protocol). I replace the default gateway
with a mechanism that packets with unknown destination are forwarded to
the BR that "owns" the source address prefix.
In fact, BRDP with BRDP based routing would upgrade DYMO to a protocol
that works well connecting DYMO MANETs to the Internet. And with scoping
RREQs, the size of DYMO MANETs would be unlimited. How nice :-)

Regards, Teco

---

From: "Charles E. Perkins" <[email-masked]>
Date: Thu, 24 Sep 2009 10:03:35 -0700

Hello Teco,

Comments inline below...

> tackle this in [Autoconf].

There seem to be big problems with the content providers, and
especially reliable delivery between the application endpoints
due to extremely lossy channel conditions over an expensive
transmission medium.
> It is a bit out of context for BRDP. As I see it, assigning globals is the

You have to admit, that section 5.3 does not indicate the solution to
the four-node problem.

> I assume unique Interface-IDs.

Enough said!  Unique interface-IDs do, in fact, enable a trivial
solution for globally unique link-locals.  There is no need to
say anything else.

However, the point of the discussion has been that we should
enable solutions where this assumption isn't automatically
valid.  And, the flip side of that coin, that we should not
require solutions to provide link-local addresses when such
addresses are not already trivially configurable.

But, previously, you said:
>
> BRDP provides a mechanism that connects all MANETs on this
> globe via the Internet without any problems.

I am disputing that claim.

> RREQs, the size of DYMO MANETs would be unlimited. How nice :-)

What's a "scoping RREQ"?  Are we wandering back into
the realm of extraordinary claims?  Why wouldn't any
other gateway protocol produce the same effect?

Regards,
Charlie P.