Subject: [Autoconf] manetarch-03

From: "Dearlove, Christopher \(UK\)" <[email-masked]>
Date: Mon, 2 Jul 2007 12:27:55 +0100

Some comments on manetarch-03. I'm not reporting
typographic errors (if the authors want those I'll
send them - at the moment they are ink on paper).

- I think it's worth a comment somewhere that MANETs
  are about dynamic networks but, the M in MANET
  notwithstanding, dynamic is not the same as mobile.
  Plenty of ad hoc networks are dynamic, even if their
  nodes don't actually move. Examples of reasons why
  include radio propagation issues (including other
  things than the nodes being mobile - e.g. introducing
  obstacles or more subtle effects), node behaviour
  changes (e.g. changing transmit power) and node
  loss (battery exhaustion, other effects). The
  reason I think this matters is because otherwise
  people can say "I don't need a MANET, my network
  isn't mobile".

- Section 2, "to list a few". Why not list all? (by
  which I mean at least one source of each, not of
  course all possible sources of each). Does any
  terminology come from RFC 2501?

- I'm not convinced that using "node" to include
  MANET protocol unaware hosts isn't sufficiently
  different from usual MANET usage so as not to be
  confusing - not here, but it used without explanation
  elsewhere. RFC 2501 for example considers a node to
  be combined router+hosts, not each of these to be
  separate nodes. (I would tend to think of a node as
  the entity that is internally wired, externally
  wireless. But that's not a definition.)

- It's been said before, but this usage of reflexive is
  not in accordance with standard mathematical terminology.
  See for example http://mathworld.wolfram.com/Reflexive.html
  The characteristic considered here is symmetry, see for
  example http://mathworld.wolfram.com/SymmetricRelation.html
  Note that what you are really saying by "asymmetric
  reachability" is that (assuming a node can reach itself,
  i.e. it is reflexive in the proper sense) that reachability
  is not an equivalence relation. Also see the next point.

- Also on what's called asymmetric reachability, this is
  said to be a property of a link. But transitivity is
  not about a link, it's about more than one link (two
  that exist and one that may not). I'd have said it's
  about interfaces, what you are saying is that reachability
  is not an equivalence relation on interfaces (but - with
  the definition that a node can reach itself - it is on
  an Ethernet, for example). Note that I'm not necessarily
  suggesting introducing the equivalence relation (though
  it works for me) I'm just suggesting reflexive -> symmetric
  and that this is about interfaces, not links. (Non-
  equivalent reachability is probably technically a better
  term.)

- The definition of Neighbour looks like a definition of a
  symmetric neighbour ("exchange" is two way). Later, under
  FBI, the undefined term symmetric neighbour is used. (It
  might be worth looking at NHDP also.)

- The Broadcast Interface definition doesn't appear to me to
  be quite right if a node has multiple MANET interfaces, but
  I may be wrong.

- Site. Is a site a set of links, or a set of nodes?

- Flooding uses "devices". What's a device?

- MANET Neighbours/MANET N-Neighbourhood. Should the former
  also be neighbourhood? Has reachable been defined? Which
  direction(s)?

- Penultimate paragraph in 2.2. Is "will" be right about
  merger. That suggests it always happens, but it might
  not - especially with a reactive protocol. (Partitioning
  yes, can't stop that happening.)

- Section 5.2 - should IPv6 LL addresses get a reference?
  Actually there's a wider issue - which IP features should
  be referenced to RFC this and that, and which are so well
  known they are just referred to? (Personally I often need
  the reference to things that are obvious to the wider IETF
  community.)

- Are we admitting that we are using link local IPv6 addresses
  beyond the mandate in RFC 4291, which says "Routers must not
  forward any packets with Link-Local source or destination
  addresses to other links.". If a MANET interface address is
  a link local address, it is going beyond that link, isn't it?
  (I have no alternative - other than undeprecating site local
  addresses, and I've no intention of suggesting that.)

- Section 5.3 vaguely refers to MANET protocols, without
  references, and also discusses WGs which will have been
  closed (we ought to hope) within the lifespan of this
  document once it's an RFC. Is this good style? (This also
  in Section 6.)

- Unreliability may also be important here. If you had all
  interfaces able to hear all others, but packets were lost
  50% of the time, then you still would have problems
  treating it as an Ethernet wouldn't you? Of course you can
  put in acknowledgements to make it reliable, probably.

- I didn't understand the point being made in the second
  half of the last paragraph of 8.2.

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