RE: [Autoconf] comments on draft-ietf-autoconf-manetarch-07.txt

["Teco Boot" <[e-mail]>]

Some comments inline.

> -----Oorspronkelijk bericht-----
> Van: Thomas Narten [mailto:[e-mail]]
> Verzonden: dinsdag 4 december 2007 14:44
> Aan: [e-mail]
> Onderwerp: [Autoconf] comments on draft-ietf-autoconf-manetarch-07.txt
> 
> 2007-11-30 review of -7
> 
> Overall. I still do not think this document is ready for
> publication. It is still to vague/muddy on the key architectural
> points  that it is supposed to explain.
> 
> My major concern is that you still do not lay out an understandable
> "architecture" that allows one to understand what an IP subnet would
> look like in MANETs.
> 
> Interface terminology is non-standard and confusing. Should use "link
> type". Really. If you want the rest of the community to be able to
> understand this stuff, you cannot redefine terminology that is already
> widely in use and understood to mean something different than who it
> is used in this document.

Maybe better definition could help.
I think it is easy to understand that a MANET Interface is an interface that
may suffer from certain link characteristics. We have similar kind of
interface types, like NBMA and P2MP. Now we want to define another.
Term MANET Interface is well known, e.g. it is used in MANET Routing
Protocol documents, including the OSPF ones.

Maybe term Semi-Broadcast Interface (SBI) should be removed, this is about
the link characteristics. Hint for editer: Change SBI into MANET and some
textual cleanup will do.

 
<snip>

>    Interface
>       A node's point of attachment to a communication link.
> 
> This is mostly fine as written, but...
> 
>    Semi-Broadcast Interface (SBI)
>       A broadcast capable interface that may exhibit asymmetric
>       reachability.  Multiple access wireless radio interfaces are
> often
>       SBI.  Note that since a SBI *may* exhibit asymmetric
> reachability,
>       it also may not.
> 
> Call it a "link" not an "interface".
> 
> Manets provide IP with a conceptual link, that has certain
> properties. What I thought the MANET architecture would provide is a
> description of the properties of that link type.
> 
>    MANET Interface
>       A MANET interface is distinguished by its potentially significant
>       time-varying asymmetric reachability (e.g., SBI) amongst
> potential
>       neighboring routers.  A more detailed discussion of MANET
>       interface characteristics is presented in Section 4.2.  The
>       addressing constraints for a MANET interface are discussed in
>       Section 5.2.
> 
> No. A MANET _link_ has these characteristics. Not the interface.
> 
> Etc.
> 
>    MANET Router (MNR)
>       A MANET router is distinguished by having one or more MANET
>       interfaces.  A MANET router may also have zero or more non-MANET
>       interfaces.  A MANET router is responsible for hiding MANETs'
>       challenging characteristics from nodes that are not MANET-aware.
>       A MANET router with a single MANET interface is illustrated in
>       Figure 1.
> 
> No. the "interface/link" hides the challenging characteristics from
> IP. Not the BR itself. This is a critical point (architecturally) to
> get right.
> 

If this is true, we do not have to do anything special.


> You really (I think) need to define an abstraction that defines an
> link type of "manet" that handles all the "interesting"
> characteristics of MANETs (like non-transitive connectivity) but that
> also presents itself to IP as a single IP subnet that has the normal
> properties.

I think there are two MANET implementation models.
One is hiding MANET form IP, e.g. a sub-IP MANET model. This is more or less
out-of-scope for IETF.
The other model is described in this document. Now we have to face the
reachability issues. I think the MANET Router shall hide this for IP hosts
and non-MANET routers. If this is arranged by using a single IP subnet or
using another addressing model is solution space.
 
There might be a discussion on supporting connectivity to (mobile) hosts via
the MANET Interface. I will post on this separately.

Teco.



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