Subject: [Ans-research] RE: [manet] Interlayer Interactions

From: Scott Corson <[email-masked]>
Date: Sat, 5 Apr 2003 09:38:35 -0500

This is a *very* old discussion. ;-)

In the absence of standardized mechanisms, I also agree with Joe that we
need code that does not require standard interlayer interaction mechanisms.

> The ANS IRTF list may want to comment and may be an 
> appropriate venue for 
> broadening the knowledge base further over time.

As to whether the ANS group will explore this issue, I would be very much in
favor of it (note the cross posting), but the issue is *broader* than ad hoc
networking.  It pertains to IP-based cellular systems, WLAN and ad hoc
schemes.  In short any link layer where intermittent and dynamic
connectivity may be a typical event. 

Of all the *trigger* and related IETF work I've seen proposed to date, IMO,
the most sensible and general approach was articulated by Phil Neumiller in
an interesting way.  The proposal is that the IETF standardize IP's
*underbelly*.  

I interpret what Phil meant as a general interface definition that would be
built into the bottomhalf of standard IP kernels.  Link layers could then be
defined or extended to operate in accordance with this interface as desired.

Most generally IP kernels understand 'point-to-point' and 'broadcast' link
layers.  What is necessary is *another* type of interface that blends and
generalizes aspects of point-to-point and broadcast link layers to
accomodate link *dynamics*.  As such I refer to it as a *triggered* or
*dynamic* interface for lack of a better name.

In wireless, link layer broadcast communication (one-to-many) is the general
case and must be supported as in Ethernet.  At the same time, point-to-point
'peer-to-peer' associations (neighbors in an ad hoc sense) arise
*dynamically* as a consequence of movement, power up, fading, etc.  Many
link layers efficiently detect the existence/non-existence and quality of
these associations.   This association information can be conveyed to an IP
stack via the triggered interface construct, and the IP stack is free to use
this information as desired (and it may ignore it as well).  This mechanism
is applicable to Ad hoc, WLAN and Cellular technologies.

For those interested, this topic is explored a bit further in 

http://www.ietf.org/internet-drafts/draft-corson-triggered-00.txt

Cheers,

-Scott
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From: Sukanta Kumar Hazra <[email-masked]>
Date: Sat, 5 Apr 2003 23:37:24 +0800

> This is a *very* old discussion. ;-)

Indeed it is a *very* old discussion. But it resurfaces ever so often
that it is imperative that something be done about it (IMHO). All the arguments
that I have come across point to the need for a standardized interface
for IP<->L2 interaction. Anyone remembers the arguments against it (as
were discussed in the IP triggers BOF).

- Sukanta

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