Subject: IP Addressing in MANET

From: Chip Elliott <[email-masked]>
Date: Fri, 06 Mar 1998 08:26:46 -0500

Charlie,

Thank you for your patient explanations. Let me try to replay
the approach you describe, and then ask one or two further
questions.

REPLAY:

1. Each wireless interface has an IP address, which is either
   configured by "home" administrators or based on MAC address,
   etc. In any case, it is assumed unique and does not change
   upon entry to a MAD net.

2. The MANET protocol(s) exchange these IP addresses,
   ie, do the usual thing for routing protocols.

3. It does not matter that the hosts in a MAD net do not
   agree on the subnet numbering scheme. In general, they
   will not. Instead wireless IP addresses are used solely
   as 32-bit unique identifiers.

QUESTIONS:

1. How does this affect the IP forwarding engine in each
   host/router? Are these wireless IP addresses just entered
   as 32-bit-long matches? Note that this has the slightly
   perverse effect of favoring a wireless route over
   (say) an Ethernet, since the Ethernet IP address will
   undoubtedly have a shorter mask. But hey, I say this is
   not a big issue.

2. I guess we're already talking about modifying the
   forwarding path, right, since in general we will forward
   packets back out the same interface they came in on?

3. With this scheme, haven't we totally given up on the
   ideas of IP Broadcast and IP Multicast? If there's no
   notion of an IP-addressable subnet, these services
   cannot be based on any standard IP mechanisms.

I'm a bit sad about throwing all of IP Multicast overboard,
if indeed that's the implication, particularly since radio
(wireless) interfaces have such nice broadcast properties.

Thanks again for your patience,

-- Chip

---

From: Joe Macker <[email-masked]>
Date: Fri, 06 Mar 1998 11:33:52 -0800

Chip:
Charlie and Vince have already expressed alot of the 2 cents I would have
added to this discussion.

Certainly I would never want to see future improved
addressing/configuration schemes stifled
(such thoughts are important in the longer term) but we have some sensible
"near term" approaches, especially when considering the stub network scope
and the use of unique router IDs within an addres space. 

>   undoubtedly have a shorter mask. But hey, I say this is

I think manet routing protocols should advertise associated subnet masks as
well as "host-like routes" translating to the the router IDs.  I am not
sure this is related to your question.  This allows for better support of
mobile platforms with multiple LANs attached.

I have putting forth the model of multiple wireless interfaces not single
ones, so packets are not necessarily forwarded out the same interface.

>   cannot be based on any standard IP mechanisms.
No,definitely not.   I would encourage the use of multicast, actually 
IMEP specifies using multicast for local discovery,etc.

>(wireless) interfaces have such nice broadcast properties.

We are not doing this, at least that is not the WG intention from my
perspective!
As I mentioned in a previous post, I believe the type of connection that
multicast logically translates to at different local MAC layers will differ
(as it does today). This is interface dependent and I am envisioning
support for multiple interface types.

IP multicast is important and at least from my perspective we are not
excluding it, quite the contrary!  The multihop routing (vs. the localized
multicast) question is a little different and if you remember from the BOFs
their was some consensus that perhaps it was a little early to work
multicast "mobile" routing standard(s) until we had a good handle on some
unicast routing solutions (thus the lack of mention in the initial
charter).  I see including "mobile" multicast routing as a natural temporal
progression of the WG and we should continue to discuss as a group when
this timeframe is appropriate.

Thanks for the good questions, as Vince had said, I think a number of these
issues have been discussed in smaller groups but they really needed to be
brought up to the mailing list level.

-Joe