Subject: [manet] MANET Multicast Address(es)

From: Ian Chakeres <[email-masked]>
Date: Sun, 13 Mar 2005 17:02:19 -0500

From the discussion in the MANET meeting Thursday I think it is agreed 
that MANET should talk with IANA about allocating some IPv4 and IPv6 
addresses for delivery of packets to nodes participating in the MANET.

What scope address should we allocate? i.e. link-local or all scope 
multicast.

Should we allocate 1 address for all MANET routing protocols?

Should we allocate 1 address for each MANET routing protocol?

Should we allocate a range of addresses?

What should we call this address? i.e. ALL MANET Routers

Please reply to the list.

Ian Chakeres

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From: Ryuji Wakikawa <[email-masked]>
Date: Mon, 14 Mar 2005 09:43:19 +0900

Hi Ian

> Should we allocate 1 address for all MANET routing protocols?

I vote for this.
No reason to have different address for each manet protocols.
Each node can distinguish packets at upper layer (i.e. UDP).

> Should we allocate 1 address for each MANET routing protocol?

If reactive nodes do not want to process proactive message
in terms of battery consumption, this is also possible.
However, I don't think there is much difference between dropping packets
before or after processing IP header.

> Should we allocate a range of addresses?

range for multicast?

> What should we call this address? i.e. ALL MANET Routers

fine.
The all MANET routers multicast address is a multicast for manet routers
which are capable of manet routing.
If this is correct, the all node multicast address can be defined as
a multicast address for  MANET routers + manet nodes?

I think it is time to define some common term in MANET working group.
It is confusing not to have common term.
I remembered  somebody raised same problem in MANET autoconf meeting  
that
people use MANET as either a routing protocol, a network,  or even a 
node

regards,
ryuji

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From: Ian Chakeres <[email-masked]>
Date: Sun, 13 Mar 2005 19:56:47 -0500

Ryuji,

Do you you think we should define 2 addresses

All MANET Nodes
All MANET Routers

What is your opinion about scope.  Should the address(es) be link-local?

Ian Chakeres

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From: Ryuji Wakikawa <[email-masked]>
Date: Mon, 14 Mar 2005 10:23:09 +0900

Hi Ian

> Do you you think we should define 2 addresses

only all manet routers.
all node multicast address (ff02::1) is already defined.
I think ff02::1 can be used for all manet nodes multicast address.

here is my understanding.
-A node joins to ff02::1 as normal,
-A manet router joins to both ff02::1 and ALL_MANET_ROUTER.

> What is your opinion about scope.  Should the address(es) be 

yes, link-local scope.
Otherwise, a node can not flood routing messages before an address 
autoconfiguration.

ryuji

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From: David Young <[email-masked]>
Date: Sun, 13 Mar 2005 20:53:21 -0600

> before or after processing IP header.

Virtually all NICs have a multicast filter.  The CPU need neither take an
interrupt, nor examine the IP or UDP headers, if the NIC can filter all
packets but the "interesting" ones, based on the multicast destination.
The CPU and battery savings might be substantial.  I don't think the
multicast address spaces are in danger of depletion.  If it's all the
same to IANA, why not use as many multicast addresses as it takes to
optimize CPU and power conservation?

Dave

-- 
David Young             OJC Technologies
[email-masked]      Urbana, IL * (217) 278-3933

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From: Marshall Eubanks <[email-masked]>
Date: Mon, 14 Mar 2005 00:48:08 -0500

I unfortunately had a conflict Thursday and couldn't make the MANET meeting.

Is this for delivery of data (in which case IANA is not likely to give
you addresses, but
there are other options)
or for control information to routers / nodes ?

In the latter case.  it will need to be link local, 
will come from 224/8, and will need to go hop by hop if it has to propagate.

Dave Meyer is the multicast technical expert for IANA, but I will be
glad to assist with any
questions. 

Regards
Marshall Eubanks

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From: Baker Fred <[email-masked]>
Date: Mon, 14 Mar 2005 01:08:50 -0500

> What should we call this address? i.e. ALL MANET Routers

What we have done in other routing protocols is provide an address or 
two for the protocol in question - "All OSPF Routers" and "All OSPF 
Designated Routers" for example.

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From: Baker Fred <[email-masked]>
Date: Mon, 14 Mar 2005 01:18:05 -0500

> Designated Routers" for example.

Having said that, I should say the operational reason.

First, we already have "all hosts" and such defined. Second, the reason 
that you want this is to target a specific function that might or might 
not be enabled in a given system. Third, operationally, you really want 
to make it straightforward for the receiving system to ignore messages 
that are not really to it. Doing it by having the routing application 
join the multicast group is at the network layer, while UDP or SCTP is 
at the next layer up.

And think about this. If it is possible to configure a multiprotocol 
router for several protocols, they may have processes running some 
number of these protocols at any given time. If process A needs a 
message stream {a} and process B needs a message stream {b}, and both 
join the same multicast group to get it, both processes will receive 
the message stream {a} union {b}. An "aw shucks" on one becomes an "aw 
shucks" on the other...

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From: "Pedro M. Ruiz" <[email-masked]>
Date: Mon, 14 Mar 2005 10:44:10 +0100

I think this might be the right approach... We can still use FF02::1for 
every MANET node, and then ask for a new address (link-local) for each 
routing protocol...

Regards, Pedro

Baker Fred wrote:

> First, we already have "all hosts" and such defined. Second, the 
> reason that you want this is to target a specific function that might 
> or might not be enabled in a given system. Third, operationally, you 
> really want to make it straightforward for the receiving system to 
> ignore messages that are not really to it. Doing it by having the 
> routing application join the multicast group is at the network layer, 
> while UDP or SCTP is at the next layer up.
>

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From: Christophe Jelger <[email-masked]>
Date: Mon, 14 Mar 2005 11:28:22 +0100

Ian/all,

Well I haven't been able to attend the IETF meeting, so I don't know how 
these discussions started but see below/inline for a few comments. I 
will send a second email to discuss related stuff.

> What scope address should we allocate? i.e. link-local or all scope 

For routing messages we probably only need an mcast link-local address 
for neighbor-to-neighbor exchange of routing data.

> Should we allocate 1 address for all MANET routing protocols?

I'm not in favor of that. For IPv6, there is already ff02::2, i.e. all 
routers, but actually it's not used by routing protocols since they use 
their own address (see below).

> Should we allocate 1 address for each MANET routing protocol?

For IPv6, there exist one address for each routing protocol : examples 
are ff02::5 and ff02::6 for OSPF, ff02::9 for RIP, ff02::d for PIM. So 
it makes sense to do the same for MANET routing protocols : a node not 
involved in some routing protocol will then not receive messages that it 
cannot process (since the corresponding Ethernet/mcast address is not 
joined by the NIC). For IPv4 however this might not be possible.

> Should we allocate a range of addresses?

No ... but I'm not sure what you mean here. What's the idea ?

> What should we call this address? i.e. ALL MANET Routers

There could be : ALL_AODV_Routers, ALL_OLSR_Routers etc ...

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From: Baker Fred <[email-masked]>
Date: Mon, 14 Mar 2005 05:45:26 -0500

> There could be : ALL_AODV_Routers, ALL_OLSR_Routers etc ...

Yes. The approach we have taken with other routing protocols is that 
protocol-specific addresses were obtained from IANA.

when we ask them for such, we want to say we are looking for a 
"multicast address of link-local scope" rather than "a link-local 
address". The latter term has been used in this thread, but I guarantee 
that Michelle will get confused if asked in those terms.

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From: Christophe Jelger <[email-masked]>
Date: Mon, 14 Mar 2005 12:07:28 +0100

Ryuji, Ian, all,

I think there definetely is a lack of definitions, but I think some are 
due to the poor definition of what a MANET is at the network-layer. Of 
course one can wonder if we need such a network-layer definition or not. 
In a stand-alone MANET we probably don't always need such a definition, 
but as soon as we want to integrate a MANET in the Internet then there 
are "rules" we cannot bypass.

Call it as you want, but people tried to overcome this situation by 
solving it in different ways : prefix continuity (my draft), MANET-flag 
for interfaces (Guillaume Chelius), set of routing entities (many 
people) : e.g. all aodv routers. There was also the idea of MANET-local 
addresses (which to some extend describe a MANET at the network layer). 
Actually whether one likes or dislikes the existing proposals, I think 
many people feel that we need some definition of a MANET at the network 
layer. Once one has a clear view of a MANET at the network layer, it 
becomes easier to define things like flooding, multicasting, addressing 
and so on.

Regards,
Christophe

Food for thougths : RFC 2501 states

 > A MANET is an autonomous system of mobile nodes.  The system
 > may operate in isolation, or may have gateways to and interface with
 > a fixed network. In the latter operational mode, it is typically
 > envisioned to operate as a "stub" network connecting to a fixed
 > internetwork.

--> In that case topologically correct global addressing clearly defines 
the MANET boundaries.

Ryuji Wakikawa wrote:
> I remembered  somebody raised same problem in MANET autoconf meeting  that
> people use MANET as either a routing protocol, a network,  or even a node
> 
> regards,
> ryuji
>

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From: Marshall Eubanks <[email-masked]>
Date: Mon, 14 Mar 2005 07:56:08 -0500

Having read through all of this, I would definitely recommend applying for
one multicast address per MANET routing protocol, and maybe also one
for all manet routers. That would be most consistent with other practice.

Regards
Marshall Eubanks

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From: "Charles E.Perkins" <[email-masked]>
Date: Mon, 14 Mar 2005 09:45:41 -0800

Hello folks,

>> Do you you think we should define 2 addresses

Yes, I do think we should have these two
addresses.

> I think ff02::1 can be used for all manet nodes multicast address.

But, the multicast group cannot contain all nodes,
if we want to restrict to a manet.  This would be
very confusing if the manet were attached to the
Internet temporarily.

> -A manet router joins to both ff02::1 and ALL_MANET_ROUTER.

This is fine, but the node could also join ALL_MANET_NODES.

For example, a message about a service which is offered
to the ad hoc population could be sent to ALL_MANET_NODES,
but a message about routing should be sent to ALL_MANET_ROUTERS.

> > What is your opinion about scope.  Should the address(es) be

If we delimit a link by the physical communications medium
connecting two nodes then this isn't a very natural fit.
The multicast group would have many more nodes than intuitively
described by a link-local address.  I think "site-local' is a
better description for the MANETcast, and it seems to be a
fully legitimate designation regardless of the disposition of
site-local unicast addresses.

> Otherwise, a node can not flood routing messages before an address

It's an interesting point to figure out what happens when
many nodes try to autoconfigure all at once, but I don't
see it as a necessary precursor to populating route table
entries at the individual nodes.

Regards,
Charlie P.

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From: gabriel montenegro <[email-masked]>
Date: Mon, 14 Mar 2005 10:07:43 -0800

> protocol-specific addresses were obtained from IANA.

I think this is the right approach. Unless there's some very
strong reason to do so, I don't believe MANET protocols should
depart from existing practice. Existing practice seems to be that
a routing protocol has its own multicast address, might as well
follow suit, specially cuz it does make sense as it eases filtering
at each router.

MANET protocols are just further examples of routing protocols (sure, they may
be optimized for different topology patterns and mobility, and
even then, the "mesh" applications move them back in the direction
of traditional routing protocols), so I don't see
why they should be treated differently.

Furthermore, I don't believe it makes sense to have
an "ALL_MANET_ROUTERS" multicast address. Given that each
manet protocol seems to work well for different scenarios, not sure
why such an address would make more sense than the "ALL_ROUTERS" multicast
address that already exists.

-gabriel

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From: Brian Haberman <[email-masked]>
Date: Tue, 15 Mar 2005 11:34:05 -0500

Hi Charlie,

> very confusing if the manet were attached to the

Keep in mind that FF02::1 is scoped to the link, so I don't
see the issue with using it instead of some special address
for ALL_MANET_NODES.

If we did have another address, doesn't that force the IP layer
to know when a particular interface is attached to a MANET?

> but a message about routing should be sent to ALL_MANET_ROUTERS.

I seem to see a consensus for each MANET routing protocol to have
its own multicast address.

As for a service offering, do you want that advertised at the link-scope
or something larger?

> site-local unicast addresses.

Yes.  The deprecation of unicast site-locals has no impact on the
multicast site-scope.

The use of site vs. link scoped multicast depends on the functionality.
Routing control messages should be link-scoped.  Higher layer
applications could use site-local depending on its reach.

Regards,
Brian