Subject: Re: [Autoconf] Goals of MANET autoconf

From: Emmanuel Baccelli <[email-masked]>
Date: Tue, 27 Nov 2007 11:19:30 +0100

All,

In order to agree on proposed or existing text, we have to agree on 
axioms. The following step would be to reshape -03 tightly around such 
axioms.

Previously, there was an agreement on the following axioms. Now does 
anybody think the following items need to be updated/completed? If so 
how exactly? Please be vocal if you think they are good enough, or not.

1. provide MANET-wide unique prefixes (up to /128) to each MANET router

2. if one or more Internet Gateway is reachable, provide routable unique 
global prefixes to each MANET router

3. detect and resolve if non-unique prefixes are assigned to MANET 
routers (e.g. as a result of a network partitioning/merger)

Regards
Emmanuel

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From: "Teco Boot" <[email-masked]>
Date: Tue, 27 Nov 2007 12:23:05 +0100

Hi Emmanual,

On item 3, the text: "as a result of a network partitioning/merger", I think
it is impossible having non-unique global addresses after a merge; where
before the merge addresses were globally unique. Or maybe earth merged with
mars;-)

And partitioning should be removed, as discussed before.

Personally I would use Addresses instead of Prefixes, to be compliant with
charter. 
For a /128 prefix, there is not much difference with an address. 
I think the Prefix Delegation discussion is interesting, but strictly spoken
we are not chartered for this. We are chartered for issues related to
"prefix and/or address providing entities". IMHO discuss PD is OK, but we
should first describe problems with address assignment before taking steps
into PD. Writing the PS this way is OK for me. But be careful, PD is a step
into solution space.

===

More on ND:
I prefer keeping ND for link-layer address determination. I don't think we
discuss replacing this.
I agree on describing problems with ND in PS first.

On problems with ND, which WG is describing problems with Redirect Messages?

I think on SBI, Redirect Messages should not be sent. As simple as that. But
where is this defined? Add something in PS that this is to be worked out?

Teco.

> -----Oorspronkelijk bericht-----
> Van: Emmanuel Baccelli [mailto:[email-masked]]
> Verzonden: dinsdag 27 november 2007 11:20
> Aan: [email-masked]
> Onderwerp: Re: [Autoconf] Goals of MANET autoconf
> 
> All,
> 
>

---

From: Emmanuel Baccelli <[email-masked]>
Date: Tue, 27 Nov 2007 14:58:52 +0100

Hi Teco,

 > And partitioning should be removed, as discussed before.

I agree with removing the mention of partitionning here. But as far as 
non-unique addresses are concerned, I disagree. There are types of 
addresses other than global. And in this case they may not be unique 
after a merger for instance. So maybe we could talk more specifically 
about non-unicity of addresses of types other than global?

> into PD. Writing the PS this way is OK for me. But be careful, PD is a step

I agree. But since we are, as you mention, to talk about "prefixes 
and/or addresses" then we should not restrain from talking about 
prefixes too, right? So how about this formulation:

1. provide MANET-scoped unique addresses and/or prefixes to each MANET 
router

2. if one or more Internet Gateway is reachable, provide routable unique 
global addresses and/or prefixes to each MANET router

3. detect and resolve if duplicated MANET-scoped addresses and/or 
prefixes are assigned to MANET routers (e.g. as a result of a network 
merger)

> I agree on describing problems with ND in PS first.

OK. So let's work on that.

---

From: "Teco Boot" <[email-masked]>
Date: Tue, 27 Nov 2007 15:46:09 +0100

Hi,

On 3, now the text includes "duplicated MANET-scoped addresses".
OK, but reworded, see below.

On changing addresses in addresses and/or prefixes, I don't know what you
intent to do with the text. It is a bit tiny for the content of a section
and a bit long for a name for a chapter.
If the PS text explains that for configuring an IP address on an interface
(assignment), a prefix length is needed and thus an IP address assignment is
the same as a prefix assignment, I am OK.
This assigned prefix is also to be added in the MANET protocol, and there it
is called a prefix.

A minor issue:
1 and 2 mentions "to each MANET router". I don't think it is mandatory to
provide addresses / prefixes to all MANET routers. Only when they need it.
Maybe a MANET Router only wants to relay (no local or global address needed)
or only want to use the Internet (only global address needed) or only want
inner-MANET communication (only local address needed).
What about changing "to each MANET router" into "to MANET routers" (like
item 3).

I don't know what MANET-scoped is. I can guess the intention. I will react
when reading PS text on this.
For now: I do not like an introduction of some kind of scoping, like
site-scope or MANET_ID. I used other wording below, for what I think what
was your intention.

Proposal with corrections, also some rewording for being more compliant with
charter:

1. provide unique local addresses and/or prefixes to MANET routers for
inner-MANET communication

2. if one or more Internet Gateway(s) is (are) reachable, provide globally
routable unique addresses and/or prefixes to MANET routers

3. detect and resolve if duplicated local addresses and/or prefixes are
assigned to MANET routers (e.g. as a result of a network merger)

Teco.

> Verzonden: dinsdag 27 november 2007 14:59
> Aan: [email-masked]

---

From: Alexandru Petrescu <[email-masked]>
Date: Tue, 27 Nov 2007 16:35:03 +0100

Emmanuel, please take it as a simple opinion.

Emmanuel Baccelli wrote:
> axioms. The following step would be to reshape -03 tightly around
> such axioms.
> 
>  anybody think the following items need to be updated/completed? If
> so how exactly? Please be vocal if you think they are good enough, or
> not.
> 
> 

What does "MANET-wide" mean?  Any relationship with the "site" term used
by RFC4193 "Unique Local IPv6 Unicast Addresses (ULA)"?  Would this
"site" used by RFC4193 address my (and Ulrich's) confusion with respect
to the manetarch document ("one or more IP hops - MANET, site, global")
and deprecated site-local addresses?

Then.

What does "unique prefix" mean?  Computing a unique value involves
comparison with other values.

Let's say for example I have this fd67::/16 prefix and I wonder whether
it's unique.  I ask left and right and two people tell me they already
use fd67::/8 and fd67:300::/24.  Is my prefix unique compared to these?
  Can I use my prefix?

Another example: I have this address and prefix fd67::1/64 and you have
this address and prefix fd67::1/63.  Can I use my prefix?  Can I use my
address?

Is there a widely agreed prefix match rule for variable-length prefixes?

Or maybe I miss something big...

> 2. if one or more Internet Gateway is reachable, provide routable
> unique global prefixes to each MANET router

YEs, makes sense to me because I see a DHCP Server on that Internet
Gateway, or maybe a Router sending RAs.  But yes, makes sense to me.

> routers (e.g. as a result of a network partitioning/merger)

I'm not sure what's meant by this.  It seems related to the "MANET-wide
unique prefixes".

Alex

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---

From: "Teco Boot" <[email-masked]>
Date: Tue, 27 Nov 2007 16:46:57 +0100

> use fd67::/8 and fd67:300::/24.  Is my prefix unique compared to these?

I think so.
Prefix is address and prefix length.

> Is there a widely agreed prefix match rule for variable-length

Longest match rule is defined in RFC1812. This is CIDR (by definition...)

Teco.

---

From: "Francisco J. Ros" <[email-masked]>
Date: Tue, 27 Nov 2007 16:55:27 +0100

Hi everyone,

On Tuesday 27 November 2007 14:58, Emmanuel Baccelli wrote:
> Hi Teco,
>
> Teco Boot a écrit :
> > Hi Emmanual,
> >
> > On item 3, the text: "as a result of a network partitioning/merger", I
> > think it is impossible having non-unique global addresses after a merge;
> > where before the merge addresses were globally unique. Or maybe earth
> > merged with mars;-)
> >
That seems to preclude the use of in-service DAD for globally routable 
addresses. However, duplicates could appear e.g. if some addresses are 
manually assigned or any node presents some kind of misbehavior. Therefore, I 
wouldn't exclude global addresses from the uniqueness check.

Regards,
fran

-- 
Francisco J. Ros, Ph.D. Student
Dept. of Information and Communications Engineering
University of Murcia, Murcia (Spain)

http://masimum.inf.um.es/fjrm/

---

From: Carlos Jesús Bernardos Cano <[email-masked]>
Date: Tue, 27 Nov 2007 16:55:01 +0100

Hi Alex,

> Is there a widely agreed prefix match rule for variable-length prefixes?

As I understand that, a prefix is unique if it is not contained within
any other prefix used within the MANET. Therefore, referring to your
examples, fd67::/16 is not unique if fd67::/8 is already used by another
MANET router. Similarly, if I'm using fd67::1/63, then you cannot use
fd67::1/64.

At least, this is my understanding... how about others?

Carlos

-- 
¡ASÓCIATE! Gratis para estudiantes  http://www.telematica.ws
 Carlos Jesús Bernardos Cano     http://www.netcoms.net
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---

From: "Teco Boot" <[email-masked]>
Date: Tue, 27 Nov 2007 17:03:14 +0100

> wouldn't exclude global addresses from the uniqueness check.

I think we agree on removing partitioning, OK?

On merges: yes, some types of address generation have a somewhat high
probability on collisions.
But we are scoped on autoconfiguration, or am I missing something?

My personal experience in real world: many years ago I had to deal with a
malware attack, utilizing duplicate checks. Still, this is one of my
nightmares. Just to place DAD in perspective, it has also a large, large
drawback. I am not against DAD, but I want to use it very carefully.

By the way, I like using anycast a lot, especially in an ad-hoc environment.
Typically addresses are configured manually and must not be blocked by
multi-link DAD.

Teco.

---

From: Alexandru Petrescu <[email-masked]>
Date: Tue, 27 Nov 2007 17:11:01 +0100

> Prefix is address and prefix length.

Ok, so for you two prefixes whose first 16bits match (fd67::/16 and 
fd67:300::/24) are not equal.  Are they aggregated?

> Longest match rule is defined in RFC1812. This is CIDR (by definition...)

Right... "longest prefix match" is what a router does when comparing a 
dst address in a packet against a set of prefixes in a routing table - 
ok, algorithm known and implemented widely.  It selects a routing table 
entry, but it doesn't detect duplicates.  There may be several entries 
in the routing table that do match; thus I wouldn't say longest prefix 
match is good at detecting duplicates.  (DAD detects duplicates easily 
because it compares 128bit apples to 128bit apples).

That algorithm would give inconsistent (to my sense) answers when the 
prefixes to be compared are variable length.  It would compare apples to 
oranges.

For example, if I try to match fd67::/16 to fd67:1000::/24 then I have 
two cases:
-I consider the /16 to be the full length, I longest prefix
  match and I find they really match(!).  So they're not unique.
-I consider the /128 to be the full address length, then I find
  fd67::/24 doesn't match at all fd67:1000::/24.  So they're unique.

That's why I don't know how to say when prefixes of variable lengths are 
unique or not.  Sorry if I miss something big... or maybe I should ask 
whether there's a widely accepted concept of prefix matching.  I may not 
be aware sorry.

Alex

---

From: "Teco Boot" <[email-masked]>
Date: Tue, 27 Nov 2007 17:15:26 +0100

> Van: Carlos Jesús Bernardos Cano [mailto:[email-masked]]
> Verzonden: dinsdag 27 november 2007 16:55
> Aan: Alexandru Petrescu
> CC: [email-masked]; Emmanuel Baccelli
> > Let's say for example I have this fd67::/16 prefix and I wonder
> > whether it's unique.  I ask left and right and two people tell me
> they
> > already use fd67::/8 and fd67:300::/24.  Is my prefix unique compared
> to these?
> >   Can I use my prefix?
> >
> > Another example: I have this address and prefix fd67::1/64 and you
> > have this address and prefix fd67::1/63.  Can I use my prefix?  Can I
> > use my address?
> >
> examples, fd67::/16 is not unique if fd67::/8 is already used by
> another MANET router. Similarly, if I'm using fd67::1/63, then you
> cannot use fd67::1/64.
> 

Please do not mess up addresses and prefixes.
fd67::/8 and fd67::1/63 are not a valid prefixes. Those are FD::/8 and
FD67:0:0:0::/63 (or FD67::/63 in short).
FD67:: is an address. fd67::1 also.

Addresses should be unique. Prefixes should be unique (forget anycast for a
second).

Check RFC1812 for some history on subnets / masks, CIDR and prefixes:
   The use of networks and subnets is now historical, although the
   language used to describe them remains in current use.  They have
   been replaced by the more tractable concept of a network prefix.  A
   network prefix is, by definition, a contiguous set of bits at the
   more significant end of the address that defines a set of systems;
   host numbers select among those systems.  There is no requirement
   that all the internet use network prefixes uniformly.  To collapse
   routing information, it is useful to divide the internet into
   addressing domains.  Within such a domain, detailed information is
   available about constituent networks; outside it, only the common
   network prefix is advertised.

Teco.

> > I'm not sure what's meant by this.  It seems related to the
> > "MANET-wide unique prefixes".
> >
> > Alex
> >
> >
> >

---

From: "Teco Boot" <[email-masked]>
Date: Tue, 27 Nov 2007 17:23:51 +0100

> Van: Alexandru Petrescu [mailto:[email-masked]]
> Verzonden: dinsdag 27 november 2007 17:11
> Aan: Teco Boot
> CC: [email-masked]
> whether

Highly depends on routing protocol.
Don't forget we do not have natural masks anymore, we have CIDR.

> because it compares 128bit apples to 128bit apples).

Current DAD is on link.
I did not check all these DAD proposals.
I think checking a routing table or any other table on /128 prefixes makes
sense. Maybe checking on other prefixes also, e.g. when generating a unique
ULA prefix, why not checking some tables? Mostly it is just burning CPU
cycles, but once in a trillion years, who knows. Or when verifying PD, maybe
there is a false node using a prefix when it should have released this. Or a
false DHCP server.

(I know the manual config stuff, false MAC addresses etc.)

Teco.

---

From: Carlos Jesús Bernardos Cano <[email-masked]>
Date: Tue, 27 Nov 2007 17:35:37 +0100

Hi Teco,

> FD67:: is an address. fd67::1 also.

	Although conceptually I agree that FD::/8 is more correct when
referring to a prefix, FD67::/8 can also be used (it is actually the
same prefix: FD::/8, nothing more). FD67::1/63 is also a valid prefix
(it's just FD67::/63). I agree FD67:: and FD67::1 are addresses (I
didn't say otherwise), but, on the other hand, we can use FD67::1/64
both to refer to a prefix or an address combined with the prefix
(RFC4291), it depends on the context (I was talking about prefixes in my
previous mail, I just copied and pasted, I agree I could have been more
correct...).

	Then, coming back to the uniqueness of addresses and prefixes, if we
are thinking about delegation of prefixes to a MANET router, which is
going to use it to configure its/their interface/s (and maybe those of
attached nodes), then prefixes should be unique in the sense that the
IPv6 addresses that can be formed out of these prefixes are unique,
compared to the addresses that can be formed out of other prefixes
delegated within the MANET. This is different from prefix aggregation in
routing, we are talking about prefix delegation within a MANET
(delegated prefixes used by MANET routers should not overlap). Maybe I'm
missing something...

	Regards,

	Carlos

---

From: Christophe Jelger <[email-masked]>
Date: Tue, 27 Nov 2007 17:40:20 +0100

longest prefix match cares about finding the ... longest match, but you 
don't have to indicate any prefix length a priori: you just use that 
later for interpreting the result

   fd67::(/16) and fd67:1000::(/24)

absolute longest match is 19 bits - interpretation: 16 <= 19 <= 24 so 
one prefix is a subpart of the other. I here want to highlight the fact 
that longest match is one thing, interpretation of the result is another 
thing.

Christophe

---

From: Christophe Jelger <[email-masked]>
Date: Tue, 27 Nov 2007 17:49:42 +0100

> (delegated prefixes used by MANET routers should not overlap). Maybe I'm

talking about overlapping prefixes is certainly much better (and 
precise) terminology than talking about unique prefixes (which can be 
confusing). Note the term "unique" is very tricky as an address is 
always unique with respect to its namespace (e.g. 10.1.2.3 is unique in 
the IPv4 namespace): whether it is used by multiple hosts or not is 
another story, but what really matters is that there is no overlap with 
respect to some scope.

---

From: "Teco Boot" <[email-masked]>
Date: Tue, 27 Nov 2007 17:52:04 +0100

> Verzonden: dinsdag 27 november 2007 17:36
> Aan: Teco Boot
> CC: 'Alexandru Petrescu'; [email-masked]; 'Emmanuel Baccelli'
> Onderwerp: RE: [Autoconf] Goals of MANET autoconf
> 
> Hi Teco,
> 
> (RFC4291), it depends on the context (I was talking about prefixes in
> my previous mail, I just copied and pasted, I agree I could have been
> more correct...).

OK. You intended "IPv6 address prefix"

> 
> 	Then, coming back to the uniqueness of addresses and prefixes, if
> we are thinking about delegation of prefixes to a MANET router, which
> is going to use it to configure its/their interface/s (and maybe those
> of attached nodes), then prefixes should be unique in the sense that
> the
> delegated within the MANET. 

I think prefix delegation is stepping into solution space. We are working on
PS now.

I would never assign a wide prefix to an interface and delegate parts of it
to other routers. This should be prohibited somewhere in an RFC. If not, I
write one!!!!

> This is different from prefix aggregation
> in routing, we are talking about prefix delegation within a MANET
> (delegated prefixes used by MANET routers should not overlap). Maybe
> I'm missing something...

What is different with existing PD? I don't get it. 
If some entity provides a prefix to you, it is owned by you, respecting
expiration timers or whatever condition (NEMO use existence of tunnel).
You can use the prefix by assigning to an interface ___or____ use the prefix
for further delegation.
Parts of the prefix could be reserved for own usage, other parts for further
delegation. 
There should not occur a collision. If so, some of the nodes is false. What
can we do? Yell? Hit someone?
OK, swap to another prefix can be used. But I prefer introducing some
security features first.

Teco.

> 
> 	Regards,
> 
> 	Carlos
> 
> >
> > Addresses should be unique. Prefixes should be unique (forget anycast
> > for a second).
> >
> > > > > 2. if one or more Internet Gateway is reachable, provide
> > > > > routable unique global prefixes to each MANET router
> > > >
> > > > YEs, makes sense to me because I see a DHCP Server on that
> > > > Internet Gateway, or maybe a Router sending RAs.  But yes, makes
> sense to me.
> > > >
> > > > > 3. detect and resolve if non-unique prefixes are assigned to
> > > > > MANET routers (e.g. as a result of a network
> > > > > partitioning/merger)
> > > >

---

From: "Francisco J. Ros" <[email-masked]>
Date: Tue, 27 Nov 2007 18:29:53 +0100

Hi Teco,

On Tuesday 27 November 2007 17:03, Teco Boot wrote:
> > > > On item 3, the text: "as a result of a network
> >
> > partitioning/merger", I
> >
> > > > think it is impossible having non-unique global addresses after a
> >
> > merge;
> >
> > > > where before the merge addresses were globally unique. Or maybe
> >
> > earth
> >
> > > > merged with mars;-)
> > > >
> > > I agree with removing the mention of partitionning here. But as far
> >
> > as
> >
Yes :)

> But we are scoped on autoconfiguration, or am I missing something?
Manually configured addresses was just an example. Depending on the final 
[autoconf] protocol(s), we could find situations where duplicated global 
addresses appear. So, in the context of the P-S, are we sure that this is 
never going to happen? If not, why exclude global addresses from the 
(in-service) uniqueness check if, in fact, it could come "for free" with the 
same mechanism for non-global?

My suggestion is not being so explicit right now, and just talk 
about "configured address uniqueness in the situation where different ad hoc 
networks merge" (from the charter).

Regards,
fran

> By the way, I like using anycast a lot, especially in an ad-hoc
> environment. Typically addresses are configured manually and must not be
> blocked by multi-link DAD.
>
> Teco.
>
> > Regards,
> > fran
> >

---

From: "Teco Boot" <[email-masked]>
Date: Tue, 27 Nov 2007 19:05:59 +0100

> Van: Francisco J. Ros [mailto:[email-masked]]
> Verzonden: dinsdag 27 november 2007 18:30
> Aan: Teco Boot
> CC: [email-masked]

Ack.
Teco

---

From: Emmanuel Baccelli <[email-masked]>
Date: Tue, 27 Nov 2007 23:20:39 +0100

OK, here is an updated tentative item list, reflecting the latest 
comments. Let us continue this healthy discussion and try to boil down 
to an expression most people agree with. So what do we think of this?

1. provide unique addresses and/or non-overlapping prefixes valid for 
communication within the MANET, to MANET routers requiring such 
configuration.

2. if one (or more) ICP is reachable, provide routable, globally unique 
addresses and/or routable non-overlapping prefixes to MANET routers 
requiring such configuration.

3. detect and resolve cases of duplicated addresses and/or prefixes
assigned to MANET routers (e.g. as a result of a network merger, or of a 
manual misconfiguration).

The term ICP here is used for being more precise than Internet Gateway, 
as defined in the tentative -03 :

Internet Configuration Provider (ICP)  - An entity that can provide 
routers requesting configuration with routable addresses or prefixes. A 
typical example of ICP is a DHCP server.

Emmanuel

---

From: mase <[email-masked]>
Date: Wed, 28 Nov 2007 14:18:25 +0900

Dear Emmanuel.

Thank you for updating goal item lists. My comments and questions are in line.

Thanks,
Kenichi

At 07:20 07/11/28, Emmanuel Baccelli wrote:
>comments. Let us continue this healthy discussion and try to boil 
>down to an expression most people agree with. So what do we think of this?
>
>1. provide unique addresses and/or non-overlapping prefixes valid 
>for communication within the MANET, to MANET routers requiring such 
>configuration.

I am aware that use of non-overlapping" has been suggeted. But, I am 
not sure about the difference between unique and non-overlapping. 
Given any scope, unique and non-overlapping have the same meaning. 
And, if so, use of two terms, one for address and the other for 
prefix is confusing.

>2. if one (or more) ICP is reachable, provide routable, globally 
>unique addresses and/or routable non-overlapping prefixes to MANET 
>routers requiring such configuration.

I am not sure why "routable"is not used in　１. and used in 2. 
Maybe, routable here means routable in the Internet toward MANET. If 
so, routable and globally unique seem redundant, because it is 
trivial that we do not use a globally unique but not routable 
address in the Internet. Am I missing something here?

>assigned to MANET routers (e.g. as a result of a network merger, or 
>of a manual misconfiguration).
>
>The term ICP here is used for being more precise than Internet 
>Gateway, as defined in the tentative -03 :
>
>routers requesting configuration with routable addresses or 
>prefixes. A typical example of ICP is a DHCP server.

"routabe" may be replaced by "globally unique".

---

From: Emmanuel Baccelli <[email-masked]>
Date: Wed, 28 Nov 2007 10:19:10 +0100

Hi Kenichi,

mase a e'crit :
> I am aware that use of non-overlapping" has been suggeted. But, I am not 
> sure about the difference between unique and non-overlapping. Given any 
> scope, unique and non-overlapping have the same meaning. And, if so, use 
> of two terms, one for address and the other for prefix is confusing.
> 

I think that the adjectives "unique addresses" and "non-overlapping
prefixes" are the more precise in order to describe what we mean here.

> I am not sure why "routable"is not used in　１. and used in 2. Maybe, 
> routable here means routable in the Internet toward MANET. If so, 
> routable and globally unique seem redundant, because it is trivial that 
> we do not use a globally unique but not routable address in the 
> Internet. Am I missing something here?
> 

By "routable" it is meant "globally unique and topologically correct",
which is different from merely "globally unique".

>> assigned to MANET routers (e.g. as a result of a network merger, or of 
>> a manual misconfiguration).
>>
>> routers requesting configuration with routable addresses or prefixes. 
>> A typical example of ICP is a DHCP server.
> 

Here again, "routable" is meant as "globally unique and topologically
correct", and not simply "globally unique". Maybe we should define the
term "routable address"?

---

From: Alexandru Petrescu <[email-masked]>
Date: Wed, 28 Nov 2007 10:40:00 +0100

Carlos Jesús Bernardos Cano wrote:
> Hi Teco,
> 
>> Please do not mess up addresses and prefixes. fd67::/8 and 
>> fd67::1/63 are not a valid prefixes. Those are FD::/8 and 
>> FD67:0:0:0::/63 (or FD67::/63 in short). FD67:: is an address. 
>> fd67::1 also.
> 
>  same prefix: FD::/8, nothing more).

Fits my understanding.

> FD67::1/63 is also a valid prefix (it's just FD67::/63).

This too.

> I agree FD67:: and FD67::1 are addresses (I didn't say otherwise), 
> but, on the other hand, we can use FD67::1/64 both to refer to a 
> prefix or an address combined with the prefix (RFC4291), it depends 
> on the context (I was talking about prefixes in my previous mail, I 
> just copied and pasted, I agree I could have been more correct...).

I agree.

>  are thinking about delegation of prefixes to a MANET router, which
> is going to use it to configure its/their interface/s (and maybe
> those of attached nodes), then prefixes should be unique in the sense
> that the IPv6 addresses that can be formed out of these prefixes are 
> unique, compared to the addresses that can be formed out of other 
> prefixes delegated within the MANET.

I agree.

> This is different from prefix aggregation in routing, we are talking
> about prefix delegation within a MANET (delegated prefixes used by
> MANET routers should not overlap). Maybe I'm missing something...

I think prefix aggregation in routing is inter-mixed with what we think 
we respect to address uniqueness and relationship between prefixes.

Alex

---

From: Alexandru Petrescu <[email-masked]>
Date: Wed, 28 Nov 2007 10:40:46 +0100

> that longest match is one thing, interpretation of the result is another 

Fits my understanding too.

Alex

---

From: Alexandru Petrescu <[email-masked]>
Date: Wed, 28 Nov 2007 10:42:01 +0100

> another story, but what really matters is that there is no overlap with 

I agree.  And I think we don't have common understanding of that scope. 
  That leads to round and round issues.

Alex

---

From: mase <[email-masked]>
Date: Wed, 28 Nov 2007 19:04:27 +0900

Hi, Emmanuel,

>prefixes" are the more precise in order to describe what we mean here.

Now, I understand. ok, but I think that we should give an explanation 
what non-overlapping prefix means in the PS document.

>which is different from merely "globally unique".

I understant. But, I just think that it is trivial that we do not use 
a globally unique but not-routable address in the Internet. If you 
think that just "globally unique" is insufficient, I still prefer 
"globally unique and topologically correct addresses and/or globally 
non-overlapping and topologically correct prefixes ". Do you think 
that the adjective "globally" is not required for non-overlapping prefixes?

>correct", and not simply "globally unique". Maybe we should define the

If we avoid use of "routable", we don't need the definition.

Thanks,
Kenichi

---

From: Alexandru Petrescu <[email-masked]>
Date: Wed, 28 Nov 2007 11:13:58 +0100

Teco Boot wrote:
> 
>> -----Oorspronkelijk bericht----- Van: Carlos Jesús Bernardos Cano 
>> [mailto:[email-masked]]
[...]
>> we are thinking about delegation of prefixes to a MANET router, 
>> which is going to use it to configure its/their interface/s (and 
>> maybe those of attached nodes), then prefixes should be unique in 
>> the sense that the IPv6 addresses that can be formed out of these 
>> prefixes are unique, compared to the addresses that can be formed 
>> out of other prefixes delegated within the MANET.
> 
> I think prefix delegation is stepping into solution space. We are 
> working on PS now.

Ok, I agree.

> I would never assign a wide prefix to an interface and delegate parts
>  of it to other routers. This should be prohibited somewhere in an 
> RFC. If not, I write one!!!!

I wouldn't agree :-)

If we look at the Figure 6 of manetarch it says that P::/62 prefix is
delegated to MANET Router, and it's not shown configured on any of its
interface, so that "P::/62" is not in any of its routing tables.  What
does then mean to "delegate P::/62 to a MANET Router".  To me it can
mean there's at least one other router having an entry in its routing
table for P::/62 with NextHop one of the MANET Router's IP address.

This will not stop that 'other' Router to have another entry with a
longer P::/63 and NextHop address of 'yet another' Router (different
than that MANET Router).

IF on the other hand we said that P::/62 and all its subprefixes are
administratively allocated to MANET Router then I'd be sure that MANET
Router is entirely in charge of P::/62 and no other Router would be in
charge of any of its subprefixes.

I will thus not agree with you to prohibit assigning one wide prefix to
one interface and delegate parts of it to other routers. (and at the
same time I think you meant short (less bits) prefix not wide). (sorry!)

Think that the prefix ::/0 is allocated to the Internet and 2001::/3 (a
subprefix of ::/0) is allocated to somebody else within that Internet.

>> This is different from prefix aggregation in routing, we are 
>> talking about prefix delegation within a MANET (delegated prefixes 
>> used by MANET routers should not overlap). Maybe I'm missing 
>> something...
> 
> What is different with existing PD? I don't get it. If some entity 
> provides a prefix to you, it is owned by you, respecting expiration 
> timers or whatever condition (NEMO use existence of tunnel). You can 
> use the prefix by assigning to an interface ___or____ use the prefix
>  for further delegation. Parts of the prefix could be reserved for
> own usage, other parts for further delegation. There should not occur
> a collision. If so, some of the nodes is false. What can we do? Yell?
>  Hit someone? OK, swap to another prefix can be used. But I prefer 
> introducing some security features first.

I kind of understand what you mean, I won't yell :-)  I think we need to
use consistently the following terms with respect  to prefixes:

"delegated"
"allocated"
"assigned"
"configured"
"provided"

I think I've read it with sometimes conflicting meanings in AUTOCONF,
MIP6 and DHC WGs discussions.  Sometimes I could understand ok even if
meanings are conflicting but sometimes the terminology conflict is
obviously the issue.  Just a thought.

Alex

---

From: Alexandru Petrescu <[email-masked]>
Date: Wed, 28 Nov 2007 11:23:49 +0100

> of two terms, one for address and the other for prefix is confusing.

I agree 'non-overlapping' has been suggested and I'm not sure either
about the difference.

If we knew the 'scope' precisely then I think I could understand better.

But 'scope' itself is not defined.

> Internet. Am I missing something here?

I agree.  BEsides, I don't think IPv6 has non-routable addresses other
than the link-local address and ULAs.  So we'd need our position with
respect to these two.  Is a MLA a link-local address?  A ULA? ("IPv6
Unique Local Address" RFC4193).

None of these two?

> "routabe" may be replaced by "globally unique".

ULAs (and link-local addresses to a certain extent) seem to be globally
unique but non-routable.

And I think Emmanuel's intention is that ICP distributes addresses that
are not ULAs nor link-local addresses.

Alex

---

From: Alexandru Petrescu <[email-masked]>
Date: Wed, 28 Nov 2007 11:37:30 +0100

> manual misconfiguration).

But we said we _can't_ detect cases of duplicated prefixes.

Given two prefixes of different lengths sometimes I think they're 
duplicates sometimes I think they're unique.

What do you think?

Alex

---

From: Emmanuel Baccelli <[email-masked]>
Date: Thu, 29 Nov 2007 14:39:50 +0100

> duplicates sometimes I think they're unique.

OK. So if we say instead "detect and resolve cases of duplicated 
addresses and overlapping prefixes", does this answer your question?

Emmanuel

---

From: Alexandru Petrescu <[email-masked]>
Date: Thu, 29 Nov 2007 15:31:56 +0100

It's good to keep an ongoing 3-item list of goals to better focus the work.

But why detecting this duplication of stuff?  What breaks if we don't? 
Detecting overlapping for the sake of qualifying it as such?

> addresses and overlapping prefixes", does this answer your question?

Detecting duplicate address use sounds ok.  But prefixes?

Why should one detect when two prefixes overlap, is this an error 
condition?  Two networks may merge, their prefixes overlap, and 
everything is fine - there's nothing to solve.

What do I miss?

I mean if we define a more precise scope/subnet/multicast structure of 
MANET then we can talk about prefixes of fixed lengths eventually 
overlapping or duplicating (compare same-prefix lengths).  Until then we 
(or just I) just turn round and round around issues we'd suppose are 
problems.

(as it was presented at a certain MANEMO activity meeting: two NEMO MRs
  connecting egress-egress do have a certain defined
  subnet/multicast/scope structure, and there may be a need to detect
  when two /64 MNPs are different.  But I can't say that in the MANET
  context because there's no structure in MANET by its own definition.
  If there's no scope/multicast/subnet structure then we can't say that
  we work towards the goal of detecting duplicate/overlapping prefixes.
  That is turning round and round for me - I can say: yes, you're right,
  that's it; as well as I can say I completely disagree.)

Alex

---

From: Emmanuel Baccelli <[email-masked]>
Date: Thu, 29 Nov 2007 16:01:20 +0100

Hi Alex

> It's good to keep an ongoing 3-item list of goals to better focus the work.

I agree. Agreeing on a few items is the first step towards a consensus 
on a whole text, is it not?

> Detecting overlapping for the sake of qualifying it as such?

If you have duplicate addresses, this breaks routing, for starters.  And 
if some routers manage independently overlapping prefixes it may lead to 
duplicate address assignment. Do you agree?

---

From: Alexandru Petrescu <[email-masked]>
Date: Thu, 29 Nov 2007 16:34:19 +0100

Emmanuel Baccelli wrote:
> I agree. Agreeing on a few items is the first step towards a 
> consensus on a whole text, is it not?

I agree.

>> But why detecting this duplication of stuff?  What breaks if we 
>> don't? Detecting overlapping for the sake of qualifying it as such?
>> 
>> 
>> 
> 
> If you have duplicate addresses, this breaks routing, for starters.

It may or it may not.  My first temptation is to say yes, duplicate
addresses is not good.  People have seen storms of packets filling
screens when two hosts configure same address on the same subnet - this
led to DAD mechanism.  That's a problem seen by many people and very
impressing such as to motivate a new and reliable mechanism.

But two duplicate addresses may not break routing, it's possible to
design translating schemes that work.

> And if some routers manage independently overlapping prefixes it may 
> lead to duplicate address assignment. Do you agree?

Certainly I don't agree.

Every two prefixes in this Internet _are_ overlapping (the only
exceptions are the pairs of prefixes whose first bit is different).  Yet
Internet works by using these overlapping prefixes.

Alex

>>>>> 3. detect and resolve cases of duplicated addresses and/or 
>>>>> prefixes assigned to MANET routers (e.g. as a result of a 
>>>>> network merger, or of a manual misconfiguration).
>>>> 
>>>> Given two prefixes of different lengths sometimes I think 
>>>> they're duplicates sometimes I think they're unique.
>>>> 
>>>> What do you think?
>>>> 
>>>> Alex
>>>> 
>>>> 
>>> 
>>> 
>> I mean if we define a more precise scope/subnet/multicast structure
>>  of MANET then we can talk about prefixes of fixed lengths 
>> eventually overlapping or duplicating (compare same-prefix 
>> lengths).  Until then we (or just I) just turn round and round 
>> around issues we'd suppose are problems.
>> 
>> (as it was presented at a certain MANEMO activity meeting: two NEMO
>>  MRs connecting egress-egress do have a certain defined 
>>  when two /64 MNPs are different.  But I can't say that in the 
>> MANET context because there's no structure in MANET by its own 
>> definition. If there's no scope/multicast/subnet structure then we 
>> can't say that we work towards the goal of detecting 
>> duplicate/overlapping prefixes. That is turning round and round for
>>  me - I can say: yes, you're right, that's it; as well as I can say
>>  I completely disagree.)
>> 
>> Alex
>> 
>> 
>>  This email has been scanned by the MessageLabs Email Security 
>> System. For more information please visit 
>> http://www.messagelabs.com/email 
> _______________________________________________ Autoconf mailing list
>  [email-masked] https://www1.ietf.org/mailman/listinfo/autoconf
>

---

From: Emmanuel Baccelli <[email-masked]>
Date: Thu, 29 Nov 2007 16:47:14 +0100

> design translating schemes that work.

So you agree it is a problem that needs attention. Good ;)

> Internet works by using these overlapping prefixes.

I see what you mean. But the routers in the Internet do not manage these 
prefixes independently, right? There is a hierarchy. In MANETs, there is 
no "natural" or "long lasting" hierarchy, or dependence... This is an 
issue. Do you agree?

Emmanuel

>>>>>> prefixes assigned to MANET routers (e.g. as a result of a network 
>>>>>> merger, or of a manual misconfiguration).
>>>>>
>>>  of MANET then we can talk about prefixes of fixed lengths eventually 
>>> overlapping or duplicating (compare same-prefix lengths).  Until then 
>>> we (or just I) just turn round and round around issues we'd suppose 
>>> are problems.
>>>
>>> That is turning round and round for

---

From: Alexandru Petrescu <[email-masked]>
Date: Thu, 29 Nov 2007 18:36:28 +0100

Emmanuel Baccelli wrote:
>>  screens when two hosts configure same address on the same subnet -
>>  this led to DAD mechanism.  That's a problem seen by many people 
>> and very impressing such as to motivate a new and reliable 
>> mechanism.
>> 

It's a pencil and paper problem.

We need problems that make a receiver break in pieces when an
emitter sends something really bad.

>>> And if some routers manage independently overlapping prefixes it 
>>> may lead to duplicate address assignment. Do you agree?
>> 
>> Certainly I don't agree.
>> 
>> exceptions are the pairs of prefixes whose first bit is different).
>>  Yet Internet works by using these overlapping prefixes.
>> 
> 
> I see what you mean. But the routers in the Internet do not manage 
> these prefixes independently, right? There is a hierarchy.

There is neither topological hierarchy nor prefix hierarchy in the
Internet.  Not even DNS.  Neither for IPv4 nor for IPv6.

One buys a router: its routing table is really empty, not even a default
route.  Then some humans add some routes that make loopless sense,
that's all.  Computers help computing the loopless paths but there's no
hardcoded universally agreed method for that, lots of heuristics
involved.  There's no hierarchy or hardcoded automatic delegation of
responsibility for prefixes.  There are humans behind all that doing
stuff that makes sense.

> In MANETs, there is no "natural" or "long lasting" hierarchy, or 
> dependence... This is an issue. Do you agree?

When you say there's no long lasting hierarchy - what do you mean?  Is
it that the prefixes are completely unaggregated?  Is it that topology
is a mesh?  Is it that the rate of change of attachment of a node from
one link to another is very high?  What do you mean more precisely?

I really can't agree with you when you try to imply that because MANETs
are unknown we have a big problem.

All that said...

If we could just describe the subnet/multicast/scope models for MANET 
networks... then we could picture the addressing architecture on it... 
and then we could talk about prefixes, addresses and the problems we 
think they have.

That's just one oppinion...

Alex