Subject: Re: [Autoconf] Re: Some Thoughts on Problem Statement.

From: Shubhranshu <[email-masked]>
Date: Wed, 28 Nov 2007 16:14:55 +0530

Please see inline comments

----- Original Message -----
From: "Alexandru Petrescu" <[email-masked]>
To: "Shubhranshu" <[email-masked]>

> Shubhranshu, thanks for your message.  To my reading, your message has
> structure in it; e.g. it says which are the cases to be followed.  It
> also seems to take into account most major ideas having already been
> exposed (since the little while I follow it).  I agree with it.  I have
> some comments.

Good to hear that.

>
> Overall, I'm trying to identify where and how do protocols break.
>
> Shubhranshu wrote:

<snip>
> Also, MANET Scope is somehting I need to understand better.  Is MANET
> Scope in any relationship with the existing scopes: link-local scope,
> global scope?  Is MANET Scope in some relationship with the scope of the
> all-manet-routers IP multicast group requested by manet-iana document?
>
> Is MANET scope in some relationship with the scopes of the following
> Ethernet MAC multicast addresses: 33::1 (all Ethernet hosts), 33::2 (all
> Ethernet routers), or other Ethernet MAC multicast group scopes?
>
> _some_ relationship?  _No_ relationship whatsoever?

IMO, MANET scope would be same as all-manet-routers multicast address
but the manet-iana document authors can confirm this.

>
> This makes me think the MANET Router doesn't communicate  to anybody
> else than self.  Its (real) network interface has no hosts attached to
> it (has Routers attached to it?), MANET interface is virtual and
> loopback interface leads to self.  I may misunderstand you.
>
> Also, I will have to read other documents to understand why the loopback
> interface needs to have address/prefix. If I understand that then maybe
> I can understand the above as well.

Not sure why you think MANET router does not communicate with anyone
else than self. Its network interface may or may not have any attached
hosts, depending on the application / deployment scenario. MANET
routers are expected to run manet-protocols on their MANET interface
only.

>
>> 2) Configuration of MANET interface:
>>
>> MANET Router uses this interface to communicate with other MANET
>> Routers. MANET routing and other MANET specific protocols are
>> expected to run on this interface. This interface SHOULD be
>> configured with a link local address and/or a /128 (in case of IPv6)
>> or with /32 (in case of IPv4) address. MANET interface may also use
>> smaller prefix provided the prefix uniqueness is guaranteed.
>> Configuration of MANET interface with a link local address and/or a
>> /128 address is straightforward, as it can use existing mechanisms,
>> except the issue of address uniqueness test over "multi-hop network".
>
> I agree.

Ok.

>
> If the MANET interface is virtual then I think there's no standard for
> defining link-local address on a virtual interface.  People do different
> things for these, sometimes random.
>
> I think a good virtual interface (MANET interface or other) would need:
> -a link-local address (/128 length).
> -a link-local prefix (the fe80 /10 length).
> -maybe a global subnet prefix with global address.
> -maybe another global subnet prefix with a global address.
>
> I think you mean that "MANET Interface" means a sort of a label we put
> on a real network interface.  Something that in some contexts some
> people call "egress interface", or "ingress interface".
>
> So, if you mean MANET Interface is a real interface, then we may already
> have a means to form a link-local address for it.

Agree, MANET interface is real interface and, in your words, MANET
interface is a sort of label we put on real network interface because
manet-protocols are suppose to run on this interface.

>
>> The probability of address duplication is quite low if most of the
>> /128 bits are randomly generated and so a node may skip address
>> uniqueness test. However, address uniqueness detection / resolution
>> is a requirement when smaller prefixes are used and also in military
>> & other critical MANET application scenarios. The address uniqueness
>> detection / resolution should be done across the entire  network thus
>>  requiring that the specific broadcast/multicast messages used for
>> this purpose be propagated "even to MANET Routers that are multi-hop
>> away". Currently there is no standard specification that addresses
>> this requirement.
>
> I think I'd suggest that when the MANET network uses subnets with
> well-defined link-layer multicast behaviour then the duplication should
> be ensured by DAD.  If the MANET network doesn't use such subnets, or
> uses SBI (semi-broadcast interface) then the address uniqueness
> detection should be indeed done across the semi-subnets (maybe define
> semi-subnet).
>
> Or maybe that address uniqueness should be _ensured_ across the entire
> MANET network, probably with a detection mechanism that acts on a scope
> lesser than the entire MANET network.

I think it needs to be done across the network. Not sure why you
suggest to use some detection mechanism to act on a scope lesser than
the entire network. May be for performance optimization ?

- Shubhranshu

>
> This is related to that MANET scope...
>
> I will read the tail of this message later.
>
> Thanks,
>
> Alex
>

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---

From: Alexandru Petrescu <[email-masked]>
Date: Wed, 28 Nov 2007 12:37:30 +0100

Shubhranshu wrote:
> <snip>
>> Also, MANET Scope is somehting I need to understand better.  Is
>> MANET Scope in any relationship with the existing scopes:
>> link-local scope, global scope?  Is MANET Scope in some
>> relationship with the scope of the all-manet-routers IP multicast
>> group requested by manet-iana document?
>> 
>> Is MANET scope in some relationship with the scopes of the
>> following Ethernet MAC multicast addresses: 33::1 (all Ethernet
>> hosts), 33::2 (all Ethernet routers), or other Ethernet MAC
>> multicast group scopes?
>> 

Ok, I would like to know whether MANET Scope is the same as
all-manet-routers multicast address scope.

If that is the case, then it is necessary what is the relationship
between that scope and Ethernet link scope.

>> This makes me think the MANET Router doesn't communicate  to
>> anybody else than self.  Its (real) network interface has no hosts
>> attached to it (has Routers attached to it?), MANET interface is
>> virtual and loopback interface leads to self.  I may misunderstand
>> you.
>> 
>> Also, I will have to read other documents to understand why the
>> loopback interface needs to have address/prefix. If I understand
>> that then maybe I can understand the above as well.
> 
> else than self. Its network interface may or may not have any
> attached hosts, depending on the application / deployment scenario.
> MANET routers are expected to run manet-protocols on their MANET
> interface only.

Ok, I understand that on some MANET Router all other nodes are connected
to the MANET Router's MANET interface(s).

>> If the MANET interface is virtual then I think there's no standard
>> for defining link-local address on a virtual interface.  People do
>> different things for these, sometimes random.
>> 
>> I think a good virtual interface (MANET interface or other) would
>> need: -a link-local address (/128 length). -a link-local prefix
>> (the fe80 /10 length). -maybe a global subnet prefix with global
>> address. -maybe another global subnet prefix with a global address.
>> 
>> 
>> I think you mean that "MANET Interface" means a sort of a label we
>> put on a real network interface.  Something that in some contexts
>> some people call "egress interface", or "ingress interface".
>> 
>> So, if you mean MANET Interface is a real interface, then we may
>> already have a means to form a link-local address for it.
> 

I understand.

>>> The probability of address duplication is quite low if most of
>>> the /128 bits are randomly generated and so a node may skip
>>> address uniqueness test. However, address uniqueness detection /
>>> resolution is a requirement when smaller prefixes are used and
>>> also in military & other critical MANET application scenarios.
>>> The address uniqueness detection / resolution should be done
>>> across the entire  network thus requiring that the specific
>>> broadcast/multicast messages used for this purpose be propagated
>>> "even to MANET Routers that are multi-hop away". Currently there
>>> is no standard specification that addresses this requirement.
>> well-defined link-layer multicast behaviour then the duplication
>> should be ensured by DAD.  If the MANET network doesn't use such
>> subnets, or uses SBI (semi-broadcast interface) then the address
>> uniqueness detection should be indeed done across the semi-subnets
>> (maybe define semi-subnet).
>> 
>> Or maybe that address uniqueness should be _ensured_ across the
>> entire MANET network, probably with a detection mechanism that acts
>> on a scope lesser than the entire MANET network.
> 

Not for performance optimization, just to say that DAD acts on the
well-define Ethernet link scope.  That is supposedly lesser scope than
MANET scope.  But I'm not sure you mean that MANET scope is lesser scope
than Ethernet, or the same scope, or wider scope.

If we say that MANET scope is same as Ethernet link scope then DAD can
work on MANET scope.

If we say MANET scope can contain several Ethernet link scopes then one
would do DAD on each of these links, each link would be a subnet.

If we say that Ethernet scope can contain several MANET scopes then IP
DAD would not work.

Alex

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