Subject: [Autoconf] call for consensus about link local address support

From: Ryuji Wakikawa <[email-masked]>
Date: Mon, 31 Aug 2009 18:59:35 +0900

Hi all,

This is consensus call about the link-local address support in MANET.
Please review the following call for consensus and vote your opinion  
by Sep10th.

DT will update the document according to our consensus.

thanks,
Thomas & ryuji

------------------------------------------------------------------
CALL FOR CONSENSUS

Deadline: 2009-09-10 6:00PM PST.

Target ID: Design Team Document
"IP Addressing Model in Ad Hoc Networks"
http://tools.ietf.org/html/draft-baccelli-autoconf-adhoc-addr-model-01

Issue (cited from the above draft):
- Use of Link Local Addresses - while the use of link local addresses on
  interfaces connecting to a MANET link is not prohibited, the semantics
  of "link local" in this context is yet to be defined, taking into
  account the unusual requirements that follow, concerning such
  addresses. These requirements include for example uniqueness within a
  scope spanning beyond a single IP hop.

Some discussions can be found at the IETF75 AUTOCONF minutes
http://www.ietf.org/proceedings/75/minutes/autoconf.txt

Please vote your preference between the following two alternatives.
If you have another alternative, please propose it and give your
reasons why you prefer that alternative.

a) The document shall support link-local addresses as required
  for nodes in a MANET in addition to unique-local and global
  addresses.

b) Support unique-local and global addresses as required for MANET
  nodes.  The document shall not prohibit using link-local addresses,
  but shall describe the difficulties inhibiting compliance in MANET
  with the standardized IPv6 properties that characterize the use of
  link-local addresses.
------------------------------------------------------------------

---

From: "Teco Boot" <[email-masked]>
Date: Tue, 1 Sep 2009 08:15:42 +0200

I go for A.

I don't feel inhibited using link-local addresses in a MANET.
Link-local addresses are mandatory [RFC4291], for sure for 
router interfaces [RFC4861].
The MANET extensions for OSPF [RFC5340] also make use of 
link-local addresses.
The link-local multicast scope spans the same topological
region as link-local unicast [RFC4291], and we use link-local
multicast for our MANET protocols [RFC5498].

I think we follow the OSPF [RFC5498] interpretation of 
link-locals:
>   IPv6 routers do not forward IPv6 datagrams having 
>   link-local source addresses 
This is slightly different than [RFC4291]:
>   Routers must not forward any packets with Link-Local 
>   source or destination addresses to other links.

Some have brought up their concerns:

  1: Scope of link-local addresses is not clearly defined:
I suggest using the OSPF interpretation above.

  2: Duplicate address detection [RFC4682] fails in a MANET:
RFC4682 mentions DAD may be disabled, where it is believed
the overhead of performing DAD outweighs its benefits. I 
think this is applicable to MANETs.
Also DAD is not required with modified EUI-64 tokens with
the "u" bit set to universal [RFC4291].
Some have proposed passive DAD, where multi-hop uniqueness
in a MANET segment is assisted by the MANET protocol. This
could work for link-locals.

  3: The current OLSRv2 / NHDP draft does not allow usage of 
     link-local addresses:
I am not sure this is true. There may be restrictions, which IMHO
can be fixed. 
Ian Chakeres has expressed concerns on MANET ML on having multiple
interfaces with same addresses. This is related to link-local 
addresses.

I am not saying we need a new Autoconf mechanism for link-local 
addresses. I just say link-locals are part of the addressing model 
that applies to MANETs.

Regards, Teco.

|-----Oorspronkelijk bericht-----
|Van: [email-masked] [mailto:[email-masked]] Namens
|Ryuji Wakikawa
|Verzonden: maandag 31 augustus 2009 12:00
|Aan: [email-masked]
|Onderwerp: [Autoconf] call for consensus about link local address
|support
|
|Hi all,
|
|This is consensus call about the link-local address support in MANET.
|Please review the following call for consensus and vote your opinion
|by Sep10th.
|
|DT will update the document according to our consensus.
|
|thanks,
|Thomas & ryuji
|
|------------------------------------------------------------------
|CALL FOR CONSENSUS
|
|Deadline: 2009-09-10 6:00PM PST.
|
|Target ID: Design Team Document
|"IP Addressing Model in Ad Hoc Networks"
|http://tools.ietf.org/html/draft-baccelli-autoconf-adhoc-addr-model-01
|
|Issue (cited from the above draft):
|- Use of Link Local Addresses - while the use of link local addresses on
|  interfaces connecting to a MANET link is not prohibited, the semantics
|  of "link local" in this context is yet to be defined, taking into
|  account the unusual requirements that follow, concerning such
|  addresses. These requirements include for example uniqueness within a
|  scope spanning beyond a single IP hop.
|
|Some discussions can be found at the IETF75 AUTOCONF minutes
|http://www.ietf.org/proceedings/75/minutes/autoconf.txt
|
|Please vote your preference between the following two alternatives.
|If you have another alternative, please propose it and give your
|reasons why you prefer that alternative.
|
|a) The document shall support link-local addresses as required
|  for nodes in a MANET in addition to unique-local and global
|  addresses.
|
|b) Support unique-local and global addresses as required for MANET
|  nodes.  The document shall not prohibit using link-local addresses,
|  but shall describe the difficulties inhibiting compliance in MANET
|  with the standardized IPv6 properties that characterize the use of
|  link-local addresses.
|------------------------------------------------------------------
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