Allow me to change the topic of this. It helps tracking the discussion.
Le 11/04/2019 à 03:53, Brian E Carpenter a écrit :
Hi Nabil,
On 11-Apr-19 03:40, NABIL BENAMAR wrote:
Do we still talk about broadcast in IPv6 ?
No, we talk about multicast. Pascal was using shorthand. But if
multicast fails with high probability, several aspects of IPv6 will
fail too, unless the LAN provides an NBMA (non-broadcast multiple
access) emulation of multicast, or suitable alternatives to SLAAC,
ND, NUD, and RA.
An earlier draft of this spec mentioned this problem:
The operation of the Neighbor Discovery protocol (ND) over
802.11-OCB links is different than over 802.11 links. In OCB,
the link layer does not ensure that all associated members
receive all messages, because there is no association
operation. Neighbor Discovery (ND) is used over 802.11-OCB.
but it was inconsistent and was removed. If Ole is correct below
about real-life conditions, the *problem* was not removed and the
draft is not going to work in the real world.
Brian,
I agree with your comments about the existence of preceding text of ND.
But please note ND works on OCB in the real world. It works when one
sets up the PHY and MAC links correctly, prior to putting IP on them.
The way to set up links prior to put IP on them could be described, but
not sure if its good to put it in an IP-over-OCB document. RFC2464 does
not tell how to click RJ45 cables in their sockets: we do it naturally,
but there is process in it (e.g. always fit the tag in the hole, and
feel and hear a click; if tag on the other way then it risks breaking;
after breaking an RJ45 socket surely IP wont work, because it is loose
and shows too many interruptions).
Similarly setting the PHY of an OCB domain such that IP can work has
process in it: select the right antennas, directionality, power levels,
channels; dont go beyond distance allowed by power levels. If that
process is not followed then there is no chance for IP (neither ND) to
work understandably. People grow white hairs because of this. More
attention to PHY and MAC prior to IP setup would reduce frustration of
the IP inclined.
It is good to keep work at levels.
Alex
Brian
On Wed, Apr 10, 2019, 14:45 Pascal Thubert (pthubert)
<pthubert@xxxxxxxxx <mailto:pthubert@xxxxxxxxx>> wrote:
Hello Ole:
Better remove, it is wrong anyway.
Because it is transitive, the description extends the so-called
subnet step by step to a potentially large number of cars such that
there is no broadcast domain that covers them all. If there is no
broadcast domain and no multicast emulation like a BSS does, how
can we run ND? Yes, it works with 3 cars in a lab.
The description looks like it is confused with the MANET / 6LoWPAN
concept of link, whereby my link joins the collection of nodes that
my radio can reach.
All the best,
Pascal
-----Original Message----- From: Ole Troan <otroan@xxxxxxxxxxxxx
<mailto:otroan@xxxxxxxxxxxxx>> Sent: mercredi 10 avril 2019
20:41 To: Alexandre Petrescu <alexandre.petrescu@xxxxxxxxx
<mailto:alexandre.petrescu@xxxxxxxxx>> Cc: Pascal Thubert
(pthubert) <pthubert@xxxxxxxxx <mailto:pthubert@xxxxxxxxx>>;
ietf@xxxxxxxx <mailto:ietf@xxxxxxxx>; its@xxxxxxxx
<mailto:its@xxxxxxxx>; int-dir@xxxxxxxx
<mailto:int-dir@xxxxxxxx>; draft-ietf-ipwave-ipv6-over-
80211ocb.all@xxxxxxxx <mailto:80211ocb.all@xxxxxxxx>; Brian E
Carpenter <brian.e.carpenter@xxxxxxxxx
<mailto:brian.e.carpenter@xxxxxxxxx>> Subject: Re: [Int-dir]
Intdir early review of draft-ietf-ipwave-ipv6-over- 80211ocb-34 -
'conforming IPv6' - fe80::/10 vs fe80::/64
You said: if OCB is still 48bit, and if there is bridging
OCB-Ethernet, then no
reason to be different than rfc2464.
I said: OCB is still 48bit, but there is no bridging
OCB-Ethernet.
The conclusion is: there is reason to be different from RFC
2464.
Why?
Now, you give a different conclusion.
Excuse me, I would like to clarify this please?
Clarify what? That a link-layer that looks an awfully lot like
Ethernet should not follow the 64-bit boundary and the definition
of the link-local address mapping of rfc2464? Section 4.5.1 is
already clear on that.
I think the only thing we are asking you is to change the
following paragraph:
OLD: A subnet is formed by the external 802.11-OCB interfaces of
vehicles that are in close range (not by their in-vehicle
interfaces). This subnet MUST use at least the link-local prefix
fe80::/10 and the interfaces MUST be assigned IPv6 addresses of
type link-local.
NEW: A subnet is formed by the external 802.11-OCB interfaces of
vehicles that are in close range (not by their in-vehicle
interfaces). A node MUST form a link-local address on this link.
Not quite sure what value that paragraph adds in the first place.
You could probable remove it.
Cheers, Ole
Alex
Le 10/04/2019 à 12:28, Ole Troan a écrit :
Alexandre, Right, so it doesn’t sound like you have any
reason to be different from
RFC2464.
Just reference or copy that text (section 5, rfc2464). Ole
On 10 Apr 2019, at 11:22, Alexandre Petrescu
<alexandre.petrescu@xxxxxxxxx
<mailto:alexandre.petrescu@xxxxxxxxx>> wrote:
Le 10/04/2019 à 11:04, Ole Troan a écrit :
"At least" does not mean "the value should be at
least 10" in that
phrase.
Do you think we should say otherwise?
To me there is nothing in the actual text to tell
me that "at least" qualifies the "/10". I think you
could rephrase as "This subnet's prefix MUST lie
within the link-local prefix fe80::/10 ..."
However, see Jinmei's messages about conformance
with RFC 4291.
I think there might be unexpected side effects from
using an address like fe80:1::1. What if some code
uses matching with fe80::/64 to test if an address
is link-local? I agree that would be faulty code,
but you would be the first to discover it.
Indeed. If you absoultely must cut and paste text
from 2464:
YEs, that is how we started. We cut and paste from
2464.
5. Link-Local Addresses The IPv6 link-local address
[AARCH] for an Ethernet interface is formed by
appending the Interface Identifier, as defined above,
to the prefix FE80::/64. 10 bits 54 bits
64 bits
+----------+-----------------------+----------------------------+
|1111111010| (zeros) | Interface
Identifier |
+----------+-----------------------+----------------------------+
I presume there is support for bridging 802.11p and
other 802.3 links?
In the IP-OBUs that I know there is IP forwarding between
802.11-OCB
(earlier 802.11p) and 802.3, not bridging.
In some IP-OBU (Internet Protocol On-Board Unit) some
non-OCB
interfaces are indeed bridged. E.g. the Ethernet interface is
bridged to the WiFi interface; that helps with DHCP, tcpdump and
others to see one a single - bridged - interface.
Bridging may be, but it is not a MUST. There is no
necessarily any bridging
between the 802.11-OCB interface and other interface, neither
bridging between the multiple 802.11-OCB interfaces that might be
present in the same computer.
Do you assume bridging of 802.11-OCB interface to Ethernet
interface is
always there?
Note: I also heard many comments suggesting that EAL is
akin to
'bridging'. I do not know whether you refer to that perspective.
If yes, we can discuss it separately.
Alex
[...]
And that the MAC address length of this link type is
also 48 bits?
YEs, the length of MAC address on 802.11 mode OCB is
also 48.
If the two assumptions above hold, then I see zero
justification for
pushing the 64 bit boundary in this draft.
Let me try to understand the first assumption.
Ole
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