On 10/27/10 01:03 PM, Dario Tedeschi wrote:
I think what needs to be specified is the following:
1. For 6LoWPAN ND packets sent to a link-local address, the hop-limit
must be set to 255 (as per RFC4861).
2. For 6LoWPAN ND packets sent to a routable address, the hop-limit
MAY be set less than 255.
That is not how RFC 4861 works. It says that NS, NA, RS, RA, and
Redirect messages all need to be sent with hoplimit 255 and checked on
receipt.
The NS, NA, and Redirect messages can have a global destination address.
I don't see any reason to change this as part of 6lowpan-nd.
What is you reason for wanting to change it?
Erik
On the receiver side, an implementation MUST discard a ND packet that
has a link-local destination and a hop-limit less than 255.
Dario
On 22/10/2010 3:11 AM, Alexandru Petrescu wrote:
Le 22/10/2010 01:50, Erik Nordmark a écrit :
On 10/13/10 05:30 AM, Daniel Gavelle wrote:
When the multi-hop NS is sent from the LR to the LBR, its hop limit
is set to 255 and then decremented on each hop. When it arrives at
the LBR, the hop limit=255 check is ignored. There are a couple of
problems with this mechanism:-
(1) If the packet enters a routing loop, it will take a long time
to die.
(2) Some stacks have a rule that packets with a hop limit of 255
should never be forwarded by the routing layer or a hop limit of
254 should never be transmitted.
These problems could be addressed by setting the hop limit to a
more typical value, e.g. 64, for the multi-hop messages.
I don't have a problem suggesting a value like 64.
But the implementations in (2) seems to be utterly broken because
there isn't any RFC that says that packets with 255 or 254 should be
treated differently when transmitting or forwarding.
Except when those packets are ND... (I mean IIRC ND spec requires to
drop RS packets whose limit is less than 255).
Alex
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