Hi Mathilde, > Like traditional entries they > contain the IPv6 address / l2 address mapping however in terms of > "conceptual sending algorithm behavior" they are more like routing table > entries.
Indeed, then you have this neighbor table collision problem if you use them as such. I think 6lowpan-nd is not clear on updating the 'conceptual sending algorithm' though and how it works over different links. This is especially a problem for example with mesh-under, where everything is on-link and you need to send directly. Regards, -Colin -----Original Message----- From: Mathilde Durvy (mdurvy) [mailto:[email protected]] Sent: October 8, 2010 1:14 PM To: Colin O'Flynn; [email protected] Subject: RE: [6lowpan] 6lowpan-nd neighbour table collision Hi Colin, Admittedly I know better 4861 than 6lowpan-nd but I think the "conceptual sending algorithm" is mostly the same. So let me try to answer based on my understanding... [Colin] I appreciate the link to that description, as it raises some other questions for me. In 6lowpan-nd it specifically says that anything but link-local is off-link, in which case you wouldn't use the NC for anything but link-local correct? [Mathilde] Correct, although you still need the NC to find the mapping between the default router IPv6 address and its L2 address [Colin] I had assumed the NC could be used to check if a specific address was on-link or not in the absence of other information. From RFC4861 definition: Neighbor Cache - A set of entries about individual neighbors to which traffic has been sent recently. Entries are keyed on the neighbor's on-link unicast IP address and contain such information as its link-layer address, a flag indicating whether the neighbor is... But 6lowpan-nd says anything but fe80:: is off-link. Thus if you have a message to a global prefix device, you always send to the default router? [Mathilde] yes; default router or next-hop as specified by the routing protocol. [Colin] Thus lacking a routing protocol, how could a 6LR send a NA to a 6LN if that 6LN registered a global address? The 6lowpan-nd-examples currently have this: If Status is a Success: 6LR ---------NA-Reg------->6LN Src= LL64 (6LR) Dst= GP16 (6LN) ARO with Status = 0 If this is 'illegal' then I take full credit for not fully understanding how IPv6 works in creating that example ;-) But I think other people were assuming that would work fine as well w/o a routing protocol. [Mathilde] ] My understanding is that registrations are treated differently as traditional ND entries (or tentative NCE). Like traditional entries they contain the IPv6 address / l2 address mapping however in terms of "conceptual sending algorithm behavior" they are more like routing table entries. -----Original Message----- From: Mathilde Durvy (mdurvy) [mailto:[email protected]] Sent: October 8, 2010 8:42 AM To: Colin O'Flynn; [email protected] Subject: RE: [6lowpan] 6lowpan-nd neighbour table collision Hi Colin, It seems to me that if the addresses are global, presumably built on a off-link prefix there is no problem. > The ABR is address fe80::33:44 so it will now send a multihop ND message. > The regular IPv6 sending algorithm will first search the NC for connectivity > before sending through the default router (fe80::11:22). Actually what the IPv6 algorithm says is " Next-hop determination for a given unicast destination operates as follows. The sender performs a longest prefix match against the Prefix List to determine whether the packet's destination is on- or off-link. If the destination is on-link, the next-hop address is the same as the packet's destination address. Otherwise, the sender selects a router from the Default Router List" " Once the IP address of the next-hop node is known, the sender examines the Neighbor Cache for link-layer information about that neighbor." Best, Mathilde _______________________________________________ 6lowpan mailing list [email protected] https://www.ietf.org/mailman/listinfo/6lowpan _______________________________________________ 6lowpan mailing list [email protected] https://www.ietf.org/mailman/listinfo/6lowpan
