Hi everyone,

First of all, I would like to apologize in advance if this is not the right 
place to ask my questions or if this topic has been mentioned in a previous 
thread, but I didn't find one that addresses my doubts.

I have read several times section 5.7 (Address Resolution) of the 
draft-ietf-6lowpan-nd-14 document, but the way Address Resolution is performed 
is not completely clear to me. I have quoted here the whole section divided in 
bits that I have commented, accordingly with my understanding of them and 
posted two final question that remains unsolved to me. I would really 
appreciate if you could give me your feedback and suggestions for my comments 
and questions:





>       The address registration mechanism and the SLLA option in Router
>    Advertisement messages provide sufficient a priori state in routers
>    and hosts to resolve an IPv6 address to its associated link-layer
>    address.  

As I understand from the document, this address registration mechanism 
registers hosts with routers and vice-versa, but it does not register hosts 
with hosts. 

> As all prefixes but the link-local prefix are always
>    assumed to be off-link, multicast-based address resolution between
>    neighbors is not needed.
> 

This paragraph is also confusing to me. As I understand, the reason why 
multicast-based address resolution is not needed is that the link-local prefix 
is on-link. If I am right, I guess that I just  have problems with the way this 
paragraph is formulated, which is a bit unclear. 

>       Link-layer addresses for neighbors are stored in Neighbor Cache
>    entries [RFC4861]. 

According to this section and to several places along the whole document, I 
clearly understand how host create NCE storing router's  information. I also 
understand the process in which a router creates a NCE due to the registration 
mechanism. However, I would like to know whether a host might create a NCE for 
another host at any moment and, how that situation would be if that is the case.

>  In order to achieve LoWPAN compression, most
>    global addresses are formed using a link-layer address.  Thus a host
>    can minimize memory usage by optimizing for this case and only
>    storing link-layer address information if it differs from the link-
>    layer address corresponding to the Interface ID of the IPv6 address
>    (i.e., differs in more than the on-link/global bit being inverted).





Thus, after going through the draft, important questions that remain unsolved 
to me are:

a) How does a host send a packet to another neighboring host?
b) Should hosts maintain NCEs for other hosts? If so, under which circumstances 
would these NCEs be created?


Thank you in advance and best regards,

Luis Maqueda






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