Mark.Andrews;
>>>>If the case is too difficult to understand, just consider a
>>>>case of "vix.net" with just a single AAAA and no A glue
>>>>returned. Then, IPv4 only host is at a loss.
>>
>>> No. It just asks the parent the missing glue records
>>> individually. In this case for ?.gtld-servers.net/A records
>>> from the root servers.
>>>
>>> The only time it will loose is when the NS RRset is too big
>>> to even allow the requested glue RRset to be added
>>> preferentially to the additional section.
>>
>>No. In general, clients can not know which nameserver needs
>>glues and to which nameserver to ask. If a delegation loop
>>involves multiple zones, clients have no reason to ask, for
>>example, a "com." zone nameserver addresses of nameservers of
>>zones under "edu."
>
>
> The fully general case doesn't work even if the parents
> return glue for out of scope servers because the caches
> will reject it.
Wrong. Though some broken implementaion may reject caching of
glue, it merely means inefficiency and does not at all mean
broken relaying.
As you said, glue is glue.
Proper implementations should cache glue as glue to be used
in an additional section but never in an answer section.
> For the cross servers under the same parent the glue can
> still be returned in the additional section even if it is
> not a server for the zone it lives in.
That is an improper workaround.
>>> Older parent servers that promote glue to answer don't even
>>> have this problem.
>>
>>Glue is glue.
>>
>>Glue information should be answered only as glue.
>
>
> I'm not suggesting otherwise. I was just pointing out that
> the older servers did do this so lack of space would never
> prevent the glue being returned.
I'm afraid you don't understand full implication of "glue is glue".
W.r.t. caching, "Glue information should be answered only as glue."
means glue information may be cached as long as the cached information
is used in answers only as glue in additional secitons.
Masataka Ohta
.
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