> Another question: What does the Map Server do if it gets a request for a 
> shorter prefix than it has an EID for. E.g., I have a

Returns an empty RLOC-set with action “native-forward” with an EID-prefix that 
is equal to the EID-prefix in the Map-Request. 

> mapping for 10/8 (and nothing else) but I get a request for 10/4. The text in 
> S 5.5 suggests that I return an empty locator set. Is that correct?

Yep. 

Dino

> 
>> On Wed, Feb 6, 2019 at 6:11 PM Eric Rescorla <[email protected]> wrote:
>> I'm trying to piece together the algorithm in 6833-bis S 5.5
>> for Map-Replies. The text says:
>> 
>>    A Map-Reply returns an EID-Prefix with a mask-length that is less
>>    than or equal to the EID being requested.
>> 
>> So, consider the case where an MS has two mappings:
>> 
>>    10/8 -> ETR1
>>    11/8 -> ETR2
>> 
>> If the Map-Request is for 10.0.0.1, then I would return
>> 
>>    10/8 -> ETR1
>> 
>> Now consider what happens when I have three mappings:
>> 
>>    10/16   -> ETR1
>>    10.0.2/24 -> ETR3 // New
>>    11/16   -> ETR2
>> 
>> Now we turn to the remainder of this section:
>> 
>>    When an EID moves out of a LISP site [I-D.ietf-lisp-eid-mobility],
>>    the database mapping system may have overlapping EID-prefixes.  Or
>>    when a LISP site is configured with multiple sets of ETRs that
>>    support different EID-prefix mask-lengths, the database mapping
>>    system may have overlapping EID-prefixes.  When overlapping EID-
>>    prefixes exist, a Map-Request with an EID that best matches any EID-
>>    Prefix MUST be returned in a single Map-Reply message.  For instance,
>>    if an ETR had database mapping entries for EID-Prefixes:
>> 
>> I'm having trouble parsing this, but what I get out of the example
>> is that the Map-Response is supposed to contain the EID-prefix that
>> best matches the request, plus whatever exceptions would be required
>> to create a correct routing table. So, that would mean in the case
>> where the Map-Request contains 10.0.0.1, the MS would have to reply
>> with:
>> 
>>    10/16   -> ETR1
>>    10.0.2/24 -> ETR3 // New
>> 
>> The first of these is necessary to provide correct routing information
>> for the requested prefix and the second to avoid providing incorrect
>> routing information for 10.0.2.1.
>> 
>> Do I have this correct? It seems like the alternative is that the MS
>> or ETR synthesize a new, more specific prefix. Is that what's intended
>> instead? The example in S 5.5 suggests otehrwise, but perhaps I am
>> misunderstanding.
>> 
>> Thanks,
>> -Ekr
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
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