Re: [Lsvr] Adoption of draft-ymbk-lsvr-l3dl-(signing|ulpc)

I likewise fell down that line of thinking but your explanation makes sense.

1) I have read and support both draft-ymbk-lsvr-l3dl-signing and draft-ymbk-lsvr-l3dl-ulpc as LSVR WG documents.
2) Not that I saw
3) See above. 
4) I don’t have anything at this time.

> On May 7, 2020, at 2:29 PM, Randy Bush <randy@psg.com> wrote:
> 
>>>> C: It feels like more text is needed around "If a peering address has
>>>> been announced as a loopback, a two or three (one or both ends could
>>>> be loopbacks) hop
>>>>   BGP session will be established. " -- how do I know it is announced
>>>> as a loopback? How do I know what route to install to reach the
>>>> loopback? etc.
>>> 
>>> l3dl 13.2 tells you it is a loopback
>> 
>> Doh, I missed that...
>> 
>>> 
>>> 13.2.  Encapsulaion Flags
>>> 
>>>   The Encapsulation Flags are a sequence of bit fields as follows:
>>> 
>>>    0           1            2            3            4  ...       7
>>>   +------------+------------+------------+------------+------------+
>>>   |  Ann/With  |   Primary  | Under/Over |  Loopback  | Reserved ..|
>>>   +------------+------------+------------+------------+------------+
>>> 
>>> so how about
>>> 
>>>   For each BGP peering on a link here MUST be one agreed encapsulation,
>>>   and the addresses used MUST be in the corresponding L3DP IPv4/IPv6
>>>   Announcement PDUs.  If a peering address has been announced as a
>>>   loopback, i.e. MUST BE flagged as such in the L3DL Encapsulation PDU,
>>>   a two or three hop BGP session will be established.  Otherwise a
>>>   direct one hop session is used.
>> 
>> Close but no cigar -- I suspect I didn't fully explain my (second) question
>> If router A says that I should peer with the loopback address
>> 192.0.2.1, I need to know how to route *to* that address
> 
> you will likely want to forward, <pedantry> not route </pedantry>, to
> the peer's address which was marked as Primary, iff it is in a subnet
> which you also share.  if not, pick a forwarding next hop that is in a
> subnet you share.  if there are multiple choices, you could have
> signaled which subnet in an Upper Layer Protocol Configuration PDU
> Attribute.
> 
> if you share no subnets, then you do not have a valid underlying l3dl
> session see l3dl
> 
>   13.  The Encapsulations
>   ....
>   Further, to consider a logical link of a type to formally be
>   established so that it may be pushed up to upper layer protocols, the
>   addressing for the type must be compatible, e.g. on the same IP
>   subnet.
> 
> yes, you have to hold a lot of gorp in your head.  sorry.
> 
> but some clarifying text might keep others from falling down this rabbit
> hole.  thanks.
> 
> randy
> 
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