Hi Uma,

On May 9, 2014, at 8:03 PM, Uma Chunduri 
<[email protected]<mailto:[email protected]>> wrote:

Hi Acee,
In-line [Uma]:

>I can see these -
>1.  RLFA TLDP session without having to worry a PQ node supports TE or
>not

I don't think this is a good use case. You need to have an the AF topology in 
order to compute the remote LFA. Also, you may inherit remote LFA targets for 
external and prefixes from other areas but you will never compute remote LFA 
targets in other areas (at least not with today's algorithms).

[Uma]: It doesn't have to be a different area. Take a simplest case of one area 
or an L2 domain; after having computed all the PQ nodes in that area/domain if 
the PQ node doesn't support TE and doesn't advertise router ID (TLV 134) which 
IP address you would pick for TLDP session ?  You can't reliably know from the 
advertised prefixes from the node that it is hosted by  the node if router ID 
is not emitted by the node (as it doesn't support TE).

The only advantage I can see is that a router can explicitly specify which 
local address it wants to use for targeted LFA sessions.


>2. Orchestration software on a controller or an application which is
>having access to
>   the topology database of the network may determine the node IP
>address without having to go through the hoops (to determine if it's
>redistributed or leaked etc..)
>   with this TLV.

Can you be more precise? If the orchestration application is going to 
orchestrate across multiple areas, I would hope it would have visibility to the 
topologies of these areas.

[Uma]: Even for a same area or domain having a node advertise it's loopback as 
router ID without relation any relation to TE (supported or not) is a benefit 
in this case.
The ability of an application on a controller to know this easily is a huge 
advantage.
Also there could be multiple loopback and each for different purposes. For e.g. 
a PCE on a controller with https://tools.ietf.org/html/draft-ietf-pce-pceps can 
know PCC address
with a firewall port/IP opened on the router for TLS connection. It would be 
great this can happen easily and automatically.

I don’t think anyone would have a firewall within an IGP routing domain. Hence, 
it would be the same purported advantage as above.

Thanks,
Acee




--
Uma C.

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