nanog mailing list archives

Re: Devil's Advocate - Segment Routing, Why?


From: Robert Raszuk <robert () raszuk net>
Date: Sun, 21 Jun 2020 23:01:03 +0200

Wouldn't T-LDP fix this, since LDP LFA is a targeted session?

Nope. You need to get to PQ node via potentially many hops. So you need to
have even ordered or independent label distribution to its loopback in
place.

Best,
R.

On Sun, Jun 21, 2020 at 10:58 PM Mark Tinka <mark.tinka () seacom mu> wrote:



On 21/Jun/20 22:21, Robert Raszuk wrote:


Well this is true for one company :) Name starts with j ....

Other company name starting with c - at least some time back by default
allocated labels for all routes in the RIB either connected or static or
sourced from IGP. Sure you could always limit that with a knob if desired.



Juniper allocates labels to the Loopback only.

Cisco allocates labels to all IGP and interface routes.

Neither allocate labels to BGP routes for the global table.



The issue with allocating labels only for BGP next hops is that your
IP/MPLS LFA breaks (or more directly is not possible) as you do not have a
label to PQ node upon failure.  Hint: PQ node is not even running BGP :).


Wouldn't T-LDP fix this, since LDP LFA is a targeted session?

Need to test.



Sure selective folks still count of "IGP Convergence" to restore
connectivity. But I hope those will move to much faster connectivity
restoration techniques soon.


We are happy :-).

Mark.


Current thread: