Rename "debug isis ti-lfa" to "debug isis lfa". Having different
debug guards for different kinds of LFA (classic, remote and TI-LFA)
doesn't make sense since all LFA solutions share code to certain
extent.
Signed-off-by: Renato Westphal <renato@opensourcerouting.org>
Do not attempt to install a TI-LFA backup nexthop if its number of
labels exceeds the locally configured MSD (Maximum Stack Depth). The
idea is to prevent forward-plane installation failures before they
happen. The MSD check should also allow the "show isis fast-reroute
summary" command (not implemented yet) to display the actual
protection coverage provided by TI-LFA, which might not be 100%
if the MSD isn't big enough.
Signed-off-by: Renato Westphal <renato@opensourcerouting.org>
When computing backup nexthops for routes that contain a Prefix-SID,
the original Prefix-SID label should be present at the end of
backup label stacks (after the repair labels). This commit fixes
that oversight in the original TI-LFA code. The SPF unit tests and
TI-LFA topotes were also updated accordingly.
Signed-off-by: Renato Westphal <renato@opensourcerouting.org>
Embed Prefix-SID information inside SPF data structures so that
Prefix-SIDs can be installed together with their associated routes
at the end of the SPF algorithm. This is different from the current
implementation where Prefix-SIDs are parsed and processed separately,
which is vastly suboptimal.
Advantages of the new code:
* No need to parse the LSPDB an additional time to detect and process
SR-related changes;
* Routes are installed with their Prefix-SID labels in the same ZAPI
message. This can prevent packet dropping for a few milliseconds
after each SPF run if there are BGP-labeled routes (e.g. L3VPN) that
recurse on IGP labeled routes;
* Much easier to support Anycast-SIDs, as the SPF code will naturally
figure out the best nexthops and use only them (that can't be done
in any reasonable way if the Prefix-SID Sub-TVLs are processed
separately);
* Less code to maintain and reduced memory footprint;
The "show isis segment-routing prefix-sids" command was removed as
it doesn't make sense anymore now that "show isis route" exists.
Prefix-SIDs are a property of routes, so what was done was to extend
the "show isis route" command with a new "prefix-sid" option that
changes the output table to show the Prefix-SID information associated
to each route.
Signed-off-by: Renato Westphal <renato@opensourcerouting.org>
This is preparatory change for the upcoming SR Prefix-SID
refactoring.
Since Prefix-SID information will be stored inside IS-IS routes
(instead of being maintained separately), it will be necessary to
have local routes in order to store local Prefix-SID information.
Signed-off-by: Renato Westphal <renato@opensourcerouting.org>
TI-LFA is a modern fast-reroute (FRR) solution that leverages Segment
Routing to pre-compute backup nexthops for all destinations in the
network, helping to reduce traffic restoration times whenever a
failure occurs. The backup nexthops are expected to be installed
in the FIB so that they can be activated as soon as a failure
is detected, making sub-50ms recovery possible (assuming an
hierarchical FIB).
TI-LFA is a huge step forward compared to prior IP-FRR solutions,
like classic LFA and Remote LFA, as it guarantees 100% coverage
for all destinations. This is possible thanks to the source routing
capabilities of SR, which allows the backup nexthops to steer traffic
around the failures (using as many SIDs as necessary). In addition
to that, the repair paths always follow the post-convergence SPF
tree, which prevents transient congestions and suboptimal routing
from happening.
Deploying TI-LFA is very simple as it only requires a single
configuration command for each interface that needs to be protected
(both link protection and node protection are available). In addition
to IPv4 and IPv6 routes, SR Prefix-SIDs and Adj-SIDs are also
protected by the backup nexthops computed by the TI-LFA algorithms.
Signed-off-by: Renato Westphal <renato@opensourcerouting.org>
