Doc: OSPF graceful restart options

diff --git a/doc/bird.sgml b/doc/bird.sgml
index edc871fbe7e467225ad8f24b8c009e2127a5bbd8..e0b60c81f45778eb8b0a2beff201517da770294c 100644 (file)
--- a/doc/bird.sgml
+++ b/doc/bird.sgml
@@ -3269,6 +3269,8 @@ protocol ospf [v2|v3] <name> {
        tick <num>;
        ecmp <switch> [limit <num>];
        merge external <switch>;
+       graceful restart <switch>|aware;
+       graceful restart time <num>;
        area <id> {
                stub;
                nssa;
@@ -3412,6 +3414,31 @@ protocol ospf [v2|v3] <name> {
        from different LSAs are treated as separate even if they represents the
        same destination. Default value is no.
 
+       <tag><label id="ospf-graceful-restart">graceful restart <m/switch/|aware</tag>
+       When an OSPF instance is restarted, neighbors break adjacencies and
+       recalculate their routing tables, which disrupts packet forwarding even
+       when the forwarding plane of the restarting router remains intact.
+       <rfc id="3623"> specifies a graceful restart mechanism to alleviate this
+       issue. For OSPF graceful restart, restarting router originates
+       Grace-LSAs, announcing intent to do graceful restart. Neighbors
+       receiving these LSAs enter helper mode, in which they ignore breakdown
+       of adjacencies, behave as if nothing is happening and keep old routes.
+       When adjacencies are reestablished, the restarting router flushes
+       Grace-LSAs and graceful restart is ended.
+
+       This option controls the graceful restart mechanism. It has three
+       states: Disabled, when no support is provided. Aware, when graceful
+       restart helper mode is supported, but no local graceful restart is
+       allowed (i.e. helper-only role). Enabled, when the full graceful restart
+       support is provided (i.e. both restarting and helper role). Note that
+       proper support for local graceful restart requires also configuration of
+       other protocols. Default: aware.
+
+       <tag><label id="ospf-graceful-restart-time">graceful restart time <m/num/</tag>
+       The restart time is announced in the Grace-LSA and specifies how long
+       neighbors should wait for proper end of the graceful restart before
+       exiting helper mode prematurely. Default: 120 seconds.
+
        <tag><label id="ospf-area">area <M>id</M></tag>
        This defines an OSPF area with given area ID (an integer or an IPv4
        address, similarly to a router ID). The most important area is the