Merge pull request #6342 from Orange-OpenSource/dev_isis_srdev_isis_sr

isisd: Preparation to merge Segment-Routing into master

8 files changed, 1065 insertions, 522 deletions

diff --git a/isisd/isis_nb_config.c b/isisd/isis_nb_config.c
index ec3b7baa31..a649e896fa 100644
--- a/isisd/isis_nb_config.c
+++ b/isisd/isis_nb_config.c
@@ -1521,7 +1521,9 @@ int isis_instance_segment_routing_msd_node_msd_modify(
 
 	area = nb_running_get_entry(args->dnode, NULL, true);
 	area->srdb.config.msd = yang_dnode_get_uint8(args->dnode, NULL);
-	isis_sr_cfg_msd_update(area);
+
+	/* Update and regenerate LSP */
+	lsp_regenerate_schedule(area, area->is_type, 0);
 
 	return NB_OK;
 }
@@ -1536,7 +1538,9 @@ int isis_instance_segment_routing_msd_node_msd_destroy(
 
 	area = nb_running_get_entry(args->dnode, NULL, true);
 	area->srdb.config.msd = 0;
-	isis_sr_cfg_msd_update(area);
+
+	/* Update and regenerate LSP */
+	lsp_regenerate_schedule(area, area->is_type, 0);
 
 	return NB_OK;
 }
diff --git a/isisd/isis_sr.c b/isisd/isis_sr.c
index 9bdb2c40e8..c24c0608b2 100644
--- a/isisd/isis_sr.c
+++ b/isisd/isis_sr.c
@@ -1,8 +1,7 @@
 /*
- * This is an implementation of Segment Routing for IS-IS
- * as per draft draft-ietf-isis-segment-routing-extensions-25
+ * This is an implementation of Segment Routing for IS-IS as per RFC 8667
  *
- * Copyright (C) 2019 Orange Labs http://www.orange.com
+ * Copyright (C) 2019 Orange http://www.orange.com
  *
  * Author: Olivier Dugeon <olivier.dugeon@orange.com>
  * Contributor: Renato Westphal <renato@opensourcerouting.org> for NetDEF
@@ -48,54 +47,96 @@
 #include "isisd/isis_zebra.h"
 #include "isisd/isis_errors.h"
 
+/* Local variables and functions */
 DEFINE_MTYPE_STATIC(ISISD, ISIS_SR_INFO, "ISIS segment routing information")
 
-static void isis_sr_prefix_uninstall(struct sr_prefix *srp);
-static void isis_sr_prefix_reinstall(struct sr_prefix *srp,
-				     bool replace_semantics);
+static void sr_prefix_uninstall(struct sr_prefix *srp);
+static void sr_prefix_reinstall(struct sr_prefix *srp, bool make_before_break);
 
-/*----------------------------------------------------------------------------*/
+/* --- RB-Tree Management functions ----------------------------------------- */
 
+/**
+ * SR Prefix comparison for RB-Tree.
+ *
+ * @param a	First SR prefix
+ * @param b	Second SR prefix
+ *
+ * @return	-1 (a < b), 0 (a == b) or +1 (a > b)
+ */
 static inline int sr_prefix_sid_compare(const struct sr_prefix *a,
 					const struct sr_prefix *b)
 {
 	return prefix_cmp(&a->prefix, &b->prefix);
 }
-DECLARE_RBTREE_UNIQ(tree_sr_node_prefix, struct sr_prefix, node_entry,
+DECLARE_RBTREE_UNIQ(srdb_node_prefix, struct sr_prefix, node_entry,
 		    sr_prefix_sid_compare)
-DECLARE_RBTREE_UNIQ(tree_sr_area_prefix, struct sr_prefix, area_entry,
+DECLARE_RBTREE_UNIQ(srdb_area_prefix, struct sr_prefix, area_entry,
 		    sr_prefix_sid_compare)
 
+/**
+ * Configured SR Prefix comparison for RB-Tree.
+ *
+ * @param a	First SR prefix
+ * @param b	Second SR prefix
+ *
+ * @return	-1 (a < b), 0 (a == b) or +1 (a > b)
+ */
 static inline int sr_prefix_sid_cfg_compare(const struct sr_prefix_cfg *a,
 					    const struct sr_prefix_cfg *b)
 {
 	return prefix_cmp(&a->prefix, &b->prefix);
 }
-DECLARE_RBTREE_UNIQ(tree_sr_prefix_cfg, struct sr_prefix_cfg, entry,
+DECLARE_RBTREE_UNIQ(srdb_prefix_cfg, struct sr_prefix_cfg, entry,
 		    sr_prefix_sid_cfg_compare)
 
+/**
+ * SR Node comparison for RB-Tree.
+ *
+ * @param a	First SR node
+ * @param b	Second SR node
+ *
+ * @return	-1 (a < b), 0 (a == b) or +1 (a > b)
+ */
 static inline int sr_node_compare(const struct sr_node *a,
 				  const struct sr_node *b)
 {
 	return memcmp(a->sysid, b->sysid, ISIS_SYS_ID_LEN);
 }
-DECLARE_RBTREE_UNIQ(tree_sr_node, struct sr_node, entry, sr_node_compare)
+DECLARE_RBTREE_UNIQ(srdb_node, struct sr_node, entry, sr_node_compare)
 
-/*----------------------------------------------------------------------------*/
+/* --- Functions used for Yang model and CLI to configure Segment Routing --- */
 
-/* Returns true if the interface/address pair corresponds to a Node-SID. */
-static bool isis_sr_prefix_is_node_sid(const struct interface *ifp,
-				       const struct prefix *prefix)
+/**
+ * Check if prefix correspond to a Node SID.
+ *
+ * @param ifp	  Interface
+ * @param prefix  Prefix to be checked
+ *
+ * @return	  True if the interface/address pair corresponds to a Node-SID
+ */
+static bool sr_prefix_is_node_sid(const struct interface *ifp,
+				  const struct prefix *prefix)
 {
 	return (if_is_loopback(ifp) && is_host_route(prefix));
 }
 
-/* Handle changes in the local SRGB configuration. */
+/**
+ * Update local SRGB configuration. SRGB is reserved though Label Manager.
+ * This function trigger the update of local Prefix-SID installation.
+ *
+ * @param area		IS-IS area
+ * @param lower_bound	Lower bound of SRGB
+ * @param upper_bound	Upper bound of SRGB
+ *
+ * @return		0 on success, -1 otherwise
+ */
 int isis_sr_cfg_srgb_update(struct isis_area *area, uint32_t lower_bound,
 			    uint32_t upper_bound)
 {
 	struct isis_sr_db *srdb = &area->srdb;
 
+	sr_debug("ISIS-Sr (%s): Update SRGB", area->area_tag);
+
 	/* First release the old SRGB. */
 	if (srdb->config.enabled)
 		isis_zebra_release_label_range(srdb->config.srgb_lower_bound,
@@ -114,11 +155,15 @@ int isis_sr_cfg_srgb_update(struct isis_area *area, uint32_t lower_bound,
 				    - srdb->config.srgb_lower_bound + 1))
 			return -1;
 
+		sr_debug("  |- Got new SRGB %u/%u",
+			 srdb->config.srgb_lower_bound,
+			 srdb->config.srgb_upper_bound);
+
 		/* Reinstall local Prefix-SIDs to update their input labels. */
 		for (int level = ISIS_LEVEL1; level <= ISIS_LEVELS; level++) {
-			frr_each (tree_sr_area_prefix,
+			frr_each (srdb_area_prefix,
 				  &area->srdb.prefix_sids[level - 1], srp) {
-				isis_sr_prefix_reinstall(srp, false);
+				sr_prefix_reinstall(srp, false);
 			}
 		}
 
@@ -132,19 +177,22 @@ int isis_sr_cfg_srgb_update(struct isis_area *area, uint32_t lower_bound,
 	return 0;
 }
 
-/* Handle changes in the local MSD configuration. */
-void isis_sr_cfg_msd_update(struct isis_area *area)
-{
-	lsp_regenerate_schedule(area, area->is_type, 0);
-}
-
-/* Handle new Prefix-SID configuration. */
+/**
+ * Add new Prefix-SID configuration to the SRDB.
+ *
+ * @param area	  IS-IS area
+ * @param prefix  Prefix to be added
+ *
+ * @return	  Newly added Prefix-SID configuration structure
+ */
 struct sr_prefix_cfg *isis_sr_cfg_prefix_add(struct isis_area *area,
 					     const struct prefix *prefix)
 {
 	struct sr_prefix_cfg *pcfg;
 	struct interface *ifp;
 
+	sr_debug("ISIS-Sr (%s): Add local prefix %pFX", area->area_tag, prefix);
+
 	pcfg = XCALLOC(MTYPE_ISIS_SR_INFO, sizeof(*pcfg));
 	pcfg->prefix = *prefix;
 	pcfg->area = area;
@@ -157,36 +205,57 @@ struct sr_prefix_cfg *isis_sr_cfg_prefix_add(struct isis_area *area,
 
 	/* Set the N-flag when appropriate. */
 	ifp = if_lookup_prefix(prefix, VRF_DEFAULT);
-	if (ifp && isis_sr_prefix_is_node_sid(ifp, prefix))
+	if (ifp && sr_prefix_is_node_sid(ifp, prefix))
 		pcfg->node_sid = true;
 
 	/* Save prefix-sid configuration. */
-	tree_sr_prefix_cfg_add(&area->srdb.config.prefix_sids, pcfg);
+	srdb_prefix_cfg_add(&area->srdb.config.prefix_sids, pcfg);
 
 	return pcfg;
 }
 
-/* Handle removal of locally configured Prefix-SID. */
+/**
+ * Removal of locally configured Prefix-SID.
+ *
+ * @param pcfg	Configured Prefix-SID
+ */
 void isis_sr_cfg_prefix_del(struct sr_prefix_cfg *pcfg)
 {
-	struct isis_area *area;
+	struct isis_area *area = pcfg->area;
 
-	area = pcfg->area;
-	tree_sr_prefix_cfg_del(&area->srdb.config.prefix_sids, pcfg);
+	sr_debug("ISIS-Sr (%s): Delete local Prefix-SID %pFX %s %u",
+		 area->area_tag, &pcfg->prefix,
+		 pcfg->sid_type == SR_SID_VALUE_TYPE_INDEX ? "index" : "label",
+		 pcfg->sid);
+
+	srdb_prefix_cfg_del(&area->srdb.config.prefix_sids, pcfg);
 	XFREE(MTYPE_ISIS_SR_INFO, pcfg);
 }
 
-/* Lookup Prefix-SID in the local configuration. */
+/**
+ * Lookup for Prefix-SID in the local configuration.
+ *
+ * @param area	  IS-IS area
+ * @param prefix  Prefix to lookup
+ *
+ * @return	  Configured Prefix-SID structure if found, NULL otherwise
+ */
 struct sr_prefix_cfg *isis_sr_cfg_prefix_find(struct isis_area *area,
 					      union prefixconstptr prefix)
 {
 	struct sr_prefix_cfg pcfg = {};
 
 	prefix_copy(&pcfg.prefix, prefix.p);
-	return tree_sr_prefix_cfg_find(&area->srdb.config.prefix_sids, &pcfg);
+	return srdb_prefix_cfg_find(&area->srdb.config.prefix_sids, &pcfg);
 }
 
-/* Fill in Prefix-SID Sub-TLV according to the corresponding configuration. */
+/**
+ * Fill in Prefix-SID Sub-TLV according to the corresponding configuration.
+ *
+ * @param pcfg	    Prefix-SID configuration
+ * @param external  False if prefix is locally configured, true otherwise
+ * @param psid	    Prefix-SID sub-TLV to be updated
+ */
 void isis_sr_prefix_cfg2subtlv(const struct sr_prefix_cfg *pcfg, bool external,
 			       struct isis_prefix_sid *psid)
 {
@@ -222,20 +291,30 @@ void isis_sr_prefix_cfg2subtlv(const struct sr_prefix_cfg *pcfg, bool external,
 	}
 }
 
-/*----------------------------------------------------------------------------*/
+/* --- Segment Routing Prefix Management functions -------------------------- */
 
-static struct sr_prefix *isis_sr_prefix_add(struct isis_area *area,
-					    struct sr_node *srn,
-					    union prefixconstptr prefix,
-					    bool local,
-					    const struct isis_prefix_sid *psid)
+/**
+ * Add Segment Routing Prefix to a given Segment Routing Node.
+ *
+ * @param area	  IS-IS area
+ * @param srn	  Segment Routing Node
+ * @param prefix  Prefix to be added
+ * @param local	  True if prefix is locally configured, false otherwise
+ * @param psid	  Prefix-SID sub-TLVs
+ *
+ * @return	  New Segment Routing Prefix structure
+ */
+static struct sr_prefix *sr_prefix_add(struct isis_area *area,
+				       struct sr_node *srn,
+				       union prefixconstptr prefix, bool local,
+				       const struct isis_prefix_sid *psid)
 {
 	struct sr_prefix *srp;
 
 	srp = XCALLOC(MTYPE_ISIS_SR_INFO, sizeof(*srp));
 	prefix_copy(&srp->prefix, prefix.p);
 	srp->sid = *psid;
-	srp->local_label = MPLS_INVALID_LABEL;
+	srp->input_label = MPLS_INVALID_LABEL;
 	if (local) {
 		srp->type = ISIS_SR_PREFIX_LOCAL;
 		isis_sr_nexthop_reset(&srp->u.local.info);
@@ -244,45 +323,89 @@ static struct sr_prefix *isis_sr_prefix_add(struct isis_area *area,
 		srp->u.remote.rinfo = NULL;
 	}
 	srp->srn = srn;
-	tree_sr_node_prefix_add(&srn->prefix_sids, srp);
+	srdb_node_prefix_add(&srn->prefix_sids, srp);
 	/* TODO: this might fail if we have Anycast SIDs in the IS-IS area. */
-	tree_sr_area_prefix_add(&area->srdb.prefix_sids[srn->level - 1], srp);
+	srdb_area_prefix_add(&area->srdb.prefix_sids[srn->level - 1], srp);
+
+	sr_debug("  |- Added new SR Prefix-SID %pFX %s %u to SR Node %s",
+		 &srp->prefix, IS_SID_VALUE(srp->sid.flags) ? "label" : "index",
+		 srp->sid.value, sysid_print(srn->sysid));
 
 	return srp;
 }
 
-static void isis_sr_prefix_del(struct isis_area *area, struct sr_node *srn,
-			       struct sr_prefix *srp)
+/**
+ * Remove given Segment Prefix from given Segment Routing Node.
+ * Prefix-SID is un-installed first.
+ *
+ * @param area	IS-IS area
+ * @param srn	Segment Routing Node
+ * @param srp	Segment Routing Prefix
+ */
+static void sr_prefix_del(struct isis_area *area, struct sr_node *srn,
+			  struct sr_prefix *srp)
 {
-	isis_sr_prefix_uninstall(srp);
-	tree_sr_node_prefix_del(&srn->prefix_sids, srp);
-	tree_sr_area_prefix_del(&area->srdb.prefix_sids[srn->level - 1], srp);
+	sr_debug("  |- Delete SR Prefix-SID %pFX %s %u to SR Node %s",
+		 &srp->prefix, IS_SID_VALUE(srp->sid.flags) ? "label" : "index",
+		 srp->sid.value, sysid_print(srn->sysid));
+
+	sr_prefix_uninstall(srp);
+	srdb_node_prefix_del(&srn->prefix_sids, srp);
+	srdb_area_prefix_del(&area->srdb.prefix_sids[srn->level - 1], srp);
 	XFREE(MTYPE_ISIS_SR_INFO, srp);
 }
 
-static struct sr_prefix *isis_sr_prefix_find_area(struct isis_area *area,
-						  int level,
-						  union prefixconstptr prefix)
+/**
+ * Find Segment Routing Prefix by Area.
+ *
+ * @param area	  IS-IS area
+ * @param level	  IS-IS level
+ * @param prefix  Prefix to lookup
+ *
+ * @return	  Segment Routing Prefix structure if found, NULL otherwise
+ */
+static struct sr_prefix *sr_prefix_find_by_area(struct isis_area *area,
+						int level,
+						union prefixconstptr prefix)
 {
 	struct sr_prefix srp = {};
 
 	prefix_copy(&srp.prefix, prefix.p);
-	return tree_sr_area_prefix_find(&area->srdb.prefix_sids[level - 1],
-					&srp);
+	return srdb_area_prefix_find(&area->srdb.prefix_sids[level - 1], &srp);
 }
 
-static struct sr_prefix *isis_sr_prefix_find_node(struct sr_node *srn,
-						  union prefixconstptr prefix)
+/**
+ * Find Segment Routing Prefix by Segment Routing Node.
+ *
+ * @param srn	  Segment Routing Node
+ * @param prefix  Prefix to lookup
+ *
+ * @return	  Segment Routing Prefix structure if found, NULL otherwise
+ */
+static struct sr_prefix *sr_prefix_find_by_node(struct sr_node *srn,
+						union prefixconstptr prefix)
 {
 	struct sr_prefix srp = {};
 
 	prefix_copy(&srp.prefix, prefix.p);
-	return tree_sr_node_prefix_find(&srn->prefix_sids, &srp);
+	return srdb_node_prefix_find(&srn->prefix_sids, &srp);
 }
 
-static struct sr_node *isis_sr_node_add(struct isis_area *area, int level,
-					const uint8_t *sysid,
-					const struct isis_router_cap *cap)
+/* --- Segment Routing Node Management functions ---------------------------- */
+
+/**
+ * Add Segment Routing Node to the Segment Routing Data Base.
+ *
+ * @param area	 IS-IS area
+ * @param level	 IS-IS level
+ * @param sysid	 Node System ID
+ * @param cap	 Segment Routing Capability sub-TLVs
+ *
+ * @return	 New Segment Routing Node structure
+ */
+static struct sr_node *sr_node_add(struct isis_area *area, int level,
+				   const uint8_t *sysid,
+				   const struct isis_router_cap *cap)
 {
 	struct sr_node *srn;
 
@@ -291,43 +414,74 @@ static struct sr_node *isis_sr_node_add(struct isis_area *area, int level,
 	memcpy(srn->sysid, sysid, ISIS_SYS_ID_LEN);
 	srn->cap = *cap;
 	srn->area = area;
-	tree_sr_node_prefix_init(&srn->prefix_sids);
-	tree_sr_node_add(&area->srdb.sr_nodes[level - 1], srn);
+	srdb_node_prefix_init(&srn->prefix_sids);
+	srdb_node_add(&area->srdb.sr_nodes[level - 1], srn);
+
+	sr_debug("  |- Added new SR Node %s", sysid_print(srn->sysid));
 
 	return srn;
 }
 
-static void isis_sr_node_del(struct isis_area *area, int level,
-			     struct sr_node *srn)
+static void sr_node_del(struct isis_area *area, int level, struct sr_node *srn)
+/**
+ * Remove Segment Routing Node from the Segment Routing Data Base.
+ * All Prefix-SID attached to this Segment Routing Node are removed first.
+ *
+ * @param area	 IS-IS area
+ * @param level	 IS-IS level
+ * @param srn	 Segment Routing Node to be deleted
+ */
 {
+
+	sr_debug("  |- Delete SR Node %s", sysid_print(srn->sysid));
+
 	/* Remove and uninstall Prefix-SIDs. */
-	while (tree_sr_node_prefix_count(&srn->prefix_sids) > 0) {
+	while (srdb_node_prefix_count(&srn->prefix_sids) > 0) {
 		struct sr_prefix *srp;
 
-		srp = tree_sr_node_prefix_first(&srn->prefix_sids);
-		isis_sr_prefix_del(area, srn, srp);
+		srp = srdb_node_prefix_first(&srn->prefix_sids);
+		sr_prefix_del(area, srn, srp);
 	}
 
-	tree_sr_node_del(&area->srdb.sr_nodes[level - 1], srn);
+	srdb_node_del(&area->srdb.sr_nodes[level - 1], srn);
 	XFREE(MTYPE_ISIS_SR_INFO, srn);
 }
 
-static struct sr_node *isis_sr_node_find(struct isis_area *area, int level,
-					 const uint8_t *sysid)
+/**
+ * Find Segment Routing Node in the Segment Routing Data Base per system ID.
+ *
+ * @param area	 IS-IS area
+ * @param level	 IS-IS level
+ * @param sysid	 Node System ID to lookup
+ *
+ * @return	 Segment Routing Node structure if found, NULL otherwise
+ */
+static struct sr_node *sr_node_find(struct isis_area *area, int level,
+				    const uint8_t *sysid)
 {
 	struct sr_node srn = {};
 
 	memcpy(srn.sysid, sysid, ISIS_SYS_ID_LEN);
-	return tree_sr_node_find(&area->srdb.sr_nodes[level - 1], &srn);
+	return srdb_node_find(&area->srdb.sr_nodes[level - 1], &srn);
 }
 
-static void isis_sr_adj_srgb_update(struct isis_area *area, uint8_t *sysid,
-				    int level)
+/**
+ * Update Segment Routing Node following an SRGB update. This function
+ * is called when a neighbor SR Node has updated its SRGB.
+ *
+ * @param area	 IS-IS area
+ * @param level	 IS-IS level
+ * @param sysid	 Segment Routing Node system ID
+ */
+static void sr_node_srgb_update(struct isis_area *area, int level,
+				uint8_t *sysid)
 {
 	struct sr_prefix *srp;
 
-	frr_each (tree_sr_area_prefix, &area->srdb.prefix_sids[level - 1],
-		  srp) {
+	sr_debug("ISIS-Sr (%s): Update neighbors SR Node with new SRGB",
+		 area->area_tag);
+
+	frr_each (srdb_area_prefix, &area->srdb.prefix_sids[level - 1], srp) {
 		struct listnode *node;
 		struct isis_nexthop *nh;
 
@@ -343,15 +497,25 @@ static void isis_sr_adj_srgb_update(struct isis_area *area, uint8_t *sysid,
 				continue;
 
 			/*
-			 * Reinstall all Prefix-SID nexthops using route replace
-			 * semantics.
+			 * The Prefix-SID input label hasn't changed. We could
+			 * re-install all Prefix-SID with "Make Before Break"
+			 * option. Zebra layer will update output label(s) by
+			 * adding new entry before removing the old one(s).
 			 */
-			isis_sr_prefix_reinstall(srp, true);
+			sr_prefix_reinstall(srp, true);
 			break;
 		}
 	}
 }
 
+/* --- Segment Routing Nexthop information Management functions ------------- */
+
+/**
+ * Update Segment Routing Nexthop.
+ *
+ * @param srnh	 Segment Routing next hop
+ * @param label	 Output MPLS label
+ */
 void isis_sr_nexthop_update(struct sr_nexthop_info *srnh, mpls_label_t label)
 {
 	srnh->label = label;
@@ -359,18 +523,31 @@ void isis_sr_nexthop_update(struct sr_nexthop_info *srnh, mpls_label_t label)
 		srnh->uptime = time(NULL);
 }
 
+/**
+ * Reset Segment Routing Nexthop.
+ *
+ * @param srnh	Segment Routing Nexthop
+ */
 void isis_sr_nexthop_reset(struct sr_nexthop_info *srnh)
 {
 	srnh->label = MPLS_INVALID_LABEL;
 	srnh->uptime = 0;
 }
 
-/*----------------------------------------------------------------------------*/
+/* --- Segment Routing Prefix-SID Management functions to configure LFIB ---- */
 
-/* Lookup IS-IS route in the SPT. */
-static struct isis_route_info *
-isis_sr_prefix_lookup_route(struct isis_area *area, enum spf_tree_id tree_id,
-			    struct sr_prefix *srp)
+/**
+ * Lookup IS-IS route in the Shortest Path Tree.
+ *
+ * @param area	   IS-IS area
+ * @param tree_id  Shortest Path Tree identifier
+ * @param srp	   Segment Routing Prefix to lookup
+ *
+ * @return	   Route Information for this prefix if found, NULL otherwise
+ */
+static struct isis_route_info *sr_prefix_lookup_route(struct isis_area *area,
+						      enum spf_tree_id tree_id,
+						      struct sr_prefix *srp)
 {
 	struct route_node *rn;
 	int level = srp->srn->level;
@@ -386,18 +563,24 @@ isis_sr_prefix_lookup_route(struct isis_area *area, enum spf_tree_id tree_id,
 	return NULL;
 }
 
-/* Calculate Prefix-SID input label. */
-static mpls_label_t isis_sr_prefix_in_label(const struct sr_prefix *srp)
+/**
+ * Compute input label for the given Prefix-SID.
+ *
+ * @param srp	Segment Routing Prefix
+ *
+ * @return	MPLS label or MPLS_INVALID_LABEL in case of SRGB overflow
+ */
+static mpls_label_t sr_prefix_in_label(const struct sr_prefix *srp)
 {
 	const struct sr_node *srn = srp->srn;
 	struct isis_area *area = srn->area;
 
-	/* Absolute SID value. */
+	/* Return SID value as MPLS label if it is an Absolute SID */
 	if (CHECK_FLAG(srp->sid.flags,
 		       ISIS_PREFIX_SID_VALUE | ISIS_PREFIX_SID_LOCAL))
 		return srp->sid.value;
 
-	/* Index SID value. */
+	/* Check that SID index falls inside the SRGB */
 	if (srp->sid.value >= (area->srdb.config.srgb_upper_bound
 			       - area->srdb.config.srgb_lower_bound + 1)) {
 		flog_warn(EC_ISIS_SID_OVERFLOW,
@@ -406,21 +589,32 @@ static mpls_label_t isis_sr_prefix_in_label(const struct sr_prefix *srp)
 		return MPLS_INVALID_LABEL;
 	}
 
+	/* Return MPLS label as SID index + SRGB_lower_bound as per RFC 8667 */
 	return (area->srdb.config.srgb_lower_bound + srp->sid.value);
 }
 
-/* Calculate Prefix-SID output label. */
-static mpls_label_t isis_sr_prefix_out_label(const struct sr_prefix *srp,
-					     const struct sr_node *srn_nexthop,
-					     const uint8_t *sysid)
+/**
+ * Compute output label for the given Prefix-SID.
+ *
+ * @param srp		Segment Routing Prefix
+ * @param srn_nexthop	Segment Routing nexthop node
+ * @param sysid		System ID of the SR node which advertised the Prefix-SID
+ *
+ * @return		MPLS label or MPLS_INVALID_LABEL in case of error
+ */
+static mpls_label_t sr_prefix_out_label(const struct sr_prefix *srp,
+					const struct sr_node *srn_nexthop,
+					const uint8_t *sysid)
 {
 	const struct sr_node *srn = srp->srn;
 
-	/* Is the adjacency the last hop? */
+	/* Check if the nexthop SR Node is the last hop? */
 	if (memcmp(sysid, srn->sysid, ISIS_SYS_ID_LEN) == 0) {
+		/* SR-Node doesn't request NO-PHP. Return Implicit NULL label */
 		if (!CHECK_FLAG(srp->sid.flags, ISIS_PREFIX_SID_NO_PHP))
 			return MPLS_LABEL_IMPLICIT_NULL;
 
+		/* SR-Node requests Implicit NULL Label */
 		if (CHECK_FLAG(srp->sid.flags, ISIS_PREFIX_SID_EXPLICIT_NULL)) {
 			if (srp->prefix.family == AF_INET)
 				return MPLS_LABEL_IPV4_EXPLICIT_NULL;
@@ -430,19 +624,19 @@ static mpls_label_t isis_sr_prefix_out_label(const struct sr_prefix *srp,
 		/* Fallthrough */
 	}
 
-	/* Absolute SID value. */
+	/* Return SID value as MPLS label if it is an Absolute SID */
 	if (CHECK_FLAG(srp->sid.flags,
 		       ISIS_PREFIX_SID_VALUE | ISIS_PREFIX_SID_LOCAL)) {
 		/*
 		 * V/L SIDs have local significance, so only adjacent routers
-		 * can use them.
+		 * can use them (RFC8667 section #2.1.1.1)
 		 */
 		if (srp->srn != srn_nexthop)
 			return MPLS_INVALID_LABEL;
 		return srp->sid.value;
 	}
 
-	/* Index SID value. */
+	/* Check that SID index falls inside the SRGB */
 	if (srp->sid.value >= srn_nexthop->cap.srgb.range_size) {
 		flog_warn(EC_ISIS_SID_OVERFLOW,
 			  "%s: SID index %u falls outside remote SRGB range",
@@ -450,88 +644,92 @@ static mpls_label_t isis_sr_prefix_out_label(const struct sr_prefix *srp,
 		return MPLS_INVALID_LABEL;
 	}
 
+	/* Return MPLS label as SID index + SRGB_lower_bound as per RFC 8667 */
 	return (srn_nexthop->cap.srgb.lower_bound + srp->sid.value);
 }
 
-/* Process local Prefix-SID and install it if possible. */
-static int isis_sr_prefix_install_local(struct sr_prefix *srp)
+/**
+ * Process local Prefix-SID and install it if possible. Input label is
+ * computed before installing it in LFIB.
+ *
+ * @param srp	Segment Routing Prefix
+ *
+ * @return	0 on success, -1 otherwise
+ */
+static int sr_prefix_install_local(struct sr_prefix *srp)
 {
+	mpls_label_t input_label;
 	const struct sr_node *srn = srp->srn;
-	struct isis_area *area = srn->area;
-	mpls_label_t local_label;
 
 	/*
-	 * No need to install LSP to local Prefix-SID unless the
+	 * No need to install Label for local Prefix-SID unless the
 	 * no-PHP option is configured.
 	 */
 	if (!CHECK_FLAG(srp->sid.flags, ISIS_PREFIX_SID_NO_PHP)
 	    || CHECK_FLAG(srp->sid.flags, ISIS_PREFIX_SID_EXPLICIT_NULL))
 		return -1;
 
-	if (IS_DEBUG_ISIS(DEBUG_SR)) {
-		zlog_debug("ISIS-SR (%s) installing Prefix-SID %pFX %s %u (%s)",
-			   area->area_tag, &srp->prefix,
-			   CHECK_FLAG(srp->sid.flags, ISIS_PREFIX_SID_VALUE)
-				   ? "label"
-				   : "index",
-			   srp->sid.value, circuit_t2string(srn->level));
-		zlog_debug("  nexthop self");
-	}
+	sr_debug("  |- Installing Prefix-SID %pFX %s %u (%s) with nexthop self",
+		 &srp->prefix, IS_SID_VALUE(srp->sid.flags) ? "label" : "index",
+		 srp->sid.value, circuit_t2string(srn->level));
 
-	/* Calculate local label. */
-	local_label = isis_sr_prefix_in_label(srp);
-	if (local_label == MPLS_INVALID_LABEL)
+	/* Compute input label and check that is valid. */
+	input_label = sr_prefix_in_label(srp);
+	if (input_label == MPLS_INVALID_LABEL)
 		return -1;
 
 	/* Update internal state. */
-	srp->local_label = local_label;
+	srp->input_label = input_label;
 	isis_sr_nexthop_update(&srp->u.local.info, MPLS_LABEL_IMPLICIT_NULL);
 
 	/* Install Prefix-SID in the forwarding plane. */
-	isis_zebra_install_prefix_sid(srp);
+	isis_zebra_send_prefix_sid(ZEBRA_MPLS_LABELS_REPLACE, srp);
 
 	return 0;
 }
 
-/* Process remote Prefix-SID and install it if possible. */
-static int isis_sr_prefix_install_remote(struct sr_prefix *srp)
+/**
+ * Process remote Prefix-SID and install it if possible. Input and Output
+ * labels are computed before installing them in LFIB.
+ *
+ * @param srp	Segment Routing Prefix
+ *
+ * @return	0 on success, -1 otherwise
+ */
+static int sr_prefix_install_remote(struct sr_prefix *srp)
 {
 	const struct sr_node *srn = srp->srn;
 	struct isis_area *area = srn->area;
 	enum spf_tree_id tree_id;
 	struct listnode *node;
 	struct isis_nexthop *nexthop;
-	mpls_label_t local_label;
+	mpls_label_t input_label;
 	size_t nexthop_num = 0;
 
-	/* Lookup associated IS-IS route. */
+	/* Lookup to associated IS-IS route. */
 	tree_id = (srp->prefix.family == AF_INET) ? SPFTREE_IPV4 : SPFTREE_IPV6;
-	srp->u.remote.rinfo = isis_sr_prefix_lookup_route(area, tree_id, srp);
+	srp->u.remote.rinfo = sr_prefix_lookup_route(area, tree_id, srp);
 	if (!srp->u.remote.rinfo)
 		/* SPF hasn't converged for this route yet. */
 		return -1;
 
-	if (IS_DEBUG_ISIS(DEBUG_SR))
-		zlog_debug("ISIS-SR (%s) installing Prefix-SID %pFX %s %u (%s)",
-			   area->area_tag, &srp->prefix,
-			   CHECK_FLAG(srp->sid.flags, ISIS_PREFIX_SID_VALUE)
-				   ? "label"
-				   : "index",
-			   srp->sid.value, circuit_t2string(srn->level));
-
-	/* Calculate local label. */
-	local_label = isis_sr_prefix_in_label(srp);
-	if (local_label == MPLS_INVALID_LABEL)
+	/* Compute input label and check that is valid. */
+	input_label = sr_prefix_in_label(srp);
+	if (input_label == MPLS_INVALID_LABEL)
 		return -1;
 
+	sr_debug("  |- Installing Prefix-SID %pFX %s %u (%s)", &srp->prefix,
+		 IS_SID_VALUE(srp->sid.flags) ? "label" : "index",
+		 srp->sid.value, circuit_t2string(srn->level));
+
+	/* Process all SPF nexthops */
 	for (ALL_LIST_ELEMENTS_RO(srp->u.remote.rinfo->nexthops, node,
 				  nexthop)) {
 		struct sr_node *srn_nexthop;
-		mpls_label_t remote_label;
+		mpls_label_t output_label;
 
 		/* Check if the nexthop advertised a SRGB. */
-		srn_nexthop =
-			isis_sr_node_find(area, srn->level, nexthop->sysid);
+		srn_nexthop = sr_node_find(area, srn->level, nexthop->sysid);
 		if (!srn_nexthop)
 			goto next;
 
@@ -545,9 +743,10 @@ static int isis_sr_prefix_install_remote(struct sr_prefix *srp)
 			&& !IS_SR_IPV6(srn_nexthop->cap.srgb)))
 			goto next;
 
-		remote_label = isis_sr_prefix_out_label(srp, srn_nexthop,
-							nexthop->sysid);
-		if (remote_label == MPLS_INVALID_LABEL)
+		/* Compute output label and check if it is valid */
+		output_label =
+			sr_prefix_out_label(srp, srn_nexthop, nexthop->sysid);
+		if (output_label == MPLS_INVALID_LABEL)
 			goto next;
 
 		if (IS_DEBUG_ISIS(DEBUG_SR)) {
@@ -555,51 +754,61 @@ static int isis_sr_prefix_install_remote(struct sr_prefix *srp)
 
 			inet_ntop(nexthop->family, &nexthop->ip, buf,
 				  sizeof(buf));
-			zlog_debug("  nexthop %s label %u", buf, remote_label);
+			zlog_debug("    |- nexthop %s label %u", buf,
+				   output_label);
 		}
 
-		isis_sr_nexthop_update(&nexthop->sr, remote_label);
+		isis_sr_nexthop_update(&nexthop->sr, output_label);
 		nexthop_num++;
 		continue;
 	next:
 		isis_sr_nexthop_reset(&nexthop->sr);
 	}
+
+	/* Check that we found at least one valid nexthop */
 	if (nexthop_num == 0) {
-		if (IS_DEBUG_ISIS(DEBUG_SR))
-			zlog_debug("  no valid nexthops");
+		sr_debug("    |- no valid nexthops");
 		return -1;
 	}
 
 	/* Update internal state. */
-	srp->local_label = local_label;
+	srp->input_label = input_label;
 
 	/* Install Prefix-SID in the forwarding plane. */
-	isis_zebra_install_prefix_sid(srp);
+	isis_zebra_send_prefix_sid(ZEBRA_MPLS_LABELS_REPLACE, srp);
 
 	return 0;
 }
 
-/* Process local or remote Prefix-SID and install it if possible. */
-static void isis_sr_prefix_install(struct sr_prefix *srp)
+/**
+ * Process local or remote Prefix-SID and install it if possible.
+ *
+ * @param srp	Segment Routing Prefix
+ */
+static void sr_prefix_install(struct sr_prefix *srp)
 {
 	const struct sr_node *srn = srp->srn;
 	struct isis_area *area = srn->area;
 	int ret;
 
+	sr_debug("ISIS-Sr (%s): Install Prefix-SID %pFX %s %u", area->area_tag,
+		 &srp->prefix, IS_SID_VALUE(srp->sid.flags) ? "label" : "index",
+		 srp->sid.value);
+
 	/* L1 routes are preferred over the L2 ones. */
 	if (area->is_type == IS_LEVEL_1_AND_2) {
 		struct sr_prefix *srp_l1, *srp_l2;
 
 		switch (srn->level) {
 		case ISIS_LEVEL1:
-			srp_l2 = isis_sr_prefix_find_area(area, ISIS_LEVEL2,
-							  &srp->prefix);
+			srp_l2 = sr_prefix_find_by_area(area, ISIS_LEVEL2,
+							&srp->prefix);
 			if (srp_l2)
-				isis_sr_prefix_uninstall(srp_l2);
+				sr_prefix_uninstall(srp_l2);
 			break;
 		case ISIS_LEVEL2:
-			srp_l1 = isis_sr_prefix_find_area(area, ISIS_LEVEL1,
-							  &srp->prefix);
+			srp_l1 = sr_prefix_find_by_area(area, ISIS_LEVEL1,
+							&srp->prefix);
 			if (srp_l1)
 				return;
 			break;
@@ -608,39 +817,38 @@ static void isis_sr_prefix_install(struct sr_prefix *srp)
 		}
 	}
 
+	/* Install corresponding LFIB entry */
 	if (srp->type == ISIS_SR_PREFIX_LOCAL)
-		ret = isis_sr_prefix_install_local(srp);
+		ret = sr_prefix_install_local(srp);
 	else
-		ret = isis_sr_prefix_install_remote(srp);
+		ret = sr_prefix_install_remote(srp);
 	if (ret != 0)
-		isis_sr_prefix_uninstall(srp);
+		sr_prefix_uninstall(srp);
 }
 
-/* Uninstall local or remote Prefix-SID. */
-static void isis_sr_prefix_uninstall(struct sr_prefix *srp)
+/**
+ * Uninstall local or remote Prefix-SID.
+ *
+ * @param srp	Segment Routing Prefix
+ */
+static void sr_prefix_uninstall(struct sr_prefix *srp)
 {
-	const struct sr_node *srn = srp->srn;
 	struct listnode *node;
 	struct isis_nexthop *nexthop;
 
-	if (srp->local_label == MPLS_INVALID_LABEL)
+	/* Check that Input Label is valid */
+	if (srp->input_label == MPLS_INVALID_LABEL)
 		return;
 
-	if (IS_DEBUG_ISIS(DEBUG_SR))
-		zlog_debug(
-			"ISIS-SR (%s) uninstalling Prefix-SID %pFX %s %u (%s)",
-			srn->area->area_tag, &srp->prefix,
-			CHECK_FLAG(srp->sid.flags, ISIS_PREFIX_SID_VALUE)
-				? "label"
-				: "index",
-			srp->sid.value, circuit_t2string(srn->level));
-
+	sr_debug("ISIS-Sr: Un-install Prefix-SID %pFX %s %u", &srp->prefix,
+		 IS_SID_VALUE(srp->sid.flags) ? "label" : "index",
+		 srp->sid.value);
 
 	/* Uninstall Prefix-SID from the forwarding plane. */
-	isis_zebra_uninstall_prefix_sid(srp);
+	isis_zebra_send_prefix_sid(ZEBRA_MPLS_LABELS_DELETE, srp);
 
 	/* Reset internal state. */
-	srp->local_label = MPLS_INVALID_LABEL;
+	srp->input_label = MPLS_INVALID_LABEL;
 	switch (srp->type) {
 	case ISIS_SR_PREFIX_LOCAL:
 		isis_sr_nexthop_reset(&srp->u.local.info);
@@ -655,81 +863,114 @@ static void isis_sr_prefix_uninstall(struct sr_prefix *srp)
 	}
 }
 
-/* Reinstall local or remote Prefix-SID. */
-static void isis_sr_prefix_reinstall(struct sr_prefix *srp,
-				     bool replace_semantics)
+/**
+ * Reinstall local or remote Prefix-SID.
+ *
+ * @param srp	Segment Routing Prefix
+ */
+static inline void sr_prefix_reinstall(struct sr_prefix *srp,
+				       bool make_before_break)
 {
 	/*
-	 * Route replace semantics can be used only when we know for sure that
+	 * Make Before Break can be used only when we know for sure that
 	 * the Prefix-SID input label hasn't changed. Otherwise we need to
 	 * uninstall the Prefix-SID first using the old input label before
 	 * reinstalling it.
 	 */
-	if (!replace_semantics)
-		isis_sr_prefix_uninstall(srp);
+	if (!make_before_break)
+		sr_prefix_uninstall(srp);
 
-	isis_sr_prefix_install(srp);
+	/* New input label is computed in sr_prefix_install() function */
+	sr_prefix_install(srp);
 }
 
-/*----------------------------------------------------------------------------*/
+/* --- IS-IS LSP Parse functions -------------------------------------------- */
 
-/* Parse all SR-related information from the given Router Capabilities TLV. */
+/**
+ * Parse all SR-related information from the given Router Capabilities TLV.
+ *
+ * @param area		IS-IS area
+ * @param level		IS-IS level
+ * @param sysid		System ID of the LSP
+ * @param router_cap	Router Capability subTLVs
+ *
+ * @return		Segment Routing Node structure for this System ID
+ */
 static struct sr_node *
-isis_sr_parse_router_cap_tlv(struct isis_area *area, int level,
-			     const uint8_t *sysid,
-			     const struct isis_router_cap *router_cap)
+parse_router_cap_tlv(struct isis_area *area, int level, const uint8_t *sysid,
+		     const struct isis_router_cap *router_cap)
 {
 	struct sr_node *srn;
 
 	if (!router_cap || router_cap->srgb.range_size == 0)
 		return NULL;
 
-	srn = isis_sr_node_find(area, level, sysid);
+	sr_debug("ISIS-Sr (%s): Parse Router Capability TLV", area->area_tag);
+
+	srn = sr_node_find(area, level, sysid);
 	if (srn) {
 		if (memcmp(&srn->cap, router_cap, sizeof(srn->cap)) != 0) {
 			srn->cap = *router_cap;
-			SET_FLAG(srn->parse_flags, F_ISIS_SR_NODE_MODIFIED);
+			srn->state = SRDB_STATE_MODIFIED;
 		} else
-			SET_FLAG(srn->parse_flags, F_ISIS_SR_NODE_UNCHANGED);
+			srn->state = SRDB_STATE_UNCHANGED;
+		sr_debug("  |- Found %s SR Node %s",
+			 srn->state == SRDB_STATE_MODIFIED ? "Modified"
+							   : "Unchanged",
+			 sysid_print(srn->sysid));
 	} else {
-		srn = isis_sr_node_add(area, level, sysid, router_cap);
-		SET_FLAG(srn->parse_flags, F_ISIS_SR_NODE_NEW);
+		srn = sr_node_add(area, level, sysid, router_cap);
+		srn->state = SRDB_STATE_NEW;
 	}
 
 	return srn;
 }
 
-/* Parse list of Prefix-SID Sub-TLVs. */
-static void isis_sr_parse_prefix_sid_subtlvs(struct sr_node *srn,
-					     union prefixconstptr prefix,
-					     bool local,
-					     struct isis_item_list *prefix_sids)
+/**
+ * Parse list of Prefix-SID Sub-TLVs.
+ *
+ * @param srn		Segment Routing Node
+ * @param prefix	Prefix to be parsed
+ * @param local		True if prefix comes from own LSP, false otherwise
+ * @param prefix_sids	Prefix SID subTLVs
+ */
+static void parse_prefix_sid_subtlvs(struct sr_node *srn,
+				     union prefixconstptr prefix, bool local,
+				     struct isis_item_list *prefix_sids)
 {
 	struct isis_area *area = srn->area;
 	struct isis_item *i;
 
+	sr_debug("ISIS-Sr (%s): Parse Prefix SID TLV", area->area_tag);
+
+	/* Parse list of Prefix SID subTLVs */
 	for (i = prefix_sids->head; i; i = i->next) {
 		struct isis_prefix_sid *psid = (struct isis_prefix_sid *)i;
 		struct sr_prefix *srp;
 
+		/* Only SPF algorithm is supported right now */
 		if (psid->algorithm != SR_ALGORITHM_SPF)
 			continue;
 
-		srp = isis_sr_prefix_find_node(srn, prefix);
+		/* Compute corresponding Segment Routing Prefix */
+		srp = sr_prefix_find_by_node(srn, prefix);
 		if (srp) {
 			if (srp->sid.flags != psid->flags
 			    || srp->sid.algorithm != psid->algorithm
 			    || srp->sid.value != psid->value) {
 				srp->sid = *psid;
-				SET_FLAG(srp->parse_flags,
-					 F_ISIS_SR_PREFIX_SID_MODIFIED);
+				srp->state = SRDB_STATE_MODIFIED;
 			} else
-				SET_FLAG(srp->parse_flags,
-					 F_ISIS_SR_PREFIX_SID_UNCHANGED);
+				srp->state = SRDB_STATE_UNCHANGED;
+			sr_debug("  |- Found %s Prefix-SID %pFX",
+				 srp->state == SRDB_STATE_MODIFIED
+					 ? "Modified"
+					 : "Unchanged",
+				 &srp->prefix);
+
 		} else {
-			srp = isis_sr_prefix_add(area, srn, prefix, local,
-						 psid);
-			SET_FLAG(srp->parse_flags, F_ISIS_SR_PREFIX_SID_NEW);
+			srp = sr_prefix_add(area, srn, prefix, local, psid);
+			srp->state = SRDB_STATE_NEW;
 		}
 		/*
 		 * Stop the Prefix-SID iteration since we only support the SPF
@@ -739,23 +980,34 @@ static void isis_sr_parse_prefix_sid_subtlvs(struct sr_node *srn,
 	}
 }
 
-/* Parse all SR-related information from the given LSP. */
-static void isis_sr_parse_lsp(struct isis_area *area, int level,
-			      struct sr_node **srn, struct isis_lsp *lsp)
+/**
+ * Parse all SR-related information from the given LSP.
+ *
+ * @param area	IS-IS area
+ * @param level	IS-IS level
+ * @param srn	Segment Routing Node
+ * @param lsp	IS-IS LSP
+ */
+static void parse_lsp(struct isis_area *area, int level, struct sr_node **srn,
+		      struct isis_lsp *lsp)
 {
 	struct isis_item_list *items;
 	struct isis_item *i;
 	bool local = lsp->own_lsp;
 
+	/* Check LSP sequence number */
 	if (lsp->hdr.seqno == 0) {
 		zlog_warn("%s: lsp with 0 seq_num - ignore", __func__);
 		return;
 	}
 
+	sr_debug("ISIS-Sr (%s): Parse LSP from node %s", area->area_tag,
+		 sysid_print(lsp->hdr.lsp_id));
+
 	/* Parse the Router Capability TLV. */
 	if (*srn == NULL) {
-		*srn = isis_sr_parse_router_cap_tlv(
-			area, level, lsp->hdr.lsp_id, lsp->tlvs->router_cap);
+		*srn = parse_router_cap_tlv(area, level, lsp->hdr.lsp_id,
+					    lsp->tlvs->router_cap);
 		if (!*srn)
 			return;
 	}
@@ -769,8 +1021,8 @@ static void isis_sr_parse_lsp(struct isis_area *area, int level,
 		if (!ir->subtlvs)
 			continue;
 
-		isis_sr_parse_prefix_sid_subtlvs(*srn, &ir->prefix, local,
-						 &ir->subtlvs->prefix_sids);
+		parse_prefix_sid_subtlvs(*srn, &ir->prefix, local,
+					 &ir->subtlvs->prefix_sids);
 	}
 
 	/* Parse Multi Topology Reachable IPv6 Prefixes TLV. */
@@ -783,78 +1035,88 @@ static void isis_sr_parse_lsp(struct isis_area *area, int level,
 		if (!ir->subtlvs)
 			continue;
 
-		isis_sr_parse_prefix_sid_subtlvs(*srn, &ir->prefix, local,
-						 &ir->subtlvs->prefix_sids);
+		parse_prefix_sid_subtlvs(*srn, &ir->prefix, local,
+					 &ir->subtlvs->prefix_sids);
 	}
 }
 
-/* Parse all SR-related information from the entire LSPDB. */
-static void isis_sr_parse_lspdb(struct isis_area *area)
+/**
+ * Parse all SR-related information from the entire LSPDB.
+ *
+ * @param area	IS-IS area
+ */
+static void parse_lspdb(struct isis_area *area)
 {
 	struct isis_lsp *lsp;
 
+	sr_debug("ISIS-Sr (%s): Parse LSP Data Base", area->area_tag);
+
+	/* Process all LSP from Level 1 & 2 */
 	for (int level = ISIS_LEVEL1; level <= ISIS_LEVELS; level++) {
 		frr_each (lspdb, &area->lspdb[level - 1], lsp) {
 			struct isis_lsp *frag;
 			struct listnode *node;
 			struct sr_node *srn = NULL;
 
+			/* Skip Pseudo ID LSP and LSP without TLVs */
 			if (LSP_PSEUDO_ID(lsp->hdr.lsp_id))
 				continue;
 			if (!lsp->tlvs)
 				continue;
 
-			isis_sr_parse_lsp(area, level, &srn, lsp);
+			/* Parse LSP, then fragment */
+			parse_lsp(area, level, &srn, lsp);
 			for (ALL_LIST_ELEMENTS_RO(lsp->lspu.frags, node, frag))
-				isis_sr_parse_lsp(area, level, &srn, frag);
+				parse_lsp(area, level, &srn, frag);
 		}
 	}
 }
 
-/* Process any new/deleted/modified Prefix-SID in the LSPDB. */
-static void isis_sr_process_prefix_changes(struct sr_node *srn,
-					   struct sr_prefix *srp)
+/**
+ * Process any new/deleted/modified Prefix-SID in the LSPDB.
+ *
+ * @param srn	Segment Routing Node
+ * @param srp	Segment Routing Prefix
+ */
+static void process_prefix_changes(struct sr_node *srn, struct sr_prefix *srp)
 {
 	struct isis_area *area = srn->area;
 
-	/* Log any Prefix-SID change in the LSPDB. */
-	if (IS_DEBUG_ISIS(DEBUG_SR)) {
-		if (CHECK_FLAG(srp->parse_flags, F_ISIS_SR_PREFIX_SID_NEW))
-			zlog_debug(
-				"ISIS-SR (%s) Prefix-SID created: %pFX (sysid %s)",
-				area->area_tag, &srp->prefix,
-				sysid_print(srn->sysid));
-		else if (CHECK_FLAG(srp->parse_flags,
-				    F_ISIS_SR_PREFIX_SID_MODIFIED))
-			zlog_debug(
-				"ISIS-SR (%s) Prefix-SID modified: %pFX (sysid %s)",
-				area->area_tag, &srp->prefix,
-				sysid_print(srn->sysid));
-		else if (!CHECK_FLAG(srp->parse_flags,
-				     F_ISIS_SR_PREFIX_SID_UNCHANGED))
-			zlog_debug(
-				"ISIS-SR (%s) Prefix-SID removed: %pFX (sysid %s)",
-				area->area_tag, &srp->prefix,
-				sysid_print(srn->sysid));
-	}
-
 	/* Install/reinstall/uninstall Prefix-SID if necessary. */
-	if (CHECK_FLAG(srp->parse_flags, F_ISIS_SR_PREFIX_SID_NEW))
-		isis_sr_prefix_install(srp);
-	else if (CHECK_FLAG(srp->parse_flags, F_ISIS_SR_PREFIX_SID_MODIFIED))
-		isis_sr_prefix_reinstall(srp, false);
-	else if (!CHECK_FLAG(srp->parse_flags,
-			     F_ISIS_SR_PREFIX_SID_UNCHANGED)) {
-		isis_sr_prefix_del(area, srn, srp);
+	switch (srp->state) {
+	case SRDB_STATE_NEW:
+		sr_debug("ISIS-Sr (%s): Created Prefix-SID %pFX for SR node %s",
+			 area->area_tag, &srp->prefix, sysid_print(srn->sysid));
+		sr_prefix_install(srp);
+		break;
+	case SRDB_STATE_MODIFIED:
+		sr_debug(
+			"ISIS-Sr (%s): Modified Prefix-SID %pFX for SR node %s",
+			area->area_tag, &srp->prefix, sysid_print(srn->sysid));
+		sr_prefix_reinstall(srp, false);
+		break;
+	case SRDB_STATE_UNCHANGED:
+		break;
+	default:
+		sr_debug("ISIS-Sr (%s): Removed Prefix-SID %pFX for SR node %s",
+			 area->area_tag, &srp->prefix, sysid_print(srn->sysid));
+		sr_prefix_del(area, srn, srp);
 		return;
 	}
 
-	srp->parse_flags = 0;
+	/* Validate SRDB State for next LSPDB parsing */
+	srp->state = SRDB_STATE_VALIDATED;
 }
 
-/* Process any new/deleted/modified SRGB in the LSPDB. */
-static void isis_sr_process_node_changes(struct isis_area *area, int level,
-					 struct sr_node *srn)
+/**
+ * Process any new/deleted/modified SRGB in the LSPDB.
+ *
+ * @param area	IS-IS area
+ * @param level	IS-IS level
+ * @param srn	Segment Routing Node
+ */
+static void process_node_changes(struct isis_area *area, int level,
+				 struct sr_node *srn)
 {
 	struct sr_prefix *srp;
 	uint8_t sysid[ISIS_SYS_ID_LEN];
@@ -862,44 +1124,46 @@ static void isis_sr_process_node_changes(struct isis_area *area, int level,
 
 	memcpy(sysid, srn->sysid, sizeof(sysid));
 
-	/* Log any SRGB change in the LSPDB. */
-	if (IS_DEBUG_ISIS(DEBUG_SR)) {
-		if (CHECK_FLAG(srn->parse_flags, F_ISIS_SR_NODE_NEW))
-			zlog_debug("ISIS-SR (%s) SRGB created (sysid %s)",
-				   area->area_tag, sysid_print(sysid));
-		else if (CHECK_FLAG(srn->parse_flags, F_ISIS_SR_NODE_MODIFIED))
-			zlog_debug("ISIS-SR (%s) SRGB modified (sysid %s)",
-				   area->area_tag, sysid_print(sysid));
-		else if (!CHECK_FLAG(srn->parse_flags,
-				     F_ISIS_SR_NODE_UNCHANGED))
-			zlog_debug("ISIS-SR (%s) SRGB removed (sysid %s)",
-				   area->area_tag, sysid_print(sysid));
-	}
-
 	/*
-	 * If an adjacent router's SRGB was changed or created, then reinstall
-	 * all Prefix-SIDs from all nodes.
+	 * If an neighbor router's SRGB was changed or created, then reinstall
+	 * all Prefix-SIDs from all nodes that use this neighbor as nexthop.
 	 */
 	adjacent = isis_adj_exists(area, level, sysid);
-	if (CHECK_FLAG(srn->parse_flags,
-		       F_ISIS_SR_NODE_NEW | F_ISIS_SR_NODE_MODIFIED)) {
+	switch (srn->state) {
+	case SRDB_STATE_NEW:
+	case SRDB_STATE_MODIFIED:
+		sr_debug("ISIS-Sr (%s): Create/Update SR node %s",
+			 area->area_tag, sysid_print(srn->sysid));
 		if (adjacent)
-			isis_sr_adj_srgb_update(area, sysid, level);
-	} else if (!CHECK_FLAG(srn->parse_flags, F_ISIS_SR_NODE_UNCHANGED)) {
-		isis_sr_node_del(area, level, srn);
+			sr_node_srgb_update(area, level, sysid);
+		break;
+	case SRDB_STATE_UNCHANGED:
+		break;
+	default:
+		/* SR capabilities have been removed. Delete SR-Node */
+		sr_debug("ISIS-Sr (%s): Remove SR node %s", area->area_tag,
+			 sysid_print(srn->sysid));
 
+		sr_node_del(area, level, srn);
+		/* and Update remaining Prefix-SID from all remaining SR Node */
 		if (adjacent)
-			isis_sr_adj_srgb_update(area, sysid, level);
+			sr_node_srgb_update(area, level, sysid);
 		return;
 	}
 
-	srn->parse_flags = 0;
+	/* Validate SRDB State for next LSPDB parsing */
+	srn->state = SRDB_STATE_VALIDATED;
 
-	frr_each_safe (tree_sr_node_prefix, &srn->prefix_sids, srp)
-		isis_sr_process_prefix_changes(srn, srp);
+	/* Finally, process all Prefix-SID of this SR Node */
+	frr_each_safe (srdb_node_prefix, &srn->prefix_sids, srp)
+		process_prefix_changes(srn, srp);
 }
 
-/* Parse and process all SR-related Sub-TLVs after running the SPF algorithm. */
+/**
+ * Parse and process all SR-related Sub-TLVs after running the SPF algorithm.
+ *
+ * @param area	IS-IS area
+ */
 void isis_area_verify_sr(struct isis_area *area)
 {
 	struct sr_node *srn;
@@ -908,40 +1172,48 @@ void isis_area_verify_sr(struct isis_area *area)
 		return;
 
 	/* Parse LSPDB to detect new/deleted/modified SR (sub-)TLVs. */
-	isis_sr_parse_lspdb(area);
+	parse_lspdb(area);
 
 	/* Process possible SR-related changes in the LDPSB. */
 	for (int level = ISIS_LEVEL1; level <= ISIS_LEVELS; level++) {
-		frr_each_safe (tree_sr_node, &area->srdb.sr_nodes[level - 1],
-			       srn)
-			isis_sr_process_node_changes(area, level, srn);
+		frr_each_safe (srdb_node, &area->srdb.sr_nodes[level - 1], srn)
+			process_node_changes(area, level, srn);
 	}
 }
 
-/*
+/**
  * Once a route is updated in the SPT, reinstall or uninstall its corresponding
  * Prefix-SID (if any).
+ *
+ * @param area		IS-IS area
+ * @param prefix	Prefix to be updated
+ * @param route_info	New Route Information
+ *
+ * @return		0
  */
-static int isis_sr_route_update(struct isis_area *area, struct prefix *prefix,
-				struct isis_route_info *route_info)
+static int sr_route_update(struct isis_area *area, struct prefix *prefix,
+			   struct isis_route_info *route_info)
 {
 	struct sr_prefix *srp;
 
 	if (!area->srdb.enabled)
 		return 0;
 
+	sr_debug("ISIS-Sr (%s): Update route for prefix %pFX", area->area_tag,
+		 prefix);
+
+	/* Lookup to Segment Routing Prefix for this prefix */
 	switch (area->is_type) {
 	case IS_LEVEL_1:
-		srp = isis_sr_prefix_find_area(area, ISIS_LEVEL1, prefix);
+		srp = sr_prefix_find_by_area(area, ISIS_LEVEL1, prefix);
 		break;
 	case IS_LEVEL_2:
-		srp = isis_sr_prefix_find_area(area, ISIS_LEVEL2, prefix);
+		srp = sr_prefix_find_by_area(area, ISIS_LEVEL2, prefix);
 		break;
 	case IS_LEVEL_1_AND_2:
-		srp = isis_sr_prefix_find_area(area, ISIS_LEVEL1, prefix);
+		srp = sr_prefix_find_by_area(area, ISIS_LEVEL1, prefix);
 		if (!srp)
-			srp = isis_sr_prefix_find_area(area, ISIS_LEVEL2,
-						       prefix);
+			srp = sr_prefix_find_by_area(area, ISIS_LEVEL2, prefix);
 		break;
 	default:
 		flog_err(EC_LIB_DEVELOPMENT, "%s: unknown area level",
@@ -949,51 +1221,38 @@ static int isis_sr_route_update(struct isis_area *area, struct prefix *prefix,
 		exit(1);
 	}
 
+	/* Skip NULL or local Segment Routing Prefix */
 	if (!srp || srp->type == ISIS_SR_PREFIX_LOCAL)
 		return 0;
 
+	/* Install or unintall Prefix-SID if route is Active or not */
 	if (CHECK_FLAG(route_info->flag, ISIS_ROUTE_FLAG_ACTIVE)) {
-		isis_sr_prefix_reinstall(srp, true);
+		/*
+		 * The Prefix-SID input label hasn't changed. We could use the
+		 * "Make Before Break" option. Zebra layer will update output
+		 * label by adding new label(s) before removing old one(s).
+		 */
+		sr_prefix_reinstall(srp, true);
 		srp->u.remote.rinfo = route_info;
 	} else {
-		isis_sr_prefix_uninstall(srp);
+		sr_prefix_uninstall(srp);
 		srp->u.remote.rinfo = NULL;
 	}
 
 	return 0;
 }
 
-/*----------------------------------------------------------------------------*/
-
-/* Install or uninstall (LAN)-Adj-SID. */
-static void isis_sr_adj_sid_install_uninstall(bool install,
-					      const struct sr_adjacency *sra)
-{
-	struct zapi_labels zl;
-	struct zapi_nexthop *znh;
-	int cmd;
-
-	cmd = install ? ZEBRA_MPLS_LABELS_ADD : ZEBRA_MPLS_LABELS_DELETE;
-
-	memset(&zl, 0, sizeof(zl));
-	zl.type = ZEBRA_LSP_ISIS_SR;
-	zl.local_label = sra->nexthop.label;
-	zl.nexthop_num = 1;
-	znh = &zl.nexthops[0];
-	znh->gate = sra->nexthop.address;
-	znh->type = (sra->nexthop.family == AF_INET)
-			    ? NEXTHOP_TYPE_IPV4_IFINDEX
-			    : NEXTHOP_TYPE_IPV6_IFINDEX;
-	znh->ifindex = sra->adj->circuit->interface->ifindex;
-	znh->label_num = 1;
-	znh->labels[0] = MPLS_LABEL_IMPLICIT_NULL;
-
-	(void)zebra_send_mpls_labels(zclient, cmd, &zl);
-}
+/* --- Segment Routing Adjacency-SID management functions ------------------- */
 
-/* Add new local Adj-SID. */
-static void isis_sr_adj_sid_add_single(struct isis_adjacency *adj, int family,
-				       bool backup)
+/**
+ * Add new local Adjacency-SID.
+ *
+ * @param adj	  IS-IS Adjacency
+ * @param family  Inet Family (IPv4 or IPv6)
+ * @param backup  True to initialize backup Adjacency SID
+ */
+static void sr_adj_sid_add_single(struct isis_adjacency *adj, int family,
+				  bool backup)
 {
 	struct isis_circuit *circuit = adj->circuit;
 	struct isis_area *area = circuit->area;
@@ -1002,8 +1261,12 @@ static void isis_sr_adj_sid_add_single(struct isis_adjacency *adj, int family,
 	struct isis_lan_adj_sid *ladj_sid;
 	union g_addr nexthop = {};
 	uint8_t flags;
-	mpls_label_t local_label;
+	mpls_label_t input_label;
+
+	sr_debug("ISIS-Sr (%s): Add %s Adjacency SID", area->area_tag,
+		 backup ? "Backup" : "Primary");
 
+	/* Determine nexthop IP address */
 	switch (family) {
 	case AF_INET:
 		if (!circuit->ip_router)
@@ -1023,31 +1286,24 @@ static void isis_sr_adj_sid_add_single(struct isis_adjacency *adj, int family,
 		exit(1);
 	}
 
+	/* Prepare Segment Routing Adjacency as per RFC8667 section #2.2 */
 	flags = EXT_SUBTLV_LINK_ADJ_SID_VFLG | EXT_SUBTLV_LINK_ADJ_SID_LFLG;
 	if (family == AF_INET6)
 		SET_FLAG(flags, EXT_SUBTLV_LINK_ADJ_SID_FFLG);
 	if (backup)
 		SET_FLAG(flags, EXT_SUBTLV_LINK_ADJ_SID_BFLG);
 
-	local_label = isis_zebra_request_dynamic_label();
+	input_label = isis_zebra_request_dynamic_label();
 	if (circuit->ext == NULL)
 		circuit->ext = isis_alloc_ext_subtlvs();
 
-	if (IS_DEBUG_ISIS(DEBUG_SR)) {
-		char buf[INET6_ADDRSTRLEN];
-
-		inet_ntop(family, &nexthop, buf, sizeof(buf));
-		zlog_debug("ISIS-SR (%s) installing Adj-SID %s%%%s label %u",
-			   area->area_tag, buf, circuit->interface->name,
-			   local_label);
-	}
-
 	sra = XCALLOC(MTYPE_ISIS_SR_INFO, sizeof(*sra));
 	sra->type = backup ? ISIS_SR_LAN_BACKUP : ISIS_SR_ADJ_NORMAL;
 	sra->nexthop.family = family;
 	sra->nexthop.address = nexthop;
-	sra->nexthop.label = local_label;
+	sra->nexthop.label = input_label;
 	switch (circuit->circ_type) {
+	/* LAN Adjacency-SID for Broadcast interface section #2.2.2 */
 	case CIRCUIT_T_BROADCAST:
 		ladj_sid = XCALLOC(MTYPE_ISIS_SUBTLV, sizeof(*ladj_sid));
 		ladj_sid->family = family;
@@ -1055,16 +1311,17 @@ static void isis_sr_adj_sid_add_single(struct isis_adjacency *adj, int family,
 		ladj_sid->weight = 0;
 		memcpy(ladj_sid->neighbor_id, adj->sysid,
 		       sizeof(ladj_sid->neighbor_id));
-		ladj_sid->sid = local_label;
+		ladj_sid->sid = input_label;
 		isis_tlvs_add_lan_adj_sid(circuit->ext, ladj_sid);
 		sra->u.ladj_sid = ladj_sid;
 		break;
+	/* Adjacency-SID for Point to Point interface section #2.2.1 */
 	case CIRCUIT_T_P2P:
 		adj_sid = XCALLOC(MTYPE_ISIS_SUBTLV, sizeof(*adj_sid));
 		adj_sid->family = family;
 		adj_sid->flags = flags;
 		adj_sid->weight = 0;
-		adj_sid->sid = local_label;
+		adj_sid->sid = input_label;
 		isis_tlvs_add_adj_sid(circuit->ext, adj_sid);
 		sra->u.adj_sid = adj_sid;
 		break;
@@ -1073,36 +1330,42 @@ static void isis_sr_adj_sid_add_single(struct isis_adjacency *adj, int family,
 			 __func__, circuit->circ_type);
 		exit(1);
 	}
+
+	/* Add Adjacency-SID in SRDB */
 	sra->adj = adj;
 	listnode_add(area->srdb.adj_sids, sra);
 	listnode_add(adj->adj_sids, sra);
 
-	isis_sr_adj_sid_install_uninstall(true, sra);
+	isis_zebra_send_adjacency_sid(ZEBRA_MPLS_LABELS_ADD, sra);
 }
 
-static void isis_sr_adj_sid_add(struct isis_adjacency *adj, int family)
+/**
+ * Add Primary and Backup local Adjacency SID.
+ *
+ * @param adj	  IS-IS Adjacency
+ * @param family  Inet Family (IPv4 or IPv6)
+ */
+static void sr_adj_sid_add(struct isis_adjacency *adj, int family)
 {
-	isis_sr_adj_sid_add_single(adj, family, false);
-	isis_sr_adj_sid_add_single(adj, family, true);
+	sr_adj_sid_add_single(adj, family, false);
+	sr_adj_sid_add_single(adj, family, true);
 }
 
-/* Delete local Adj-SID. */
-static void isis_sr_adj_sid_del(struct sr_adjacency *sra)
+/**
+ * Delete local Adj-SID.
+ *
+ * @param sra	Segment Routing Adjacency
+ */
+static void sr_adj_sid_del(struct sr_adjacency *sra)
 {
 	struct isis_circuit *circuit = sra->adj->circuit;
 	struct isis_area *area = circuit->area;
 
-	if (IS_DEBUG_ISIS(DEBUG_SR)) {
-		char buf[INET6_ADDRSTRLEN];
+	sr_debug("ISIS-Sr (%s): Delete Adjacency SID", area->area_tag);
 
-		inet_ntop(sra->nexthop.family, &sra->nexthop.address, buf,
-			  sizeof(buf));
-		zlog_debug("ISIS-SR (%s) uninstalling Adj-SID %s%%%s",
-			   area->area_tag, buf, circuit->interface->name);
-	}
-
-	isis_sr_adj_sid_install_uninstall(false, sra);
+	isis_zebra_send_adjacency_sid(ZEBRA_MPLS_LABELS_DELETE, sra);
 
+	/* Release dynamic label and remove subTLVs */
 	switch (circuit->circ_type) {
 	case CIRCUIT_T_BROADCAST:
 		isis_zebra_release_dynamic_label(sra->u.ladj_sid->sid);
@@ -1118,13 +1381,20 @@ static void isis_sr_adj_sid_del(struct sr_adjacency *sra)
 		exit(1);
 	}
 
+	/* Remove Adjacency-SID from the SRDB */
 	listnode_delete(area->srdb.adj_sids, sra);
 	listnode_delete(sra->adj->adj_sids, sra);
 	XFREE(MTYPE_ISIS_SR_INFO, sra);
 }
 
-/* Remove all Adj-SIDs associated to an adjacency that is going down. */
-static int isis_sr_adj_state_change(struct isis_adjacency *adj)
+/**
+ * Remove all Adjacency-SIDs associated to an adjacency that is going down.
+ *
+ * @param adj	IS-IS Adjacency
+ *
+ * @return	0
+ */
+static int sr_adj_state_change(struct isis_adjacency *adj)
 {
 	struct sr_adjacency *sra;
 	struct listnode *node, *nnode;
@@ -1136,30 +1406,40 @@ static int isis_sr_adj_state_change(struct isis_adjacency *adj)
 		return 0;
 
 	for (ALL_LIST_ELEMENTS(adj->adj_sids, node, nnode, sra))
-		isis_sr_adj_sid_del(sra);
+		sr_adj_sid_del(sra);
 
 	return 0;
 }
 
-/*
- * Adjacency now has one or more IPv4/IPv6 addresses. Add new IPv4 or IPv6
- * Adj-SID accordingly.
+/**
+ * When IS-IS Adjacency got one or more IPv4/IPv6 addresses, add new IPv4 or
+ * IPv6 address to corresponding Adjacency-SID accordingly.
+ *
+ * @param adj	  IS-IS Adjacency
+ * @param family  Inet Family (IPv4 or IPv6)
+ *
+ * @return	  0
  */
-static int isis_sr_adj_ip_enabled(struct isis_adjacency *adj, int family)
+static int sr_adj_ip_enabled(struct isis_adjacency *adj, int family)
 {
 	if (!adj->circuit->area->srdb.enabled)
 		return 0;
 
-	isis_sr_adj_sid_add(adj, family);
+	sr_adj_sid_add(adj, family);
 
 	return 0;
 }
 
-/*
- * Adjacency doesn't have any IPv4 or IPv6 addresses anymore. Delete the
- * corresponding Adj-SID(s) accordingly.
+/**
+ * When IS-IS Adjacency doesn't have any IPv4 or IPv6 addresses anymore,
+ * delete the corresponding Adjacency-SID(s) accordingly.
+ *
+ * @param adj	  IS-IS Adjacency
+ * @param family  Inet Family (IPv4 or IPv6)
+ *
+ * @return	  0
  */
-static int isis_sr_adj_ip_disabled(struct isis_adjacency *adj, int family)
+static int sr_adj_ip_disabled(struct isis_adjacency *adj, int family)
 {
 	struct sr_adjacency *sra;
 	struct listnode *node, *nnode;
@@ -1169,18 +1449,26 @@ static int isis_sr_adj_ip_disabled(struct isis_adjacency *adj, int family)
 
 	for (ALL_LIST_ELEMENTS(adj->adj_sids, node, nnode, sra))
 		if (sra->nexthop.family == family)
-			isis_sr_adj_sid_del(sra);
+			sr_adj_sid_del(sra);
 
 	return 0;
 }
 
-static int isis_sr_if_new_hook(struct interface *ifp)
+/**
+ * Activate local Prefix-SID when loopback interface goes up for IS-IS.
+ *
+ * @param ifp	Loopback Interface
+ *
+ * @return	0
+ */
+static int sr_if_new_hook(struct interface *ifp)
 {
 	struct isis_circuit *circuit;
 	struct isis_area *area;
 	struct connected *connected;
 	struct listnode *node;
 
+	/* Get corresponding circuit */
 	circuit = circuit_scan_by_ifp(ifp);
 	if (!circuit)
 		return 0;
@@ -1201,7 +1489,7 @@ static int isis_sr_if_new_hook(struct interface *ifp)
 		if (!pcfg)
 			continue;
 
-		if (isis_sr_prefix_is_node_sid(ifp, &pcfg->prefix)
+		if (sr_prefix_is_node_sid(ifp, &pcfg->prefix)
 		    && !pcfg->node_sid) {
 			pcfg->node_sid = true;
 			lsp_regenerate_schedule(area, area->is_type, 0);
@@ -1211,58 +1499,113 @@ static int isis_sr_if_new_hook(struct interface *ifp)
 	return 0;
 }
 
-/*----------------------------------------------------------------------------*/
+/* --- Segment Routing Show information functions --------------------------- */
 
-static void isis_sr_show_prefix_sid_local(struct vty *vty, struct ttable *tt,
-					  const struct isis_area *area,
-					  const struct sr_prefix *srp)
+/**
+ * Show LFIB operation in human readable format.
+ *
+ * @param buf	     Buffer to store string output. Must be pre-allocate
+ * @param size	     Size of the buffer
+ * @param label_in   Input Label
+ * @param label_out  Output Label
+ *
+ * @return	     String containing LFIB operation in human readable format
+ */
+static char *sr_op2str(char *buf, size_t size, mpls_label_t label_in,
+		       mpls_label_t label_out)
+{
+	if (size < 24)
+		return NULL;
+
+	if (label_in == MPLS_INVALID_LABEL) {
+		snprintf(buf, size, "no-op.");
+		return buf;
+	}
+
+	switch (label_out) {
+	case MPLS_LABEL_IMPLICIT_NULL:
+		snprintf(buf, size, "Pop(%u)", label_in);
+		break;
+	case MPLS_LABEL_IPV4_EXPLICIT_NULL:
+	case MPLS_LABEL_IPV6_EXPLICIT_NULL:
+		snprintf(buf, size, "Swap(%u, null)", label_in);
+		break;
+	case MPLS_INVALID_LABEL:
+		snprintf(buf, size, "no-op.");
+		break;
+	default:
+		snprintf(buf, size, "Swap(%u, %u)", label_in, label_out);
+		break;
+	}
+	return buf;
+}
+
+/**
+ * Show Local Prefix-SID.
+ *
+ * @param vty	VTY output
+ * @param tt	Table format
+ * @param area	IS-IS area
+ * @param srp	Segment Routing Prefix
+ */
+static void show_prefix_sid_local(struct vty *vty, struct ttable *tt,
+				  const struct isis_area *area,
+				  const struct sr_prefix *srp)
 {
 	const struct sr_nexthop_info *srnh = &srp->u.local.info;
 	char buf_prefix[BUFSIZ];
-	char buf_llabel[BUFSIZ];
-	char buf_rlabel[BUFSIZ];
+	char buf_oper[BUFSIZ];
+	char buf_iface[BUFSIZ];
 	char buf_uptime[BUFSIZ];
 
-	if (srp->local_label != MPLS_INVALID_LABEL)
-		label2str(srp->local_label, buf_llabel, sizeof(buf_llabel));
-	else
-		snprintf(buf_llabel, sizeof(buf_llabel), "-");
 	if (srnh->label != MPLS_INVALID_LABEL) {
-		label2str(srnh->label, buf_rlabel, sizeof(buf_rlabel));
+		struct interface *ifp;
+		ifp = if_lookup_prefix(&srp->prefix, VRF_DEFAULT);
+		if (ifp)
+			strlcpy(buf_iface, ifp->name, sizeof(buf_iface));
+		else
+			snprintf(buf_iface, sizeof(buf_iface), "-");
 		log_uptime(srnh->uptime, buf_uptime, sizeof(buf_uptime));
 	} else {
-		snprintf(buf_rlabel, sizeof(buf_rlabel), "-");
+		snprintf(buf_iface, sizeof(buf_iface), "-");
 		snprintf(buf_uptime, sizeof(buf_uptime), "-");
 	}
+	sr_op2str(buf_oper, sizeof(buf_oper), srp->input_label,
+		  MPLS_LABEL_IMPLICIT_NULL);
 
-	ttable_add_row(tt, "%s|%u|%s|local|%s|%s",
+	ttable_add_row(tt, "%s|%u|%s|-|%s|%s",
 		       prefix2str(&srp->prefix, buf_prefix, sizeof(buf_prefix)),
-		       srp->sid.value, buf_llabel, buf_rlabel, buf_uptime);
+		       srp->sid.value, buf_oper, buf_iface, buf_uptime);
 }
 
-static void isis_sr_show_prefix_sid_remote(struct vty *vty, struct ttable *tt,
-					   const struct isis_area *area,
-					   const struct sr_prefix *srp)
+/**
+ * Show Remote Prefix-SID.
+ *
+ * @param vty	VTY output
+ * @param tt	Table format
+ * @param area	IS-IS area
+ * @param srp	Segment Routing Prefix
+ */
+static void show_prefix_sid_remote(struct vty *vty, struct ttable *tt,
+				   const struct isis_area *area,
+				   const struct sr_prefix *srp)
 {
 	struct isis_nexthop *nexthop;
 	struct listnode *node;
 	char buf_prefix[BUFSIZ];
-	char buf_llabel[BUFSIZ];
+	char buf_oper[BUFSIZ];
 	char buf_nhop[BUFSIZ];
 	char buf_iface[BUFSIZ];
-	char buf_rlabel[BUFSIZ];
 	char buf_uptime[BUFSIZ];
 	bool first = true;
 
 	(void)prefix2str(&srp->prefix, buf_prefix, sizeof(buf_prefix));
-	if (srp->local_label != MPLS_INVALID_LABEL)
-		label2str(srp->local_label, buf_llabel, sizeof(buf_llabel));
-	else
-		snprintf(buf_llabel, sizeof(buf_llabel), "-");
 
 	if (!srp->u.remote.rinfo) {
 		ttable_add_row(tt, "%s|%u|%s|-|-|-", buf_prefix, srp->sid.value,
-			       buf_llabel);
+			       sr_op2str(buf_oper, sizeof(buf_oper),
+					 srp->input_label,
+					 MPLS_LABEL_IMPLICIT_NULL));
 		return;
 	}
 
@@ -1278,54 +1621,58 @@ static void isis_sr_show_prefix_sid_remote(struct vty *vty, struct ttable *tt,
 		else
 			snprintf(buf_iface, sizeof(buf_iface), "ifindex %u",
 				 nexthop->ifindex);
-		if (nexthop->sr.label == MPLS_INVALID_LABEL) {
-			snprintf(buf_rlabel, sizeof(buf_rlabel), "-");
+		if (nexthop->sr.label == MPLS_INVALID_LABEL)
 			snprintf(buf_uptime, sizeof(buf_uptime), "-");
-		} else {
-			label2str(nexthop->sr.label, buf_rlabel,
-				  sizeof(buf_rlabel));
+		else
 			log_uptime(nexthop->sr.uptime, buf_uptime,
 				   sizeof(buf_uptime));
-		}
+		sr_op2str(buf_oper, sizeof(buf_oper), srp->input_label,
+			  nexthop->sr.label);
 
 		if (first)
-			ttable_add_row(tt, "%s|%u|%s|%s, %s|%s|%s", buf_prefix,
-				       srp->sid.value, buf_llabel, buf_nhop,
-				       buf_iface, buf_rlabel, buf_uptime);
+			ttable_add_row(tt, "%s|%u|%s|%s|%s|%s", buf_prefix,
+				       srp->sid.value, buf_oper, buf_nhop,
+				       buf_iface, buf_uptime);
 		else
-			ttable_add_row(tt, "|||%s, %s|%s|%s", buf_nhop,
-				       buf_iface, buf_rlabel, buf_uptime);
+			ttable_add_row(tt, "|||%s|%s|%s|%s", buf_oper, buf_nhop,
+				       buf_iface, buf_uptime);
 		first = false;
 	}
 }
 
-static void isis_sr_show_prefix_sids(struct vty *vty, struct isis_area *area,
-				     int level)
+/**
+ * Show Prefix-SIDs.
+ *
+ * @param vty	VTY output
+ * @param area	IS-IS area
+ * @param level	IS-IS level
+ */
+static void show_prefix_sids(struct vty *vty, struct isis_area *area, int level)
 {
 	struct sr_prefix *srp;
 	struct ttable *tt;
 
-	if (tree_sr_area_prefix_count(&area->srdb.prefix_sids[level - 1]) == 0)
+	if (srdb_area_prefix_count(&area->srdb.prefix_sids[level - 1]) == 0)
 		return;
 
 	vty_out(vty, " IS-IS %s Prefix-SIDs:\n\n", circuit_t2string(level));
 
 	/* Prepare table. */
 	tt = ttable_new(&ttable_styles[TTSTYLE_BLANK]);
-	ttable_add_row(tt, "Prefix|SID|In Label|Nexthop|Out Label|Uptime");
+	ttable_add_row(tt, "Prefix|SID|Label Op.|Nexthop|Interface|Uptime");
 	tt->style.cell.rpad = 2;
 	tt->style.corner = '+';
 	ttable_restyle(tt);
 	ttable_rowseps(tt, 0, BOTTOM, true, '-');
 
-	frr_each (tree_sr_area_prefix, &area->srdb.prefix_sids[level - 1],
-		  srp) {
+	/* Process all Prefix-SID from the SRDB */
+	frr_each (srdb_area_prefix, &area->srdb.prefix_sids[level - 1], srp) {
 		switch (srp->type) {
 		case ISIS_SR_PREFIX_LOCAL:
-			isis_sr_show_prefix_sid_local(vty, tt, area, srp);
+			show_prefix_sid_local(vty, tt, area, srp);
 			break;
 		case ISIS_SR_PREFIX_REMOTE:
-			isis_sr_show_prefix_sid_remote(vty, tt, area, srp);
+			show_prefix_sid_remote(vty, tt, area, srp);
 			break;
 		}
 	}
@@ -1341,6 +1688,9 @@ static void isis_sr_show_prefix_sids(struct vty *vty, struct isis_area *area,
 	ttable_del(tt);
 }
 
+/**
+ * Declaration of new show commands.
+ */
 DEFUN(show_sr_prefix_sids, show_sr_prefix_sids_cmd,
       "show isis segment-routing prefix-sids",
       SHOW_STR PROTO_HELP
@@ -1355,15 +1705,89 @@ DEFUN(show_sr_prefix_sids, show_sr_prefix_sids_cmd,
 			area->area_tag ? area->area_tag : "null");
 
 		for (int level = ISIS_LEVEL1; level <= ISIS_LEVELS; level++)
-			isis_sr_show_prefix_sids(vty, area, level);
+			show_prefix_sids(vty, area, level);
+	}
+
+	return CMD_SUCCESS;
+}
+
+/**
+ * Show Segment Routing Node.
+ *
+ * @param vty	VTY output
+ * @param area	IS-IS area
+ * @param level	IS-IS level
+ */
+static void show_node(struct vty *vty, struct isis_area *area, int level)
+{
+	struct sr_node *srn;
+	struct ttable *tt;
+
+	if (srdb_area_prefix_count(&area->srdb.prefix_sids[level - 1]) == 0)
+		return;
+
+	vty_out(vty, " IS-IS %s SR-Node:\n\n", circuit_t2string(level));
+
+	/* Prepare table. */
+	tt = ttable_new(&ttable_styles[TTSTYLE_BLANK]);
+	ttable_add_row(tt, "System ID|SRGB|Algorithm|MSD");
+	tt->style.cell.rpad = 2;
+	tt->style.corner = '+';
+	ttable_restyle(tt);
+	ttable_rowseps(tt, 0, BOTTOM, true, '-');
+
+	/* Process all SR-Node from the SRDB */
+	frr_each (srdb_node, &area->srdb.sr_nodes[level - 1], srn) {
+		ttable_add_row(tt, "%s|%u - %u|%s|%u", sysid_print(srn->sysid),
+			       srn->cap.srgb.lower_bound,
+			       srn->cap.srgb.lower_bound
+				       + srn->cap.srgb.range_size - 1,
+			       srn->cap.algo[0] == SR_ALGORITHM_SPF ? "SPF"
+								    : "S-SPF",
+			       srn->cap.msd);
+	}
+
+	/* Dump the generated table. */
+	if (tt->nrows > 1) {
+		char *table;
+
+		table = ttable_dump(tt, "\n");
+		vty_out(vty, "%s\n", table);
+		XFREE(MTYPE_TMP, table);
+	}
+	ttable_del(tt);
+}
+
+DEFUN(show_sr_node, show_sr_node_cmd,
+      "show isis segment-routing node",
+      SHOW_STR PROTO_HELP
+      "Segment-Routing\n"
+      "Segment-Routing node\n")
+{
+	struct listnode *node;
+	struct isis_area *area;
+
+	for (ALL_LIST_ELEMENTS_RO(isis->area_list, node, area)) {
+		vty_out(vty, "Area %s:\n",
+			area->area_tag ? area->area_tag : "null");
+
+		for (int level = ISIS_LEVEL1; level <= ISIS_LEVELS; level++)
+			show_node(vty, area, level);
 	}
 
 	return CMD_SUCCESS;
 }
 
-/*----------------------------------------------------------------------------*/
 
-/* Try to enable SR on the given IS-IS area. */
+/* --- IS-IS Segment Routing Management function ---------------------------- */
+
+/**
+ * Enable SR on the given IS-IS area.
+ *
+ * @param area	IS-IS area
+ *
+ * @return	0 on success, -1 otherwise
+ */
 int isis_sr_start(struct isis_area *area)
 {
 	struct isis_sr_db *srdb = &area->srdb;
@@ -1380,11 +1804,10 @@ int isis_sr_start(struct isis_area *area)
 			    - srdb->config.srgb_lower_bound + 1))
 		return -1;
 
-	if (IS_DEBUG_ISIS(DEBUG_SR))
-		zlog_debug("ISIS-SR (%s) Starting Segment Routing",
-			   area->area_tag);
+	sr_debug("ISIS-Sr: Starting Segment Routing for area %s",
+		 area->area_tag);
 
-	/* Create Adj-SIDs for existing adjacencies. */
+	/* Create Adjacency-SIDs from existing IS-IS Adjacencies. */
 	for (ALL_LIST_ELEMENTS_RO(area->circuit_list, node, circuit)) {
 		struct isis_adjacency *adj;
 		struct listnode *anode;
@@ -1397,54 +1820,55 @@ int isis_sr_start(struct isis_area *area)
 					     circuit->u.bc.adjdb[level - 1],
 					     anode, adj)) {
 					if (adj->ipv4_address_count > 0)
-						isis_sr_adj_sid_add(adj,
-								    AF_INET);
+						sr_adj_sid_add(adj, AF_INET);
 					if (adj->ipv6_address_count > 0)
-						isis_sr_adj_sid_add(adj,
-								    AF_INET6);
+						sr_adj_sid_add(adj, AF_INET6);
 				}
 			}
 			break;
 		case CIRCUIT_T_P2P:
 			adj = circuit->u.p2p.neighbor;
 			if (adj && adj->ipv4_address_count > 0)
-				isis_sr_adj_sid_add(adj, AF_INET);
+				sr_adj_sid_add(adj, AF_INET);
 			if (adj && adj->ipv6_address_count > 0)
-				isis_sr_adj_sid_add(adj, AF_INET6);
+				sr_adj_sid_add(adj, AF_INET6);
 			break;
 		default:
 			break;
 		}
 	}
 
-	/* Regenerate LSPs. */
+	/* Regenerate LSPs to advertise Segment Routing capabilities. */
 	lsp_regenerate_schedule(area, area->is_type, 0);
 
 	return 0;
 }
 
-/* Disable SR on the given IS-IS area. */
+/**
+ * Disable SR on the given IS-IS area.
+ *
+ * @param area	IS-IS area
+ */
 void isis_sr_stop(struct isis_area *area)
 {
 	struct isis_sr_db *srdb = &area->srdb;
 	struct sr_adjacency *sra;
 	struct listnode *node, *nnode;
 
-	if (IS_DEBUG_ISIS(DEBUG_SR))
-		zlog_debug("ISIS-SR (%s) Stopping Segment Routing",
-			   area->area_tag);
+	sr_debug("ISIS-Sr: Stopping Segment Routing for area %s",
+		 area->area_tag);
 
-	/* Uninstall Adj-SIDs. */
+	/* Uninstall all local Adjacency-SIDs. */
 	for (ALL_LIST_ELEMENTS(area->srdb.adj_sids, node, nnode, sra))
-		isis_sr_adj_sid_del(sra);
+		sr_adj_sid_del(sra);
 
-	/* Uninstall Prefix-SIDs. */
+	/* Uninstall all Prefix-SIDs from all SR Node. */
 	for (int level = ISIS_LEVEL1; level <= ISIS_LEVELS; level++) {
-		while (tree_sr_node_count(&srdb->sr_nodes[level - 1]) > 0) {
+		while (srdb_node_count(&srdb->sr_nodes[level - 1]) > 0) {
 			struct sr_node *srn;
 
-			srn = tree_sr_node_first(&srdb->sr_nodes[level - 1]);
-			isis_sr_node_del(area, level, srn);
+			srn = srdb_node_first(&srdb->sr_nodes[level - 1]);
+			sr_node_del(area, level, srn);
 		}
 	}
 
@@ -1452,21 +1876,30 @@ void isis_sr_stop(struct isis_area *area)
 	isis_zebra_release_label_range(srdb->config.srgb_lower_bound,
 				       srdb->config.srgb_upper_bound);
 
-	/* Regenerate LSPs. */
+	/* Regenerate LSPs to advertise that the Node is no more SR enable. */
 	lsp_regenerate_schedule(area, area->is_type, 0);
 }
 
+/**
+ * IS-IS Segment Routing initialization for given area.
+ *
+ * @param area	IS-IS area
+ */
 void isis_sr_area_init(struct isis_area *area)
 {
 	struct isis_sr_db *srdb = &area->srdb;
 
+	sr_debug("ISIS-Sr (%s): Initialize Segment Routing SRDB",
+		 area->area_tag);
+
+	/* Initialize Segment Routing Data Base */
 	memset(srdb, 0, sizeof(*srdb));
 	srdb->enabled = false;
 	srdb->adj_sids = list_new();
 
 	for (int level = ISIS_LEVEL1; level <= ISIS_LEVELS; level++) {
-		tree_sr_node_init(&srdb->sr_nodes[level - 1]);
-		tree_sr_area_prefix_init(&srdb->prefix_sids[level - 1]);
+		srdb_node_init(&srdb->sr_nodes[level - 1]);
+		srdb_area_prefix_init(&srdb->prefix_sids[level - 1]);
 	}
 
 	/* Pull defaults from the YANG module. */
@@ -1482,9 +1915,14 @@ void isis_sr_area_init(struct isis_area *area)
 	srdb->config.srgb_upper_bound = SRGB_UPPER_BOUND;
 #endif
 	srdb->config.msd = 0;
-	tree_sr_prefix_cfg_init(&srdb->config.prefix_sids);
+	srdb_prefix_cfg_init(&srdb->config.prefix_sids);
 }
 
+/**
+ * Terminate IS-IS Segment Routing for the given area.
+ *
+ * @param area	IS-IS area
+ */
 void isis_sr_area_term(struct isis_area *area)
 {
 	struct isis_sr_db *srdb = &area->srdb;
@@ -1494,32 +1932,39 @@ void isis_sr_area_term(struct isis_area *area)
 		isis_sr_stop(area);
 
 	/* Clear Prefix-SID configuration. */
-	while (tree_sr_prefix_cfg_count(&srdb->config.prefix_sids) > 0) {
+	while (srdb_prefix_cfg_count(&srdb->config.prefix_sids) > 0) {
 		struct sr_prefix_cfg *pcfg;
 
-		pcfg = tree_sr_prefix_cfg_first(&srdb->config.prefix_sids);
+		pcfg = srdb_prefix_cfg_first(&srdb->config.prefix_sids);
 		isis_sr_cfg_prefix_del(pcfg);
 	}
 }
 
+/**
+ * IS-IS Segment Routing global initialization.
+ */
 void isis_sr_init(void)
 {
 	install_element(VIEW_NODE, &show_sr_prefix_sids_cmd);
+	install_element(VIEW_NODE, &show_sr_node_cmd);
 
 	/* Register hooks. */
-	hook_register(isis_adj_state_change_hook, isis_sr_adj_state_change);
-	hook_register(isis_adj_ip_enabled_hook, isis_sr_adj_ip_enabled);
-	hook_register(isis_adj_ip_disabled_hook, isis_sr_adj_ip_disabled);
-	hook_register(isis_route_update_hook, isis_sr_route_update);
-	hook_register(isis_if_new_hook, isis_sr_if_new_hook);
+	hook_register(isis_adj_state_change_hook, sr_adj_state_change);
+	hook_register(isis_adj_ip_enabled_hook, sr_adj_ip_enabled);
+	hook_register(isis_adj_ip_disabled_hook, sr_adj_ip_disabled);
+	hook_register(isis_route_update_hook, sr_route_update);
+	hook_register(isis_if_new_hook, sr_if_new_hook);
 }
 
+/**
+ * IS-IS Segment Routing global terminate.
+ */
 void isis_sr_term(void)
 {
 	/* Unregister hooks. */
-	hook_unregister(isis_adj_state_change_hook, isis_sr_adj_state_change);
-	hook_unregister(isis_adj_ip_enabled_hook, isis_sr_adj_ip_enabled);
-	hook_unregister(isis_adj_ip_disabled_hook, isis_sr_adj_ip_disabled);
-	hook_unregister(isis_route_update_hook, isis_sr_route_update);
-	hook_unregister(isis_if_new_hook, isis_sr_if_new_hook);
+	hook_unregister(isis_adj_state_change_hook, sr_adj_state_change);
+	hook_unregister(isis_adj_ip_enabled_hook, sr_adj_ip_enabled);
+	hook_unregister(isis_adj_ip_disabled_hook, sr_adj_ip_disabled);
+	hook_unregister(isis_route_update_hook, sr_route_update);
+	hook_unregister(isis_if_new_hook, sr_if_new_hook);
 }
diff --git a/isisd/isis_sr.h b/isisd/isis_sr.h
index 286ebeb953..dec329ab48 100644
--- a/isisd/isis_sr.h
+++ b/isisd/isis_sr.h
@@ -1,8 +1,7 @@
 /*
- * This is an implementation of Segment Routing for IS-IS
- * as per draft draft-ietf-isis-segment-routing-extensions-25
+ * This is an implementation of Segment Routing for IS-IS as per RFC 8667
  *
- * Copyright (C) 2019 Orange Labs http://www.orange.com
+ * Copyright (C) 2019 Orange http://www.orange.com
  *
  * Author: Olivier Dugeon <olivier.dugeon@orange.com>
  * Contributor: Renato Westphal <renato@opensourcerouting.org> for NetDEF
@@ -55,30 +54,31 @@
 #define SRGB_LOWER_BOUND               16000
 #define SRGB_UPPER_BOUND               23999
 
-PREDECL_RBTREE_UNIQ(tree_sr_node)
-PREDECL_RBTREE_UNIQ(tree_sr_node_prefix)
-PREDECL_RBTREE_UNIQ(tree_sr_area_prefix)
-PREDECL_RBTREE_UNIQ(tree_sr_prefix_cfg)
+/* Segment Routing Data Base (SRDB) RB-Tree structure */
+PREDECL_RBTREE_UNIQ(srdb_node)
+PREDECL_RBTREE_UNIQ(srdb_node_prefix)
+PREDECL_RBTREE_UNIQ(srdb_area_prefix)
+PREDECL_RBTREE_UNIQ(srdb_prefix_cfg)
 
-/* SR Adj-SID type. */
+/* Segment Routing Adjacency-SID type. */
 enum sr_adj_type {
 	ISIS_SR_ADJ_NORMAL = 0,
 	ISIS_SR_LAN_BACKUP,
 };
 
-/* SR Adjacency. */
+/* Segment Routing Adjacency. */
 struct sr_adjacency {
 	/* Adjacency type. */
 	enum sr_adj_type type;
 
-	/* Adj-SID nexthop information. */
+	/* Adjacency-SID nexthop information. */
 	struct {
 		int family;
 		union g_addr address;
 		mpls_label_t label;
 	} nexthop;
 
-	/* (LAN-)Adj-SID Sub-TLV. */
+	/* (LAN-)Adjacency-SID Sub-TLV. */
 	union {
 		struct isis_adj_sid *adj_sid;
 		struct isis_lan_adj_sid *ladj_sid;
@@ -88,32 +88,40 @@ struct sr_adjacency {
 	struct isis_adjacency *adj;
 };
 
-/* SR Prefix-SID type. */
+/* Segment Routing Prefix-SID type. */
 enum sr_prefix_type {
 	ISIS_SR_PREFIX_LOCAL = 0,
 	ISIS_SR_PREFIX_REMOTE,
 };
 
-/* SR Nexthop Information. */
+/* Segment Routing Nexthop Information. */
 struct sr_nexthop_info {
 	mpls_label_t label;
 	time_t uptime;
 };
 
-/* SR Prefix-SID. */
+/* State of Object (SR-Node and SR-Prefix) stored in SRDB */
+enum srdb_state {
+	SRDB_STATE_VALIDATED = 0,
+	SRDB_STATE_NEW,
+	SRDB_STATE_MODIFIED,
+	SRDB_STATE_UNCHANGED
+};
+
+/* Segment Routing Prefix-SID. */
 struct sr_prefix {
-	/* RB-tree entries. */
-	struct tree_sr_node_prefix_item node_entry;
-	struct tree_sr_area_prefix_item area_entry;
+	/* SRDB RB-tree entries. */
+	struct srdb_node_prefix_item node_entry;
+	struct srdb_area_prefix_item area_entry;
 
 	/* IP prefix. */
 	struct prefix prefix;
 
-	/* SID value, algorithm and flags. */
+	/* SID value, algorithm and flags subTLVs. */
 	struct isis_prefix_sid sid;
 
-	/* Local label value. */
-	mpls_label_t local_label;
+	/* Input label value. */
+	mpls_label_t input_label;
 
 	/* Prefix-SID type. */
 	enum sr_prefix_type type;
@@ -128,20 +136,17 @@ struct sr_prefix {
 		} remote;
 	} u;
 
-	/* Backpointer to SR node. */
+	/* Backpointer to Segment Routing node. */
 	struct sr_node *srn;
 
-	/* Flags used while the LSPDB is being parsed. */
-	uint8_t parse_flags;
-#define F_ISIS_SR_PREFIX_SID_NEW	0x01
-#define F_ISIS_SR_PREFIX_SID_MODIFIED	0x02
-#define F_ISIS_SR_PREFIX_SID_UNCHANGED	0x04
+	/* SR-Prefix State used while the LSPDB is being parsed. */
+	enum srdb_state state;
 };
 
-/* SR node. */
+/* Segment Routing node. */
 struct sr_node {
-	/* RB-tree entry. */
-	struct tree_sr_node_item entry;
+	/* SRDB RB-tree entry. */
+	struct srdb_node_item entry;
 
 	/* IS-IS level: ISIS_LEVEL1 or ISIS_LEVEL2. */
 	int level;
@@ -149,39 +154,38 @@ struct sr_node {
 	/* IS-IS node identifier. */
 	uint8_t sysid[ISIS_SYS_ID_LEN];
 
-	/* IS-IS node capabilities (SRGB, SR Algorithms, etc). */
+	/* Segment Routing node capabilities (SRGB, SR Algorithms) subTLVs. */
 	struct isis_router_cap cap;
 
 	/* List of Prefix-SIDs advertised by this node. */
-	struct tree_sr_node_prefix_head prefix_sids;
+	struct srdb_node_prefix_head prefix_sids;
 
 	/* Backpointer to IS-IS area. */
 	struct isis_area *area;
 
-	/* Flags used while the LSPDB is being parsed. */
-	uint8_t parse_flags;
-#define F_ISIS_SR_NODE_NEW		0x01
-#define F_ISIS_SR_NODE_MODIFIED		0x02
-#define F_ISIS_SR_NODE_UNCHANGED	0x04
+	/* SR-Node State used while the LSPDB is being parsed. */
+	enum srdb_state state;
 };
 
-/* NOTE: these values must be in sync with the YANG module. */
+/* SID type. NOTE: these values must be in sync with the YANG module. */
 enum sr_sid_value_type {
 	SR_SID_VALUE_TYPE_INDEX = 0,
 	SR_SID_VALUE_TYPE_ABSOLUTE = 1,
 };
 
-/* NOTE: these values must be in sync with the YANG module. */
+#define IS_SID_VALUE(flag) CHECK_FLAG(flag, ISIS_PREFIX_SID_VALUE)
+
+/* Last Hop Behavior. NOTE: these values must be in sync with the YANG module */
 enum sr_last_hop_behavior {
 	SR_LAST_HOP_BEHAVIOR_EXP_NULL = 0,
 	SR_LAST_HOP_BEHAVIOR_NO_PHP = 1,
 	SR_LAST_HOP_BEHAVIOR_PHP = 2,
 };
 
-/* SR Prefix-SID configuration. */
+/* Segment Routing Prefix-SID configuration. */
 struct sr_prefix_cfg {
-	/* RB-tree entry. */
-	struct tree_sr_prefix_cfg_item entry;
+	/* SRDB RB-tree entry. */
+	struct srdb_prefix_cfg_item entry;
 
 	/* IP prefix. */
 	struct prefix prefix;
@@ -202,21 +206,21 @@ struct sr_prefix_cfg {
 	struct isis_area *area;
 };
 
-/* Per-area IS-IS Segment Routing information. */
+/* Per-area IS-IS Segment Routing Data Base (SRDB). */
 struct isis_sr_db {
-	/* Operational status of Segment Routing. */
+	/* Global Operational status of Segment Routing. */
 	bool enabled;
 
-	/* Adj-SIDs. */
+	/* List of local Adjacency-SIDs. */
 	struct list *adj_sids;
 
-	/* SR information from all nodes. */
-	struct tree_sr_node_head sr_nodes[ISIS_LEVELS];
+	/* Segment Routing Node information per IS-IS level. */
+	struct srdb_node_head sr_nodes[ISIS_LEVELS];
 
-	/* Prefix-SIDs. */
-	struct tree_sr_area_prefix_head prefix_sids[ISIS_LEVELS];
+	/* Segment Routing Prefix-SIDs per IS-IS level. */
+	struct srdb_area_prefix_head prefix_sids[ISIS_LEVELS];
 
-	/* Area SR configuration. */
+	/* Area Segment Routing configuration. */
 	struct {
 		/* Administrative status of Segment Routing. */
 		bool enabled;
@@ -229,14 +233,13 @@ struct isis_sr_db {
 		uint8_t msd;
 
 		/* Prefix-SID mappings. */
-		struct tree_sr_prefix_cfg_head prefix_sids;
+		struct srdb_prefix_cfg_head prefix_sids;
 	} config;
 };
 
 /* Prototypes. */
 extern int isis_sr_cfg_srgb_update(struct isis_area *area, uint32_t lower_bound,
 				   uint32_t upper_bound);
-extern void isis_sr_cfg_msd_update(struct isis_area *area);
 extern struct sr_prefix_cfg *
 isis_sr_cfg_prefix_add(struct isis_area *area, const struct prefix *prefix);
 extern void isis_sr_cfg_prefix_del(struct sr_prefix_cfg *pcfg);
diff --git a/isisd/isis_tlvs.c b/isisd/isis_tlvs.c
index be88ee85a6..923956fa6d 100644
--- a/isisd/isis_tlvs.c
+++ b/isisd/isis_tlvs.c
@@ -284,7 +284,7 @@ static void format_item_ext_subtlvs(struct isis_ext_subtlvs *exts,
 		sbuf_push(buf, indent,
 			  "Unidir. Utilized Bandwidth: %g (Bytes/sec)\n",
 			  exts->use_bw);
-	/* Segment Routing Adjacency */
+	/* Segment Routing Adjacency  as per RFC8667 section #2.2.1 */
 	if (IS_SUBTLV(exts, EXT_ADJ_SID)) {
 		struct isis_adj_sid *adj;
 
@@ -315,6 +315,7 @@ static void format_item_ext_subtlvs(struct isis_ext_subtlvs *exts,
 					: '0');
 		}
 	}
+	/* Segment Routing LAN-Adjacency as per RFC8667 section #2.2.2 */
 	if (IS_SUBTLV(exts, EXT_LAN_ADJ_SID)) {
 		struct isis_lan_adj_sid *lan;
 
@@ -476,6 +477,7 @@ static int pack_item_ext_subtlvs(struct isis_ext_subtlvs *exts,
 		stream_putc(s, ISIS_SUBTLV_DEF_SIZE);
 		stream_putf(s, exts->use_bw);
 	}
+	/* Segment Routing Adjacency as per RFC8667 section #2.2.1 */
 	if (IS_SUBTLV(exts, EXT_ADJ_SID)) {
 		struct isis_adj_sid *adj;
 
@@ -495,6 +497,7 @@ static int pack_item_ext_subtlvs(struct isis_ext_subtlvs *exts,
 
 		}
 	}
+	/* Segment Routing LAN-Adjacency as per RFC8667 section #2.2.2 */
 	if (IS_SUBTLV(exts, EXT_LAN_ADJ_SID)) {
 		struct isis_lan_adj_sid *lan;
 
@@ -721,7 +724,7 @@ static int unpack_item_ext_subtlvs(uint16_t mtid, uint8_t len, struct stream *s,
 				SET_SUBTLV(exts, EXT_USE_BW);
 			}
 			break;
-		/* Segment Routing Adjacency */
+		/* Segment Routing Adjacency as per RFC8667 section #2.2.1 */
 		case ISIS_SUBTLV_ADJ_SID:
 			if (subtlv_len != ISIS_SUBTLV_ADJ_SID_SIZE
 			    && subtlv_len != ISIS_SUBTLV_ADJ_SID_SIZE + 1) {
@@ -749,6 +752,7 @@ static int unpack_item_ext_subtlvs(uint16_t mtid, uint8_t len, struct stream *s,
 				SET_SUBTLV(exts, EXT_ADJ_SID);
 			}
 			break;
+		/* Segment Routing LAN-Adjacency as per RFC8667 section 2.2.2 */
 		case ISIS_SUBTLV_LAN_ADJ_SID:
 			if (subtlv_len != ISIS_SUBTLV_LAN_ADJ_SID_SIZE
 			    && subtlv_len != ISIS_SUBTLV_LAN_ADJ_SID_SIZE + 1) {
@@ -789,7 +793,7 @@ static int unpack_item_ext_subtlvs(uint16_t mtid, uint8_t len, struct stream *s,
 	return 0;
 }
 
-/* Functions for Sub-TLV 3 SR Prefix-SID */
+/* Functions for Sub-TLV 3 SR Prefix-SID as per RFC8667 section 2.1 */
 static struct isis_item *copy_item_prefix_sid(struct isis_item *i)
 {
 	struct isis_prefix_sid *sid = (struct isis_prefix_sid *)i;
@@ -2585,7 +2589,7 @@ out:
 	return 1;
 }
 
-/* Functions related to TLV 242 Router Capability */
+/* Functions related to TLV 242 Router Capability as per RFC7981 */
 static struct isis_router_cap *copy_tlv_router_cap(
 			       const struct isis_router_cap *router_cap)
 {
@@ -2614,7 +2618,7 @@ static void format_tlv_router_cap(const struct isis_router_cap *router_cap,
 		  router_cap->flags & ISIS_ROUTER_CAP_FLAG_D ? '1' : '0',
 		  router_cap->flags & ISIS_ROUTER_CAP_FLAG_S ? '1' : '0');
 
-	/* SR Global Block */
+	/* Segment Routing Global Block as per RFC8667 section #3.1 */
 	if (router_cap->srgb.range_size != 0)
 		sbuf_push(buf, indent,
 			"  Segment Routing: I:%s V:%s, SRGB Base: %d Range: %d\n",
@@ -2623,7 +2627,7 @@ static void format_tlv_router_cap(const struct isis_router_cap *router_cap,
 			router_cap->srgb.lower_bound,
 			router_cap->srgb.range_size);
 
-	/* SR Algorithms */
+	/* Segment Routing Algorithms as per RFC8667 section #3.2 */
 	if (router_cap->algo[0] != SR_ALGORITHM_UNSET) {
 		sbuf_push(buf, indent, "    Algorithm: %s",
 			  router_cap->algo[0] == 0 ? "0: SPF"
@@ -2637,7 +2641,7 @@ static void format_tlv_router_cap(const struct isis_router_cap *router_cap,
 		sbuf_push(buf, indent, "\n");
 	}
 
-	/* SR Node MSSD */
+	/* Segment Routing Node MSD as per RFC8491 section #2 */
 	if (router_cap->msd != 0)
 		sbuf_push(buf, indent, "    Node MSD: %d\n", router_cap->msd);
 }
@@ -2674,7 +2678,7 @@ static int pack_tlv_router_cap(const struct isis_router_cap *router_cap,
 	stream_put_ipv4(s, router_cap->router_id.s_addr);
 	stream_putc(s, router_cap->flags);
 
-	/* Add SRGB if set */
+	/* Add SRGB if set as per RFC8667 section #3.1 */
 	if ((router_cap->srgb.range_size != 0)
 	    && (router_cap->srgb.lower_bound != 0)) {
 		stream_putc(s, ISIS_SUBTLV_SID_LABEL_RANGE);
@@ -2685,7 +2689,7 @@ static int pack_tlv_router_cap(const struct isis_router_cap *router_cap,
 		stream_putc(s, ISIS_SUBTLV_SID_LABEL_SIZE);
 		stream_put3(s, router_cap->srgb.lower_bound);
 
-		/* Then SR Algorithm if set */
+		/* Then SR Algorithm if set as per RFC8667 section #3.2 */
 		for (nb_algo = 0; nb_algo < SR_ALGORITHM_COUNT; nb_algo++)
 			if (router_cap->algo[nb_algo] == SR_ALGORITHM_UNSET)
 				break;
@@ -2695,7 +2699,7 @@ static int pack_tlv_router_cap(const struct isis_router_cap *router_cap,
 			for (int i = 0; i < nb_algo; i++)
 				stream_putc(s, router_cap->algo[i]);
 		}
-		/* And finish with MSD if set */
+		/* And finish with MSD if set as per RFC8491 section #2 */
 		if (router_cap->msd != 0) {
 			stream_putc(s, ISIS_SUBTLV_NODE_MSD);
 			stream_putc(s, ISIS_SUBTLV_NODE_MSD_SIZE);
@@ -4602,6 +4606,7 @@ void isis_tlvs_add_oldstyle_ip_reach(struct isis_tlvs *tlvs,
 	append_item(&tlvs->oldstyle_ip_reach, (struct isis_item *)r);
 }
 
+/* Add IS-IS SR Adjacency-SID subTLVs */
 void isis_tlvs_add_adj_sid(struct isis_ext_subtlvs *exts,
 			   struct isis_adj_sid *adj)
 {
@@ -4609,6 +4614,7 @@ void isis_tlvs_add_adj_sid(struct isis_ext_subtlvs *exts,
 	SET_SUBTLV(exts, EXT_ADJ_SID);
 }
 
+/* Delete IS-IS SR Adjacency-SID subTLVs */
 void isis_tlvs_del_adj_sid(struct isis_ext_subtlvs *exts,
 			   struct isis_adj_sid *adj)
 {
@@ -4618,6 +4624,7 @@ void isis_tlvs_del_adj_sid(struct isis_ext_subtlvs *exts,
 		UNSET_SUBTLV(exts, EXT_ADJ_SID);
 }
 
+/* Add IS-IS SR LAN-Adjacency-SID subTLVs */
 void isis_tlvs_add_lan_adj_sid(struct isis_ext_subtlvs *exts,
 			       struct isis_lan_adj_sid *lan)
 {
@@ -4625,6 +4632,7 @@ void isis_tlvs_add_lan_adj_sid(struct isis_ext_subtlvs *exts,
 	SET_SUBTLV(exts, EXT_LAN_ADJ_SID);
 }
 
+/* Delete IS-IS SR LAN-Adjacency-SID subTLVs */
 void isis_tlvs_del_lan_adj_sid(struct isis_ext_subtlvs *exts,
 			       struct isis_lan_adj_sid *lan)
 {
diff --git a/isisd/isis_tlvs.h b/isisd/isis_tlvs.h
index c3b25669b6..f468d85bbd 100644
--- a/isisd/isis_tlvs.h
+++ b/isisd/isis_tlvs.h
@@ -135,10 +135,7 @@ struct isis_threeway_adj {
 	uint32_t neighbor_circuit_id;
 };
 
-/*
- * Segment Routing subTLV's as per
- * draft-ietf-isis-segment-routing-extension-25
- */
+/* Segment Routing subTLV's as per RFC8667 */
 #define ISIS_SUBTLV_SRGB_FLAG_I		0x80
 #define ISIS_SUBTLV_SRGB_FLAG_V		0x40
 #define IS_SR_IPV4(srgb)               (srgb.flags & ISIS_SUBTLV_SRGB_FLAG_I)
@@ -216,7 +213,7 @@ struct isis_router_cap {
 	struct in_addr router_id;
 	uint8_t flags;
 
-	/* draft-ietf-segment-routing-extensions-25 */
+	/* RFC 8667 section #3 */
 	struct isis_srgb srgb;
 	uint8_t algo[SR_ALGORITHM_COUNT];
 	/* RFC 8491 */
@@ -344,7 +341,7 @@ struct isis_subtlvs {
 
 	/* draft-baker-ipv6-isis-dst-src-routing-06 */
 	struct prefix_ipv6 *source_prefix;
-	/* draft-ietf-isis-segment-routing-extensions-25 */
+	/* RFC 8667 section #2.4 */
 	struct isis_item_list prefix_sids;
 };
 
@@ -394,15 +391,17 @@ enum isis_tlv_type {
 	/* RFC 5307 */
 	ISIS_SUBTLV_LLRI = 4,
 
+	/* RFC 8491 */
+	ISIS_SUBTLV_NODE_MSD = 23,
+
 	/* RFC 5316 */
 	ISIS_SUBTLV_RAS = 24,
 	ISIS_SUBTLV_RIP = 25,
 
-	/* draft-isis-segment-routing-extension-25 */
+	/* RFC 8667 section #2 */
 	ISIS_SUBTLV_SID_LABEL = 1,
 	ISIS_SUBTLV_SID_LABEL_RANGE = 2,
 	ISIS_SUBTLV_ALGORITHM = 19,
-	ISIS_SUBTLV_NODE_MSD = 23,
 	ISIS_SUBTLV_PREFIX_SID = 3,
 	ISIS_SUBTLV_ADJ_SID = 31,
 	ISIS_SUBTLV_LAN_ADJ_SID = 32,
@@ -421,21 +420,26 @@ enum isis_tlv_type {
 
 /* subTLVs size for TE and SR */
 enum ext_subtlv_size {
+	/* RFC 5307 */
 	ISIS_SUBTLV_LLRI_SIZE = 8,
 
+	/* RFC 5305 & RFC 6119 */
 	ISIS_SUBTLV_UNRSV_BW_SIZE = 32,
 	ISIS_SUBTLV_TE_METRIC_SIZE = 3,
 	ISIS_SUBTLV_IPV6_ADDR_SIZE = 16,
 
-	/* draft-isis-segment-routing-extension-25 */
+	/* RFC 8491 */
+	ISIS_SUBTLV_NODE_MSD_SIZE = 2,
+
+	/* RFC 8667 section #2 */
 	ISIS_SUBTLV_SID_LABEL_SIZE = 3,
 	ISIS_SUBTLV_SID_LABEL_RANGE_SIZE = 9,
 	ISIS_SUBTLV_ALGORITHM_SIZE = 4,
-	ISIS_SUBTLV_NODE_MSD_SIZE = 2,
 	ISIS_SUBTLV_ADJ_SID_SIZE = 5,
 	ISIS_SUBTLV_LAN_ADJ_SID_SIZE = 11,
 	ISIS_SUBTLV_PREFIX_SID_SIZE = 5,
 
+	/* RFC 7810 */
 	ISIS_SUBTLV_MM_DELAY_SIZE = 8,
 
 	ISIS_SUBTLV_HDR_SIZE = 2,
diff --git a/isisd/isis_zebra.c b/isisd/isis_zebra.c
index d4b9d2a621..e0bf0cee14 100644
--- a/isisd/isis_zebra.c
+++ b/isisd/isis_zebra.c
@@ -49,6 +49,7 @@
 #include "isisd/isis_lsp.h"
 #include "isisd/isis_route.h"
 #include "isisd/isis_zebra.h"
+#include "isisd/isis_adjacency.h"
 #include "isisd/isis_te.h"
 #include "isisd/isis_sr.h"
 
@@ -253,8 +254,12 @@ void isis_zebra_route_del_route(struct prefix *prefix,
 	zclient_route_send(ZEBRA_ROUTE_DELETE, zclient, &api);
 }
 
-/* Install Prefix-SID in the forwarding plane. */
-void isis_zebra_install_prefix_sid(const struct sr_prefix *srp)
+/**
+ * Install Prefix-SID in the forwarding plane through Zebra.
+ *
+ * @param srp	Segment Routing Prefix-SID
+ */
+static void isis_zebra_prefix_install_prefix_sid(const struct sr_prefix *srp)
 {
 	struct zapi_labels zl;
 	struct zapi_nexthop *znh;
@@ -265,7 +270,7 @@ void isis_zebra_install_prefix_sid(const struct sr_prefix *srp)
 	/* Prepare message. */
 	memset(&zl, 0, sizeof(zl));
 	zl.type = ZEBRA_LSP_ISIS_SR;
-	zl.local_label = srp->local_label;
+	zl.local_label = srp->input_label;
 
 	switch (srp->type) {
 	case ISIS_SR_PREFIX_LOCAL:
@@ -314,15 +319,19 @@ void isis_zebra_install_prefix_sid(const struct sr_prefix *srp)
 	(void)zebra_send_mpls_labels(zclient, ZEBRA_MPLS_LABELS_REPLACE, &zl);
 }
 
-/* Uninstall Prefix-SID from the forwarding plane. */
-void isis_zebra_uninstall_prefix_sid(const struct sr_prefix *srp)
+/**
+ * Uninstall Prefix-SID from the forwarding plane through Zebra.
+ *
+ * @param srp	Segment Routing Prefix-SID
+ */
+static void isis_zebra_uninstall_prefix_sid(const struct sr_prefix *srp)
 {
 	struct zapi_labels zl;
 
 	/* Prepare message. */
 	memset(&zl, 0, sizeof(zl));
 	zl.type = ZEBRA_LSP_ISIS_SR;
-	zl.local_label = srp->local_label;
+	zl.local_label = srp->input_label;
 
 	if (srp->type == ISIS_SR_PREFIX_REMOTE) {
 		/* Update route in the RIB too. */
@@ -336,6 +345,69 @@ void isis_zebra_uninstall_prefix_sid(const struct sr_prefix *srp)
 	(void)zebra_send_mpls_labels(zclient, ZEBRA_MPLS_LABELS_DELETE, &zl);
 }
 
+/**
+ * Send Prefix-SID to ZEBRA for installation or deletion.
+ *
+ * @param cmd	ZEBRA_MPLS_LABELS_REPLACE or ZEBRA_ROUTE_DELETE
+ * @param srp	Segment Routing Prefix-SID
+ */
+void isis_zebra_send_prefix_sid(int cmd, const struct sr_prefix *srp)
+{
+
+	if (cmd != ZEBRA_MPLS_LABELS_REPLACE
+	    && cmd != ZEBRA_MPLS_LABELS_DELETE) {
+		flog_warn(EC_LIB_DEVELOPMENT, "%s: wrong ZEBRA command",
+			  __func__);
+		return;
+	}
+
+	sr_debug("  |- %s label %u for prefix %pFX",
+		 cmd == ZEBRA_MPLS_LABELS_REPLACE ? "Update" : "Delete",
+		 srp->input_label, &srp->prefix);
+
+	if (cmd == ZEBRA_MPLS_LABELS_REPLACE)
+		isis_zebra_prefix_install_prefix_sid(srp);
+	else
+		isis_zebra_uninstall_prefix_sid(srp);
+}
+
+/**
+ * Send (LAN)-Adjacency-SID to ZEBRA for installation or deletion.
+ *
+ * @param cmd	ZEBRA_MPLS_LABELS_ADD or ZEBRA_ROUTE_DELETE
+ * @param sra	Segment Routing Adjacency-SID
+ */
+void isis_zebra_send_adjacency_sid(int cmd, const struct sr_adjacency *sra)
+{
+	struct zapi_labels zl;
+	struct zapi_nexthop *znh;
+
+	if (cmd != ZEBRA_MPLS_LABELS_ADD && cmd != ZEBRA_MPLS_LABELS_DELETE) {
+		flog_warn(EC_LIB_DEVELOPMENT, "%s: wrong ZEBRA command",
+			  __func__);
+		return;
+	}
+
+	sr_debug("  |- %s label %u for interface %s",
+		 cmd == ZEBRA_MPLS_LABELS_ADD ? "Add" : "Delete",
+		 sra->nexthop.label, sra->adj->circuit->interface->name);
+
+	memset(&zl, 0, sizeof(zl));
+	zl.type = ZEBRA_LSP_ISIS_SR;
+	zl.local_label = sra->nexthop.label;
+	zl.nexthop_num = 1;
+	znh = &zl.nexthops[0];
+	znh->gate = sra->nexthop.address;
+	znh->type = (sra->nexthop.family == AF_INET)
+			    ? NEXTHOP_TYPE_IPV4_IFINDEX
+			    : NEXTHOP_TYPE_IPV6_IFINDEX;
+	znh->ifindex = sra->adj->circuit->interface->ifindex;
+	znh->label_num = 1;
+	znh->labels[0] = MPLS_LABEL_IMPLICIT_NULL;
+
+	(void)zebra_send_mpls_labels(zclient, cmd, &zl);
+}
+
 static int isis_zebra_read(ZAPI_CALLBACK_ARGS)
 {
 	struct zapi_route api;
diff --git a/isisd/isis_zebra.h b/isisd/isis_zebra.h
index cca2b08811..b143d34626 100644
--- a/isisd/isis_zebra.h
+++ b/isisd/isis_zebra.h
@@ -36,6 +36,7 @@ void isis_zebra_stop(void);
 
 struct isis_route_info;
 struct sr_prefix;
+struct sr_adjacency;
 
 void isis_zebra_route_add_route(struct prefix *prefix,
 				struct prefix_ipv6 *src_p,
@@ -43,8 +44,8 @@ void isis_zebra_route_add_route(struct prefix *prefix,
 void isis_zebra_route_del_route(struct prefix *prefix,
 				struct prefix_ipv6 *src_p,
 				struct isis_route_info *route_info);
-void isis_zebra_install_prefix_sid(const struct sr_prefix *srp);
-void isis_zebra_uninstall_prefix_sid(const struct sr_prefix *srp);
+void isis_zebra_send_prefix_sid(int cmd, const struct sr_prefix *srp);
+void isis_zebra_send_adjacency_sid(int cmd, const struct sr_adjacency *sra);
 int isis_distribute_list_update(int routetype);
 void isis_zebra_redistribute_set(afi_t afi, int type);
 void isis_zebra_redistribute_unset(afi_t afi, int type);
diff --git a/isisd/isisd.h b/isisd/isisd.h
index 56ea0993fd..439428d797 100644
--- a/isisd/isisd.h
+++ b/isisd/isisd.h
@@ -254,6 +254,12 @@ extern struct thread_master *master;
 			zlog_debug(__VA_ARGS__);                               \
 	} while (0)
 
+#define sr_debug(...)                                                          \
+	do {                                                                   \
+		if (IS_DEBUG_ISIS(DEBUG_SR))                                   \
+			zlog_debug(__VA_ARGS__);                               \
+	} while (0)
+
 #define DEBUG_TE                         DEBUG_LSP_GEN
 
 #define IS_DEBUG_ISIS(x)                 (isis->debugs & x)