diff --git a/33128/r18/TS33128Payloads.asn b/33128/r18/TS33128Payloads.asn
index 7659f718673bc5b2f993cf1843141689e67e175f..d4452b196dda51e46af43c5ac122d12cd0a590f0 100644
--- a/33128/r18/TS33128Payloads.asn
+++ b/33128/r18/TS33128Payloads.asn
@@ -238,10 +238,13 @@ XIRIEvent ::= CHOICE
     -- RCS events, see clause 7.13.3
     rCSRegistration                                     [140] RCSRegistration,
     rCSMessage                                          [141] RCSMessage,
-    rcsCapabilityDiscovery                              [142] RCSCapabilityDiscovery,
+    rCSCapabilityDiscovery                              [142] RCSCapabilityDiscovery,
+    rCSSessionEstablishment                             [143] RCSSessionEstablishment,
+    rCSSessionModification                              [144] RCSSessionModification,
+    rCSSessionRelease                                   [145] RCSSessionRelease,
 
     -- AMF events, see clause 6.2.2.2.X, continued from tag 139
-    aMFUEPolicyTransfer                                 [143] AMFUEPolicyTransfer
+    aMFUEPolicyTransfer                                 [146] AMFUEPolicyTransfer
 }
 
 -- ==============
@@ -472,10 +475,13 @@ IRIEvent ::= CHOICE
     -- RCS events, see clause 7.13.3
     rCSRegistration                                     [140] RCSRegistration,
     rCSMessage                                          [141] RCSMessage,
-    rcsCapabilityDiscovery                              [142] RCSCapabilityDiscovery,
+    rCSCapabilityDiscovery                              [142] RCSCapabilityDiscovery,
+    rCSSessionEstablishment                             [143] RCSSessionEstablishment,
+    rCSSessionModification                              [144] RCSSessionModification,
+    rCSSessionRelease                                   [145] RCSSessionRelease,
 
     -- AMF events, see clause 6.2.2.3, continued from tag 139
-    aMFUEPolicyTransfer                                 [143] AMFUEPolicyTransfer
+    aMFUEPolicyTransfer                                 [146] AMFUEPolicyTransfer
 }
 
 IRITargetIdentifier ::= SEQUENCE
@@ -4209,6 +4215,47 @@ RCSMessage ::= SEQUENCE
     messagePayload          [12] RCSPayload
 }
 
+-- See clause 7.13.3.4.2.1 for details of this structure
+RCSSessionEstablishment ::= SEQUENCE
+{
+    rCSTargetIdentities     [1] SEQUENCE SIZE (1..MAX) OF RCSIdentity,
+    conversationID          [2] RCSConversationID,
+    contributionID          [3] RCSContributionID,
+    inReplyToContributionID [4] RCSContributionID OPTIONAL,
+    sessionReplaces         [5] RCSContributionID OPTIONAL,
+    rCSSessionType          [6] RCSSessionType,
+    sessionDirection        [7] Direction,
+    rCSSessionMessage       [8] RCSSIPSessionMessage,
+    location                [9] Location
+}
+
+-- See clause 7.13.3.4.3.1 for details of this structure
+RCSSessionModification ::= SEQUENCE
+{
+    rCSTargetIdentities     [1] SEQUENCE SIZE (1..MAX) OF RCSIdentity,
+    conversationID          [2] RCSConversationID,
+    contributionID          [3] RCSContributionID,
+    inReplyToContributionID [4] RCSContributionID OPTIONAL,
+    sessionReplaces         [5] RCSContributionID OPTIONAL,
+    rCSSessionType          [6] RCSSessionType,
+    sessionDirection        [7] Direction,
+    sessionEndpoints        [8] RCSSessionEndpoints,
+    rCSSIPSessionMessage    [9] RCSSIPSessionMessage,
+    location                [10] Location
+}
+
+-- See clause 7.13.3.4.4.1 for details of this structure
+RCSSessionRelease ::= SEQUENCE
+{
+    rCSTargetIdentities     [1] SEQUENCE SIZE (1..MAX) OF RCSIdentity,
+    conversationID          [2] RCSConversationID,
+    contributionID          [3] RCSContributionID,
+    rCSSessionType          [4] RCSSessionType,
+    sessionDirection        [5] Direction,
+    rCSSIPSessionMessage    [6] RCSSIPSessionMessage,
+    location                [7] Location
+}
+
 -- See clause 7.13.3.5 for details of this structure
 RCSCapabilityDiscovery ::= SEQUENCE
 {
@@ -4219,6 +4266,7 @@ RCSCapabilityDiscovery ::= SEQUENCE
     location                      [5] Location OPTIONAL
 }
 
+
 -- ==============
 -- RCS Parameters
 -- ==============
@@ -4235,8 +4283,6 @@ RCSDestination ::= SEQUENCE SIZE (1..MAX) OF RCSIdentity
 
 RCSGroupChatSessionID ::= SIPURI
 
-RCSServerURI ::= UTF8String
-
 RCSIdentity ::= CHOICE
 {
     fiveGSIdentities [1] FiveGSSubscriberIDs,
@@ -4260,6 +4306,44 @@ RCSRegistrationType ::= ENUMERATED
     networkDeregistration(4)
 }
 
+RCSServerURI ::= UTF8String
+
+RCSSessionEndpoints ::= ENUMERATED
+{
+    remoteOnly(1),
+    locatlOnly(2),
+    localAndRemote(3)
+}
+
+RCSSessionLeg ::= ENUMERATED
+{
+    remoteLeg(1),
+    localLeg(2)
+}
+
+RCSSessionType ::= ENUMERATED
+{
+    largeMessageStandalone(1),
+    oneTo1Chat(2)
+}
+
+RCSSIPSessionMessage ::= SEQUENCE
+{
+    sessionLeg       [1] RCSSessionLeg,
+    sIPMessage       [2] IMSPayload,
+    rCSSessionResult [3] RCSSessionResult
+}
+
+RCSSessionResult ::= ENUMERATED
+{
+    newLegRequested(1),
+    newLegEstablished(2),
+    legModificationRequested(3),
+    legModificationComplete(4),
+    legRemovalRequest(5),
+    legRemovalComplete(6)
+}
+
 -- =================
 -- EES definitions
 -- =================