diff --git a/README.md b/README.md
index 2a27804d7..105e483f3 100755
--- a/README.md
+++ b/README.md
@@ -155,6 +155,7 @@ For previous versions, please read:
 
 ## V4 changes
 
+* v4.0, 2021-02-05, RTC: Refine UDP packet peer fast id. 4.0.68
 * v4.0, 2021-02-04, RTC: Reuse UDP socket to receive packet. 4.0.67
 * v4.0, 2021-02-04, At least wait 1ms when <1ms, to avoid epoll_wait spin loop. 4.0.66
 * v4.0, 2021-01-31, Enable -std=c++11 by default. 4.0.65
diff --git a/trunk/src/app/srs_app_conn.cpp b/trunk/src/app/srs_app_conn.cpp
index c7a4d3a84..707aa4af8 100644
--- a/trunk/src/app/srs_app_conn.cpp
+++ b/trunk/src/app/srs_app_conn.cpp
@@ -127,6 +127,12 @@ void SrsResourceManager::add_with_id(const std::string& id, ISrsResource* conn)
     conns_id_[id] = conn;
 }
 
+void SrsResourceManager::add_with_fast_id(uint64_t id, ISrsResource* conn)
+{
+    add(conn);
+    conns_fast_id_[id] = conn;
+}
+
 void SrsResourceManager::add_with_name(const std::string& name, ISrsResource* conn)
 {
     add(conn);
@@ -144,6 +150,12 @@ ISrsResource* SrsResourceManager::find_by_id(std::string id)
     return (it != conns_id_.end())? it->second : NULL;
 }
 
+ISrsResource* SrsResourceManager::find_by_fast_id(uint64_t id)
+{
+    map<uint64_t, ISrsResource*>::iterator it = conns_fast_id_.find(id);
+    return (it != conns_fast_id_.end())? it->second : NULL;
+}
+
 ISrsResource* SrsResourceManager::find_by_name(std::string name)
 {
     map<string, ISrsResource*>::iterator it = conns_name_.find(name);
@@ -316,6 +328,15 @@ void SrsResourceManager::dispose(ISrsResource* c)
         }
     }
 
+    for (map<uint64_t, ISrsResource*>::iterator it = conns_fast_id_.begin(); it != conns_fast_id_.end();) {
+        if (c != it->second) {
+            ++it;
+        } else {
+            // Use C++98 style: https://stackoverflow.com/a/4636230
+            conns_fast_id_.erase(it++);
+        }
+    }
+
     vector<ISrsResource*>::iterator it = std::find(conns_.begin(), conns_.end(), c);
     if (it != conns_.end()) {
         conns_.erase(it);
diff --git a/trunk/src/app/srs_app_conn.hpp b/trunk/src/app/srs_app_conn.hpp
index c61bbefbe..8af94e956 100644
--- a/trunk/src/app/srs_app_conn.hpp
+++ b/trunk/src/app/srs_app_conn.hpp
@@ -76,6 +76,8 @@ private:
     std::vector<ISrsResource*> conns_;
     // The connections with resource id.
     std::map<std::string, ISrsResource*> conns_id_;
+    // The connections with resource fast(int) id.
+    std::map<uint64_t, ISrsResource*> conns_fast_id_;
     // The connections with resource name.
     std::map<std::string, ISrsResource*> conns_name_;
 public:
@@ -91,9 +93,11 @@ public:
 public:
     void add(ISrsResource* conn);
     void add_with_id(const std::string& id, ISrsResource* conn);
+    void add_with_fast_id(uint64_t id, ISrsResource* conn);
     void add_with_name(const std::string& name, ISrsResource* conn);
     ISrsResource* at(int index);
     ISrsResource* find_by_id(std::string id);
+    ISrsResource* find_by_fast_id(uint64_t id);
     ISrsResource* find_by_name(std::string name);
 public:
     void subscribe(ISrsDisposingHandler* h);
diff --git a/trunk/src/app/srs_app_listener.cpp b/trunk/src/app/srs_app_listener.cpp
index b93769e9d..e2b1d4c13 100755
--- a/trunk/src/app/srs_app_listener.cpp
+++ b/trunk/src/app/srs_app_listener.cpp
@@ -293,6 +293,8 @@ SrsUdpMuxSocket::SrsUdpMuxSocket(srs_netfd_t fd)
 
     fromlen = 0;
     peer_port = 0;
+
+    fast_id_ = 0;
 }
 
 SrsUdpMuxSocket::~SrsUdpMuxSocket()
@@ -327,7 +329,9 @@ int SrsUdpMuxSocket::recvfrom(srs_utime_t timeout)
             peer_ip = it->second;
         }
 
+        peer_id_ = "";
         peer_port = ntohs(addr->sin_port);
+        fast_id_ = uint64_t(peer_port)<<48 | uint64_t(addr->sin_addr.s_addr);
         parsed = true;
     }
 
@@ -403,10 +407,17 @@ int SrsUdpMuxSocket::get_peer_port() const
 
 std::string SrsUdpMuxSocket::peer_id()
 {
-    char id_buf[1024];
-    int len = snprintf(id_buf, sizeof(id_buf), "%s:%d", peer_ip.c_str(), peer_port);
+    if (peer_id_.empty()) {
+        static char id_buf[128];
+        int len = snprintf(id_buf, sizeof(id_buf), "%s:%d", peer_ip.c_str(), peer_port);
+        peer_id_ = string(id_buf, len);
+    }
+    return peer_id_;
+}
 
-    return string(id_buf, len);
+uint64_t SrsUdpMuxSocket::fast_id()
+{
+    return fast_id_;
 }
 
 SrsUdpMuxSocket* SrsUdpMuxSocket::copy_sendonly()
@@ -423,6 +434,10 @@ SrsUdpMuxSocket* SrsUdpMuxSocket::copy_sendonly()
     sendonly->peer_ip   = peer_ip;
     sendonly->peer_port = peer_port;
 
+    // Copy the fast id.
+    sendonly->peer_id_ = peer_id_;
+    sendonly->fast_id_ = fast_id_;
+
     return sendonly;
 }
 
diff --git a/trunk/src/app/srs_app_listener.hpp b/trunk/src/app/srs_app_listener.hpp
index 0f856548c..6d4a5dabd 100644
--- a/trunk/src/app/srs_app_listener.hpp
+++ b/trunk/src/app/srs_app_listener.hpp
@@ -145,8 +145,14 @@ private:
     srs_netfd_t lfd;
     sockaddr_storage from;
     int fromlen;
+private:
     std::string peer_ip;
     int peer_port;
+private:
+    // Cache for peer id.
+    std::string peer_id_;
+    // For IPv4 client, we use 8 bytes int id to find it fastly.
+    uint64_t fast_id_;
 public:
     SrsUdpMuxSocket(srs_netfd_t fd);
     virtual ~SrsUdpMuxSocket();
@@ -161,6 +167,7 @@ public:
     std::string get_peer_ip() const;
     int get_peer_port() const;
     std::string peer_id();
+    uint64_t fast_id();
     SrsUdpMuxSocket* copy_sendonly();
 };
 
diff --git a/trunk/src/app/srs_app_rtc_conn.cpp b/trunk/src/app/srs_app_rtc_conn.cpp
index c7830d19c..78cf2bc3b 100644
--- a/trunk/src/app/srs_app_rtc_conn.cpp
+++ b/trunk/src/app/srs_app_rtc_conn.cpp
@@ -2257,7 +2257,12 @@ void SrsRtcConnection::update_sendonly_socket(SrsUdpMuxSocket* skt)
     // If no cache, build cache and setup the relations in connection.
     if (!addr_cache) {
         peer_addresses_[peer_id] = addr_cache = skt->copy_sendonly();
-        server_->insert_into_id_sessions(peer_id, this);
+        _srs_rtc_manager->add_with_id(peer_id, this);
+
+        uint64_t fast_id = skt->fast_id();
+        if (fast_id) {
+            _srs_rtc_manager->add_with_fast_id(fast_id, this);
+        }
     }
 
     // Update the transport.
diff --git a/trunk/src/app/srs_app_rtc_server.cpp b/trunk/src/app/srs_app_rtc_server.cpp
index 24fe1e721..322547bba 100644
--- a/trunk/src/app/srs_app_rtc_server.cpp
+++ b/trunk/src/app/srs_app_rtc_server.cpp
@@ -300,10 +300,19 @@ srs_error_t SrsRtcServer::on_udp_packet(SrsUdpMuxSocket* skt)
 {
     srs_error_t err = srs_success;
 
-    string peer_id = skt->peer_id();
+    SrsRtcConnection* session = NULL;
     char* data = skt->data(); int size = skt->size();
 
-    SrsRtcConnection* session = (SrsRtcConnection*)_srs_rtc_manager->find_by_id(peer_id);
+    uint64_t fast_id = skt->fast_id();
+    // Try fast id first, if not found, search by long peer id.
+    if (fast_id) {
+        session = (SrsRtcConnection*)_srs_rtc_manager->find_by_fast_id(fast_id);
+    }
+    if (!session) {
+        string peer_id = skt->peer_id();
+        session = (SrsRtcConnection*)_srs_rtc_manager->find_by_id(peer_id);
+    }
+
     if (session) {
         // Switch to the session to write logs to the context.
         session->switch_to_context();
@@ -326,12 +335,14 @@ srs_error_t SrsRtcServer::on_udp_packet(SrsUdpMuxSocket* skt)
 
     // For STUN, the peer address may change.
     if (srs_is_stun((uint8_t*)data, size)) {
+        string peer_id = skt->peer_id();
+
         SrsStunPacket ping;
         if ((err = ping.decode(data, size)) != srs_success) {
             return srs_error_wrap(err, "decode stun packet failed");
         }
-        srs_info("recv stun packet from %s, use-candidate=%d, ice-controlled=%d, ice-controlling=%d",
-            peer_id.c_str(), ping.get_use_candidate(), ping.get_ice_controlled(), ping.get_ice_controlling());
+        srs_info("recv stun packet from %s, fast=%" PRId64 ", use-candidate=%d, ice-controlled=%d, ice-controlling=%d",
+            peer_id.c_str(), fast_id, ping.get_use_candidate(), ping.get_ice_controlled(), ping.get_ice_controlling());
 
         if (!session) {
             session = find_session_by_username(ping.get_username());
@@ -344,8 +355,8 @@ srs_error_t SrsRtcServer::on_udp_packet(SrsUdpMuxSocket* skt)
 
         // TODO: FIXME: For ICE trickle, we may get STUN packets before SDP answer, so maybe should response it.
         if (!session) {
-            return srs_error_new(ERROR_RTC_STUN, "no session, stun username=%s, peer_id=%s",
-                ping.get_username().c_str(), peer_id.c_str());
+            return srs_error_new(ERROR_RTC_STUN, "no session, stun username=%s, peer_id=%s, fast=%" PRId64,
+                ping.get_username().c_str(), peer_id.c_str(), fast_id);
         }
 
         return session->on_stun(skt, &ping);
@@ -353,7 +364,8 @@ srs_error_t SrsRtcServer::on_udp_packet(SrsUdpMuxSocket* skt)
 
     // For DTLS, RTCP or RTP, which does not support peer address changing.
     if (!session) {
-        return srs_error_new(ERROR_RTC_STUN, "no session, peer_id=%s", peer_id.c_str());
+        string peer_id = skt->peer_id();
+        return srs_error_new(ERROR_RTC_STUN, "no session, peer_id=%s, fast=%" PRId64, peer_id.c_str(), fast_id);
     }
 
     if (srs_is_dtls((uint8_t*)data, size)) {
@@ -576,11 +588,6 @@ srs_error_t SrsRtcServer::setup_session2(SrsRtcConnection* session, SrsRequest*
     return err;
 }
 
-void SrsRtcServer::insert_into_id_sessions(const string& peer_id, SrsRtcConnection* session)
-{
-    _srs_rtc_manager->add_with_id(peer_id, session);
-}
-
 SrsRtcConnection* SrsRtcServer::find_session_by_username(const std::string& username)
 {
     ISrsResource* conn = _srs_rtc_manager->find_by_name(username);
diff --git a/trunk/src/app/srs_app_rtc_server.hpp b/trunk/src/app/srs_app_rtc_server.hpp
index e1f7d7397..8dd4b5530 100644
--- a/trunk/src/app/srs_app_rtc_server.hpp
+++ b/trunk/src/app/srs_app_rtc_server.hpp
@@ -122,8 +122,6 @@ public:
     // We start offering, create_session2 to generate offer, setup_session2 to handle answer.
     srs_error_t create_session2(SrsRequest* req, SrsSdp& local_sdp, const std::string& mock_eip, bool unified_plan, SrsRtcConnection** psession);
     srs_error_t setup_session2(SrsRtcConnection* session, SrsRequest* req, const SrsSdp& remote_sdp);
-public:
-    void insert_into_id_sessions(const std::string& peer_id, SrsRtcConnection* session);
 public:
     SrsRtcConnection* find_session_by_username(const std::string& ufrag);
 // interface ISrsHourGlass
diff --git a/trunk/src/core/srs_core_version4.hpp b/trunk/src/core/srs_core_version4.hpp
index 672284cf9..72b58e431 100644
--- a/trunk/src/core/srs_core_version4.hpp
+++ b/trunk/src/core/srs_core_version4.hpp
@@ -24,6 +24,6 @@
 #ifndef SRS_CORE_VERSION4_HPP
 #define SRS_CORE_VERSION4_HPP
 
-#define SRS_VERSION4_REVISION 67
+#define SRS_VERSION4_REVISION 68
 
 #endif