diff --git a/Makefile b/Makefile
index 8264ca1..35e2809 100644
--- a/Makefile
+++ b/Makefile
@@ -1,7 +1,7 @@
 VERSION=1.1.10
 
 CFLAGS+= -O2 -Wall -Wextra -Wshadow\
-	-rdynamic -D_XOPEN_SOURCE=700 -D_DEFAULT_SOURCE\
+	-rdynamic -D_XOPEN_SOURCE=700 -D_DEFAULT_SOURCE -D_GNU_SOURCE\
 	-D_FILE_OFFSET_BITS=64 -DVERSION=\"$(VERSION)\"\
 	`pkg-config --cflags-only-I gumbo libcurl fuse uuid expat`
 LIBS = -pthread -lgumbo -lcurl -lfuse -lcrypto -luuid -lexpat
diff --git a/src/cache.c b/src/cache.c
index aaefd6a..0d2c1fc 100644
--- a/src/cache.c
+++ b/src/cache.c
@@ -116,26 +116,45 @@ void CacheSystem_init(const char *path, int url_supplied)
         exit_failure();
     }
 
-    /* Handle the case of missing '/' */
-    if (path[strnlen(path, MAX_PATH_LEN) - 1] == '/') {
-        META_DIR = path_append(path, "meta/");
-        DATA_DIR = path_append(path, "data/");
-    } else {
-        META_DIR = path_append(path, "/meta/");
-        DATA_DIR = path_append(path, "/data/");
-    }
+    META_DIR = path_append(path, "meta/");
+    DATA_DIR = path_append(path, "data/");
 
     /* Check if directories exist, if not, create them */
     if (mkdir(META_DIR, S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH)
         && (errno != EEXIST)) {
         fprintf(stderr, "CacheSystem_init(): mkdir(): %s\n",
                     strerror(errno));
+        exit_failure();
     }
 
     if (mkdir(DATA_DIR, S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH)
         && (errno != EEXIST)) {
         fprintf(stderr, "CacheSystem_init(): mkdir(): %s\n",
                 strerror(errno));
+        exit_failure();
+    }
+
+    if (CONFIG.sonic_mode) {
+        char *sonic_path;
+        /* Create "rest" sub-directory for META_DIR */
+        sonic_path = path_append(META_DIR, "rest/");
+        if (mkdir(sonic_path, S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH)
+            && (errno != EEXIST)) {
+            fprintf(stderr, "CacheSystem_init(): mkdir(): %s\n",
+                    strerror(errno));
+            exit_failure();
+        }
+        free(sonic_path);
+
+        /* Create "rest" sub-directory for DATA_DIR */
+        sonic_path = path_append(DATA_DIR, "rest/");
+        if (mkdir(sonic_path, S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH)
+            && (errno != EEXIST)) {
+            fprintf(stderr, "CacheSystem_init(): mkdir(): %s\n",
+                    strerror(errno));
+            exit_failure();
+        }
+        free(sonic_path);
     }
 
     CACHE_SYSTEM_INIT = 1;
@@ -410,6 +429,7 @@ static long Data_write(Cache *cf, const uint8_t *buf, off_t len,
         fprintf(stderr,
                 "Data_write(): fwrite(): requested %ld, returned %ld!\n",
                 len, byte_written);
+                exit_failure();
         if (ferror(cf->dfp)) {
             /* filesystem error */
             fprintf(stderr,
@@ -558,6 +578,11 @@ static int Cache_exist(const char *fn)
  */
 void Cache_delete(const char *fn)
 {
+    if (CONFIG.sonic_mode) {
+        Link *link = path_to_Link(fn);
+        fn = link->sonic_id_str;
+    }
+
     char *metafn = path_append(META_DIR, fn);
     char *datafn = path_append(DATA_DIR, fn);
     if (!access(metafn, F_OK)) {
@@ -642,7 +667,12 @@ static int Meta_create(Cache *cf)
 int Cache_create(Link *this_link)
 {
     char *fn;
-    fn = curl_easy_unescape(NULL, this_link->f_url + ROOT_LINK_OFFSET, 0, NULL);
+    if (!CONFIG.sonic_mode) {
+        fn = curl_easy_unescape(NULL, this_link->f_url + ROOT_LINK_OFFSET, 0,
+                                NULL);
+    } else {
+        fn = this_link->sonic_id_str;
+    }
     fprintf(stderr, "Cache_create(): Creating cache files for %s.\n", fn);
 
     Cache *cf = Cache_alloc();
@@ -655,6 +685,7 @@ int Cache_create(Link *this_link)
 
     if (Meta_create(cf)) {
         fprintf(stderr, "Cache_create(): cannot create metadata.\n");
+        exit_failure();
     }
 
     if (fclose(cf->mfp)) {
@@ -689,23 +720,33 @@ int Cache_create(Link *this_link)
      * function returns 0 on success.
      */
     int res = -(!Cache_exist(fn));
-    curl_free(fn);
+    if (!CONFIG.sonic_mode) {
+        curl_free(fn);
+    }
+
     return res;
 }
 
 Cache *Cache_open(const char *fn)
 {
-    /* Check if both metadata and data file exist */
-    if (!Cache_exist(fn)) {
-        return NULL;
-    }
-
     /* Obtain the link structure memory pointer */
     Link *link = path_to_Link(fn);
     if (!link) {
         return NULL;
     }
 
+    /* Check if both metadata and data file exist */
+    if (!CONFIG.sonic_mode) {
+        if (!Cache_exist(fn)) {
+            return NULL;
+        }
+    } else {
+        if (!Cache_exist(link->sonic_id_str)) {
+            return NULL;
+        }
+        fn = link->sonic_id_str;
+    }
+
     /*---------------- Cache_open() critical section -----------------*/
 
     #ifdef CACHE_LOCK_DEBUG
diff --git a/src/link.c b/src/link.c
index a92b922..8495ee7 100644
--- a/src/link.c
+++ b/src/link.c
@@ -49,24 +49,24 @@ LinkTable *LinkSystem_init(const char *url)
         ROOT_LINK_OFFSET += 1;
     }
 
-    /* -----------  Enable cache system --------------------*/
-    /* For now, disable cache mode if sonic mode is enabled */
-    if (!CONFIG.sonic_mode) {
-        if (CONFIG.cache_enabled) {
-            if (CONFIG.cache_dir) {
-                CacheSystem_init(CONFIG.cache_dir, 0);
-            } else {
-                CacheSystem_init(url, 1);
-            }
+    /* ---------------------  Enable cache system -------------------- /
+     *
+     * Note that cache system is enabled automatically if sonic mode is
+     * enabled
+     */
+    if (CONFIG.cache_enabled || CONFIG.sonic_mode) {
+        if (CONFIG.cache_dir) {
+            CacheSystem_init(CONFIG.cache_dir, 0);
+        } else {
+            CacheSystem_init(url, 1);
         }
-    } else {
-        sonic_config_init(url, CONFIG.sonic_username, CONFIG.sonic_password);
     }
 
     /* ----------- Create the root link table --------------*/
     if (!CONFIG.sonic_mode) {
         ROOT_LINK_TBL = LinkTable_new(url);
     } else {
+        sonic_config_init(url, CONFIG.sonic_username, CONFIG.sonic_password);
         ROOT_LINK_TBL = sonic_LinkTable_new(0);
     }
     return ROOT_LINK_TBL;
@@ -360,9 +360,11 @@ DataStruct Link_to_DataStruct(Link *head_link)
 {
     char *url = head_link->f_url;
     CURL *curl = Link_to_curl(head_link);
+
     DataStruct buf;
     buf.size = 0;
     buf.data = NULL;
+
     curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void *)&buf);
 
     /* If we get temporary HTTP failure, wait for 5 seconds before retry */
@@ -385,7 +387,6 @@ DataStruct Link_to_DataStruct(Link *head_link)
         }
     } while (HTTP_temp_failure(http_resp));
 
-
     curl_easy_getinfo(curl, CURLINFO_FILETIME, &(head_link->time));
     curl_easy_cleanup(curl);
     return buf;
@@ -705,8 +706,23 @@ long path_download(const char *path, char *output_buf, size_t size,
     PTHREAD_MUTEX_LOCK(&link_lock);
     PTHREAD_MUTEX_UNLOCK(&link_lock);
 
+    DataStruct header;
+    header.size = 0;
+    header.data = NULL;
+    curl_easy_setopt(curl, CURLOPT_HEADERDATA, (void *)&header);
+
     transfer_blocking(curl);
 
+    /* Check for range seek support */
+    if (!CONFIG.sonic_mode) {
+        if (!strcasestr((header.data), "Accept-Ranges: bytes")) {
+            fprintf(stderr, "Error: This web server does not support HTTP \
+range requests\n");
+            exit(EXIT_FAILURE);
+        }
+    }
+    free(header.data);
+
     long http_resp;
     curl_easy_getinfo(curl, CURLINFO_RESPONSE_CODE, &http_resp);
     if ( !(
diff --git a/src/link.h b/src/link.h
index ac881be..2971b04 100644
--- a/src/link.h
+++ b/src/link.h
@@ -73,6 +73,10 @@ struct Link {
      * \details We use linkname to store filename
      */
     int sonic_id;
+    /**
+     * \brief Sonic Music Directory ID in string format
+     */
+    char sonic_id_str[MAX_FILENAME_LEN+1];
 };
 
 struct LinkTable {
diff --git a/src/sonic.c b/src/sonic.c
index 38b4ef1..6080aa3 100644
--- a/src/sonic.c
+++ b/src/sonic.c
@@ -140,6 +140,8 @@ static void XMLCALL XML_process_single_element(void *data, const char *elem,
     for (int i = 0; attr[i]; i += 2) {
         if (!strcmp("id", attr[i])) {
             link->sonic_id = atoi(attr[i+1]);
+            snprintf(link->sonic_id_str, MAX_FILENAME_LEN, "%d",
+                     link->sonic_id);
             id_set = 1;
             continue;
         }
diff --git a/src/util.h b/src/util.h
index b99fd68..48892ec 100644
--- a/src/util.h
+++ b/src/util.h
@@ -80,8 +80,7 @@ extern ConfigStruct CONFIG;
  * \brief append a path
  * \details This function appends a path with the next level, while taking the
  * trailing slash of the upper level into account.
- *
- * Please free the char * after use.
+ * \note You need to free the char * after use.
  */
 char *path_append(const char *path, const char *filename);