From Vincent Helfre:

Implementation of a dissector for SNDCP XID parameters

svn path=/trunk/; revision=25889

2 files changed, 994 insertions, 55 deletions

diff --git a/epan/dissectors/packet-gprs-llc.c b/epan/dissectors/packet-gprs-llc.c
index ae8938fe5d..6814786dba 100644
--- a/epan/dissectors/packet-gprs-llc.c
+++ b/epan/dissectors/packet-gprs-llc.c
@@ -130,10 +130,12 @@ static gint ett_ui = -1;
 static gint ett_llcgprs_sframe = -1;
 
 static dissector_handle_t data_handle;
+static dissector_handle_t sndcp_xid_handle;
 
 static gboolean ignore_cipher_bit = FALSE;
 
 static dissector_table_t llcgprs_subdissector_table;
+
 static const value_string sapi_t[] = {
 	{  0, "Reserved"},
 	{  1, "GPRS Mobility Management" },
@@ -314,27 +316,29 @@ typedef enum {
 	FCS_NOT_COMPUTED
 } fcs_status_t;
 
+
 /* sub-dissector for XID data */
 static void llc_gprs_dissect_xid(tvbuff_t *tvb, 
-								guint16 offset, 
-								guint16 llc_data_length, 
-								guint8 info_len,
-								proto_item *llcgprs_tree,
-								proto_tree *ui_tree,
-								proto_item *ui_ti _U_)
+								 packet_info *pinfo,
+								 proto_item *llcgprs_tree)
+
 {
 	guint8 xid_param_len = 0, byte1 = 0, byte2 = 0, item_len = 0, tmp = 0;
-	guint16 location = offset;
-	int loop_counter = 0;
-	proto_item *u_ti;
+	guint16 location = 0;
+	guint16 loop_counter = 0;
+	proto_item *u_ti = NULL;
 	proto_item *uinfo_field = NULL;
 	proto_tree *uinfo_tree = NULL;
+	proto_tree *xid_tree = NULL;
+	guint16 info_len;
+
+	info_len = tvb_reported_length(tvb);
 
-	u_ti = proto_tree_add_text(llcgprs_tree, tvb, offset, (llc_data_length-2),
+	u_ti = proto_tree_add_text(llcgprs_tree, tvb, 0, info_len,
 		"Information Field: Length = %u", info_len);
-	ui_tree = proto_item_add_subtree(u_ti, ett_ui);
+	xid_tree = proto_item_add_subtree(u_ti, ett_ui);
 
-	while (location < (offset + info_len))
+	while (location < info_len)
 	{
 		/* parse the XID parameters */
 		byte1 = tvb_get_guint8(tvb, location);
@@ -370,53 +374,78 @@ static void llc_gprs_dissect_xid(tvbuff_t *tvb,
 		tmp =  byte1 & 0x7C;
 		tmp = tmp >> 2;
 
-		if (( xid_param_len > 0 ) && ( xid_param_len <=4 ))
+		if (tmp == 0xB) /* L3 XID parameters, call the SNDCP-XID dissector */
 		{
-			unsigned long value = 0;
-			int i;
-			for (i=1;i<=xid_param_len;i++) 
-			{
-				value <<= 8;
-				value |= (unsigned long)tvb_get_guint8(tvb, location+i );
+			tvbuff_t	*sndcp_xid_tvb;
+
+			uinfo_field = proto_tree_add_text(xid_tree, tvb, location, item_len,
+				"XID parameter Type: L3 parameters");
+			uinfo_tree = proto_item_add_subtree(uinfo_field, ett_ui);
+			proto_tree_add_uint(uinfo_tree, hf_llcgprs_xid_xl, tvb, location, 1, byte1);
+			proto_tree_add_uint(uinfo_tree, hf_llcgprs_xid_type, tvb, location, 1, byte1);
+			proto_tree_add_uint(uinfo_tree, hf_llcgprs_xid_len1, tvb, location,	1, byte1);
+			if (byte1 & 0x80) {
+				proto_tree_add_uint(uinfo_tree, hf_llcgprs_xid_len2, tvb, location+1, 1, byte2);
+				proto_tree_add_uint(uinfo_tree, hf_llcgprs_xid_spare, tvb, location+1, 1, byte2);
+			}
+
+			if (xid_param_len) {
+				sndcp_xid_tvb = tvb_new_subset (tvb, location+2, xid_param_len, xid_param_len);
+				if(sndcp_xid_handle)
+					call_dissector(sndcp_xid_handle, sndcp_xid_tvb, pinfo, uinfo_tree);
 			}
-			uinfo_field = proto_tree_add_text(ui_tree, tvb, location, item_len,
-				"XID Parameter Type: %s - Value: %lu",
-				val_to_str(tmp, xid_param_type_str,"Reserved Type:%X"),value);
+
+			location += item_len;
 		}
 		else
 		{
-			uinfo_field = proto_tree_add_text(ui_tree, tvb, location, item_len,
-				"XID Parameter Type: %s",
-				val_to_str(tmp, xid_param_type_str,"Reserved Type:%X"));
-		}
-		uinfo_tree = proto_item_add_subtree(uinfo_field, ett_ui);
-		proto_tree_add_uint(uinfo_tree, hf_llcgprs_xid_xl, tvb, location,
-			1, byte1);
-		proto_tree_add_uint(uinfo_tree, hf_llcgprs_xid_type, tvb, location,
-			1, byte1);
-		proto_tree_add_uint(uinfo_tree, hf_llcgprs_xid_len1, tvb, location,
-			1, byte1);
-
-		if (byte1 & 0x80) {
-			/* length continued into byte 2 */
-			proto_tree_add_uint(uinfo_tree, hf_llcgprs_xid_len2, tvb, location,
-				1, byte2);
-			proto_tree_add_uint(uinfo_tree, hf_llcgprs_xid_spare, tvb, location,
-				1, byte2);
-
-			/* be sure to account for the second byte of length */
-			location++;
-		}
-
-		location++;
-		for (loop_counter = 0; loop_counter < xid_param_len; loop_counter++)
-		{
-			/* grab the information in the XID param */
-			byte2 = tvb_get_guint8(tvb, location);
-			proto_tree_add_uint(uinfo_tree, hf_llcgprs_xid_byte, tvb, location,
-				1, byte2);
+			if (( xid_param_len > 0 ) && ( xid_param_len <=4 ))
+			{
+				guint32 value = 0;
+				guint8 i;
+				for (i=1;i<=xid_param_len;i++) 
+				{
+					value <<= 8;
+					value |= (guint32)tvb_get_guint8(tvb, location+i );
+				}
+				uinfo_field = proto_tree_add_text(xid_tree, tvb, location, item_len,
+					"XID Parameter Type: %s - Value: %lu",
+					val_to_str(tmp, xid_param_type_str,"Reserved Type:%X"),value);
+			}
+			else
+			{
+				uinfo_field = proto_tree_add_text(xid_tree, tvb, location, item_len,
+					"XID Parameter Type: %s",
+					val_to_str(tmp, xid_param_type_str,"Reserved Type:%X"));
+			}
+			uinfo_tree = proto_item_add_subtree(uinfo_field, ett_ui);
+			proto_tree_add_uint(uinfo_tree, hf_llcgprs_xid_xl, tvb, location,
+				1, byte1);
+			proto_tree_add_uint(uinfo_tree, hf_llcgprs_xid_type, tvb, location,
+				1, byte1);
+			proto_tree_add_uint(uinfo_tree, hf_llcgprs_xid_len1, tvb, location,
+				1, byte1);
+
+			if (byte1 & 0x80) {
+				/* length continued into byte 2 */
+				proto_tree_add_uint(uinfo_tree, hf_llcgprs_xid_len2, tvb, location,
+					1, byte2);
+				proto_tree_add_uint(uinfo_tree, hf_llcgprs_xid_spare, tvb, location,
+					1, byte2);
+
+				/* be sure to account for the second byte of length */
+				location++;
+			}
 
 			location++;
+			for (loop_counter = 0; loop_counter < xid_param_len; loop_counter++)
+			{
+				/* grab the information in the XID param */
+				byte2 = tvb_get_guint8(tvb, location);
+				proto_tree_add_uint(uinfo_tree, hf_llcgprs_xid_byte, tvb, location,
+					1, byte2);
+				location++;
+			}
 		}
 	}
 }
@@ -428,7 +457,7 @@ dissect_llcgprs(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
 {
 	guint8 addr_fld=0, sapi=0, ctrl_fld_fb=0, frame_format, tmp=0 ;
 	guint16 offset=0 , epm = 0, nu=0,ctrl_fld_ui_s=0,crc_length=0, llc_data_length=0 ;
-	proto_item *ti, *addres_field_item, *ctrl_field_item, *ui_ti = NULL;
+	proto_item *ti, *addres_field_item, *ctrl_field_item, *ui_ti;
 	proto_tree *llcgprs_tree=NULL , *ad_f_tree =NULL, *ctrl_f_tree=NULL, *ui_tree=NULL;
 	tvbuff_t *next_tvb;
 	guint length;
@@ -1048,7 +1077,10 @@ dissect_llcgprs(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
 				/* Info field, if it exists, consists of XID parameters */
 				if (tree)
 				{
-					llc_gprs_dissect_xid(tvb, offset, llc_data_length, info_len, llcgprs_tree, ui_tree, ui_ti);
+					tvbuff_t	*xid_tvb;
+					xid_tvb = tvb_new_subset (tvb, offset, info_len, info_len);
+
+					llc_gprs_dissect_xid(xid_tvb, pinfo, llcgprs_tree);
 				}
 				break;
 			case U_SABM:
@@ -1057,7 +1089,10 @@ dissect_llcgprs(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
 				/* Info field consists of XID parameters */
 				if (tree)
 				{
-					llc_gprs_dissect_xid(tvb, offset, llc_data_length, info_len, llcgprs_tree, ui_tree, ui_ti);
+					tvbuff_t	*xid_tvb;
+					xid_tvb = tvb_new_subset (tvb, offset, info_len, info_len);
+
+					llc_gprs_dissect_xid(xid_tvb, pinfo, llcgprs_tree);
 				}
 				break;
 			case U_FRMR:
@@ -1195,6 +1230,7 @@ proto_register_llcgprs(void)
 				{ "Spare","llcgprs.xidspare", FT_UINT8, BASE_HEX, NULL, 0x03, "Ignore", HFILL}},
 		{&hf_llcgprs_xid_byte,
 				{ "Parameter Byte","llcgprs.xidbyte", FT_UINT8, BASE_HEX, NULL, 0xFF, "Data", HFILL}},
+
 		/* FRMR Parsing Information */
 		{&hf_llcgprs_frmr_cf,
 				{ "Control Field Octet","llcgprs.frmrrfcf", FT_UINT16, BASE_DEC, NULL,
@@ -1253,6 +1289,7 @@ proto_register_llcgprs(void)
 	proto_llcgprs = proto_register_protocol("Logical Link Control GPRS",
 	    "GPRS-LLC", "llcgprs");
 	llcgprs_subdissector_table = register_dissector_table("llcgprs.sapi","GPRS LLC SAPI", FT_UINT8,BASE_HEX);
+
 /* Required function calls to register the header fields and subtrees used */
 	proto_register_field_array(proto_llcgprs, hf, array_length(hf));
 	proto_register_subtree_array(ett, array_length(ett));
@@ -1279,5 +1316,6 @@ proto_reg_handoff_llcgprs(void)
 	dissector_add("wtap_encap", WTAP_ENCAP_GPRS_LLC, gprs_llc_handle);
 
 	data_handle = find_dissector("data");
+	sndcp_xid_handle  = find_dissector("sndcpxid");
 }
 
diff --git a/epan/dissectors/packet-sndcp-xid.c b/epan/dissectors/packet-sndcp-xid.c
new file mode 100644
index 0000000000..c23334becd
--- /dev/null
+++ b/epan/dissectors/packet-sndcp-xid.c
@@ -0,0 +1,901 @@
+/* packet-sndcp-xid.c
+ * Routines for Subnetwork Dependent Convergence Protocol (SNDCP) XID dissection
+ * Used to dissect XID compression parameters negotiated in GSM (TS44.065)
+ * Copyright 2008, Vincent Helfre <vincent.helfre [AT] ericsson.com>
+ *
+ * $Id$
+ *
+ * Wireshark - Network traffic analyzer
+ * By Gerald Combs <gerald@wireshark.org>
+ * Copyright 1998 Gerald Combs
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ */
+
+#ifdef HAVE_CONFIG_H
+# include "config.h"
+#endif
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <glib.h>
+
+#include <epan/packet.h>
+
+
+/* Parameter types: TS 44.065 §8
+*/
+#define SNDCP_VERSION_PAR_TYPE 0
+#define DATA_COMPRESSION_PAR_TYPE 1
+#define PROTOCOL_COMPRESSION_PAR_TYPE 2
+
+/* Algorithm identifiers: TS 44.065 §6.6.1.1.4 and §6.5.1.1.4
+*/
+#define ALGO_V42BIS 0
+#define ALGO_V44 1
+#define ALGO_RFC1144 0
+#define ALGO_RFC2507 1
+#define ALGO_ROHC 2
+
+static const value_string sndcp_xid_dcomp_algo_str[] = {
+	{0x0, "V.42 bis"},
+	{0x1, "V.44"},
+	{0, NULL}
+};
+
+static const value_string sndcp_xid_pcomp_algo_str[] = {
+	{0x0, "RFC 1144"},
+	{0x1, "RFC 2507"},
+	{0x2, "ROHC (RFC 3095)"},
+	{0, NULL}
+};
+
+typedef struct
+{
+	guint8 nb_of_dcomp_pcomp; /* note that a DCOMP or a PCOMP is 4 bit wide */
+	guint16 (**func_array_ptr) (tvbuff_t *, proto_tree *, guint16);
+} algo_parameters_t;
+
+/* Initialize the protocol and registered fields 
+*/
+static int proto_sndcp_xid   = -1;
+
+/* These fields are used to store store the algorithm ID
+* When the P bit is not set, try to decode the algo based on what whas stored.
+* Entity ranges from 0 to 31 (§6.5.1.1.3)
+*/
+static guint8 dcomp_entity_algo_id[32]={-1, -1, -1, -1, -1, -1, -1, -1, 
+										-1, -1, -1, -1, -1, -1, -1, -1, 
+										-1, -1, -1, -1, -1, -1, -1, -1, 
+										-1, -1, -1, -1, -1, -1, -1, -1};
+static guint8 pcomp_entity_algo_id[32]={-1, -1, -1, -1, -1, -1, -1, -1, 
+										-1, -1, -1, -1, -1, -1, -1, -1, 
+										-1, -1, -1, -1, -1, -1, -1, -1, 
+										-1, -1, -1, -1, -1, -1, -1, -1};
+
+
+
+/* L3 XID parsing */
+static int hf_sndcp_xid_type = -1;
+static int hf_sndcp_xid_len = -1;
+static int hf_sndcp_xid_value = -1;
+static int hf_sndcp_xid_comp_pbit = -1;
+static int hf_sndcp_xid_comp_spare_byte1 = -1;
+static int hf_sndcp_xid_comp_entity = -1;
+static int hf_sndcp_xid_comp_spare_byte2 = -1;
+static int hf_sndcp_xid_comp_algo_id = -1;
+static int hf_sndcp_xid_comp_len = -1;
+/* There is currently a maximum of 15 DCOMP/PCOMP: §6.5.1.1.5 */
+static int hf_sndcp_xid_comp[15] = {-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1}; 
+static int hf_sndcp_xid_comp_spare = -1;
+
+static int hf_element_applicable_nsapi_15 = -1;
+static int hf_element_applicable_nsapi_14 = -1;
+static int hf_element_applicable_nsapi_13 = -1;
+static int hf_element_applicable_nsapi_12 = -1;
+static int hf_element_applicable_nsapi_11 = -1;
+static int hf_element_applicable_nsapi_10 = -1;
+static int hf_element_applicable_nsapi_9 = -1;
+static int hf_element_applicable_nsapi_8 = -1;
+static int hf_element_applicable_nsapi_7 = -1;
+static int hf_element_applicable_nsapi_6 = -1;
+static int hf_element_applicable_nsapi_5 = -1;
+static int hf_element_applicable_nsapi_spare = -1;
+
+static int hf_sndcp_xid_rfc1144_s0 = -1;
+static int hf_sndcp_xid_rfc2507_f_max_period_msb = -1;
+static int hf_sndcp_xid_rfc2507_f_max_period_lsb = -1;
+static int hf_sndcp_xid_rfc2507_f_max_time = -1;
+static int hf_sndcp_xid_rfc2507_max_header = -1;
+static int hf_sndcp_xid_rfc2507_tcp_space = -1;
+static int hf_sndcp_xid_rfc2507_non_tcp_space_msb = -1;
+static int hf_sndcp_xid_rfc2507_non_tcp_space_lsb = -1;
+static int hf_sndcp_xid_rohc_max_cid_spare = -1;
+static int hf_sndcp_xid_rohc_max_cid_msb = -1;
+static int hf_sndcp_xid_rohc_max_cid_lsb = -1;
+static int hf_sndcp_xid_rohc_max_header = -1;
+static int hf_sndcp_xid_rohc_profile_msb = -1;
+static int hf_sndcp_xid_rohc_profile_lsb = -1;
+
+static int hf_sndcp_xid_V42bis_p0_spare = -1;
+static int hf_sndcp_xid_V42bis_p0 = -1;
+static int hf_sndcp_xid_V42bis_p1_msb = -1;
+static int hf_sndcp_xid_V42bis_p1_lsb = -1;
+static int hf_sndcp_xid_V42bis_p2 = -1;
+static int hf_sndcp_xid_V44_c0 = -1;
+static int hf_sndcp_xid_V44_c0_spare = -1;
+static int hf_sndcp_xid_V44_p0_spare = -1;
+static int hf_sndcp_xid_V44_p0 = -1;
+static int hf_sndcp_xid_V44_p1t_msb = -1;
+static int hf_sndcp_xid_V44_p1t_lsb = -1;
+static int hf_sndcp_xid_V44_p1r_msb = -1;
+static int hf_sndcp_xid_V44_p1r_lsb = -1;
+static int hf_sndcp_xid_V44_p3t_msb = -1;
+static int hf_sndcp_xid_V44_p3t_lsb = -1;
+static int hf_sndcp_xid_V44_p3r_msb = -1;
+static int hf_sndcp_xid_V44_p3r_lsb = -1;
+
+
+/* Initialize the subtree pointers 
+*/
+static gint ett_sndcp_xid                = -1;
+static gint ett_sndcp_xid_version_field  = -1;
+static gint ett_sndcp_comp_field        = -1;
+
+/* dissectors for the data portion of this protocol
+ */
+static dissector_handle_t data_handle;
+
+static void parse_compression_parameters(tvbuff_t *tvb, proto_tree *tree, boolean dcomp);
+/******************************************************/
+/* Compression algorithms element dissector functions */
+/******************************************************/
+static guint16 parse_applicable_nsapi(tvbuff_t *tvb, proto_tree *tree, guint16 offset)
+{
+	guint8 nsapi_byte1, nsapi_byte2;
+	nsapi_byte1 = tvb_get_guint8(tvb, offset);
+	nsapi_byte2 = tvb_get_guint8(tvb, offset+1);
+
+	proto_tree_add_uint(tree, hf_element_applicable_nsapi_15, tvb, offset, 1, nsapi_byte1);
+	proto_tree_add_uint(tree, hf_element_applicable_nsapi_14, tvb, offset, 1, nsapi_byte1);
+	proto_tree_add_uint(tree, hf_element_applicable_nsapi_13, tvb, offset, 1, nsapi_byte1);
+	proto_tree_add_uint(tree, hf_element_applicable_nsapi_12, tvb, offset, 1, nsapi_byte1);
+	proto_tree_add_uint(tree, hf_element_applicable_nsapi_11, tvb, offset, 1, nsapi_byte1);
+	proto_tree_add_uint(tree, hf_element_applicable_nsapi_10, tvb, offset, 1, nsapi_byte1);
+	proto_tree_add_uint(tree, hf_element_applicable_nsapi_9, tvb, offset, 1, nsapi_byte1);
+	proto_tree_add_uint(tree, hf_element_applicable_nsapi_8, tvb, offset, 1, nsapi_byte1);
+
+	proto_tree_add_uint(tree, hf_element_applicable_nsapi_7, tvb, offset+1, 1, nsapi_byte2);
+	proto_tree_add_uint(tree, hf_element_applicable_nsapi_6, tvb, offset+1, 1, nsapi_byte2);
+	proto_tree_add_uint(tree, hf_element_applicable_nsapi_5, tvb, offset+1, 1, nsapi_byte2);
+	proto_tree_add_uint(tree, hf_element_applicable_nsapi_spare, tvb, offset+1, 1, nsapi_byte2);
+
+	return 2U; 
+}
+
+static guint16 parse_rfc1144_s0(tvbuff_t *tvb, proto_tree *tree, guint16 offset)
+{
+	guint8 s0;
+	s0 = tvb_get_guint8(tvb, offset);
+
+	proto_tree_add_uint(tree, hf_sndcp_xid_rfc1144_s0, tvb, offset, 1, s0);
+
+	return 1U; 
+}
+
+static guint16 parse_rfc2507_f_max_period(tvbuff_t *tvb, proto_tree *tree, guint16 offset)
+{
+	guint8 f_max_period_byte1, f_max_period_byte2;
+	f_max_period_byte1 = tvb_get_guint8(tvb, offset);
+	f_max_period_byte2 = tvb_get_guint8(tvb, offset+1);
+
+	proto_tree_add_uint(tree, hf_sndcp_xid_rfc2507_f_max_period_msb, tvb, offset, 1, f_max_period_byte1);
+	proto_tree_add_uint(tree, hf_sndcp_xid_rfc2507_f_max_period_lsb, tvb, offset, 1, f_max_period_byte2);
+
+	return 2U; 
+}
+
+static guint16 parse_rfc2507_f_max_time(tvbuff_t *tvb, proto_tree *tree, guint16 offset)
+{
+	guint8 f_max_time;
+	f_max_time = tvb_get_guint8(tvb, offset);
+
+	proto_tree_add_uint(tree, hf_sndcp_xid_rfc2507_f_max_time, tvb, offset, 1, f_max_time);
+
+	return 1U; 
+}
+
+static guint16 parse_rfc2507_max_header(tvbuff_t *tvb, proto_tree *tree, guint16 offset)
+{
+	guint8 max_header;
+	max_header = tvb_get_guint8(tvb, offset);
+
+	proto_tree_add_uint(tree, hf_sndcp_xid_rfc2507_max_header, tvb, offset, 1, max_header);
+
+	return 1U; 
+}
+
+static guint16 parse_rfc2507_tcp_space(tvbuff_t *tvb, proto_tree *tree, guint16 offset)
+{
+	guint8 tcp_space;
+	tcp_space = tvb_get_guint8(tvb, offset);
+
+	proto_tree_add_uint(tree, hf_sndcp_xid_rfc2507_tcp_space, tvb, offset, 1, tcp_space);
+
+	return 1U; 
+}
+
+static guint16 parse_rfc2507_non_tcp_space(tvbuff_t *tvb, proto_tree *tree, guint16 offset)
+{
+	guint8 tcp_space_msb, tcp_space_lsb;
+	tcp_space_msb = tvb_get_guint8(tvb, offset);
+	tcp_space_lsb = tvb_get_guint8(tvb, offset+1);
+
+	proto_tree_add_uint(tree, hf_sndcp_xid_rfc2507_non_tcp_space_msb, tvb, offset, 1, tcp_space_msb);
+	proto_tree_add_uint(tree, hf_sndcp_xid_rfc2507_non_tcp_space_lsb, tvb, offset, 1, tcp_space_lsb);
+
+	return 2U; 
+}
+
+static guint16 parse_rohc_max_cid(tvbuff_t *tvb, proto_tree *tree, guint16 offset)
+{
+	guint8 max_cid_msb, max_cid_lsb;
+	max_cid_msb = tvb_get_guint8(tvb, offset);
+	max_cid_lsb = tvb_get_guint8(tvb, offset+1);
+
+	proto_tree_add_uint(tree, hf_sndcp_xid_rohc_max_cid_spare, tvb, offset, 1, max_cid_msb);
+	proto_tree_add_uint(tree, hf_sndcp_xid_rohc_max_cid_msb, tvb, offset, 1, max_cid_msb);
+	proto_tree_add_uint(tree, hf_sndcp_xid_rohc_max_cid_lsb, tvb, offset+1, 1, max_cid_lsb);
+
+	return 2U; 
+}
+static guint16 parse_rohc_max_header(tvbuff_t *tvb, proto_tree *tree, guint16 offset)
+{
+	guint8 max_header;
+
+	max_header = tvb_get_guint8(tvb, offset+1);
+
+	proto_tree_add_uint(tree, hf_sndcp_xid_rohc_max_header, tvb, offset+1, 1, max_header);
+
+	return 2U; 
+}
+
+static guint16 parse_rohc_profile(tvbuff_t *tvb, proto_tree *tree, guint16 offset)
+{
+	guint8 profile_msb, profile_lsb;
+	profile_msb = tvb_get_guint8(tvb, offset);
+	profile_lsb = tvb_get_guint8(tvb, offset+1);
+
+	proto_tree_add_uint(tree, hf_sndcp_xid_rohc_profile_msb, tvb, offset, 1, profile_msb);
+	proto_tree_add_uint(tree, hf_sndcp_xid_rohc_profile_lsb, tvb, offset+1, 1, profile_lsb);
+
+	return 2U; 
+}
+
+static guint16 parse_V42bis_p0(tvbuff_t *tvb, proto_tree *tree, guint16 offset)
+{
+	guint8 p0;
+
+	p0 = tvb_get_guint8(tvb, offset);
+
+	proto_tree_add_uint(tree, hf_sndcp_xid_V42bis_p0_spare, tvb, offset, 1, p0);
+	proto_tree_add_uint(tree, hf_sndcp_xid_V42bis_p0, tvb, offset, 1, p0);
+
+	return 1U; 
+}
+
+static guint16 parse_V42bis_p1(tvbuff_t *tvb, proto_tree *tree, guint16 offset)
+{
+	guint8 p1_msb, p1_lsb;
+
+	p1_msb = tvb_get_guint8(tvb, offset);
+	p1_lsb = tvb_get_guint8(tvb, offset+1);
+
+	proto_tree_add_uint(tree, hf_sndcp_xid_V42bis_p1_msb, tvb, offset, 1, p1_msb);
+	proto_tree_add_uint(tree, hf_sndcp_xid_V42bis_p1_lsb, tvb, offset+1, 1, p1_lsb);
+
+	return 2U; 
+}
+
+static guint16 parse_V42bis_p2(tvbuff_t *tvb, proto_tree *tree, guint16 offset)
+{
+	guint8 p2;
+
+	p2 = tvb_get_guint8(tvb, offset);
+
+	proto_tree_add_uint(tree, hf_sndcp_xid_V42bis_p2, tvb, offset, 1, p2);
+
+	return 1U; 
+}
+
+static guint16 parse_V44_c0(tvbuff_t *tvb, proto_tree *tree, guint16 offset)
+{
+	guint8 c0;
+
+	c0 = tvb_get_guint8(tvb, offset);
+	proto_tree_add_uint(tree, hf_sndcp_xid_V44_c0_spare, tvb, offset, 1, c0);
+	proto_tree_add_uint(tree, hf_sndcp_xid_V44_c0, tvb, offset, 1, c0);
+
+	return 1U; 
+}
+
+static guint16 parse_V44_p0(tvbuff_t *tvb, proto_tree *tree, guint16 offset)
+{
+	guint8 p0;
+
+	p0 = tvb_get_guint8(tvb, offset);
+
+	proto_tree_add_uint(tree, hf_sndcp_xid_V44_p0_spare, tvb, offset, 1, p0);
+	proto_tree_add_uint(tree, hf_sndcp_xid_V44_p0, tvb, offset, 1, p0);
+
+	return 1U; 
+}
+
+
+static guint16 parse_V44_p1t(tvbuff_t *tvb, proto_tree *tree, guint16 offset)
+{
+	guint8 p1t_msb, p1t_lsb;
+
+	p1t_msb = tvb_get_guint8(tvb, offset);
+	p1t_lsb = tvb_get_guint8(tvb, offset+1);
+
+	proto_tree_add_uint(tree, hf_sndcp_xid_V44_p1t_msb, tvb, offset, 1, p1t_msb);
+	proto_tree_add_uint(tree, hf_sndcp_xid_V44_p1t_lsb, tvb, offset+1, 1, p1t_lsb);
+
+	return 2U; 
+}
+
+static guint16 parse_V44_p1r(tvbuff_t *tvb, proto_tree *tree, guint16 offset)
+{
+	guint8 p1r_msb, p1r_lsb;
+
+	p1r_msb = tvb_get_guint8(tvb, offset);
+	p1r_lsb = tvb_get_guint8(tvb, offset+1);
+
+	proto_tree_add_uint(tree, hf_sndcp_xid_V44_p1r_msb, tvb, offset, 1, p1r_msb);
+	proto_tree_add_uint(tree, hf_sndcp_xid_V44_p1r_lsb, tvb, offset+1, 1, p1r_lsb);
+
+	return 2U; 
+}
+
+static guint16 parse_V44_p3t(tvbuff_t *tvb, proto_tree *tree, guint16 offset)
+{
+	guint8 p3t_msb, p3t_lsb;
+
+	p3t_msb = tvb_get_guint8(tvb, offset);
+	p3t_lsb = tvb_get_guint8(tvb, offset+1);
+
+	proto_tree_add_uint(tree, hf_sndcp_xid_V44_p3t_msb, tvb, offset, 1, p3t_msb);
+	proto_tree_add_uint(tree, hf_sndcp_xid_V44_p3t_lsb, tvb, offset+1, 1, p3t_lsb);
+
+	return 2U; 
+}
+
+static guint16 parse_V44_p3r(tvbuff_t *tvb, proto_tree *tree, guint16 offset)
+{
+	guint8 p3r_msb, p3r_lsb;
+
+	p3r_msb = tvb_get_guint8(tvb, offset);
+	p3r_lsb = tvb_get_guint8(tvb, offset+1);
+
+	proto_tree_add_uint(tree, hf_sndcp_xid_V44_p3r_msb, tvb, offset, 1, p3r_msb);
+	proto_tree_add_uint(tree, hf_sndcp_xid_V44_p3r_lsb, tvb, offset+1, 1, p3r_lsb);
+
+	return 2U; 
+}
+
+
+/***************************************************/
+/* Compression algorithms element dissector arrays */
+/***************************************************/
+static guint16 (*rfc1144_elem_fcn[])(tvbuff_t *, proto_tree *, guint16) = {
+    parse_applicable_nsapi,
+	parse_rfc1144_s0,
+	NULL
+};
+
+
+static guint16 (*rfc2507_elem_fcn[])(tvbuff_t *, proto_tree *, guint16) = {
+	parse_applicable_nsapi,
+	parse_rfc2507_f_max_period,
+	parse_rfc2507_f_max_time,
+	parse_rfc2507_max_header,
+	parse_rfc2507_tcp_space,
+	parse_rfc2507_non_tcp_space,
+	NULL
+};
+
+static guint16 (*rohc_elem_fcn[])(tvbuff_t *, proto_tree *, guint16) = {
+	parse_applicable_nsapi,
+	parse_rohc_max_cid,
+	parse_rohc_max_header,
+	parse_rohc_profile, /* Profile 1 */
+	parse_rohc_profile, /* Profile 2 */
+	parse_rohc_profile, /* Profile 3 */
+	parse_rohc_profile, /* Profile 4 */
+	parse_rohc_profile, /* Profile 5 */
+	parse_rohc_profile, /* Profile 6 */
+	parse_rohc_profile, /* Profile 7 */
+	parse_rohc_profile, /* Profile 8 */
+	parse_rohc_profile, /* Profile 9 */
+	parse_rohc_profile, /* Profile 10 */
+	parse_rohc_profile, /* Profile 11 */
+	parse_rohc_profile, /* Profile 12 */
+	parse_rohc_profile, /* Profile 13 */
+	parse_rohc_profile, /* Profile 14 */
+	parse_rohc_profile, /* Profile 15 */
+	parse_rohc_profile, /* Profile 16 */
+	NULL
+};
+
+/* Array containing the number of pcomp and the function array pointer */
+static algo_parameters_t pcomp_algo_pars[] = {
+	{2, rfc1144_elem_fcn},
+	{5, rfc2507_elem_fcn},
+	{2, rohc_elem_fcn}
+};
+
+/* Data compression algorithms */
+
+static guint16 (*v42bis_elem_fcn[])(tvbuff_t *, proto_tree *, guint16) = {
+	parse_applicable_nsapi,
+	parse_V42bis_p0,
+	parse_V42bis_p1,
+	parse_V42bis_p2,
+	NULL
+};
+
+static guint16 (*v44_elem_fcn[])(tvbuff_t *, proto_tree *, guint16) = {
+	parse_applicable_nsapi,
+	parse_V44_c0,
+	parse_V44_p0,
+	parse_V44_p1t,
+	parse_V44_p1r,
+	parse_V44_p3t,
+	parse_V44_p3r,
+	NULL
+};
+
+/* Array containing the number of dcomp and the function array pointer */
+static algo_parameters_t dcomp_algo_pars[] = {
+	{1, v42bis_elem_fcn},
+	{2, v44_elem_fcn},
+
+};
+
+/* Code to actually dissect the packets 
+*/
+static void
+dissect_sndcp_xid(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
+{
+	/* Set up structures needed to add the protocol subtree and manage it 
+	*/
+	proto_item *ti, *version_item, *dcomp_item, *pcomp_item;
+	proto_tree *sndcp_xid_tree = NULL, *version_tree = NULL, *dcomp_tree, *pcomp_tree = NULL;
+	guint16 offset = 0, l3_param_len;
+	guint8 parameter_type, parameter_len;
+
+	/* create display subtree for the protocol 
+	*/
+	if (tree) {
+		ti         = proto_tree_add_item(tree, proto_sndcp_xid, tvb, 0, -1, FALSE);
+		sndcp_xid_tree = proto_item_add_subtree(ti, ett_sndcp_xid);
+	}
+	l3_param_len = tvb_reported_length(tvb);
+
+	while (offset < l3_param_len)
+	{
+		parameter_type = tvb_get_guint8(tvb, offset);
+		parameter_len = tvb_get_guint8(tvb, offset+1);
+
+		if (parameter_type == SNDCP_VERSION_PAR_TYPE)
+		{
+			guint8 value = tvb_get_guint8(tvb, offset+2);
+			version_item = proto_tree_add_text(tree, tvb, offset, parameter_len+2,
+					"Version (SNDCP version number) - Value %d", value);
+		
+			version_tree = proto_item_add_subtree(version_item, ett_sndcp_xid_version_field);
+			proto_tree_add_uint(version_tree, hf_sndcp_xid_type, tvb, offset,
+			1, parameter_type);
+			proto_tree_add_uint(version_tree, hf_sndcp_xid_len, tvb, offset+1,
+			1, parameter_len);
+			proto_tree_add_uint(version_tree, hf_sndcp_xid_value, tvb, offset+2,
+			1, value);
+			offset += 3;
+		}
+
+		else if (parameter_type == DATA_COMPRESSION_PAR_TYPE)
+		{
+			tvbuff_t * dcomp_tvb;
+
+			dcomp_item = proto_tree_add_text(tree, tvb, offset, parameter_len+2,
+				"Data Compression");
+			dcomp_tree = proto_item_add_subtree(dcomp_item, ett_sndcp_comp_field);
+			proto_tree_add_uint(dcomp_tree, hf_sndcp_xid_type, tvb, offset,
+			1, parameter_type);
+			proto_tree_add_uint(dcomp_tree, hf_sndcp_xid_len, tvb, offset+1,
+			1, parameter_len);
+			offset += 2;
+
+			dcomp_tvb = tvb_new_subset(tvb, offset, parameter_len, parameter_len);
+			parse_compression_parameters(dcomp_tvb, dcomp_tree, TRUE);
+			offset += parameter_len;
+
+
+		}
+		else if (parameter_type == PROTOCOL_COMPRESSION_PAR_TYPE)
+		{
+			tvbuff_t * pcomp_tvb;
+
+			pcomp_item = proto_tree_add_text(tree, tvb, offset, parameter_len+2,
+				"Protocol Control Information Compression");
+			pcomp_tree = proto_item_add_subtree(pcomp_item, ett_sndcp_comp_field);
+			proto_tree_add_uint(pcomp_tree, hf_sndcp_xid_type, tvb, offset,
+			1, parameter_type);
+			proto_tree_add_uint(pcomp_tree, hf_sndcp_xid_len, tvb, offset+1,
+			1, parameter_len);
+			offset += 2;
+
+			pcomp_tvb = tvb_new_subset(tvb, offset, parameter_len, parameter_len);
+			parse_compression_parameters(pcomp_tvb, pcomp_tree, FALSE);
+			offset += parameter_len;
+
+		}
+		else
+		{
+			break; /* error: exit */
+		}
+	}
+}
+
+
+static void parse_compression_parameters(tvbuff_t *tvb, proto_tree *tree, boolean dcomp)
+{
+	guint8 entity, len, algo_id;
+	guint8 number_of_comp, i;
+	gboolean p_bit_set;
+	algo_parameters_t * algo_pars;
+	guint8 function_index;
+	proto_item *comp_entity_field = NULL;
+	proto_tree *comp_entity_tree = NULL;
+	guint16 tvb_len, offset=0 , new_offset, entity_offset;
+	value_string const * comp_algo_str;
+
+	tvb_len = tvb_reported_length(tvb);
+	if (tvb_len < 3) return; /* entity, algo and length bytes should always be present §6.5.1.1 and §6.6.1.1 */
+
+	/* Loop to decode each entity (cf Figure 10) */
+	while (offset < tvb_len)
+	{
+		/* Read the entity byte */
+		entity = tvb_get_guint8(tvb, offset);
+		p_bit_set = ((entity & 0x80) == 0x80) ? 1 : 0;
+		entity = entity & 0x1F;
+
+		/* P bit is set: means that algo identifier and dcomp are present */
+		if (p_bit_set)
+		{
+			/* Read the algorithm id. TODO: store the algo in a different variable for each different entity */
+			algo_id = tvb_get_guint8(tvb, offset+1) & 0x1F;
+
+			/* sanity check: check that the algo id that will be used inside the array has a valid range */
+			if (dcomp)
+			{
+				if(algo_id <= ALGO_V44)
+				{
+					algo_pars = dcomp_algo_pars;
+					dcomp_entity_algo_id[entity] = algo_id;
+					comp_algo_str = sndcp_xid_dcomp_algo_str;
+				}
+				else return; 
+			}
+			else
+			{
+				if (algo_id <= ALGO_ROHC)
+				{
+					algo_pars = pcomp_algo_pars;
+					pcomp_entity_algo_id[entity] = algo_id;
+					comp_algo_str = sndcp_xid_pcomp_algo_str;
+				}
+				else return;
+			}
+
+			/* Read the length */
+			len = tvb_get_guint8(tvb, offset+2);
+
+			comp_entity_field = proto_tree_add_text(tree, tvb, offset, len + 3,
+				"Entity %d, Algorithm %s",
+				entity & 0x1F, val_to_str(algo_id & 0x1F, comp_algo_str,"Undefined Algorithm Identifier:%X"));
+			comp_entity_tree = proto_item_add_subtree(comp_entity_field, ett_sndcp_comp_field);
+
+			proto_tree_add_uint(comp_entity_tree, hf_sndcp_xid_comp_pbit, tvb, offset, 1, p_bit_set << 7);
+			proto_tree_add_uint(comp_entity_tree, hf_sndcp_xid_comp_spare_byte1, tvb, offset, 1, entity);
+			proto_tree_add_uint(comp_entity_tree, hf_sndcp_xid_comp_entity, tvb, offset, 1, entity);
+
+			proto_tree_add_uint(comp_entity_tree, hf_sndcp_xid_comp_spare_byte2, tvb, offset+1, 1, algo_id);
+			proto_tree_add_uint(comp_entity_tree, hf_sndcp_xid_comp_algo_id, tvb, offset+1, 1, algo_id);
+			proto_tree_add_uint(comp_entity_tree, hf_sndcp_xid_comp_len, tvb, offset+2, 1, len);
+
+			/* Read the dcomp/pcomp field */
+			offset += 3; /* entity_offset will be used as the offset from length byte */
+			number_of_comp = algo_pars[algo_id].nb_of_dcomp_pcomp;
+
+			for (i=0; i < (number_of_comp+1) / 2; i++)
+			{
+				guint8 byte;
+
+				byte = tvb_get_guint8(tvb, offset+i);
+				proto_tree_add_uint(comp_entity_tree, hf_sndcp_xid_comp[2*i], tvb, offset+i, 1, byte);
+
+				/* if there is an even number of dcomp/pcomp */
+				if (2*i+1 < number_of_comp)
+				{
+					proto_tree_add_uint(comp_entity_tree, hf_sndcp_xid_comp[2*i+1], tvb, offset+i, 1, byte);
+				}
+				/* else there is padding in the end */
+				else
+				{
+					proto_tree_add_uint(comp_entity_tree, hf_sndcp_xid_comp_spare, tvb, offset+i, 1, byte);
+				}
+
+			}
+			entity_offset = i;
+			function_index = 0;
+
+			/* Process the elements byte per byte */
+			while ((entity_offset < len) && (algo_pars[algo_id].func_array_ptr[function_index] != NULL))
+			{
+				new_offset = offset+entity_offset;
+				entity_offset += algo_pars[algo_id].func_array_ptr[function_index](tvb, comp_entity_tree, new_offset);
+				function_index++;
+			}
+			offset += entity_offset;
+
+		}
+		else /* P bit not set */
+		{
+			len = tvb_get_guint8(tvb, offset+1);
+
+			if (dcomp)
+			{
+				algo_pars = dcomp_algo_pars;
+				algo_id = dcomp_entity_algo_id[entity];
+				comp_algo_str = sndcp_xid_dcomp_algo_str;
+			}
+			else
+			{
+				algo_pars = pcomp_algo_pars;
+				algo_id = pcomp_entity_algo_id[entity];
+				comp_algo_str = sndcp_xid_pcomp_algo_str;
+			}
+			comp_entity_field = proto_tree_add_text(tree, tvb, offset, len + 2,
+				"Entity %d decoded as Algorithm %s",
+				entity & 0x1F, val_to_str(algo_id & 0x1F, comp_algo_str,"Undefined Algorithm Identifier:%X"));
+
+			comp_entity_tree = proto_item_add_subtree(comp_entity_field, ett_sndcp_comp_field);
+
+			proto_tree_add_uint(comp_entity_tree, hf_sndcp_xid_comp_pbit, tvb, offset, 1, p_bit_set << 7);
+			proto_tree_add_uint(comp_entity_tree, hf_sndcp_xid_comp_spare_byte1, tvb, offset, 1, entity);
+			proto_tree_add_uint(comp_entity_tree, hf_sndcp_xid_comp_entity, tvb, offset, 1, entity);
+			proto_tree_add_uint(comp_entity_tree, hf_sndcp_xid_comp_len, tvb, offset+2, 1, len);
+
+			offset += 2;
+			entity_offset = 0;
+			function_index = 0;
+
+			if (dcomp)
+			{
+				if (algo_id > ALGO_V44) return;
+			}
+			else
+			{
+				if (algo_id > ALGO_ROHC) return;
+			}
+
+			/* Process the elements byte per byte */
+			while ((entity_offset < len) && (algo_pars[algo_id].func_array_ptr[function_index] != NULL))
+			{
+				new_offset = offset+entity_offset;
+				entity_offset += algo_pars[algo_id].func_array_ptr[function_index](tvb, comp_entity_tree, new_offset);
+				function_index++;
+			}
+			offset += entity_offset;
+		}
+	}
+
+	/* Else if length is lower than 3, the packet is not correctly formatted */
+}
+
+/* Register the protocol with Wireshark 
+   this format is required because a script is used to build the C function
+   that calls all the protocol registration.
+*/
+
+void
+proto_register_sndcp_xid(void)
+{                 
+  /* Setup list of header fields
+   */
+  static hf_register_info hf[] = {
+    		/* L3 XID Parameter Parsing Info */
+		{&hf_sndcp_xid_type,
+				{ "Parameter type","llcgprs.l3xidpartype", FT_UINT8, BASE_DEC, NULL, 0xFF, "Data", HFILL}},
+		{&hf_sndcp_xid_len,
+				{ "Length","llcgprs.l3xidparlen", FT_UINT8, BASE_DEC, NULL, 0xFF, "Data", HFILL}},
+		{&hf_sndcp_xid_value,
+				{ "Value","llcgprs.l3xidparvalue", FT_UINT8, BASE_DEC, NULL, 0xFF, "Data", HFILL}},
+		{&hf_sndcp_xid_comp_pbit,
+				{ "P bit","llcgprs.l3xiddcomppbit", FT_UINT8, BASE_DEC, NULL, 0x80, "Data", HFILL}},
+		{&hf_sndcp_xid_comp_spare_byte1,
+				{ "Spare","llcgprs.l3xidspare", FT_UINT8, BASE_HEX, NULL, 0x60, "Ignore", HFILL}},
+		{&hf_sndcp_xid_comp_entity,
+				{ "Entity","llcgprs.l3xidentity", FT_UINT8, BASE_DEC, NULL, 0x1F, "Data", HFILL}},
+		{&hf_sndcp_xid_comp_spare_byte2,
+				{ "Spare","llcgprs.l3xidspare", FT_UINT8, BASE_HEX, NULL, 0xE0, "Ignore", HFILL}},
+		{&hf_sndcp_xid_comp_algo_id,
+				{ "Algorithm identifier","llcgprs.l3xidalgoid", FT_UINT8, BASE_DEC, NULL, 0x1F, "Data", HFILL}},
+		{&hf_sndcp_xid_comp_len,
+				{ "Length","llcgprs.l3xidcomplen", FT_UINT8, BASE_DEC, NULL, 0xFF, "Data", HFILL}},
+		{&hf_sndcp_xid_comp[0],
+				{ "DCOMP1","llcgprs.l3xiddcomp", FT_UINT8, BASE_DEC, NULL, 0xF0, "Data", HFILL}},
+		{&hf_sndcp_xid_comp[1],
+				{ "DCOMP2","llcgprs.l3xiddcomp", FT_UINT8, BASE_DEC, NULL, 0x0F, "Data", HFILL}},
+		{&hf_sndcp_xid_comp[2],
+				{ "DCOMP3","llcgprs.l3xiddcomp", FT_UINT8, BASE_DEC, NULL, 0xF0, "Data", HFILL}},
+		{&hf_sndcp_xid_comp[3],
+				{ "DCOMP4","llcgprs.l3xiddcomp", FT_UINT8, BASE_DEC, NULL, 0x0F, "Data", HFILL}},
+		{&hf_sndcp_xid_comp[4],
+				{ "DCOMP5","llcgprs.l3xiddcomp", FT_UINT8, BASE_DEC, NULL, 0xF0, "Data", HFILL}},
+		{&hf_sndcp_xid_comp[5],
+				{ "DCOMP6","llcgprs.l3xiddcomp", FT_UINT8, BASE_DEC, NULL, 0x0F, "Data", HFILL}},
+		{&hf_sndcp_xid_comp[6],
+				{ "DCOMP7","llcgprs.l3xiddcomp", FT_UINT8, BASE_DEC, NULL, 0xF0, "Data", HFILL}},
+		{&hf_sndcp_xid_comp[7],
+				{ "DCOMP8","llcgprs.l3xiddcomp", FT_UINT8, BASE_DEC, NULL, 0x0F, "Data", HFILL}},
+		{&hf_sndcp_xid_comp[8],
+				{ "DCOMP9","llcgprs.l3xiddcomp", FT_UINT8, BASE_DEC, NULL, 0xF0, "Data", HFILL}},
+		{&hf_sndcp_xid_comp[9],
+				{ "DCOMP10","llcgprs.l3xiddcomp", FT_UINT8, BASE_DEC, NULL, 0x0F, "Data", HFILL}},
+		{&hf_sndcp_xid_comp[10],
+				{ "DCOMP11","llcgprs.l3xiddcomp", FT_UINT8, BASE_DEC, NULL, 0xF0, "Data", HFILL}},
+		{&hf_sndcp_xid_comp[11],
+				{ "DCOMP12","llcgprs.l3xiddcomp", FT_UINT8, BASE_DEC, NULL, 0x0F, "Data", HFILL}},
+		{&hf_sndcp_xid_comp[12],
+				{ "DCOMP13","llcgprs.l3xiddcomp", FT_UINT8, BASE_DEC, NULL, 0xF0, "Data", HFILL}},
+		{&hf_sndcp_xid_comp[13],
+				{ "DCOMP14","llcgprs.l3xiddcomp", FT_UINT8, BASE_DEC, NULL, 0x0F, "Data", HFILL}},
+		{&hf_sndcp_xid_comp[14],
+				{ "DCOMP15","llcgprs.l3xiddcomp", FT_UINT8, BASE_DEC, NULL, 0xF0, "Data", HFILL}},
+		{&hf_sndcp_xid_comp_spare,
+				{ "Spare","llcgprs.l3xidspare", FT_UINT8, BASE_HEX, NULL, 0x0F, "Ignore", HFILL}},
+ 		{&hf_element_applicable_nsapi_15,
+				{ "NSAPI 15","sndcpxid.nsapi15", FT_UINT8, BASE_DEC, NULL, 0x80, "Data", HFILL}},
+ 		{&hf_element_applicable_nsapi_14,
+				{ "NSAPI 14","sndcpxid.nsapi14", FT_UINT8, BASE_DEC, NULL, 0x40, "Data", HFILL}},
+ 		{&hf_element_applicable_nsapi_13,
+				{ "NSAPI 13","sndcpxid.nsapi13", FT_UINT8, BASE_DEC, NULL, 0x20, "Data", HFILL}},
+ 		{&hf_element_applicable_nsapi_12,
+				{ "NSAPI 12","sndcpxid.nsapi12", FT_UINT8, BASE_DEC, NULL, 0x10, "Data", HFILL}},
+ 		{&hf_element_applicable_nsapi_11,
+				{ "NSAPI 11","sndcpxid.nsapi11", FT_UINT8, BASE_DEC, NULL, 0x08, "Data", HFILL}},
+ 		{&hf_element_applicable_nsapi_10,
+				{ "NSAPI 10","sndcpxid.nsapi10", FT_UINT8, BASE_DEC, NULL, 0x04, "Data", HFILL}},
+ 		{&hf_element_applicable_nsapi_9,
+				{ "NSAPI 9","sndcpxid.nsapi9", FT_UINT8, BASE_DEC, NULL, 0x02, "Data", HFILL}},
+ 		{&hf_element_applicable_nsapi_8,
+				{ "NSAPI 8","sndcpxid.nsapi8", FT_UINT8, BASE_DEC, NULL, 0x01, "Data", HFILL}},
+ 		{&hf_element_applicable_nsapi_7,
+				{ "NSAPI 7","sndcpxid.nsapi7", FT_UINT8, BASE_DEC, NULL, 0x80, "Data", HFILL}},
+ 		{&hf_element_applicable_nsapi_6,
+				{ "NSAPI 6","sndcpxid.nsapi6", FT_UINT8, BASE_DEC, NULL, 0x40, "Data", HFILL}},
+ 		{&hf_element_applicable_nsapi_5,
+				{ "NSAPI 5","sndcpxid.nsapi5", FT_UINT8, BASE_DEC, NULL, 0x20, "Data", HFILL}},
+ 		{&hf_element_applicable_nsapi_spare,
+				{ "Spare","sndcpxid.spare", FT_UINT8, BASE_DEC, NULL, 0x1F, "Ignore", HFILL}},
+ 		{&hf_sndcp_xid_rfc1144_s0,
+				{ "S0 - 1","sndcpxid.rfc1144_s0", FT_UINT8, BASE_DEC, NULL, 0xFF, "Data", HFILL}},
+ 		{&hf_sndcp_xid_rfc2507_f_max_period_msb,
+				{ "F Max Period MSB","sndcpxid.rfc2507_f_max_period_msb", FT_UINT8, BASE_HEX, NULL, 0xFF, "Data", HFILL}},
+ 		{&hf_sndcp_xid_rfc2507_f_max_period_lsb,
+				{ "F Max Period LSB","sndcpxid.rfc2507_f_max_period_lsb", FT_UINT8, BASE_HEX, NULL, 0xFF, "Data", HFILL}},
+ 		{&hf_sndcp_xid_rfc2507_f_max_time,
+				{ "F Max Time","sndcpxid.rfc2507_f_max_time", FT_UINT8, BASE_DEC, NULL, 0xFF, "Data", HFILL}},
+ 		{&hf_sndcp_xid_rfc2507_max_header,
+				{ "Max Header","sndcpxid.rfc2507_max_header", FT_UINT8, BASE_DEC, NULL, 0xFF, "Data", HFILL}},
+ 		{&hf_sndcp_xid_rfc2507_tcp_space,
+				{ "TCP Space","sndcpxid.rfc2507_max_tcp_space", FT_UINT8, BASE_DEC, NULL, 0xFF, "Data", HFILL}},
+ 		{&hf_sndcp_xid_rfc2507_non_tcp_space_msb,
+				{ "TCP non space MSB","sndcpxid.rfc2507_max_non_tcp_space_msb", FT_UINT8, BASE_HEX, NULL, 0xFF, "Data", HFILL}},
+ 		{&hf_sndcp_xid_rfc2507_non_tcp_space_lsb,
+				{ "TCP non space LSB","sndcpxid.rfc2507_max_non_tcp_space_lsb", FT_UINT8, BASE_HEX, NULL, 0xFF, "Data", HFILL}},
+ 		{&hf_sndcp_xid_rohc_max_cid_spare,
+				{ "Spare","sndcpxid.rohc_max_cid_spare", FT_UINT8, BASE_DEC, NULL, 0xC0, "Ignore", HFILL}},
+ 		{&hf_sndcp_xid_rohc_max_cid_msb,
+				{ "Max CID MSB","sndcpxid.rohc_max_cid_msb", FT_UINT8, BASE_HEX, NULL, 0x3F, "Data", HFILL}},
+ 		{&hf_sndcp_xid_rohc_max_cid_lsb,
+				{ "Max CID LSB","sndcpxid.rohc_max_cid_lsb", FT_UINT8, BASE_HEX, NULL, 0xFF, "Data", HFILL}},
+ 		{&hf_sndcp_xid_rohc_max_header,
+				{ "Max header","sndcpxid.rohc_max_header", FT_UINT8, BASE_DEC, NULL, 0xFF, "Data", HFILL}},
+ 		{&hf_sndcp_xid_rohc_profile_msb,
+				{ "Profile MSB","sndcpxid.rohc_profile_msb", FT_UINT8, BASE_HEX, NULL, 0xFF, "Data", HFILL}},
+ 		{&hf_sndcp_xid_rohc_profile_lsb,
+				{ "Profile LSB","sndcpxid.rohc_profile_lsb", FT_UINT8, BASE_HEX, NULL, 0xFF, "Data", HFILL}},
+ 		{&hf_sndcp_xid_V42bis_p0_spare,
+				{ "Spare","sndcpxid.V42bis_p0spare", FT_UINT8, BASE_DEC, NULL, 0xFC, "Ignore", HFILL}},
+ 		{&hf_sndcp_xid_V42bis_p0,
+				{ "P0","sndcpxid.V42bis_p0", FT_UINT8, BASE_HEX, NULL, 0x03, "Data", HFILL}},
+ 		{&hf_sndcp_xid_V42bis_p1_msb,
+				{ "P1 MSB","sndcpxid.V42bis_p1_msb", FT_UINT8, BASE_HEX, NULL, 0xFF, "Data", HFILL}},
+ 		{&hf_sndcp_xid_V42bis_p1_lsb,
+				{ "P1 LSB","sndcpxid.V42bis_p1_lsb", FT_UINT8, BASE_HEX, NULL, 0xFF, "Data", HFILL}},
+ 		{&hf_sndcp_xid_V42bis_p2,
+				{ "P2","sndcpxid.V42bis_p2", FT_UINT8, BASE_HEX, NULL, 0xFF, "Data", HFILL}},
+ 		{&hf_sndcp_xid_V44_c0_spare,
+				{ "P2","sndcpxid.V44_c0_spare", FT_UINT8, BASE_HEX, NULL, 0x3F, "Ignore", HFILL}},
+ 		{&hf_sndcp_xid_V44_c0,
+				{ "P2","sndcpxid.V44_c0", FT_UINT8, BASE_HEX, NULL, 0xC0, "Data", HFILL}},
+ 		{&hf_sndcp_xid_V44_p0_spare,
+				{ "Spare","sndcpxid.V44_p0spare", FT_UINT8, BASE_DEC, NULL, 0xFC, "Ignore", HFILL}},
+ 		{&hf_sndcp_xid_V44_p0,
+				{ "P0","sndcpxid.V44_p0", FT_UINT8, BASE_HEX, NULL, 0x03, "Data", HFILL}},
+ 		{&hf_sndcp_xid_V44_p1t_msb,
+				{ "P1t MSB","sndcpxid.V44_p1t_msb", FT_UINT8, BASE_HEX, NULL, 0xFF, "Data", HFILL}},
+ 		{&hf_sndcp_xid_V44_p1t_lsb,
+				{ "P1t LSB","sndcpxid.V44_p1t_lsb", FT_UINT8, BASE_HEX, NULL, 0xFF, "Data", HFILL}},
+ 		{&hf_sndcp_xid_V44_p1r_msb,
+				{ "P1r MSB","sndcpxid.V44_p1r_msb", FT_UINT8, BASE_HEX, NULL, 0xFF, "Data", HFILL}},
+ 		{&hf_sndcp_xid_V44_p1r_lsb,
+				{ "P1r LSB","sndcpxid.V44_p1r_lsb", FT_UINT8, BASE_HEX, NULL, 0xFF, "Data", HFILL}},
+ 		{&hf_sndcp_xid_V44_p3t_msb,
+				{ "P3t MSB","sndcpxid.V44_p3t_msb", FT_UINT8, BASE_HEX, NULL, 0xFF, "Data", HFILL}},
+ 		{&hf_sndcp_xid_V44_p3t_lsb,
+				{ "P3t LSB","sndcpxid.V44_p3t_lsb", FT_UINT8, BASE_HEX, NULL, 0xFF, "Data", HFILL}},
+ 		{&hf_sndcp_xid_V44_p3r_msb,
+				{ "P3r MSB","sndcpxid.V44_p3r_msb", FT_UINT8, BASE_HEX, NULL, 0xFF, "Data", HFILL}},
+ 		{&hf_sndcp_xid_V44_p3r_lsb,
+				{ "P3r LSB","sndcpxid.V44_p3r_lsb", FT_UINT8, BASE_HEX, NULL, 0xFF, "Data", HFILL}},
+				
+ };
+
+   /* Setup protocol subtree array */
+  static gint *ett[] = {
+    &ett_sndcp_xid,
+    &ett_sndcp_xid_version_field,
+	&ett_sndcp_comp_field
+  };  
+
+  /* Register the protocol name and description */
+  proto_sndcp_xid = proto_register_protocol("Subnetwork Dependent Convergence Protocol XID",
+					"SNDCP XID", "sndcpxid");
+
+  /* Required function calls to register the header fields and subtrees used */
+  proto_register_field_array(proto_sndcp_xid, hf, array_length(hf));
+  proto_register_subtree_array(ett, array_length(ett));
+  register_dissector("sndcpxid", dissect_sndcp_xid, proto_sndcp_xid);
+}
+
+/* If this dissector uses sub-dissector registration add a registration routine.
+   This format is required because a script is used to find these routines and
+   create the code that calls these routines.
+*/
+void
+proto_reg_handoff_sndcp_xid(void)
+{
+  /* Find data handle for upper layer dissectors 
+   */
+  data_handle = find_dissector("data");
+}