  Header                        SIP stack support			SIP parser support
1. Accept	                    Yes	 				Yes
2. Accept-Encoding                  Yes					Yes
3. Accept-Language	            Yes					Yes
4. CallID			    Yes					Yes
5. Contact			    Yes					Yes
6. CSeq				    Yes					Yes
7. Date				    Yes					Yes
8. Encryption			    Yes					Yes
9. Expires			    Yes 				Yes
10.From				    Yes					Yes
11.Record-Route			    Yes					Yes
12.Timestamp			    Yes          			Yes
13.To				    Yes					Yes
14.Via				    Yes					Yes
15.Content-Encoding		    Yes					Yes
16.Content-Length		    Yes				        Yes
17.Content-Type			    Yes					Yes
18.Authorization		    Yes					Yes
19.Contact			    Yes					Yes
20.Hide				    Yes					Yes
21.Max-Forwards		            Yes					Yes
22.Organization			    Yes					Yes
23.Priority			    Yes					Yes
24.Proxy-Authorization		    Yes					Yes
25.Proxy-Require		    Yes					Yes
26.Route			    Yes					Yes
27.Require			    Yes					Yes
28.Response-Key			    Yes					Yes
29.Subject			    Yes					Yes
30.User-Agent			    Yes					Yes
31.Allow			    Yes					Yes
32.Proxy-Authenticate		    Yes					Yes
33.Retry-After			    Yes					Yes
34.Server			    Yes					Yes
35.Unsupported			    Yes                                 Yes
36.Warning			    Yes					Yes
37.WWW-Authenticate		    Yes					Yes
