SIP codes

Code	Definition
100	Trying
180	Ringing
181	Call is being forwarded
182	Queued
183	Session in progress
200	OK
202	Accepted: Used for referrals
300	Multiple choices
301	Moved permanently
302	Moved temporarily
305	Use proxy
380	Alternate service
400	Bad request
401	Unauthorized: Used only by registrars. Proxies should use Proxy authorization 407.
402	Payment required (reserved for future use)
403	Forbidden
404	Not found (User not found)
405	Method not allowed
406	Not acceptable
407	Proxy authentication required
408	Request timeout (could not find the user in time)
410	Gone (the user existed once, but is not available here any more)
413	Request entity too large
414	Request-URI too long
415	Unsupported media type
416	Unsupported URI scheme
420	Bad extension (Bad SIP protocol extension used. Not understood by the server.)
421	Extension required
423	Interval too brief
480	Temporarily unavailable
481	Call/transaction does not exist
482	Loop detected
483	Too many hops
484	Address incomplete
485	Ambiguous
486	Busy here
487	Request terminated
488	Not acceptable here
491	Request pending
493	Undecipherable (could not decrypt S/MIME body part)
500	Server internal error
501	Not implemented (The SIP request method is not implementedhere.)
502	Bad gateway
503	Service unavailable
504	Server timeout
505	Version not supported (The server does not support this version of the SIP protocol.)
513	Message too large
600	Busy everywhere
603	Decline
604	Does not exist anywhere
606	Not acceptable