Contents
APPENDIX
A
SIP Compliance
This appendix describes Cisco SIP proxy server (Cisco SPS) compliance with the Internet Engineering
Task Force (IETF) definition of Session Initiation Protocol (SIP) as described in the following RFCs.
1
RFC
2543 SIP: Session Initiation Protocol (March 1999)
3261 SIP: Session Initiation Protocol (June 2002)
3263 SIP: Locating SIP Servers (June 2002)
1. Not all supported RFCs are listed.
Title
• RFC 2543 and RFC 3261
–
SIP Functions, page A-2
–
SIP Methods, page A-2
–
SIP Responses, page A-2
–
SIP Header Fields, page A-6
–
SIP Transport Layer Protocols, page A-7
–
SIP Security, page A-8
• RFC 3263
–
SIP DNS Records Usage, page A-8
Cisco SIP Proxy Server Administrator Guide
A-1
RFC 2543 and RFC 3261
RFC 2543 and RFC 3261
SIP Functions
Table A-1 SIP Functions
Function Supported?
Proxy server Yes (transaction stateful, parallel forking, and
Redirect server Yes
Registrar server Yes
SIP Methods
Cisco SPS supports five of the six methods used by SIP. It handles unknown methods such as
NEWMETHOD in the same manner as known methods such as OPTIONS and REFER.
Appendix A SIP Compliance
recursive)
SIP Responses
Table A-2 SIP Methods
Method Supported? Cisco SPS Action
ACK Yes Forwards ACK requests.
BYE Yes Forwards BYE requests.
CANCEL Yes Forwards CANCEL requests.
INFO Yes Forwards INFO requests.
INVITE Yes Forwards INVITE requests.
NOTIFY Yes Forwards NOTIFY requests.
OPTIONS Yes Responds to OPTIONS requests.
REFER Yes Forwards REFER requests.
REGISTER Yes Supports both user and device registration.
SUBSCRIBE Yes Forwards SUBSCRIBE requests.
UPDATE Yes Forwards UPDATE requests.
1. The SPS can generate a local ACK for a non-200 OK final response to an INVITE request.
2. The SPS can generate a local CANCEL for a pending branch when it receives a 200 OK or 6xx response from the branch.
1
2
A-2
Cisco SPS supports the following SIP responses:
• 1xx Response—Information Responses
• 2xx Response—Successful Responses
• 3xx Response—Redirection Responses
• 4xx Response—Request Failure Responses
Cisco SIP Proxy Server Administrator Guide
Appendix A SIP Compliance
RFC 2543 and RFC 3261
• 5xx Response—Server Failure Responses
• 6xx Response—Global Responses
Table A-3 SIP Responses
SIP Response Meaning Supported? Cisco SPS Action
1xx Response—Information Responses
100 Trying Action is being taken on behalf of the
caller, but the called party is not yet
located.
180 Ringing Called party is located and is being
notified of the call.
181 Call is being forwarded Call is being rerouted to another
destination.
182 Queued Called party is not currently available or
elects to queue the call rather than reject
it.
183 Session progress System performs inband alerting for the
caller.
2xx Response—Successful Responses
200 OK Request has been successfully
processed. The action taken depends on
the request made.
3xx Response—Redirection Responses
300 Multiple choices Address resolves to more than one
location. All locations are provided and
the user or UA can select which location
to use.
301 Moved permanently User is no longer available at the
specified location. An alternate location
is included in the header.
302 Moved temporarily User is temporarily unavailable at the
specified location. An alternate location
is included in the header.
305 Use proxy Caller must use a proxy to contact the
called party.
380 Alternative service Call is unsuccessful, but alternative
services are available.
Yes Generates and forwards this
response for an incoming
INVITE. Upon receiving this
response, waits for a 180
Ringing, 183 Session progress,
or 200 OK response.
Yes Forwards this response.
Yes
Yes
Yes
Yes Generates this response to a
REGISTER or CANCEL
request. Otherwise forwards this
response.
Yes Does not generate this response.
If recursive is enabled, recurses
on all contacts; otherwise
forwards this response.
Yes
Yes In redirect mode, generates this
response when it locates one or
more contacts. In proxy mode, if
recursive is enabled, recurses on
all contacts; otherwise forwards
this response.
Yes Does not generate this response.
If recursive is enabled, recurses
Yes
on all contacts; otherwise
forwards this response.
Cisco SIP Proxy Server Administrator Guide
A-3
Appendix A SIP Compliance
RFC 2543 and RFC 3261
Table A-3 SIP Responses (continued)
SIP Response Meaning Supported? Cisco SPS Action
4xx Response—Request Failure Responses
400 Bad Request Request can not be understood because
of an illegal format.
Yes Generates and forwards this
response.
401 Unauthorized Request requires user authentication. Yes Forwards this response. If it is
configured as a registrar and
authentication is enabled,
generates this response.
402 Payment required Payment is required for server to
complete the call.
403 Forbidden Server has received and understood the
See Cisco SPS
action
In registrar mode and if proxied
by the proxy server, generates
this response.
request but will not provide the service.
404 Not found Server has definite information that the
user does not exist in the specified
Yes Generates and forwards this
response.
domain.
405 Method not allowed Method specified in the request is not
allowed. The response contains a list of
See Cisco SPS
action
Forwards this response.
allowed methods.
406 Not acceptable Requested resource can generate only
responses that have unacceptable
content as specified in the accept header
of the request.
407 Proxy authentication
required
408 Request timeout Server could not produce a response
Similar to the 401 Unauthorized
response, but client must first
authenticate itself with the proxy.
before the expiration timeout.
Yes Forwards this response. If
authentication is enabled,
generates this response.
See Cisco SPS
action
Generates and forwards this
response.
409 Conflict Request cannot be processed because of
a conflict with the current state of the
resource.
410 Gone A resource is no longer available at the
server and no forwarding address is
See Cisco SPS
action
Forwards this response.
known.
411 Length required User refuses to accept the request
Yes
without a defined content length.
413 Request entity too large Server refuses to process the request
because it is larger than the server is
See Cisco SPS
action
willing or able to process. If a retry after
header field is contained in this
response, the user can attempt the call
once again in the retry time provided.
414 Request-URI too long Server refuses to process the request
because the Request-URI is too long for
Yes Generates and forwards this
response.
the server to interpret.
A-4
Cisco SIP Proxy Server Administrator Guide
Appendix A SIP Compliance
RFC 2543 and RFC 3261
Table A-3 SIP Responses (continued)
SIP Response Meaning Supported? Cisco SPS Action
415 Unsupported media Server refuses to process the request
because the format of the body is not
supported by the destination endpoint.
420 Bad extension Server cannot understand the protocol
extension indicated in the Require
header.
480 Temporarily
unavailable
481 Call leg/transaction
does not exist
Called party was contacted but is
temporarily unavailable.
Server ignores the request because it is
either a BYE for which there is no
matching leg ID or a CANCEL for
which there is no matching transaction.
482 Loop detected Server received a request that includes
itself in the path.
483 Too many hops Server received a request that requires
more hops than allowed by the
Max-Forwards header.
484 Address incomplete Server received a request that contains
an incomplete address.
485 Ambiguous Server received a request that contains
an ambiguous called-party address. It
can provide possible alternative
addresses.
486 Busy here Called party was contacted but his or
her system is unable to take additional
calls.
487 Busy here; request
cancelled
Request was terminated by a BYE or
CANCEL request.
488 Not acceptable media An error in handling the request
occurred.
Yes Forwards this response.
Yes Generates and forwards this
response.
Yes Forwards this response. If
preauthentication is enabled and
fails, generates this response.
Yes Generates and forwards this
response.
See Cisco SPS
Forwards this response.
action
Yes
See Cisco SPS
action
Cisco SIP Proxy Server Administrator Guide
A-5
Appendix A SIP Compliance
RFC 2543 and RFC 3261
Table A-3 SIP Responses (continued)
SIP Response Meaning Supported? Cisco SPS Action
5xx Response—Server Failure Responses
500 Server internal error Server or gateway encountered an
unexpected error that prevents it from
processing the request.
501 Not implemented Server or gateway does not support the
functions required to complete the
request.
502 Bad gateway Server or gateway received an invalid
response from a downstream server.
503 Service unavailable Server or gateway is unable to process
the request due to an overload or
maintenance problem.
504 Gateway timeout Server or gateway did not receive a
timely response from another server
(such as a location server).
505 Version not supported Server or gateway does not support the
version of the SIP protocol used in the
request.
6xx Response—Global Responses
600 Busy everywhere Called party was contacted but is busy
and cannot take the call at this time.
603 Decline Called party was contacted but cannot
or does not want to participate in the
call.
604 Does not exist anywhere Server has authoritative information
that the called party does not exist in the
network.
606 Not acceptable Called party was contacted, but some
aspect of the session description was
unacceptable.
Yes Generates and forwards this
response.
See Cisco SPS
Forwards this response.
action
Yes Generates and forwards this
response.
See Cisco SPS
Forwards this response.
action
Yes
See Cisco SPS
Forwards this response.
action
SIP Header Fields
Note All SIP header fields that concern the Cisco SPS are correctly handled and parsed except for the Hide
and Encryption header fields. Header fields that do not directly affect the Cisco SPS or that are unknown
to it are passed unaltered in the SIP request.
Cisco SIP Proxy Server Administrator Guide
A-6
Appendix A SIP Compliance
Table A-4 SIP Header Fields
Header Field Supported? Header Field Supported?
Accept Yes Organization Yes
Accept-Encoding Yes MIME-Version Yes
Accept-Language Yes Priority Yes
Alert-Info Yes Proxy-Authenticate Yes
Allow Yes Proxy Authorization Yes
Also Yes Proxy-Require Yes
Authorization Yes Record-Route Yes
Call-ID Yes Require Yes
Call-Info Yes Response-Key Yes
Contact Yes Retry-After Yes
Content-Disposition Yes Route Yes
Content-Encoding Yes Server Yes
Content-Length Yes Subject Yes
Content-Type Yes Supported Yes
Cseq Yes Timestamp Yes
Date Yes To Yes
Encryption
Error-Info Yes User-Agent Yes
Expires Yes Via Yes
From Yes Warning Yes
In-Reply-To Yes WWW-Authenticate Yes
Max-Forwards Yes
1. When a SIP message is received that contains this header field, the message is processed with the field ignored.
RFC 2543 and RFC 3261
1
No Unsupported Yes
SIP Transport Layer Protocols
Table A-5 SIP Transport Layer Protocols
Transport Layer Protocol Supported?
Unicast UDP Yes
Multicast UDP No
TCP Yes
TLS Yes
Cisco SIP Proxy Server Administrator Guide
A-7
RFC 3263
SIP Security
Table A-6 SIP Security
Mode Supported?
Encryption Mode
End-to-end No
Hop-by-Hop Yes
Authentication Mode
1
Basic
Digest Yes
Proxy Yes
1. Due to its weak security, basic authentication has been deprecated. This is a
change from RFC 2543. It is not disabled or removed from Cisco SPS, but will no
longer be supported or extended to interwork with new or modified functionality.
We strongly discourage the use of basic authentication.
Yes
Appendix A SIP Compliance
RFC 3263
SIP DNS Records Usage
Table A-7 SIN DNS Records Usage
DNS Resource Record Type Supported?
AYes
NAPTR Yes
SRV Yes
A-8
Cisco SIP Proxy Server Administrator Guide
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