Table Of Contents
SIP Compliance for Cisco Unity (All Versions of Cisco Unity)
How SIP Integration with Cisco Unity Works
SIP Methods
SIP Responses
SIP Header Fields
SIP Session Description Protocol (SDP) Usage
Transport Layer Protocols
SIP Security
SIP DNS Records Usage
SIP DTMF Digit Transport
Codec Support
Additional References
SIP Compliance for Cisco Unity (All Versions of Cisco Unity)
Revised August 3, 2007
Cisco Unity 4.0(1) and later complies with the Session Initiation Protocol (SIP) RFC 2543 standard. This white paper contains the following sections:
•
How SIP Integration with Cisco Unity Works
•SIP Methods
•SIP Responses
•SIP Header Fields
•SIP Session Description Protocol (SDP) Usage
•Transport Layer Protocols
•SIP Security
•SIP DNS Records Usage
•SIP DTMF Digit Transport
•Codec Support
•Additional References
How SIP Integration with Cisco Unity Works
SIP is the Internet Engineering Task Force's (IETF's) standard for multimedia calls over IP. SIP is a peer-to-peer, ASCII-based protocol that uses requests and responses to establish, maintain, and terminate calls (or sessions) between two or more end points. A SIP network uses the following components.
SIP proxy server
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The proxy server is an intermediate device that receives SIP requests from a client and then forwards the requests on the client's behalf. Proxy servers receive SIP messages and forward them to the next SIP server in the network. Proxy servers can provide functions such as authentication, authorization, network access control, routing, reliable request retransmission, and security.
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Redirect server
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Provides the client with information about the next hop or hops that a message should take and then the client contacts the next hop server or user agent server directly.
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Registrar server
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Processes requests from user agent clients for registration of their current location. Registrar servers are often installed on the redirect or proxy server.
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Phones
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Can act as either a server or client. Softphones (PCs that have phone capabilities installed) and Cisco SIP IP phones can initiate SIP requests and respond to requests.
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Gateways
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Provide call control. Gateways provide many services, the most common being a translation function between SIP call endpoints and other terminal types. This function includes translation between transmission formats and between communications procedures. In addition, the gateway translates between audio and video codecs and performs call setup and clearing on both the LAN side and the switched-circuit network side.
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Cisco Unity accepts calls from a proxy server. Cisco Unity relies on a proxy server or call agent to authenticate calls.
SIP uses a request/response method to establish communications between various components in the network and to ultimately establish a conference (call or session) between two or more endpoints. A single call may involve several clients and servers.
Users in a SIP network are identified by:
•A unique phone or extension number.
•A unique SIP address, which is similar to an e-mail address and uses the format sip:<userID>@<domain>. The user ID can be either a user name or an E.164 address.
When a user initiates a call, a SIP request typically goes to a SIP server (either a proxy server or a redirect server). The request includes the caller's address (From) and the address of the called party (To).
SIP messages are in text format using ISO 10646 in UTF-8 encoding (like HTML). In addition to the address information, a SIP message contains a start-line specifying the method and the protocol, a number of header fields specifying call properties and service information, and an optional message body which can contain a session description.
The proxy servers that are qualified for integrating with Cisco Unity are listed in the Session Initiation Protocol (SIP) Integration Guide at http://www.cisco.com/en/US/products/sw/voicesw/ps2237/products_installation_and_configuration_guides_list.html.
SIP Methods
Method
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Supported?
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Comments
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INVITE
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Yes
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OPTIONS
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Yes
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Incoming only.
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ACK
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Yes
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BYE
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Yes
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CANCEL
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Yes
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REGISTER
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Yes
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Outgoing only.
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REFER
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Yes
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Outgoing only.
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NOTIFY
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Yes
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Used for message waiting indicators (MWIs); unsolicited NOTIFY.
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SIP Responses
1xx Response—Information Responses
Response
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Supported?
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Comments
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100 Trying
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Yes
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180 Ringing
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Yes
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181 Call Is Being Forwarded
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See comment
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Cisco Unity does not generate these responses. However, Cisco Unity does handle receiving them and processes the responses the same way it processes the 100 Trying response.
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182 Queued
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183 Session Progress
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2xx Response—Successful Responses
Response
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Supported?
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Comments
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200 OK
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Yes
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202 Accepted
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Yes
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Cisco Unity does not generate this response. However, Cisco Unity does handle receiving it and processes the response the same way it processes the 200 OK response.
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3xx Response—Redirection Responses
Response
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Supported?
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Comments
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300 Multiple Choices
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No
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301 Moved Permanently
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No
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302 Moved Temporarily
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No
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305 Use Proxy
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No
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380 Alternate Service
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No
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4xx Response—Request Failure Responses
Response
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Supported?
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Comments
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400 Bad Request
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See comment
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Cisco Unity does not generate this response. For an incoming response, Cisco Unity initiates a graceful call disconnect.
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401 Unauthorized
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Yes
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Cisco Unity does not generate this response. However, Cisco Unity accepts the response and sends a new request containing the authentication information in the format of the HTTP digest as modified by RFC 2543.
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402 Payment Required
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See comment
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Cisco Unity does not generate these responses. For an incoming response, Cisco Unity initiates a graceful call disconnect.
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403 Forbidden
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404 Not Found
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405 Method Not Allowed
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406 Not Acceptable
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407 Proxy Authentication Required
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See comment
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Cisco Unity does not generate this response. However, Cisco Unity accepts the response and sends a new request containing the authentication information in the format of the HTTP digest as modified by RFC 2543.
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408 Request Timeout
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See comment
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Upon receiving this response, Cisco Unity considers the call to be ringing but not answered (ring-no-answer).
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409 Conflict
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See comment
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Cisco Unity does not generate these responses. For an incoming response, Cisco Unity initiates a graceful call disconnect.
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410 Gone
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411 Length Required
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413 Request Entity Too Large
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414 Request—URL Too Long
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415 Unsupported Media
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420 Bad Extension
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480 Temporarily Unavailable
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481 Call Leg/Transaction Does Not Exist
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Yes
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Cisco Unity generates this response when it cannot match the response to an existing transaction (for example, the call has been terminated).
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482 Loop Detected
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See comment
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Cisco Unity does not generate these responses. For an incoming response, Cisco Unity initiates a graceful call disconnect.
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483 Too Many Hops
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484 Address Incomplete
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485 Ambiguous
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486 Busy Here
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Yes
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Upon receiving this response, Cisco Unity considers the call to be busy. Cisco Unity generates this response when all Cisco Unity lines are busy.
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487 Request Canceled
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See comment
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Cisco Unity does not generate these responses. For an incoming response, Cisco Unity initiates a graceful call disconnect.
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488 Not Acceptable
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5xx Response—Server Failure Responses
Response
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Supported?
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Comments
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500 Internal Server Error
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See comments
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Cisco Unity does not generate this response. For an incoming response, Cisco Unity initiates a graceful call disconnect.
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501 Not Implemented
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Cisco Unity generates this response when the method request is not recognized.
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502 Bad Gateway
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Cisco Unity does not generate these responses. For an incoming response, Cisco Unity initiates a graceful call disconnect.
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503 Service Unavailable
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504 Gateway Timeout
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505 Version Not Supported
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6xx Response—Global Responses
Response
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Supported?
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Comments
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600 Busy Everywhere
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See comments
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Cisco Unity does not generate these responses. For an incoming response, Cisco Unity initiates a graceful call disconnect.
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603 Decline
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604 Does Not Exist Anywhere
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606 Not Acceptable
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SIP Header Fields
All unsupported SIP headers are ignored if received.
Header Field
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Supported?
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Comments
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Accept
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No
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Accept-Encoding
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No
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Accept-Language
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No
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Alert-Info
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No
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Allow
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No
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Authentication-Info
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No
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Authorization
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Yes
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Call-ID
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Yes
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CC-Diversion/Diversion
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Yes
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Contact
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Yes
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Content-Disposition
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No
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Content-Encoding
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No
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Content-Language
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No
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Content-Length
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Yes
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Content-Type
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Yes
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Cseq
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Yes
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Date
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No
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Error-Info
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No
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Expires
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Yes
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Only for REGISTER response.
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From
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Yes
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In-Reply-To
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No
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Max-Forwards
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Yes: Cisco Unity 4.0(2) and later
No: Cisco Unity 4.0(1)
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Min-Expires
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No
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MIME-Version
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No
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Organization
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No
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Priority
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No
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Proxy-Authenticate
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Yes
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Proxy-Authorization
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Yes
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Proxy-Require
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No
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Record-Route
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Yes
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Referred-By
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Yes
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Cisco Unity generates this header as part of the REFER request.
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Referred-To
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Yes
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Cisco Unity generates this header as part of the REFER request.
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Replaces
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Yes
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Cisco Unity generates this header as part of the REFER request.
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Reply-To
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No
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Requested-By
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No
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Require
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Yes: Cisco Unity 4.0(2) and later
No: Cisco Unity 4.0(1)
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Retry-After
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No
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Route
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No
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Server
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No
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Subject
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No
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Supported
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No
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Timestamp
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No
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To
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Yes
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Unsupported
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Yes: Cisco Unity 4.0(2) and later
No: Cisco Unity 4.0(1)
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User-Agent
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No
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Via
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Yes
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Warning
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No
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WWW-Authenticate
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Yes
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SIP Session Description Protocol (SDP) Usage
SDP Header
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Supported?
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v (Protocol version)
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Yes
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o (Owner/creator and session identifier)
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Yes
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s (Session name)
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Yes
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t (Time description)
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Yes
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c (Connection information)
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Yes
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m (Media name and transport address)
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Yes
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a (Media attribute lines)
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Yes
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Transport Layer Protocols
Protocol
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Supported?
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Unicast UDP
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Yes
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Multicast UDP
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No
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TCP
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Yes: Cisco Unity 4.0(4) and later
No: Cisco Unity 4.0(1) through 4.0(3)
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SIP Security
Encryption Mode
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Security Method
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Supported?
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Authentication
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Basic Authentication
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No
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Digest Authentication
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Yes
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Proxy Authentication
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No
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PGP
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No
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SIP DNS Records Usage
DNS Resource Record Type
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Supported?
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Type A
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Yes
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Type SRV
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No
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SIP DTMF Digit Transport
Cisco Unity supports DTMF Relay in accordance with RFC 2833. The DTMF Relay is based on the transmission of Named Telephony Events (NTE) over the RTP stream. The default RTP payload used for transmission of DTMF is 101. Cisco Unity treats any incoming RTP payload above 90 as a DTMF event.
DTMF Digit Transport Type
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Supported?
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RFC 2833
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Yes
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In-band tones
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No
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Codec Support
Codec Type
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Supported?
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G.711 Mu-Law
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Yes
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G.729a
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Yes
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Additional References
Session Initiation Protocol (SIP) Integration Guide for Cisco Unity at http://www.cisco.com/en/US/products/sw/voicesw/ps2237/products_installation_and_configuration_guides_list.html
© 2007 Cisco Systems, Inc. All rights reserved.
