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SIP Compliance for Cisco Unity (All Versions of Cisco Unity)

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SIP Compliance for Cisco Unity (All Versions of Cisco Unity)

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

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.

Redirect server

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.

Registrar server

Processes requests from user agent clients for registration of their current location. Registrar servers are often installed on the redirect or proxy server.

Phones

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.

Gateways

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.


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
Supported?
Comments

INVITE

Yes

 

OPTIONS

Yes

Incoming only.

ACK

Yes

 

BYE

Yes

 

CANCEL

Yes

 

REGISTER

Yes

Outgoing only.

REFER

Yes

Outgoing only.

NOTIFY

Yes

Used for message waiting indicators (MWIs); unsolicited NOTIFY.


SIP Responses

1xx Response—Information Responses

Response
Supported?
Comments

100 Trying

Yes

 

180 Ringing

Yes

 

181 Call Is Being Forwarded

See comment

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.

182 Queued

183 Session Progress


2xx Response—Successful Responses

Response
Supported?
Comments

200 OK

Yes

 

202 Accepted

Yes

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.


3xx Response—Redirection Responses

Response
Supported?
Comments

300 Multiple Choices

No

 

301 Moved Permanently

No

 

302 Moved Temporarily

No

 

305 Use Proxy

No

 

380 Alternate Service

No

 


4xx Response—Request Failure Responses

Response
Supported?
Comments

400 Bad Request

See comment

Cisco Unity does not generate this response. For an incoming response, Cisco Unity initiates a graceful call disconnect.

401 Unauthorized

Yes

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.

402 Payment Required

See comment

Cisco Unity does not generate these responses. For an incoming response, Cisco Unity initiates a graceful call disconnect.

403 Forbidden

404 Not Found

405 Method Not Allowed

406 Not Acceptable

407 Proxy Authentication Required

See comment

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.

408 Request Timeout

See comment

Upon receiving this response, Cisco Unity considers the call to be ringing but not answered (ring-no-answer).

409 Conflict

See comment

Cisco Unity does not generate these responses. For an incoming response, Cisco Unity initiates a graceful call disconnect.

410 Gone

411 Length Required

413 Request Entity Too Large

414 Request—URL Too Long

415 Unsupported Media

420 Bad Extension

480 Temporarily Unavailable

481 Call Leg/Transaction Does Not Exist

Yes

Cisco Unity generates this response when it cannot match the response to an existing transaction (for example, the call has been terminated).

482 Loop Detected

See comment

Cisco Unity does not generate these responses. For an incoming response, Cisco Unity initiates a graceful call disconnect.

483 Too Many Hops

484 Address Incomplete

485 Ambiguous

486 Busy Here

Yes

Upon receiving this response, Cisco Unity considers the call to be busy. Cisco Unity generates this response when all Cisco Unity lines are busy.

487 Request Canceled

See comment

Cisco Unity does not generate these responses. For an incoming response, Cisco Unity initiates a graceful call disconnect.

488 Not Acceptable


5xx Response—Server Failure Responses

Response
Supported?
Comments

500 Internal Server Error

See comments

Cisco Unity does not generate this response. For an incoming response, Cisco Unity initiates a graceful call disconnect.

501 Not Implemented

Cisco Unity generates this response when the method request is not recognized.

502 Bad Gateway

Cisco Unity does not generate these responses. For an incoming response, Cisco Unity initiates a graceful call disconnect.

503 Service Unavailable

504 Gateway Timeout

505 Version Not Supported


6xx Response—Global Responses

Response
Supported?
Comments

600 Busy Everywhere

See comments

Cisco Unity does not generate these responses. For an incoming response, Cisco Unity initiates a graceful call disconnect.

603 Decline

604 Does Not Exist Anywhere

606 Not Acceptable


SIP Header Fields

All unsupported SIP headers are ignored if received.

Header Field
Supported?
Comments

Accept

No

 

Accept-Encoding

No

 

Accept-Language

No

 

Alert-Info

No

 

Allow

No

 

Authentication-Info

No

 

Authorization

Yes

 

Call-ID

Yes

 

CC-Diversion/Diversion

Yes

 

Contact

Yes

 

Content-Disposition

No

 

Content-Encoding

No

 

Content-Language

No

 

Content-Length

Yes

 

Content-Type

Yes

 

Cseq

Yes

 

Date

No

 

Error-Info

No

 

Expires

Yes

Only for REGISTER response.

From

Yes

 

In-Reply-To

No

 

Max-Forwards

Yes: Cisco Unity 4.0(2) and later

No: Cisco Unity 4.0(1)

 

Min-Expires

No

 

MIME-Version

No

 

Organization

No

 

Priority

No

 

Proxy-Authenticate

Yes

 

Proxy-Authorization

Yes

 

Proxy-Require

No

 

Record-Route

Yes

 

Referred-By

Yes

Cisco Unity generates this header as part of the REFER request.

Referred-To

Yes

Cisco Unity generates this header as part of the REFER request.

Replaces

Yes

Cisco Unity generates this header as part of the REFER request.

Reply-To

No

 

Requested-By

No

 

Require

Yes: Cisco Unity 4.0(2) and later

No: Cisco Unity 4.0(1)

 

Retry-After

No

 

Route

No

 

Server

No

 

Subject

No

 

Supported

No

 

Timestamp

No

 

To

Yes

 

Unsupported

Yes: Cisco Unity 4.0(2) and later

No: Cisco Unity 4.0(1)

 

User-Agent

No

 

Via

Yes

 

Warning

No

 

WWW-Authenticate

Yes

 


SIP Session Description Protocol (SDP) Usage

SDP Header
Supported?

v (Protocol version)

Yes

o (Owner/creator and session identifier)

Yes

s (Session name)

Yes

t (Time description)

Yes

c (Connection information)

Yes

m (Media name and transport address)

Yes

a (Media attribute lines)

Yes


Transport Layer Protocols

Protocol
Supported?

Unicast UDP

Yes

Multicast UDP

No

TCP

Yes: Cisco Unity 4.0(4) and later

No: Cisco Unity 4.0(1) through 4.0(3)


SIP Security

Encryption Mode
Security Method
Supported?

Authentication

Basic Authentication

No

Digest Authentication

Yes

Proxy Authentication

No

PGP

No


SIP DNS Records Usage

DNS Resource Record Type
Supported?

Type A

Yes

Type SRV

No


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
Supported?

RFC 2833

Yes

In-band tones

No


Codec Support

Codec Type
Supported?

G.711 Mu-Law

Yes

G.729a

Yes


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