INVITE

Y

Establishes a session; CallManager originates and receives this message.

ACK

Y

Acknowledges the establishment of a session; CallManager sends and receives this message.

OPTIONS

Y

Queries a User Agent (UA) about its capabilities; CallManager never sends this message but does respond to it.

BYE

Y

Terminates an established session. CallManager sends and receives this message.

CANCEL

Y

Rescinds an INVITE before the session is established.

REGISTER

N

Registers SIP addresses with a registrar. CallManager never sends this message and responds with a 405 Method Not Allowed if it receives it.

PRACK

Y

Acknowledges the receipt of a provisional response (such as 180 Alerting) by the UA; used only when reliable provisional responses are in effect.

UPDATE

Y

Allows session parameters for an unestablished session to be changed. CallManager never sends this message but can accept it.

1xx messages indicate events that occur as a session is being established

100 Trying

Y

Indicates that the Proxy or UA has been able to resolve an address and continue routing. CallManager supports sending and receiving this message.

180 Ringing

Y

Indicates the target UA is ringing. CallManager sends and receives this message.

181 Call Forward

N

CallManager cannot send or receive this message.

182 Call Queued

N

CallManager cannot send or receive this message.

183 Progress

Y

CallManager can receive and send this message. CallManager may connect media on receipt of this message.

2xx messages confirm the establishment of a session

200 OK

Y

Confirms that a session has been established.

3xx messages indicate that the session being established should be established to or via a different SIP entity

300–302, 305, 380

Y

CallManager never sends these messages. When it receives this class of message, CallManager attempts to re-establish the session to the contacts listed in the message.

4xx messages are definitive, final failure responses from the target of the request

4xx

Y

CallManager sends and receives this message. CallManager initiates a call disconnect upon receiving this message.

5xx messages indicate that an unexpected condition was encountered that prevented the establishment of the session

5xx

Y

CallManager sends this message. Upon receiving this message, CallManager issues a new request if the response contains an alternate contact. Otherwise, CallManager ends the call.

6xx messages indicate that the target of the request was busy and cannot accept the incoming call

6xx

Y

CallManager never sends this message. CallManager disconnects the call upon receiving this message.

From

All

From: callerName <sip:cgpn@CCM_IP_addr>

callerName is the caller’s display name; cgpn is the caller’s number; CCM_IP_addr is the IP address of CallManager.

To

All

To: calledName <sip:cdpn@destIP;user=phone>

calledName is the name of the call target, if available; cdpn is the number of the called party; destIP is the resolved IP address of the target of the SIP trunk.

Via

All

Via:SIP/2.0 IPaddr:port;branch=number

IPaddr is the IP address of CallManager; port is the port assigned to CallManager’s SIP trunk; branch is a unique number that identifies each branch of an outgoing forked call. CallManager SIP trunks don’t support forking, which means CallManager issues only a single request with a single branch identifier.

Call-ID

All

Call-ID: number@IPaddr

number is a unique call identifier determined by CallManager; IPaddr is the IP address of CallManager.

Contact

All

Contact: <sip:cgpn@IPaddr:localPort;user=phone>

IPAddr is the IP address of CallManager; cgpn is the calling number; localPort is the incoming port assigned to the issuing SIP trunk.

Cseq

All

Cseq: number method

number is a number that increments for each subsequent outgoing request; method is the name of the request (INVITE, ACK, and so on).

Max-Forwards

All

Max-Forwards: number

number indicates the maximum number of times that the message can propagate from call agent to call agent before the request expires. CallManager sets this value to 6 for originated SIP calls.

Remote-Party-Id

INVITE

Remote-Party-Id: calledName <sip:cdpn@called_IP_address;user=phone>;party=calling;screen=no;privacy=off

Indicates the display information for the party issuing the response. user indicates the class of responding device; party indicates the role of the responder in the call; screen indicates whether an intermediary entity has validated the display information; privacy indicates whether the information should be displayed to the requestor.

Diversion

INVITE

Diversion: <sip:divertingNumber @diverting_IP_address >;reason=no-answer

Indicates the prior history of the call. If the call has been previously diverted, this information must be communicated to the downstream voice mail server. reason indicates the reason for the diversion.

From

All

From: <sip:cgpn@CCM_IP_Addr>;tag=16777234

cgpn is the number of the caller; CCM_IP_Addr is the address that issued the request; tag is part of a unique call identifier.

To

All

To: <sip:cdpn@destIP>;tag=xxyyzz

cdpn is the number of the responder; destIP is the IP address of the responder; tag is part of a unique call identifier.

Via

All

Via: SIP/2.0/TCP

CCM_IP_Addr:localPort;received=CCM_IP_Addr; branch=z9hG4bKfe8d27ec

The Via chain—this header often occurs multiple times in a SIP request—indicates the path that the request took. branch is a unique identifier that indicates which fork of a branching call is issuing the response.

Contact

All

Contact: <sip:cdpn@destIP:calledPort>

The Contact represents the address of the specific entity that is responding to the message.

Remote-Party-Id

18X

2XX

Remote-Party-Id: calledName <sip:cdpn@destIP;user=phone>;party=called; screen=no;privacy=off

Indicates the display information for the party issuing the response. user indicates the class of the responding device; party indicates the role of the responder in the call; screen indicates whether an intermediary entity has validated the display information; privacy indicates whether the information should be displayed to the requestor.

OffHook

-->

When you perform any number of off-hook actions, such as lifting the handset of IP Phone A or pressing the NewCall softkey, the phone reports off-hook to CallManager.

SetLamp

<--

CallManager sends this message for several possible reasons. SetLamp has a lineInstance field. When the lineInstance field is 0, it lights or extinguishes the MWI lamp. If the lineInstance is other than 0, it turns on the envelope icon next to the line button on which a message is waiting. If the line button can be lit, it will be lit as well.

CallState

<--

CallManager sends the CallState information, which the Cisco IP Phones 79xx series use to update the icon of the appropriate line as a visual indication of call state.

SelectSoftKeys

<--

CallManager sends SelectSoftKeys to activate a set of softkeys and a mask to select which softkeys are enabled and which keys are disabled. Cisco 79xx series IP Phones use softkeys.

DisplayPrompt Status

<--

CallManager sends the DisplayPromptStatus to update the prompt line, which is the display line just above the softkey text line on Cisco 79xx series IP Phones. This initial prompt for off-hook state is “Enter number.” For idle state, the phone displays “Your current options.”

The prompt message is associated with a particular line. If a different line is selected, the prompt changes to the prompt associated with the selected line.

DisplayText

<--

CallManager sends the text to update the display of a limited-display phone, such as the 30VIP.

ActivateCallPlane

<--

CallManager sends ActivateCallPlane to activate the call plane for the specified line. In this case, the call is line 1 as the default because no specific line was selected. Cisco 79xx series IP Phones use the ActivateCallPlane command.

StartTone

<--

CallManager directs the phone to play an inside dial tone. The phone internally generates a dial tone.

KeyPad Button

-->

As you enter the number of the desired destination—Phone B in this case—the phone sends a KeyPadButton for each digit dialed. The KeyPadButton messages continue until CallManager determines that you have entered the required number of digits to reach your destination. When CallManager determines the called party—Phone B in this case—CallManager initiates the message sequence to Phone B to extend the call to Phone B.

StopTone

<--

CallManager directs the phone to stop playing dial tone after you enter the first digit.

SelectSoftKeys

<--

CallManager sends SelectSoftKeys to activate the next set of softkeys and the mask to select which softkeys are enabled and which softkeys are disabled. Cisco 79xx series IP Phones use softkeys.

CallState

-->

CallManager sends CallState information, which Cisco 79xx series IP Phones use to update the call state information and the icon of the appropriate line as a visual indication of call state. In this case, the call state indicates an incoming call.

SelectSoftKeys

-->

CallManager sends SelectSoftKeys to Phone B to activate the appropriate softkeys.

DisplayPrompt Status

-->

CallManager sends DisplayPromptStatus to Phone B to update the display associated with the particular line of the incoming call. This display persists for the selected line until it is changed by another DisplayPromptStatus message of an equal or higher priority.

DisplayPriNotify

-->

CallManager sends DisplayPriNotify to Phone B to indicate an incoming call. DisplayPriNotify, which has an associated timeout that defaults to 10 seconds, updates the display immediately and is not associated with a particular line. The priority of the incoming call is included with the notification.

CallInfo

-->

CallManager sends CallInfo to the station to provide the specific information about the call, which includes calling and called party name and number, the line number for the call, and the type of call (inbound, outbound, or forwarded). In this case, the call type is inbound. The name might not be provided in all cases. A gateway call, for example, might not provide calling party name.

SetLamp

-->

CallManager sends this message for several possible reasons. SetLamp has a lineInstance field. When the lineInstance field is 0, it lights or extinguishes the MWI lamp. If the lineInstance is other than 0, it turns on the envelope icon next to the line button on which a message is waiting. If the line button can be lit, it will be lit as well.

SetRinger

-->

CallManager sends the SetRinger to Phone B to cause the phone to ring, indicating an incoming call. The ring type is InsideRing, as distinguished from OutsideRing, because this is an internal call from Phone A to Phone B.

StartTone

<--

CallManager sends StartTone to Phone A to initiate the ringback tone to the caller at Phone A. The tone is generated internally by Phone A.

CallState

<--

CallManager updates the call state of Phone A to indicate that Phone B is now ringing.

SelectSoftKeys

<--

CallManager sends SelectSoftKeys to Phone A to activate the appropriate softkeys for the ringing call.

DisplayPrompt Status

<--

CallManager sends DisplayPromptStatus to Phone A to display the prompt appropriate for the updated softkeys.

CallInfo

<--

CallManager sends CallInfo to Phone A to provide the specific information about the call, which includes calling and called party name and number, the line number for the call, and the type of call. Because Phone A originated the call, the call is outbound.

OffHook

<--

When you perform any number of off-hook actions, such as lifting the handset of Phone B or pressing the Answer softkey, the phone reports off-hook to CallManager.

SetRinger

-->

CallManager turns off the ringer because the call has been answered.

SetLamp

-->

CallManager uses this message to set the line lamp of the line answered on Phone B.

CallState

-->

CallManager updates the call state information for the call because it has changed from ringing to answered.

ActivateCallPlane

-->

CallManager activates the call plane for the line that was answered.

StopTone

<--

-->

CallManager stops the ringback tone on Phone A and the ringer tone on Phone B.

OpenReceive Channel (audio)

<--

-->

CallManager sends OpenReceiveChannel to both Phone A and B to cause the phone to begin receiving audio sent from the other phone. This is only half of the audio path, and because neither phone is transmitting at this point, the connection is not yet fully established.

OpenMultiMedia ReceiveChannel (video)

<--

-->

CallManager sends OpenMultiMediaReceiveChannel (video) to both Phone A and B to cause the phone to begin receiving video sent from the other phone. This is only half of the video path, and because neither phone is transmitting at this point, the connection is not yet fully established.

OpenMultiMedia ReceiveChannel (data)

<--

-->

CallManager sends OpenMultiMediaReceiveChannel (data) to both Phone A and B to cause the phone to begin receiving data sent from the other phone. This is only half of the data path, and because neither phone is transmitting at this point, the connection is not yet fully established.

CallState

<--

-->

The call state is updated to connected for both Phone A and B.

SelectSoftKeys

<--

-->

The softkeys are updated on both Phone A and B.

DisplayPrompt Status

<--

-->

The prompt line is updated on both Phone A and B.

CallInfo

<--

-->

The call info is updated for both Phone A and B.

Open Receive Channel Ack (audio)

-->

Open Receive Channel Ack (audio)

<--

Both phones have responded with an OpenReceiveChannelAck (audio), indicating that they are ready to receive audio transmission.

Open MultiMedia Receive Channel Ack (video)

-->

Open MultiMedia Receive Channel Ack (video)

<--

Both phones have responded with an OpenMultiMediaReceiveChannelAck (video), indicating that they are ready to receive video transmission.

Open MultiMedia Receive Channel Ack (data)

-->

Open MultiMedia Receive Channel Ack (data)

<--

Both phones have responded with an OpenMultiMediaReceiveChannelAck (data), indicating that they are ready to receive data transmission.

StartMedia Transmission (audio)

<--

-->

CallManager sends StartMediaTransmission (audio) to both Phone A and B to cause the phone to begin sending audio to the other phone. Because both phones are transmitting and receiving audio at this point, the audio connection is now fully established.

StartMultiMedia Transmission (video)

<--

-->

CallManager sends StartMultiMediaTransmission (video) to both Phone A and B to cause the phone to begin sending video to the other phone. Because both phones are transmitting and receiving video at this point, the video connection is now fully established.

StartMultiMedia Transmission (data)

<--

-->

CallManager sends StartMultiMediaTransmission (data) to both Phone A and B to cause the phone to begin sending data to the other phone. Because both phones are transmitting and receiving data at this point, the data connection is now fully established.