Internet Engineering Task Force Christian Huitema
`INTERNET DRAFT Flemming Andreasen
`<draft-huitema-megaco-mgcp-flows-01.txt> Bellcore
`January 20, 1999 Mauricio Arango
`Expires: June 18, 1999 RSL COM
` Prakash K
` TELESOFT INC
`
` Media Gateway Control Protocol (MGCP) Call Flows
` Christian Huitema, Flemming Andreasen, Mauricio Arango, Prakash K
`
`Status of this document
`
`This document is an Internet-Draft and is in full conformance with all
`provisions of Section 10 of RFC2026 except for the right to produce
`derivative works.
`
`This document is an Internet-Draft. Internet-Drafts are working docu-
`ments of the Internet Engineering Task Force (IETF), its areas, and its
`working groups. Note that other groups may also distribute working
`documents as Internet-Drafts.
`
`Internet-Drafts are draft documents valid for a maximum of six months
`and may be updated, replaced, or obsoleted by other documents at any
`time. It is inappropriate to use Internet- Drafts as reference material
`or to cite them other than as "work in progress."
`
`To view the entire list of current Internet-Drafts, please check the
`"1id-abstracts.txt" listing contained in the Internet-Drafts Shadow
`Directories on ftp.is.co.za (Africa), ftp.nordu.net (Northern Europe),
`ftp.nis.garr.it (Southern Europe), munnari.oz.au (Pacific Rim),
`ftp.ietf.org (US East Coast), or ftp.isi.edu (US West Coast).
`
`Abstract
`
`The Media Gateway Control Protocol (MGCP) organizes the communication
`between a Media Gateway controller, or call agent, and a Media Gateway,
`e.g. a Voice over IP gateway or a Network Access Server. MGCP is
`defined in a companion document [1]. This document provides example of
`MGCP usage by providing a variety of call flows, in the case of
`telephony and network access servers.
`
`Huitema, Andreasen, Arango, Prakash [Page 1]
`
`Ex. 1023
`YMax Corporation
`Page 1 of 125
`
`

`
`
`Internet draft MGCP Call Flows 20 January 1999
`
`Table of Contents Page
`
`1. Introduction .............................................. 2
`2. Internet Telephony Call Flows. ............................ 2
`3. Interaction between an MGCP gateway and an H.323 entity ... 2
`4. Interworking between SIP and MGCP ......................... 2
`5. Data calls ................................................ 2
`6. Audit and Restart ......................................... 2
`7. Using MGCP to control an IVR .............................. 2
`8. Acknowledgements .......................................... 2
`9. References ................................................ 2
`10. Authors’ Addresses ....................................... 2
`
`Huitema, Andreasen, Arango, Prakash [Page 2]
`
`Ex. 1023
`YMax Corporation
`Page 2 of 125
`
`

`
`
`Internet draft MGCP Call Flows 20 January 1999
`
`1. Introduction
`
`In order to understand the way the MGCP interface will be used, we have
`described here several possible call flows between a TGW, which is a
`trunking gateway that implements MGCP, and an RGW, which is a residen-
`tial gateway that implements MGCP, as well as several call flows
`describing how MGCP could be used to control a network access service.
`For each of these call flows it is assumed that the default event pack-
`ages are as follows:
`
`TGW Trunk package
`
`RGW Line package
`
`NAS Network Access Server package
`
`The diagrams also show a Common Database (CDB) that can be queried for
`authorization and routing information, and an Accounting Gateway (ACC)
`that collects accounting information at the start and the end of calls.
`
`These diagrams are solely meant to exhibit the behavior of the MGCP, and
`to help understanding this protocol. They are not meant as a tutorial on
`the implementation of a Call Agent. They may very well include miscel-
`laneous errors and imprecisions.
`
`Huitema, Andreasen, Arango, Prakash [Page 3]
`
`Ex. 1023
`YMax Corporation
`Page 3 of 125
`
`

`
`
`Internet draft MGCP Call Flows 20 January 1999
`
`2. Internet Telephony Call Flows.
`
`We present seven Internet Telephony call flows:
`
`* A basic call between two "trunking gateways",
`
`* A basic call from a "residential gateway" to a "trunking gateway",
`
`* A basic call from a "trunking gateway" to a "residential gateway".
`
`* A basic call from an R2 trunk in a TGW to an SS7 trunk in a TGW.
`
`* A basic call from an ISDN trunk in a business gateway to an SS7
` trunk in a TGW.
`
`* A basic call with continuity test, from a "trunking gateway" to a
` "residential gateway".
`
`* A "hairpin" connection between two endpoints on a trunking gateway,
` using regular call set-up procedures.
`
`* A "hairpin" connection between two endpoints on a residential gate-
` way, using accelerated procedures.
`
`Huitema, Andreasen, Arango, Prakash [Page 4]
`
`Ex. 1023
`YMax Corporation
`Page 4 of 125
`
`

`
`
`Internet draft MGCP Call Flows 20 January 1999
`
`2.1. Connection from a TGW to another TGW
`
`The figure below gives the flow that results in a connection between two
`trunking gateways.
`
` ______________________________________
` | sw1| SG1| TGW1| CA | TGW2| SG2|
` |____|_____|______|______|______|_____|
` | IAM| -> | | | | |
` | | IAM| - - | -> | | |
` | | | <- | CRCX| | |
` | | | ACK | -> | | |
` | | | | CRCX| -> | |
` | | | | <-| ACK | |
` | | | | IAM | - - | -> |
` | | | | | | IAM|
` | | | | | | <-|
` | | | | <-| - - | ACM|
` | | | <- | ACM | | |
` | <-| - -| ACM | | | |
` | | ...| | | | |
` | | | | | | <-|
` | | | | <-| - - | ACM|
` | | | <- | MDCX| | |
` | | | ACK | -> | | |
` | | <-| - - | ANM | | |
` | <-| ANM| | | | |
` | REL| -> | | | | |
` | | REL| - - | -> | | |
` | | | <- | DLCX| | |
` | | | Perf| -> | | |
` | | | data| | | |
` | | <-| - - | RLC | | |
` | <-| RLC| | | | |
` | | | | DLCX| -> | |
` | | | | <-| Perf| |
` | | | | | data| |
` | | | | REL | - - | -> |
` | | | | | | REL|
` | | | | | | <-|
` | | | | <-| - - | RLC|
` |____|_____|______|______|______|_____|
`
`During these exchanges the MGCP is used by the Call Agent to control the
`two endpoints located on the two TGW.
`
`The exchanges start with the arrival from the first switch (SW1) of an
`
`Huitema, Andreasen, Arango, Prakash [Page 5]
`
`Ex. 1023
`YMax Corporation
`Page 5 of 125
`
`

`
`
`Internet draft MGCP Call Flows 20 January 1999
`
`SS7/ISUP "IAM" message, relayed by the signalling gateway to the Call
`Agent. The call agent performs the routing, and determines that the
`call will have to be relayed towards the second switch (SW2), using a
`trunk located on TGW2.
`
`The call agent starts the exchange by seizing the endpoint referenced in
`the IAM message:
`
` CRCX 1204 trunk-group-1/17@tgw1.whatever.net MGCP 0.1
` C: A3C47F21456789F0
` L: p:10, a:G.711
` M: recvonly
`
`Upon reception of that command, the trunking gateway prepares a connec-
`tion description.
`
` 200 1204 OK
` I:FDE234C8
`
` v=0
` c=IN IP4 128.96.41.1
` m=audio 3456 RTP/AVP 0
`
`The call agent, upon reception of this acknowledgement, sends a connec-
`tion request to the trunking gateway, asking the gateway to reserve a
`trunk in the group connected to the second switch:
`
` CRCX 1205 trunk-group-2/$@tgw2.whatever.net MGCP 0.1
` C: A3C47F21456789F0
` M: sendrecv
`
` v=0
` c=IN IP4 128.96.41.1
` m=audio 3456 RTP/AVP 0
`
`The call agent selects a trunk in the group, and acknowledges the crea-
`tion:
`
` 200 1204 OK
` I:abc0
`
` v=0
` c=IN IP4 128.96.63.25
` m=audio 1296 RTP/AVP 0
`
`Huitema, Andreasen, Arango, Prakash [Page 6]
`
`Ex. 1023
`YMax Corporation
`Page 6 of 125
`
`

`
`
`Internet draft MGCP Call Flows 20 January 1999
`
`The two commands have created a one way path, suitable for forwarding
`ring tones and announcements to the calling party. The call agent can
`now relay the call by sending an IAM message to the second switch. When
`the ACM is received, it is immediately relayed to the first switch.
`
`After some time, the call is answered, and an ANM message is relayed
`from the second switch to the call agent. The call agent will first
`validate the call by asking the first end-point to place the connection
`in duplex mode:
`
` MDCX 1206 trunk-group-1/17@tgw1.whatever.net MGCP 0.1
` C: A3C47F21456789F0
` I:FDE234C8
` M: sendrecv
`
` v=0
` c=IN IP4 128.96.63.25
` m=audio 1296 RTP/AVP 0
`
`The trunking gateway executes and acknowledges the modification:
`
` 200 1206 OK
`
` The call agent can now relay the ANM message to the calling
` switch, and both parties can talk.
`
` At the end of the call, in our example, the calling party hangs
` up. The first switch sends a release message to the call agent,
` through the signalling gateway. The call agent releases the
` connection on the first endpoint:
`
` DLCX 1207 trunk-group-1/17@tgw1.whatever.net MGCP 0.1
` C: A3C47F21456789F0
` I:FDE234C8
`
` The gateway acknowledges the deletion, sending the connection
` parameters:
`
` 250 1217 OK
` P: PS=1245, OS=62345, PR=780, OR=45123, PL=10, JI=27,LA=48
`
` The call agent can now confirm the release of the trunk, sending
` an RLC message to the first switch.
`
` In parallel, the call agent releases the connection to the
` second endpoint:
`
`Huitema, Andreasen, Arango, Prakash [Page 7]
`
`Ex. 1023
`YMax Corporation
`Page 7 of 125
`
`

`
`
`Internet draft MGCP Call Flows 20 January 1999
`
` DLCX 1208 trunk-group-2/13@tgw2.whatever.net MGCP 0.1
` C: A3C47F21456789F0
` I:abc0
`
` The gateway acknowledges the deletion, sending the connection
` parameters:
`
` 250 1218 OK
` P: PS=790, OS=45700, PR=1230, OR=61875, PL=15, JI=27,LA=48
`
` After receiving the acknowledgement, the call agent can relay
` the release message to the second switch. The switch will in
` turn acknowledge the release.
`
`Huitema, Andreasen, Arango, Prakash [Page 8]
`
`Ex. 1023
`YMax Corporation
`Page 8 of 125
`
`

`
`
`Internet draft MGCP Call Flows 20 January 1999
`
` 2.2. Basic call, RGW to TGW
`
` ______________________________________________________________________
` | Usr | RGW | CA | CDB| ACC| TGW | SS7/| CO |
` | | | | | | | ISUP| |
` |_______|__________|______________|_____|_____|__________|______|_____|
` | | <- | RQNT | | | | | |
` | | Ack | -> | | | | | |
` | Off | | | | | | | |
` | -hook | (local | | | | | | |
` | (Dial | action) | | | | | | |
` | -tone)| | | | | | | |
` | Digits| Notify | -> | | | | | |
` | | <- | Ack | | | | | |
` | (pro- | <- | CRCX+RQNT | | | | | |
` | gress)| Ack | -> | | | | | |
` | | | Query | | | | | |
` | | | (E.164 S,D) | -> | | | | |
` | | | <- | IP | | | | |
` | | | CRCX | - -| - -| -> | | |
` | | | | | | (cut in)| | |
` | | | <- | - -| - -| ack | | |
` | | | IAM | - -| - -| - - | -> | |
` | | <- | MDCX | | | | IAM | -> |
` | | Ack | -> | | | | <- | ACM|
` | | | <- | - -| - -| - - | ACM | |
` | | <- | Notification| | | | | |
` | | | Request | | | | | |
` | | Ack | -> | | | | | |
` | | | | | | | <- | ANM|
` | | | <- | - -| - -| - - | ANM | |
` | | <- | MDCX+RQNT | | | | | |
` | | Ack | -> | | | | | |
` | | (cut in)| Call start | - -| -> | | | |
` |_______|__________|______________|_____|_____|__________|______|_____|
`
`Huitema, Andreasen, Arango, Prakash [Page 9]
`
`Ex. 1023
`YMax Corporation
`Page 9 of 125
`
`

`
`
`Internet draft MGCP Call Flows 20 January 1999
`
` __________________________________________________________________
` | Usr | RGW | CA | CDB| ACC| TGW | SS7/| CO |
` | | | | | | | ISUP| |
` |________|________|______________|_____|_____|_______|______|_____|
` | | | | | | | <- | REL|
` | | | <- | - -| - -| - - | REL | |
` | | <- | Delete | | | | | |
` | | | Connection | | | | | |
` | | | Delete | | | | | |
` | | | Connection | - -| - -| -> | | |
` | | Perf | | | | | | |
` | | Data | -> | | | | | |
` | | | <- | - -| - -| perf | | |
` | | | | | | data | | |
` | | | Call end | - -| -> | | | |
` | On-hook| Notify| -> | | | | | |
` | | <- | Ack | | | | | |
` | | <- | Notification| | | | | |
` | | | Request | | | | | |
` | | Ack | -> | | | | | |
` |________|________|______________|_____|_____|_______|______|_____|
`
` During these exchanges the MGCP is used by the Call Agent to
` control both the TGW and the residential gateway. The exchanges
` occur on two sides.
`
` The first command is a NotificationRequest, sent by the Call
` Agent to the residential gateway. The request will consist of
` the following lines:
`
` RQNT 1201 endpoint/1@rgw-2567.whatever.net MGCP 0.1
` N: ca@ca1.whatever.net:5678
` X: 0123456789AC
` R: hd(E(dl;hu, D/[0-9#*T](D);)
` D: (0T|00T|[1-7]xxx|8xxxxxxx|#xxxxxxx|*xx|91xxxxxxxxxx|9011x.T)
` S:
`
` That transaction illustrates the power of the "embedded" action.
` The gateway is instructed to look for an off-hook event, and,
` upon its detection, to provide a dial-tone and to start looking
` for DTMF digits. The gateway immediately acknowledges the com-
` mand, repeating in the acknowledgement message the transaction
` id that the Call Agent attached to the query.
`
` 200 1201 OK
`
`Huitema, Andreasen, Arango, Prakash [Page 10]
`
`Ex. 1023
`YMax Corporation
`Page 10 of 125
`
`

`
`
`Internet draft MGCP Call Flows 20 January 1999
`
` When the off hook event is noticed, the gateway provides the
` dial tone to the line (the delay between off-hook and dialtone
` is thus minimal.)
`
` The gateway will start accumulating digits according to that
` digit map. When it has noticed a sufficient set of values, it
` will notify the observed string to the Call Agent:
`
` NTFY 2002 endpoint/1@rgw-2567.whatever.net MGCP 0.1
` N: ca@ca1.whatever.net:5678
` X: 0123456789AC
` O: 912018294266
`
` The Call Agent immediately acknowledges that notification.
`
` 200 2002 OK
`
` The Call Agent will then seize the incoming circuit, creating a
` connection. The create connection commands piggybacks a notifi-
` cation request, to stop collecting digits yet continue watch for
` an on-hook transition:
`
` CRCX 1204 endpoint/1@rgw-2567.whatever.net MGCP 0.1
` C: A3C47F21456789F0
` L: p:10, a:G.711;G.726-32
` M: recvonly
` X: D/0123456789AD
` R: hu
` S:
`
` We should note at this point that the call agent could send
` the acknowledgement of the Notify and the CRCX in a single
` UDP packet, as explained in the "piggy backing" section of
` [1]. There are many possible groupings of that nature in
` the various examples.
`
` The gateway immediately acknowledges the creation, sending back
` the identification of the newly created connection and the ses-
` sion description used to receive audio data:
`
` 200 1204 OK
` I:FDE234C8
`
` v=0
` c=IN IP4 128.96.41.1
`
`Huitema, Andreasen, Arango, Prakash [Page 11]
`
`Ex. 1023
`YMax Corporation
`Page 11 of 125
`
`

`
`
`Internet draft MGCP Call Flows 20 January 1999
`
` m=audio 3456 RTP/AVP 0 96
` a=rtpmap:96 G726-32/8000
`
` The SDP announcement, in our example, specifies the address at
` which the gateway is ready to receive audio data (128.96.41.1),
` the transport protocol (RTP), the RTP port (3456) and the audio
` profile (AVP). The audio profile refers to RFC 1890, which
` defines that the payload type 0 has been assigned for G.711
` transmission. The gateway is also ready to use ADPCM encoding at
` 32 kbps (G.726 -4). There is no standard payload type associated
` to ADPCM, so the gateway mentions its readiness to use a non
` standard payload associated to the dynamic type 96. The "rtpmap"
` attribute entry associates the payload type 96 to G726-32/4.
`
` The Call Agent, having seized the incoming trunk and completed a
` routing look up to identify the outgoing gateway, must now seize
` the outgoing trunk. It does so by sending a connection command
` to the e-gress gateway:
`
` CRCX 1205 card23/21@trgw-7.whatever.net MGCP 0.1
` C: A3C47F21456789F0
` L: p:10, a:G.711;G.726-32
` M: sendrecv
`
` v=0
` c=IN IP4 128.96.41.1
` m=audio 3456 RTP/AVP 0 96
` a=rtpmap:96 G726-32/8000
`
` The CreateConnection command has the same parameters as the com-
` mand sent to the ingress gateway, with two differences:
`
` * The EndpointId points towards the outgoing trunk,
`
` * The message carries the session description returned by the
` ingress gateway,
`
` * Because the session description is present, the "mode"
` parameter is set to "send/receive".
`
` We observe that the call identifier is identical for the two
` connections. This is normal: the two connections belong to the
` same call, which has a global identifier in our system.
`
` The trunking gateway will acknowledge the connection command,
` sending in the session description its own parameters such as
`
`Huitema, Andreasen, Arango, Prakash [Page 12]
`
`Ex. 1023
`YMax Corporation
`Page 12 of 125
`
`

`
`
`Internet draft MGCP Call Flows 20 January 1999
`
` address, ports and RTP profile:
`
` 200 1205 OK
` I:32F345E2
`
` v=0
` c=IN IP4 128.96.63.25
` m=audio 1296 RTP/AVP 0 96
` a=rtpmap:96 G726-32/8000
`
` The Call Agent will relay the information to the ingress gate-
` way, using a ModifyConnection command:
`
` MDCX 1206 endpoint/1@rgw-2567.whatever.net MGCP 0.1
` C: A3C47F21456789F0
` I:FDE234C8
` M: recvonly
`
` v=0
` c=IN IP4 128.96.63.25
` m=audio 1296 RTP/AVP 0 96
` a=rtpmap:96 G726-32/8000
`
` The residential gateway immediately acknowledges the modifica-
` tion:
`
` 200 1206 OK
`
` At this stage, the Call Agent has established a half duplex
` transmission path. The phone attached to the residential gateway
` will be able to receive the signals, such as tones or announce-
` ments, that the remote switch may send through the trunking
` gateway.
`
` When the call progresses, the Call Agent will receive from the
` remote switch progress messages, for example an "address com-
` plete" message (ACM). The Call Agent will analyze the message to
` determine whether signal are transmitted in band. If this is not
` the case, the Call Agent will instruct the RGW to generate ring-
` ing tones by sending a NotificationRequest:
`
` RQNT 1207 endpoint/1@rgw-2567.whatever.net MGCP 0.1
` X: 0123456789AE
` R: hu
` S: v
`
`Huitema, Andreasen, Arango, Prakash [Page 13]
`
`Ex. 1023
`YMax Corporation
`Page 13 of 125
`
`

`
`
`Internet draft MGCP Call Flows 20 January 1999
`
` The gateway immediately acknowledges the command:
`
` 200 1207 OK
`
` After the called user answers the call, the Call Agent will
` receive an answering message (ANM) from the CO switch. At that
` point, it will send a ModifyConnection command, to the residen-
` tial gateway, to place the connection in full duplex mode. The
` command embeds NotificationRequest to stop the ringing tones.
`
` MDCX 1209 endpoint/1@rgw-2567.whatever.net MGCP 0.1
` C: A3C47F21456789F0
` I:FDE234C8
` M: sendrecv
` X: 0123456789AF
` R: hu
` S:
`
` The residential gateway will acknowledge this command:
`
` 200 1209 OK
`
` At this point, the connection is established.
`
` When the Call Agent receives the REL message from the CO switch,
` it will have to tear down the call. It will do so by sending to
` both gateways a DeleteConnection command:
`
` DLCX 1210 endpoint/1@rgw-2567.whatever.net MGCP 0.1
` C: A3C47F21456789F0
` I:FDE234C8
`
` DLCX 1211 card23/21@trgw-7.whatever.net MGCP 0.1
` C: A3C47F21456789F0
` I:32F345E2
`
` The gateways will respond with acknowledgements that should
` include a "call parameters" header fields:
`
` 250 1210 OK
` P: PS=1245, OS=62345, PR=780, OR=45123, PL=10, JI=27,LA=48
`
` 250 1211 OK
` P: PS=790, OS=45700, PR=1230, OR=61875, PL=15, JI=27,LA=48
`
`Huitema, Andreasen, Arango, Prakash [Page 14]
`
`Ex. 1023
`YMax Corporation
`Page 14 of 125
`
`

`
`
`Internet draft MGCP Call Flows 20 January 1999
`
` At this point, the phone attached to the residential gateway, in
` our scenario, goes on-hook. This event is notified to the Call
` Agent, according to the policy received in the last Notifica-
` tionRequest by sending a Notify command:
`
` NTFY 2005 endpoint/1@rgw-2567.whatever.net MGCP 0.1
` X: 0123456789AF
` O: hu
`
` After this notification, the Call Agent should send an ack-
` nowledgement:
`
` 200 2005 OK
`
` It should then issue a new NotificationRequest, to be ready to
` receive the next off-hook detected by the residential gateway:
`
` RQNT 1212 endpoint/1@rgw-2567.whatever.net MGCP 0.1
` X: 0123456789B0
` R: hd(E(dl;hu, [0-9#*T](D);)
` D: (0T|00T|[1-7]xxx|8xxxxxxx|#xxxxxxx|*xx|91xxxxxxxxxx|9011x.T)
` S:
`
` The gateway will acknowledge this message:
`
` 200 1212 OK
`
` Both gateways, at this point, are ready for the next call.
`
`Huitema, Andreasen, Arango, Prakash [Page 15]
`
`Ex. 1023
`YMax Corporation
`Page 15 of 125
`
`

`
`
`Internet draft MGCP Call Flows 20 January 1999
`
` 2.3. Basic call, TGW to RGW
`
` ___________________________________________________________________
` | CO | SS7/| TGW | CA | CDB| ACC| RGW | Usr |
` | | ISUP| | | | | | |
` |____|______|__________|_______________|_____|_____|________|______|
` | IAM| -> | | | | | | |
` | | IAM | - - | -> | | | | |
` | | | | Check | -> | | | |
` | | | | <- | IP | | | |
` | | | <- | Create | | | | |
` | | | | Connection | | | | |
` | | | Ack | -> | | | | |
` | | | | Create | | | | |
` | | | | Connection | - -| - -| -> | |
` | | | | <- | - -| - -| Ack | |
` | | | <- | Modify | | | | |
` | | | | Connection | | | | |
` | | | Ack | -> | | | | |
` | | | | Notification | | | | |
` | | | | Request | - -| - -| -> | ring|
` | | | | <- | - -| - -| Ack | |
` | | <- | - - | ACM | | | | |
` | <- | ACM | | | | | | |
` | | | | | | | | off |
` | | | | | | | | hook|
` | | | | <- | - -| - -| Notify| |
` | | | | Ack | - -| - -| -> | |
` | | | | Notification | | | | |
` | | | | Request | - -| - -| -> | |
` | | | | <- | - -| - -| Ack | |
` | | | <- | Modify | | | | |
` | | | | Connection | | | | |
` | | | Ack | -> | | | | |
` | | | (cut-in)| Call start | - -| -> | | |
` | | <- | - - | ANM | | | | |
` | <- | ANM | | | | | | |
` |____|______|__________|_______________|_____|_____|________|______|
`
`Huitema, Andreasen, Arango, Prakash [Page 16]
`
`Ex. 1023
`YMax Corporation
`Page 16 of 125
`
`

`
`
`Internet draft MGCP Call Flows 20 January 1999
`
` _____________________________________________________________
` | CO| SS7/| TGW | CA | CDB| ACC| RGW | Usr |
` | | ISUP| | | | | | |
` |___|______|______|______________|_____|_____|________|______|
` | | | | | | | | on |
` | | | | | | | | hook|
` | | | | <- | - -| - -| Notify| |
` | | | | Ack | - -| - -| -> | |
` | | | | Delete | | | | |
` | | | | Connection | - -| - -| -> | |
` | | | <- | Delete | | | | |
` | | | | Connection | | | | |
` | | <- | - - | REL | | | | |
` | <-| REL | | | | | | |
` | | | Perf| | | | | |
` | | | data| -> | | | | |
` | | | | <- | - -| - -| perf | |
` | | | | | | | data | |
` | | | | Call end | - -| -> | | |
` | | | | Notification| | | | |
` | | | | Request | - -| - -| -> | |
` | | | | <- | - -| - -| Ack | |
` |___|______|______|______________|_____|_____|________|______|
`
` This diagram shows the various exchange of messages during a
` call from a telephone user on the circuit-switched PSTN to a
` residential user connected to a residential gateway. During
` these exchanges the Call Agent uses MGCP to control both the TGW
` and the residential gateway. The exchanges occur on two sides.
`
` Upon reception of the IAM message, the Call Agent immediately
` sends a CreateConnection request to the trunking gateway to con-
` nect to the incoming trunk, creating a connection:
`
` CRCX 1237 card23/21@trgw-7.whatever.net MGCP 0.1
` C: A3C47F21456789F0
` L: p:10, a:G.711;G.726-32
` M: recvonly
`
` The trunking gateway immediately acknowledges the creation,
` sending back the identification of the newly created connection
` and the session description used to receive audio data:
`
` 200 1237 OK
`
`Huitema, Andreasen, Arango, Prakash [Page 17]
`
`Ex. 1023
`YMax Corporation
`Page 17 of 125
`
`

`
`
`Internet draft MGCP Call Flows 20 January 1999
`
` I: FDE234C8
`
` v=0
` c=IN IP4 128.96.41.1
` m=audio 3456 RTP/AVP 0 96
` a=rtpmap:96 G726-32/8000
`
` The SDP announcement, in our example, specifies the address at
` which the gateway is ready to receive audio data (128.96.41.1),
` the transport protocol (RTP), the RTP port (3456) and the audio
` pro