Media Gateway Control Protocol

1
Media Gateway Control Protocol

• Introduction
• Media gateway Control Interface
• Entity Naming (Endpoint, Call, Connection, CA)
• Digit Maps
• Events
• Commands
• Protocol Description
• Call Flow for RGW to TGW
• Usage of Commands

2
Introduction

• Components

SS7 Network
Internet
Signaling (SS7) Gateway
SCP
Call Agent
SIGTRAN
STP
MGCP
MGCP
Trunking Gateway
Residential Gateway
Trunking Gateway
Residential Gateway
CO Switch
Trunking Gateway
Residential Gateway
RTP
3
Introduction

• Types of Media Gateway
• Trunking Gateway to CO/Switches
• Residential Gateway to PSTN Phones
• Access Gateway
• Business Gateway
• Concept of Call Agent
• call control intelligent outside gateways
• master/slave
• undefined CA to CA maybe H.323, SIP

4
Introduction

• Relation with H.323 Standards

Internet
Signaling (SS7) Gateway
SS7/ISUP
SIGTRAN
Gatekeeper
CO Switch
Call Agent
H.225/RAS H.225/Q.931 H.245
Terminal or Gateway
MGCP
Trunking Gateway
RTP
5
H323, SIP MGCP

• H.323 , SIP
• peer-to-peer
• internet oriented
• intelligent endpoint
• optional GK
• decentralized
• Problems
• maintenance
• cost scalability of large systems
• signaling media control are coupled
• interoperability with SS7

• MGCP
• client-server
• traditional telephony
• intelligent server
• dumb terminal
• centralized
• Concept
• gateway decomposed
• separate call control from media ports
• CA, MG, SG
• interoperability with PSTN

6
Media gateway Control Interface

• Endpoints
• Types
• Digital Channel
• Analog line
• IVR endpoint
• Naming GWs Domain Name Local Name
• Local Name
• physical interface name / circuit number
• e.g., galant.ccl.itri.org.tw/X35V3A4/15
• Wild-carded
• e.g., galant.ccl.itri.org.tw/X35V3A4/
• e.g., galant.ccl.itri.org.tw/X35V3A4/

DS0 endpoint
(Channel)
Analog endpoint
(Connections)
(Line)
IVR endpoint
7
Media gateway Control Interface

• Calls Connections Call Agents
• Call Identifier (Call ID)
• Created by CA
• Unique in the Whole System
• Connection ID
• Created by GW
• Unique under Its GW
• Usage of a Connection ID on the same EP
• Waiting Period at least 3 minutes
• CA Identifier (its domain name)
• Redundant CAs reliability
• CA GW keep time-to-live record they read
  from DNS

8
Media gateway Control Interface

• Digit Map
• CA ask GW to collect user dialed digits
• Created by CA
• Sent to Gateways
• Usage
• Gateways detect digits, letters, or timer
• e.g., (11x080xxxxxx03xxxxxxx002x.T)
• Match accumulated digits
• under-qualified, do nothing further
• matched, send the collected digits to CA
• over-qualified, send the digits to CA

Inter-digit Timer
9
Media gateway Control Interface

• Events
• package name(o) / event name
• package
• Generic Media (G)
• DTMF (D)
• MF (M)
• Trunk (T)
• Line (L)
• Handset (H)
• RTP (R)
• Network Access Server (N)
• Announcement Server (A)
• Script

Gateway
Supported packages
Trunk GW (ISUP) Trunk GW (MF) Network Access
Server Combined NAS/VOIP GW Access GW
(VOIP) Access GW (VOIP NAS) Residential
GW Announcement GW
G, D, T, R G, M, D, T, R G, M, T, N G, M, D, T,
N, R G, M, D, R G, M, D, N, R G, D, L, R A, R
10
Media Gateway Control Interface

• Commands
• 9 commands to handle Connection/Endpoints
• EndpointConfiguration (coding charateristics)
• NotificationRequest (requested events)
• Notify (GW detected events)
• CreateConnection
• ModifyConnection
• DeleteConnection (GW also)
• AuditEndpoint (query status)
• AuditConnection (query status)
• RestartInProgress (GW taken in/out of service)
• All commands are acknowledged.

EPCF RQNT NTFY CRCX MDCX DLCX AUEP AUCX RSIP
11
Protocol Description

• Transactions (simple text format)
• command
• header
• a command line (case insensitive)
• Action TransId Endpoint Version
• RQNT 1201 endpoint/1_at_rgw.net MGCP 1.0
• a set of parameter lines
• parameter name (upper case) value
• X 0123456789B1 (RequestIdentifier)
• R hd (requestedEvent hang down)
• S rg (signalRequest ring tone)
• session description

12
Protocol Description

• Transactions
• response
• header
• a response line
• Response code TransId Commentary
• 200 1201 OK
• a set of parameter lines (optional)
• after CreateCX(/MDCX/DLCX/Audit/Restart)
• I A3C47F21456789F0 (ConnectionId)
• session description
• Session Description Protocol
• separated from header by an empty line

13
Call Flow for RGW to TGW
14
Call Flow for RGW to TGW
15
Call Flow for RGW to TGW

• RQNT(1) NotificationRequest
• RQNT 1201 hrd3/15_at_rgw.whatever.net MGCP 1.0
• N CA_at_ca.whatever.net5678
• X 0123456789AC
• R hd(E(R(hu(N)),S(dl),D/(D)))
• D (11x080xxxxxx57xxxxx002x.T)
• ACK to RQNT(1)
• 200 1201 OK

N NotifyEntity X RequestIdentifier R
RequestEvents D DigitMap
E Embedded(enable) Request R Notification
Request N Notify immediately S Signal
Request D Digit Map
16
Call Flow for RGW to TGW

• NTFY(2) Notify from RGW
• NTFY 2002 hrd3/15_at_rgw.whatever.net MGCP 1.0
• N CA_at_ca.whatever.net5678
• X 0123456789AC
• O 5721043
• ACK to NTFY(2)
• 200 2002 OK

N NotifyEntity X RequestIdentifier O
ObservedEvent
17
Call Flow for RGW to TGW

• CRCX(3) CreateConnection
• CRCX 1204 hrd3/15_at_rgw.whatever.net MGCP 1.0
• C A3C47F21456789F0
• L p10, a G.711 G.726-32
• M recvonly
• X 0123456789AD
• R hu
• ACK to CRCX(3)
• 200 1204 OK
• I FDE234C8
• Session Description

C CallId L LocalCXOptions p packetize
period(ms) a Compression Algo. M Mode X
RequestIdentifier R RequestEvents I ConnectionId
18
Call Flow for RGW to TGW

• CRCX(4) CreateConnection
• CRCX 1205 card6/5_at_tgw.whatever.net MGCP 1.0
• C A3C47F21456789F0
• L p10, a G.711 G.726-32
• M sendrecv
• Session Description from ACK(3)
• ACK to CRCX(4)
• 200 1205 OK
• I 32F345E2
• Session Description

C CallId M Mode I ConnectionId
19
Call Flow for RGW to TGW

• MDCX(5) ModifyConnection
• MDCX 1206 hrd3/15_at_rgw.whatever.net MGCP 1.0
• C A3C47F21456789F0
• I FDE234C8
• M recvonly
• Session Description from ACK(4)
• ACK to MDCX(5)
• 200 1206 OK

C CallId I ConnectionId M Mode
20
Call Flow for RGW to TGW

• RQNT(6) NotificationRequest
• RQNT 1207 hrd3/15_at_rgw.whatever.net MGCP 1.0
• N CA_at_ca.whatever.net5678
• X 012345789AE
• R hu
• S v (alerting)
• ACK to RQNT(6)
• 200 1207 OK

N NotifyEntity X RequestIdentifier R
RequestEvents S SignalRequests
21
Call Flow for RGW to TGW

• MDCX(7) ModifyConnection
• MDCX 1209 hrd3/15_at_rgw.whatever.net MGCP 1.0
• C A3C47F21456789F0
• I FDE234C8
• M sendrecv
• X 012345789AF
• R hu
• ACK to MDCX(7)
• 200 1209 OK

C CallId I ConnectionId M Mode
22
Call Flow for RGW to TGW

• DLCX(8) DeleteConnection
• DLCX 1210 hrd3/15_at_rgw.whatever.net MGCP 1.0
• C A3C47F21456789F0
• I FDE234C8
• ACK to DLCX(8)
• 200 1210 OK
• P PS1245, OS62345, PR780, OR45123, PL10,
  JI27, LA48

C CallId I ConnectionId
PS Packets sent OS Octets sent PR Packets
received OR Octets received PL Packets lost JI
Average Jitter (ms) LA Average Latency (ms)
23
Usage of Commands

• NotificationRequest()
• EndpointId,
• NotifiedEntity,
• RequestedEvents,
• RequestIdentifier,
• DigitMap,
• SignalRequests,
• QuarantineHandling,
• DetectEvents,
• encapsulated EndpointConfiguration

Request
Request
Notify
Time
Quarantine Period
Q
T
Q process/discard step/loop (notify) T
events to detect during quarantine
24
Usage of Commands

• CreateConnection()
• CallId,
• EndpointId,
• NotifiedEntity,
• LocalConnectionOptiona,
• Mode,
• RemoteConnectDescptrSecondEndpointId
• EncapsulatedNotificationRequest,
• encapsulated EndpointConfiguration

Hairpin Connection
25
Usage of Commands

• DeleteConnection()
• Delete one connection from Call Agent
• ConnectionId in the parameter line
• GW Connection parameters
• Multiple connection from Call agent
• only EndpontId (and CallId) in the parameter line
• GW No connection parameter
• From gateway
• Reason-Code Connection-Parameters in Command

26
MGCP Applications (1)

• IP Switch

IP Networks
Call Agent
27
MGCP Applications (2)

• IP PBX

IP Networks
Call Agent