1. VOIP Introduction -MGCP
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Topics
Topics
VOIP Introduction
MSAN VOIP module introduction
Basic Voip Service Provision
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What is MGCP “
Media Gateway Control Protocol - A protocol for controlling media gateways from external call control elements called media gateway controllers or call agents. ”
IETF RFC 3435 Media Gateway Control Protocol
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What is MGC and MG
Media Gateway Controller (MGC):
Central point of intelligence for call signaling
Maintains the state of each MG and responds appropriately to any event notification
Media Gateway (MG):
Provides translations between circuit switched networks and packet switched networks
Sends notification to the call agent about endpoint events
Execute commands from the call agents
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5. Soft Switch Architecture-MGC, MG
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6. VOIP Network Architecture
SS7 Network
Internet
SCP
Signaling
(SS7)
Gateway
MGCP/ MEGACO
SIGTRAN
Call
Agent
STP
MGCP/ MEGACO
Trunking
Gateway
Residential
Gateway
Trunking
Gateway
Residential
Gateway CO
Switch
Trunking
Gateway
Residential
Gateway
RTP
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7. MGCP in the protocol stack
Call Control and Signaling
Signaling and
Gateway Control
Media
Audio/
Video
H.323
H.225
H.245
Q.931
RAS
SIP
MGCP/Megaco
RTP
RTCP
RTSP
TCP
UDP IP
MGCP UDP port could be 2427 or 2727
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8. Protocol Evolution Megaco/H.248 MGCP MDCP IETF RFC 3015/3525
MGCP proposal by merging IPDC and SGCP
IPDC
MGCP
RFC 2705/3435
SGCP
Lucent submits MDCP
to ITU-T SG16
(Nov 1999)
MDCP
(proposal)
Consensus between IETF and ITU on Megaco Protocol
(March 99)
IETF
RFC 3015/3525
Megaco/H.248
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Characteristics
A master/slave protocol.
Assumes limited intelligence at the edge (endpoints) and intelligence at the core (call agent).
Used between call agents and media gateways.
Differs from SIP and H.323 which are peer-to-peer protocols.
Text encoding
Use ASCII.
Use SDP to describe the media
SDP Session Description Protocol RFC2327
Description of connection parameters such as IP addresses, UDP port and RTP profiles
Packages define extensions
Modular and extensible protocol, achieved by the concept of packages
Many defined in RFC3660, e.g. Line package (L),DTMF package (D)
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The MGCP Model
Endpoints
Sources or sinks of media
Trunk interfaces
POTS line interfaces
Announcement endpoint
Connections
Allocation of IP resources to an endpoint
An ad hoc relationship is established from a circuited-switched line and an RTP port on the IP side.
A single endpoint can have several connections
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Function of MGCP
The primary function of MGCP is to enable
The connections to be created
The session descriptions to be exchanged between the connections
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Example MGCP Message
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13. MGCP key point--Endpoint Identifier (1)
Domain Name + Local Name
Local Name
A hierarchical form: X/Y/Z
e.g. To identify DS0 number 7 within DS1 number 12 on DS3 number 4 at gateway.somenetwork.net
Plain form: xxx
e.g.
Wild-cards
$, any;
e.g., CA wants to create a connection on an endpoint in a gateway and does not really care which endpoint is used.
*, all;
e.g., MG uses this format to register.
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14. MGCP key point--MGCP Commands (2)
All commands are acknowledged.
Call Agent Commands:
EndpointConfiguration(EPCF)
NotificationRequest(RQNT)
CreateConnection(CRCX)
ModifyConnection(MDCX)
DeleteConnection(DLCX)
AuditEndpoint(AUEP)
AuditConnection(AUCX)
Gateway Commands:
Notify(NTFY)
DeleteConnection(DLCX)
RestartInProgress(RSIP)
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15. MGCP key point--MGCP Packages (3)
Group events and signals into packages
Generic Media (G)
DTMF (D)
MF (M)
Trunk (T)
Line (L)
Handset (H)
RTP (R)
Network Access Server (N)
Announcement Server (A)
The experimental packages have names beginning with the two character “x-”.
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
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16. MGCP key point– Registration (4)
Use RSIP command
Restart Method:
-Forced
-Restart
-Disconnected
-Graceful
-Cancel-graceful
Three levels of register in the system
- System level
- Endpoint level
- Board level
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17. Register (typical system register )
MGC MG
(2) 200 OK
(1) RSIP
(*, RM:restart)
(3) AUEP
(0, F:A)
(4) 200 OK
Reply with capability
(5) RQNT
(*, R:L/hd)
(6) 200 OK
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18. Register (single endpoint register )
MGC MG
(2) 200 OK
(1) RSIP
(249, RM:Forced)
(4) 200 OK
(3) RSIP
(249, RM:Restart)
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19. Register ( typical re-establish)
MGC MG
(2) 200 OK
(1) RSIP
(*, RM:Disconnected)
(3) DLCX
(*)
(4) 250 OK
(5) RQNT
(*, R:L/hd)
(6) 200 OK
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20. MGCP key point– Heartbeat (5)
Method to detect communication between MG and MGC
Two types
- MGC control heartbeat
- MG control heartbeat
- Two types are independent
Implement on MG side
- Create a timer when system first register done, timer length is
configurable
- In the interval of the timer, if there are messages between MG and MGC,
do nothing but restart the timer
- If no messages have been exchanged, MG sends the heartbeat message
- If no response to the heartbeat after time out, MG will try to register again
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Heartbeat messages
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22. MGCP key point-- Digit Map (6)
CA ask GW to collect user dialed digits
- Created by CA
Usage
- Gateways detect a set of digits.
e.g., (11x|080xxxxxx|03xxxxxxx|002x.T)
Request event:R:L/hu(N),D/[0-9#*ABCDT](D),L/oc(N)
- 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
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23. Basic call flow example--establish
MGC
MG2
(6) CRCX
(L:G729,p:10-30,m:inactive)
(7) 200 OK
(L:G729,p:20)
MG1
(1) NTFY
(O:hd)
(2) RQNT
(R:hu,hf)
(3) RQNT
(S:l/dl,R:hu,hf,D:digitMap)
(4) NTFY
(O:dialed No.)
(5) RQNT
(8) CRCX
(L:G729,p:20,m:inactive)
(9) 200 OK
(10) MDCX
(11) 200 OK
(12) RQNT
(R:hd,S:rg,ci)
(14) NTFY
(16) RQNT
(17) MDCX
(m:sndRcv)
(18) MDCX
(13) RQNT
(R:hu,hf, S:rt)
(15) RQNT
(R:hu,hf, S:)
Caller
Off hook
Dial Num
Callee off hook
In conversation
Stop tone
Callee ring
Ring back tone
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24. Basic call flow example-- disconnect
MGC
MG2
MG1
In conversation
(1) NTFY
(O:hu)
(2) DLCX
(R:hd)
(3) DLCX
(R:hu,hf, S:cg)
(4) NTFY
(5) RQNT
On hook
Congestion tone
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25. Basic call flow example-- Call waiting
MGC
MG3
MG1
MG1&MG2 already In conversation
(1) NTFY
(O:hd)
(2) RQNT
(S:dl,D:Digitmap)
(6) RQNT
(S:L/wt,ci:MG3)
Call waiting tone
Off hook
Dial tone
(3) NTFY
(O:Dialed MG1)
(4) CRCX
(L:G729,p:20,m:rcvonly)
(5) 200 OK
(7) MDCX
(8) 200 OK
(9) NTFY
(O:L/hf)
Flash hook
(10) MDCX
(L:G729,p:20,m:sndrcv)
(12) 200 OK
(11) MDCX
(13) 200 OK
MG1&MG3 In conversation
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26. Basic call example--Three way call
MGC
MG1
(1) NTFY
(O:hf)
Flash hook
MG1 & MG3 In conversation
MG2
MG3
MG1&MG2 already In conversation
(2) RQNT
(S:dl,R:Digitmap)
(5) CRCX
(O:MG3 numbers)
(3) MDCX
(Announcement address)
MG2 hear announcement
MG3 numbers
(L:G729,p:20)
(4) NTFY
(6) 200 OK
(7) RQNT
(S:L/rg,ci)
MG3 rings
(9) NTFY
(O:hd)
MG3 off hook
(10) MDCX
(m:sndrcv,MG1 SDP )
(11) MDCX
(m:sndrcv,MG3 SDP )
(8) RQNT
(S:g/rt)
Ring back
(12) NTFY
(14) RQNT
(13) MDCX
MG3 hear announcement
Press 3
Dial tone
(15) NTFY
(O:3)
(16) MDCX
(Media server for bridge SDP)
(18) MDCX
(17) MDCX
MG1 & MG2 & MG3 In conversation
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27. UTStarcom Confidential
Topics
Topics
VOIP Introduction
MSAN VOIP Module Introduction
Basic Voip Service Provision
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28. UTStarcom Confidential
VOIP module--SCM4
Functions of SCM4:
Provide control function
Provide whole node management
Provide configuration functions
Manages all POTS ports, DSP channels and the relevant timeslot resources
Traces the status of each POTS port and DSP channel
Connects with MGA (Media Gateway Application) for call control
Communicates with VPM to for enhanced establishment of time slots and DSP channels
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VOIP module-- VPM
VPM (Voice Processing Module), implementing the VoIP function.
Provide TDM-to-IP conversation
120 channel VPM capacity (with minimum RTP payload size of 20ms)
A-Law to/from U-law conversion
G.711,G.723, G.726, G.729AB voice coding
Provide call progress tones
Voice Activity Detection (VAD)
Jitter buffer management
Echo cancellation management
DTMF tone detection or generation
RFC 1889 RTP/RTCP
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30. Relationship to Other Software
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VOIP module-- IVD
Provide ATM to IP conversation
Supports 24 FXS ports, 24 ADSL ports, and 24 splitter ports
Provides one or two Ethernet uplink interfaces
IP-based ADSL, supporting ADSL2/ADSL2+. (IMA and ATM are optional).
Providing an SNMP interface to SCM4
Supports FXS and enables V5 or VoIP-based applications
Supports loop-testing (including POTS and ADSL)
Controlled by the SCM4 (System Control Module of the iAN-8000).
Hot swappable
Fault management and alarm/event notifications
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Function description
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33. Software module decomposition
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IVD Management
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Managed message flow
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36. Message exchange between IVD and SCM4
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37. UTStarcom Confidential
Service Flow
TDM bus
ADSL Modem
ADSL2+
FE/GE Bus
FXS
Splitter E1
VPM
4Khz, after split
iAN-8000
ICM
Internet
V5.2 SW or
mSwitch TG
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38. UTStarcom Confidential
Topics
Topics
VOIP Introduction
MSAN VOIP module introduction
Basic Voip Service Provision
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39. Provision in MSAN—Domain name
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40. Provision in MSAN—call server
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41. Provision in MSAN—User Class
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42. Provision in MSAN—Logical ID
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Provision in MSAN—vpm
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44. Provision in MSAN—Country Profile
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45. Provision in MSAN—Voip Status&port number
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46. Provision in MSAN—MGC authentication
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47. Provision in MSAN—Codec profile
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48. UTStarcom Confidential
Thanks
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