mgcp and where/how we use it in osmocom file14/05/18 (c) 2017 sysmocom gmbh 1 mgcp and where/how we...
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14/05/18 (c) 2017 sysmocom GmbH 1
MGCPand where/how we use it in Osmocom
Philipp Maier <pmaier@sysmocom.de>
14/05/18 (c) 2017 sysmocom GmbH 2
Agenda
➔ The MGCP Protocol➔ Practical Applications
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MGCP: History➔ MGCP = Media Gateway Control Protocol➔ Successor:
– SGCP = Simple Gateway Control Protocol
(Deveoloped by Bellcore + Cisco)– IPDC = Internet protocol Device control
(Developed by Level 3 Communications)➔ ITEF Standard since January 2003
(RFC 3435 by F. Andreasen, B. Foster, Cisco Systems)➔ MGCP also includes SDP = Session description Protocol
(M. Handley, V. Jacobson, ISI/LBNL, April 1998, RFC 2327) https://tools.ietf.org/html/rfc2327https://tools.ietf.org/html/rfc3435
(Source: Wikipedia, Richardson Public Library local history archives)
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MGCP: Protocol Introduction➔ Intended use:
– Switching of RTP connections– Media conversion– Trascoding
➔ Text based messages (ASCII)➔ Request / Response oriented➔ Fixed roles: Client / Server➔ Runs on UDP Port 2427
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MGCP: Command verbs EPCF = EndpointConfiguration
CRCX = CreateConnection
MDCX = ModifyConnection
DLCX = DeleteConnection
RQNT = NotificationRequest
NTFY = Notify
AUEP = AuditEndpoint
AUCX = AuditConnection
RSIP = RestartInProgres
EPCF = EndpointConfiguration
CRCX = CreateConnection
MDCX = ModifyConnection
DLCX = DeleteConnection
RQNT = NotificationRequest
NTFY = Notify
AUEP = AuditEndpoint
AUCX = AuditConnection
RSIP = RestartInProgres
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MGCP: Endpoints and connectionsEndpoint #1 (rtpbridge/1@mgw.osmocom.org)
Connection #1
Connection #2
Media gateways are organized in endpoints and connections
RTP
RTP
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MGCP: Request Example
➔ Create a connection on eindpoint on trunk “rtpbridge”, endpoint 0
➔ CallId is 2➔ Codec is AMR, Packet interval 20ms➔ Bidirectional connection➔ I am (local) listening on: 127.0.0.1:8000 for
incomingRTP voice data
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MGCP: Response Example
➔ Your request has been fullfilled➔ The connection identifier is:
3743261195238232C4C62FBA08D7BE92➔ I am (remote) listening on 127.0.0.1:4004 for
incoming RTP voice data
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A typical MGCP session
Make a connection, I do not know the IP/Port on my side yet...
Ok, I made the connection The IP/Port on my side is...
Update the connection I made, The port IP/Port on my side is...
Ok, I updated the connection, The IP/Port on my side is...Make another connection, IP/port on my side is...
Ok, I have created another connection, the IP/Port on my side is...
Delete all connections I made
Ok, I have deleted all your connections
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Agenda
➔ The MGCP Protocol➔ Practical Applications
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Separation of BTSs from the Core
BTS
BSC
MGW
Abis/RSLA
RTP RTP
UmAbis/RSL
➔ Each handover causes a changeof the RTP connection (IP/Port)
➔ The Core network expects a constantRTP connection (IP/Port)=> BTSs need to be separated from the core network
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Separation of BTSs from the Core
BTS
BSC
MGW
Abis/RSLA
RTP
RTPUm
Abis/RSL
➔ Each handover causes a changeof the RTP connection (IP/Port)
➔ The Core network expects a constantRTP connection (IP/Port)=> BTSs need to be separated from the core network
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MSC co-located MGW
MSC
MGW
A
osmo-sip-connector
MNCCSIP
RTP
RTP
➔ Osmo-msc requires a co-located MGW to provide local switching(internal mncc) or interfacing with an external PBX/VoIP network (external mncc)
➔ In the Future: osmo-mgw will provide transcoding to match on the external legs codec requirements.
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Also exotic topoplogies are thinkable
BTS
BSC-NAT
MGW(osmo-bsc_mgcp)
IPA-M
UX (SCCP-L
ITE)
RTPRTP
Um
Abis/RSLMSC
MGCPMGCP
BSC
RTP IPA-M
UX (SCCP-L
ITE+ M
GCP)
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MGCPand where/how we use it in Osmocom
Philipp Maier <pmaier@sysmocom.de>
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