MGCP and where/how we use it in Osmocom file14/05/18 (c) 2017 sysmocom GmbH 1 MGCP and where/how we...
15
14/05/18 (c) 2017 sysmocom GmbH 1 MGCP and where/how we use it in Osmocom Philipp Maier <[email protected]>
Transcript of MGCP and where/how we use it in Osmocom file14/05/18 (c) 2017 sysmocom GmbH 1 MGCP and where/how we...
14/05/18 (c) 2017 sysmocom GmbH 1
MGCPand where/how we use it in Osmocom
Philipp Maier <[email protected]>
14/05/18 (c) 2017 sysmocom GmbH 2
Agenda
➔ The MGCP Protocol➔ Practical Applications
14/05/18 (c) 2017 sysmocom GmbH 3
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)
14/05/18 (c) 2017 sysmocom GmbH 4
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
14/05/18 (c) 2017 sysmocom GmbH 5
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
14/05/18 (c) 2017 sysmocom GmbH 6
MGCP: Endpoints and connectionsEndpoint #1 (rtpbridge/[email protected])
Connection #1
Connection #2
Media gateways are organized in endpoints and connections
RTP
RTP
14/05/18 (c) 2017 sysmocom GmbH 7
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
14/05/18 (c) 2017 sysmocom GmbH 8
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
14/05/18 (c) 2017 sysmocom GmbH 9
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
14/05/18 (c) 2017 sysmocom GmbH 10
Agenda
➔ The MGCP Protocol➔ Practical Applications
14/05/18 (c) 2017 sysmocom GmbH 11
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
14/05/18 (c) 2017 sysmocom GmbH 12
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
14/05/18 (c) 2017 sysmocom GmbH 13
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.
14/05/18 (c) 2017 sysmocom GmbH 14
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)
14/05/18 (c) 2017 sysmocom GmbH 15
MGCPand where/how we use it in Osmocom
Philipp Maier <[email protected]>
