Media Gateway Control Protocol (MGCP) PTCL Training & Development MGCP

Used between SoftSwitch and IAD(integrated access device)/AG (access gateway)/TMG (trunk media gateway)/UMG (universal media gateway) The Softswitch (MGC) Controls Media Gateways by means of MGCP is a signaling and call control protocol used within Voice over IP (VoIP) systems that typically interoperates with the public switched telephone network (PSTN)protocolVoice over IPpublic switched telephone network In essence MGCP is a Master (softswitch) and Slave(Media Gateways) Protocol MGCP uses SDP for media transporting Media Gateway Control Protocol (MGCP)

MGCP Call Flow Scenario SG SS RTP/UDP/IP phone LE TMG/UMG 1 TMG/UMG 2 SG: To establish call b/w PSTN & SS IAM ACM MDCX CRCX ACM CRCX RESP LEGENDS: IAM- Initial Address Message ACM- Address Completion Message CRCX- Create Connection MDCX – Modify connection (add video) RESP – Response to connection ANM = Answer Message Media Stream

MGCP Messages……. CommandDirection of Flow and Command itself Endpoint ConfigurationMGC to MG EPCX Create ConnectionMGC to MG CRCX Modify ConnectionMGC to MG MDCX Delete ConnectionMGC to MG DLCX Notification RequestMGC to MG RQNT NotifyMG to MGC NTFY Audit EndpointMGC to MG AUEP Audit connectionMGC to MG AUCX Restart In ProgressMG to MGC RSIP

OFF Hook ACM ANM IP NEWTORK RESP MDCX OFF hook Ringing IAM MGCP CRCX MGCP IAM ACM ANM CRCX RESP Phone MG2LEX1MGCMG1 Phone LEX2MGC

MEGACO was designed after some limitations in MGCP like MGCP could handle low density ITU-T developed MDCP whereas IETF had developed MGCP A compromise between the two originated in the form of MEGACO- Protocol or MEGACOP ITU-T (SG-16) also developed H.248 in parallel to MEGACO Finally ITU-T & IETF agreed upon that both MEGACO & H.248 shall be identical MEGACO/H.248, point of origin…

MEGACO defines the rules/protocols for the Sofswitch to control MGWs Typically MEGACO/H.248 provides support for media streams It provides support for VoIP & multimedia support for PSTN or VoIP within the IP network MEGACO provides base architecture for controlling MGWs –how MGWs can be controlled by SS (MGC) MEGACO/H.248 works for a distributed architecture MEGACO/H.248, functions

MEGACO provides: Total control over Media Gateways MGs Call admission and billing Signaling interface to PSTN Translation for H.323 or SIP protocols The Softswitch (MGController) instructs MGWs like: To sense off-hook condition To apply dial-tone & collect dialed digits To ADD any call connection and its context (coders required) To add UDP port numbers etc MEGACO/H.248, workings..

Two terminologies are used: – Termination and Context Termination: – A termination is a logical entity that transmit/receive media stream or control streams – For example: Endpoint is a termination Context: -- It is the association between two Terminations (Endpoints) For example: between two Endpoints (Local Call) between two RTP ports (Transit Call) MGCP and MEGACO base model

MEGACO Terminations and Context MGCP and MEGACO base model Termination X X Simple Context Voice Call Multimedia Context (Conference Call) Null Context No Connection Context

MGCP terms basic constructs as Endpoints & Connections Endpoints: source/sink of data Connections: an association between two Endpoints MGACO terms basic constructs as Terminations & Contexts Termination: an entity within a MGW that source/sinks data Context: an association between two Terminations Possible Contexts:Origin & Dest in same MGW (local call) Between two diff MGW (transit call) MGCP and MEGACO base model

Sofswitch MGC creates new Context inside MG by ADD MGC adds, subtracts Terminations to a Context MGW NOTIFIES MGC of events (off-hook, on-hook) inside MG MGC audits (checks) Context & Termination between MGWs MGC uses Service Change command (adding video/data) during a call to inform MGW MEGACO and SoftSwitch!

MEGACO/H.248 define aspects of signaling as Packages: – Commonly defined functions like: Connectivity, Transfer and Hold etc Examples of Packages are: Transactions = Number Contexts = Number, $ Termination = Identity or $ Package Data = off-hook, on-hook, port # Events, Signals, statistics = ring back tones, tone itself, time to ring MEGACO Packages….

MessagesDescription of Messages AddAddition of a Termination to a context. First Add message creates new context ModifyModification of features of termination, dial tone SubtractRemoval of a termination fro a context (disconnection) MoveRemoval of a termination from context and addition of this termination to another context (Conference Call) Audit ValueRequests Information about features, events, signals When SS learns features like PRI/BRI or any other Audit CapabilitiesRequests Information about all possible features, events, signals allowed for this termination NotifyNotification on Events (off-hook, on-hook) Service ChangeNotification of changes of termination like dead, bad MEGACO Messages