150 likes | 396 Views
Recommendation H.248 „Gateway Control Protocol“. Gateway. GK. MGC. SG. IP-Network. SCN. H.248. MG. signalling media. IP.... Internet Protocol GK.. Gatekeeper MGC. Media Gateway Controler MG.... Media Gateway SG... Signalling Gateway SCN.. Circuit switched Network. can include:
E N D
Recommendation H.248 „Gateway Control Protocol“ Gateway GK MGC SG IP-Network SCN H.248 MG signalling media IP.... Internet ProtocolGK.. GatekeeperMGC. Media Gateway ControlerMG.... Media GatewaySG... Signalling GatewaySCN.. Circuit switched Network can include: MCU.. Multipoint control unitIVR..... Integrated voice response unit
Media Gateway Termination SCN BearerChannel Context * Termination RTP Stream Termination SCN BearerChannel Context Null Context * Termination RTP Stream Termination SCN BearerChannel Context * Termination RTP Stream Termination SCN BearerChannel Figure 1: Example of H.248 Connection Model
Media Gateway Context C1 Context C1 * * Termination T2 RTP Stream Termination T1 SCN BearerChannel Termination T2 RTP Stream Termination T1 SCN BearerChannel Context C2 Context C2 * * Termination T3 SCN BearerChannel Termination T3 SCN BearerChannel Figure 2: Example Call Waiting Scenario / Alerting Applied to T1
Context assocation betweena number of Terminations attributes ( Context ID, topology, priority ...) creating contexts deleting contexts modifying contexts (e.g. add additional )
Terminations (Termination ID... assigned by the MG at the time of creation) Proporties Events (?, probably unneccessary)(trigger notification messages to MGC or action by the MG) Signals(tones, announcements, line signals.....) Statistics grouped in a setof Descriptors („Parameters“)included in commands
Proporties (Proporty Name, Proporty ID) common proporties specific to media streams receiving flowproporties(local) localproporties(local controlbetween MGand MGC) transmitting flowproporties(remote)
Descriptor Name Descripton Modem Identifies modem type and proporties when applicable Mux Describes multiplex type for multimedia terminations (e.g. H.221,H.223, H.225.0) and Terminations forming the input mux Media A list of media straeam specifications (see 7.1.4) TerminationState Proporties of Termination (which can be defined in Packages) that are not stream specific Stream A list of remote/local/localControl descriptors for a single stream Local Contains protorties that specify the media flows that the MG receives from the remote entity. Remote Contains porporties that specify the media flows that the MG sends to the remote entity. LocalControl Contains proporties (which can be defined in packages) that are of interest between the MG and the MGC Events Describes events to be detected by the MG and what to do when an event is detected EventBuffer Describes events to be detected by the MG when Event Buffering is active Signals Describes signals and/or actions to be applied (e.g. Busy Tone) to the Terminations Audit In Audit commands, identifies which information is desired Packages In AuditValue, returns a list of Packages realized by Termination DigitMap Instructions for handling DTMF tones at the MG ServiceChange In ServiceChange, what, why service change occurred, etc. ObservedEvents In Notify or AuditValue, report of events observed
Commands H.248 provides commands for manipulating the logical entities: Context Termination MGCMG AddModifySubstractMoveAudit ValueAudit CapabilitiesService Change NotifyService Change
TRANSACTIONx CTXTID1 COMMAND1 COMMAND2 COMMAND3 COMMAND4 CTXTID2 COMMAND1 CTXTID3 COMMAND1 COMMAND2 COMMAND3
Properties Events Signals Statistics Packages optional
Package Package name: unique string name Package ID: unique serial number Version: integer (1 to 99) Registeredwith IANA Basic Packages (Annex E) • Generic • Root • Tone Generator • Tone Detection • Basic DTMF Generator • DTMF Detection • Call Progress Tones Generator • Call Progress Tones Detection • Network Package • RTP • TDM circuit • Analogue Line Supervision • Basic continuity • others (not in Annex E)
Encoding MGC H.248 Annex A (ASN.1) Annex C (media description) Annex B (Text encoding) SDP (media description) MG MG
Transport MGC MGCAnnex H MGCAnnex I TCP UDP/ALF SCTP • MTP 3B/N-SAL/AAL5 • SSCOP... (Q.2110) • Type 5 ALL with ALF and should besupported „ATM“ TCP or UDP/ALF SCTP MG MG MG
H.248 Annex A Binary encoding (ASN.1) Annex B Text encoding Annex C Tags for media stream properties Annec D Transport over IP Annex E Basic Packages AnnexF Text conversation and fax packages AnnexG User Interface Elements and Actions packages Annex H SCTP Transport Annex I ATM Transport Annex J Dynamic Tone Definition package Annex K Generic Announcement package Annex L Error Code Descriptions Annex M Advanced audio server package Appendix A Example call flows