Miroslav Voz ňák VŠB - Technical University of Ostrava Department of Telecommunications

1. 454-319/1: Voice over IP Lecture No.3 H.323, protocol model and elements Miroslav Vozňák VŠB - Technical University of Ostrava Department of Telecommunications Faculty of Electrical Engineering and Computer Science 17. listopadu 15, 708 33 Ostrava – Poruba mailto:miroslav.voznak@vsb.cz http://homel.vsb.cz/~voz29 Miroslav Voznak, lecture on H.323

2. H.32x family – multimedia communication over • H.320 – N-ISDN • H.321 – B-ISDN • H.322 – LAN with guaranteed QoS • H.323 – packed based multimedia systems • H.324 – PSTN, H.324 M (Mobile extension) in 3GPP • H.325 – protocol definition (2008), will be used in NGN Miroslav Voznak, lecture on H.323

3. H.323 • was first approved in 02/1996 • H.323v1 - The Visual telephone System And Equipment For Local Area Network Which Provide a Non Guaranteed Quality of Service • H.323 is a standard that specifies the components, protocols and procedures that provide multimedia communication services (real-time audio, video, and data communications) over packet networks, including Internet protocol (IP) based networks. H.323 is part of a family of ITU-T recommendations called H.32x that provides multimedia communication services over a variety of networks. Miroslav Voznak, lecture on H.323

4. H.323 is an umbrella of various protocols • H.323 signaling • H.225.0/RAS, Registration Admission and Status • H.225.0/Q.931, Call Signaling • H.245, Media Control • H.323 media • audio codecs – ITU-T G.711, G.728, G.729, G.723.1 ... • video codecs – ITU-T H.261, H.263 • data – ITU-T T.120 Miroslav Voznak, lecture on H.323

5. H.323v1, 96 • w/o security • the issues in establishing a connection (H.245) • H.323v2, 98 • was first approved in 1998 as The Packet-based multimedia communications systems • Fast Connect (Fast Start fields in Q.931) • Supplementary services - H.450.x - Call Transfer and Call Diversion Miroslav Voznak, lecture on H.323

6. H.323v2, 98 • H.235, Security • H.245 tunelling • overlap (a method of dialing) • empty capability set (restart H.245) • new type of alias address (URL, email) • RIP (setting of a new expiration time of sent requests) • TTL • alternate GK (backup) • RAS QoS (EP can indicate a capability to reserve resources, GK answers where the responsibility for resource reservation is) Miroslav Voznak, lecture on H.323

7. H.323v3, 99 • Simple Endpoint Terminal (SET) is defined in Annex F of H.323, only audio • H.450.x – call hold, call park, pickup, MWI, call waiting • H.341 – MIB (Management Information Base) for SNMP-based management of endpoints Miroslav Voznak, lecture on H.323

8. H.323v4, 2000 • gateway decomposition, ITU-T H.248 (MG and MGC) • H.450.x - name identification, call completion, call offer, call intrusion • improving alternate GK, EP indicates whether supports an alternate GK procedure • load balancing across GK (alternate GK) • bandwith management • transparent tunnel for non-H.323 protocols such as QSIG and ISUP • Fast Connect and H.245 Parallel simultaneously Miroslav Voznak, lecture on H.323

9. H.323v5, 2003 • GEF (General Extensibility Framework), ITU-T H.460.1 • number portability, circuit status map, call priority designation, transport of duplicate Q.931 IE, extended fast connect, digit maps, QoS monitoring and reporting • Annex O – use of URL and DNS • Annex P - modem relay Miroslav Voznak, lecture on H.323

10. H.323v6, 2006 • assigned GK (hot standby whereas alternate GK is cold standby) • improving H.235 – security, SRTP • delayed call establishment • Situation in ITU-T Study Group 16 • H.323 is richer than SIP, but ... • is looking for something that is truly innovative(H.325) • H.325 will be released in 2008 Miroslav Voznak, lecture on H.323

11. Elements of H.323 systems • endpoints (EP) are terminals, gateways, MCU’s • gatekeeper (GK) • A collection of all endpoints managed by a single GK is anH.323 zone. • A zone includes at least one endpoint and has only one gatekeeper. • A zone is independent of network topology and may be comprised of different network segments connected through routers (Internet – generally). Miroslav Voznak, lecture on H.323

12. Terminals (TE) • soft phones (do you know an open-source soft phone?) • HW telephones (a lot of vendors, price starts at 30 EUR) • IVR and Voicemail systems • + video • Multipoint Control Unit (MCU) • contains MC (multipoint controller) and MP (multipoint processor) • MCU enables the multipoint conferences,MC is responsible for call signaling and MP for media mixing, switching Miroslav Voznak, lecture on H.323

13. Gateway (GW) • gateways interface H.323 to other networks • PSTN, ISDN, .... • contains MG and MGC parts which may exist separately or together • a performance depends on used codecs, numb. of DSP, CPU, • ISDN PRI or BRI cards in PCI slot • FXS, FXO, EM ... • echo-cancellation Miroslav Voznak, lecture on H.323

14. Gatekeeper (GK) • is a optional component • is primarily used for address translation E.164 - IP • allows a admission control in zone • is a logical component of H.323 architecture • makes a decision on the model of connection • provides a call-control services for H.323 endpoints • uses RAS signaling (defined in ITU-T H.225) Miroslav Voznak, lecture on H.323

15. Mandatory Gatekeeper Functions • address translation • admission control • bandwith control • zone management • Optional Gatekeeper Functions • Call-control signaling • Call authorization • Call management Miroslav Voznak, lecture on H.323

16. protocol model – H.323 stack H.323 Application RAS H.245 RTP / RTCP H.225.0 Call Signaling H.225.0 Layer Miroslav Voznak, lecture on H.323

17. Miroslav Voznak, lecture on H.323

18. H.323 • “Umbrella” document describing the usage of other related documents • H.225.0 • describes signaling protocols • RAS • Q.931 • H.245 • media control protocol Miroslav Voznak, lecture on H.323

19. H.235 • Security • H.450.x • Supplementary services • H.460.x • Various H.323 extensions • H.341 • SNMP Miroslav Voznak, lecture on H.323

20. T.38 • Fax relay • E.164 • Numbering plan • DTMF • in-band, G.711 • out-of-band, RFC 2833 Miroslav Voznak, lecture on H.323

21. Architecture • H.323 zone – a single GK and EP’s connected to it, although there may be more GK’s provides logical function of GK for zone • Administrative domain – a collection of zones which are under administrative control • there is no limitation of number of EP’s within Zone • there is no limitation of number of Zones within Administrative domain Miroslav Voznak, lecture on H.323

22. RAS (Registration, Admission, and Status) • RAS messages have three types: • Request (xRQ • Reject (xRJ) • Confirm (xCF) • RAS is carried out via UDP • port 1719 (unicast) • and port 1718 (multicast) • Only UDP is defined for RAS communications • GRQ and LRQ messages may be send multicast Miroslav Voznak, lecture on H.323

23. RAS • GRQ/GCF/GRJ • Gatekeeper Request/Confirm/Reject UDP 1718 (224.0.1.41) • RRQ/RCF/RRJ • Registration Request/Confirm/Reject • URQ/UCF/URJ • Unregister Request/Confirm/Reject • ARQ/ACF/ARJ • Admission Request/Confirm/Reject Miroslav Voznak, lecture on H.323

24. RAS • IRQ/IRR/ • Information Request/Request Response, Status • LRQ/LCF/LRJ • Location Request/Confirm/Reject • BRQ/BCF/BRJ • Bandwidth Request/Confirm/Reject • DRQ/DCF/DRJ • Disengage Request/Confirm/Reject Miroslav Voznak, lecture on H.323

25. Thank you for your attentionmiroslav.voznak@vsb.cz Miroslav Voznak, lecture on H.323