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H.323 Gatekeepers Lucent Technologies - elemedia.

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1 H.323 Gatekeepers Lucent Technologies - elemedia

2 2 Agenda Introduction Overview of Gatekeeper Functions Why are Gatekeepers Useful? Gatekeeper Concepts Signalling Models Gatekeeper Operations Signalling Flows Policy/Service Examples Gatekeepers and H.323v2 Beyond H.323v2

3 3 H.323 Components Terminal Gateway (GW) Gatekeeper (GK) Multipoint Control Unit (MCU) –Multipoint Controller (MC) –Multipoint Processor (MP) INTRODUCTION Terminal 1Terminal 2Gatekeeper 1Gatekeeper 2Gatekeeper 3 MC MP MCMPMC MPMC Gateway 1Gateway 2Gateway 3MCU 1MCU 2 LAN GW, GK & MCU can be a single device

4 4 Gatekeeper in H.323 Gatekeepers are optional Mandatory functions if present: –Address translation (routing) to determine destination address of H.323 endpoint for a call –Admission control to determine whether to allow endpoints to originate and terminate calls –Bandwidth control to, at a minimum, process bandwidth requests (can be a null function) –Zone management INTRODUCTION

5 5 Gatekeeper in H.323 (contd.) Gatekeeper optional functions: –Call control signalling to handle directly the Q.931 signalling between the H.323 endpoints –Call authorization using some policy (e.g. subscription status) –Bandwidth management to process bandwidth requests using some policy (e.g. based on current conditions) –Call management to process call requests using some policy (e.g. based on endpoint status) –Gatekeeper management information (MIB) –Bandwidth reservation for terminals not capable of performing it –Directory services INTRODUCTION

6 6 Why are Gatekeepers Useful? Centralized Management –Authentication, routing, call detail recording, etc. Isolate Endpoints from Network Internals –Knowledge of naming structures, gateway routing algorithms, etc, stays in network Interface to New and Existing Network Databases –LDAP directories, RADIUS servers, SCPs, etc. Interfaces to Other H.323 Networks –Calls between service providers INTRODUCTION

7 7 Gatekeeper Standards INTRODUCTION Standards specify the communications between H.323 entities and Gatekeepers (RAS messages) Standards specify the services a Gatekeeper must provide BUT Standards DO NOT specify how the Gatekeeper should provide those services Standards DO NOT fully specify how Gatekeepers locate other Gatekeepers

8 8 H.323 ZONE Simply defined as the collection of H.323 devices managed by a single gatekeeper Boundaries of a zone can be based on administrative, naming structure, geographic, engineering (or other) criteria Calls between endpoints in a zone handled by a single gatekeeper Calls between endpoints in different zones might involve gatekeepers from both zones CONCEPTS AND FUNCTIONS

9 9 Gatekeeper Components CONCEPTS AND FUNCTIONS Q.931/ASN Encode/Decode and Transport Protocol Procedures: RAS, Q.931, H.245, H.450 Policy Features & Services Management Endpoint & Conference State Data H.323 Network Based Information and Control TCAP/SS7 LDAP SNMP RADIUS et al. Protocols:

10 10 Signalling Models The signalling model determines which protocol messages pass through the gatekeeper, and which pass directly between the two endpoints The more messages that are routed between the gatekeeper, the more informational and control it has -- and more load and responsibility The gatekeeper ultimately decides the signalling model Media never passes through the gatekeeper function (although a proxy could be co-located on same host) SIGNALLING MODELS

11 11 Signalling Models The following signalling model scenarios show calls between a PC terminal and a PSTN gateway, but generally apply to any call between two H.323 endpoints CONCEPTS AND FUNCTIONS Notes:

12 12 Direct Endpoint Call Signalling SIGNALLING MODELS Call Signalling (Q.931) Address Translation Admission Control Bandwidth Control (RAS) GK TerminalGateway Call Control (H.245) Media Stream (RTP)

13 13 Direct Endpoint Call Signalling Gatekeeper participates in call admission but has limited direct knowledge of connected calls Due to limited involvement, single gatekeeper can process large number of calls Limits service management functions: gatekeeper cannot determine call completion rates, for example Limits centralized security: gatekeeper cannot validate Q.931 message fields (e.g. caller’s ID) Limits call detail recording function: gatekeeper depends on endpoint(s) for call duration information, for example SIGNALLING MODELS

14 14 Gatekeeper Routed Call Signalling (Q.931) SIGNALLING MODELS Call Signalling (Q.931) Address Translation Admission Control Bandwidth Control (RAS) GK TerminalGateway Call Control (H.245) Media Stream (RTP)

15 15 Gatekeeper Routed Call Signalling (Q.931) Gatekeeper aware of connection state of call but not media usage (no access to H.245 signalling) More load on gatekeeper as it must process Q.931 messages and maintain Q.931 signalling channel Service management functions can include connection statistics but not media usage Gatekeeper can validate Q.931 message parameters such as calling party information Call detail recording functions enhanced by direct knowledge of connection state SIGNALLING MODELS

16 16 Direct Endpoint Call Signalling w/UUIE SIGNALLING MODELS Call Signalling (Q.931) Address Translation Admission Control Bandwidth Control Q.931 UUIE Notification (v2) (RAS) GK TerminalGateway Call Control (H.245) Media Stream (RTP)

17 17 Direct Endpoint Call Signalling w/UUIE Hybrid between direct call signalling and gatekeeper routed signalling Q.931 messages do not flow through the gatekeeper, but gatekeeper is notified of Q.931 content in RAS messages. SIGNALLING MODELS

18 18 Gatekeeper Routed Call Signalling (Q.931/H.245) SIGNALLING MODELS Call Signalling (Q.931) Address Translation Admission Control Bandwidth Control (RAS) GK TerminalGateway Call Control (H.245) Media Stream (RTP)

19 19 Gatekeeper Routed Call Signalling (Q.931/H.245) Gatekeeper aware of connection state of call and media channels in use (can audit bandwidth usage) Highest load on gatekeeper as it must process Q.931 and H.245 messages and maintain the corresponding signalling channels Service management functions can include connection and media usage statistics Call detail recording functions further enhanced by direct knowledge of media usage SIGNALLING MODELS

20 20 Gatekeeper Operations and Policy List of parameters in messages is not inclusive Parameter names displayed as follows: –  –  –   LDAP/TCAP message content is paraphrased for illustration GATEKEEPER OPERATIONS Notes:

21 21 Endpoint/GK Discovery       (2) I can be your GK GATEKEEPER OPERATIONS         (1) Who is my GK? Endpoint GK (1) GRQ (2) GCF/GRJ

22 22 Endpoint/GK Discovery Processing Discovery can be multicast (most useful for LAN environments) or unicast based on endpoint configuration data Possible acceptance criteria to be used by gatekeeper: – IP address (or IP subnet) of endpoint – Gatekeeper ID supplied by endpoint – Aliases supplied by endpoint – Gatekeeper load Gatekeeper might need to consult external database (e.g. LDAP directory) GATEKEEPER OPERATIONS

23 23 Endpoint/GK Registration          GATEKEEPER OPERATIONS          Endpoint GK (1) RRQ (2) RCF/RRJ (1) Here are my aliases and IP address (2) OK

24 24 Endpoint/GK Registration Processing Gatekeeper might authenticate endpoint – H323v1 must use ad hoc/proprietary methods such as supplied aliases, IP address, etc. – H.323v2 can use encrypted password or certificates Gatekeeper might authorize endpoint – Validate list of supplied aliases Associate aliases with the IP address for later location Gatekeeper assigns and returns Endpoint ID to be used in subsequent messages GATEKEEPER OPERATIONS

25 25 Example: Reservation Authorization via LDAP GATEKEEPER OPERATIONS LDAP SEARCH: Filter: e164= AND h323ID=johnDoe LDAP Directory containing subscriber data GK RRQ RCF/RRJ Register: johnDoe Needs to authorize aliases LDAP SEARCH RESULT: Entry: e164= h323ID=johnDoe status=active

26 26 Call Admission          GATEKEEPER OPERATIONS Endpoint GK (1) ARQ (2) ACF/ARJ (2) Yes, contact this IP address (1) Can I call using 16 Kb/sec?           

27 27 Call Admission Processing Gatekeeper might authenticate endpoint to ensure it is registered and check if it is authorized to make call Gatekeeper must determine call model – Endpoint can ask for preference but gatekeeper will decide Gatekeeper might check for bandwidth If direct signalling, gatekeeper supplies destination endpoint address (discussed later) If gatekeeper routed signalling, it supplies its own address and can defer routing GATEKEEPER OPERATIONS

28 28 Example: Admission Authorization via SS7 GATEKEEPER OPERATIONS GK ARQ ACF/ARJ Admit: johnDoe Calling card: Needs to authorize calling card number TCAP QUERY: Invoke: Provide Value Digits = Pin=8459 TCAP END: Return Result: Record Status Indicator Service Control Point containing calling card info (e.g. LIDB in the US)

29 29 Q.931 Setup GATEKEEPER OPERATIONS Endpoint (1) Connect me to           (2) Determine gateway SETUP (2) Start PSTN origination GK GW

30 30 Setup Processing Gatekeeper associates Setup with previous admission using Conference ID Destination determined using Calling Party Number or destination alias(es) External databases might be consulted to determine destination endpoint: – Map full destination alias to a terminal – Map leading digits of E.164 number to gateway(s) Setup message is forwarded to destination GATEKEEPER OPERATIONS

31 31 Example: Endpoint Location Via LDAP GATEKEEPER OPERATIONS Endpoint (1) Connect me to SETUP (3) Start PSTN origination GK GW LDAP SEARCH: Filter: E164=1414 OR E164= LDAP SEARCH RESULT: IP= STATE=IS IP= STATE=IS LDAP DIRECTORY (2) Query LDAP Directory

32 32 Example: Endpoint Location Via SS7 GATEKEEPER OPERATIONS Endpoint (1) Connect me to SETUP (3) Start PSTN origination GK GW SCP PROVIDING FREEPHONE SERVICE (2) Freephone! - Query SCP - Translate E.164 TCAP QUERY: Invoke: Provide Instructions Digits= et al. TCAP END: Invoke: Connect: Digits= et al.

33 33 Remaining Call Setup GATEKEEPER OPERATIONS ALERTING CALL PROCEEDING CONNECT ACF ARQ Terminal Gatekeeper Gateway ALERTING CALL PROCEEDING

34 34 Remaining Call Setup Processing Gatekeeper processes terminating admissions request doing potential authorization and bandwidth checks Gatekeeper primarily a “pipe” for Q.931 messages but might authorize some fields (e.g. Display) Gatekeeper substitutes its own address in “h245address” fields if it wishes to route H.245 GATEKEEPER OPERATIONS

35 35 Stable Call Processing Gatekeeper verifies calls are “alive” using one of the following techniques: – Wait for periodic IRRs (as requested in the ACF) – Periodically send an IRQ, expecting an IRR – Periodically send a Q.931 Status Enquiry, expecting a Status Gatekeeper might receive bandwidth changes requests (BRQ) and must allow (BCF) or deny (BRJ) the request GATEKEEPER OPERATIONS

36 36 Call Teardown GATEKEEPER OPERATIONS RELEASE COMPLETE DCF DRQ Terminal Gatekeeper Gateway RELEASE COMPLETE DRQ DCF

37 37 Call Teardown Processing Gatekeeper processes Release Complete, noting the time and forwards it to the other endpoint Gatekeeper processes DRQ from both endpoints and releases any allocated bandwidth Gatekeeper might create call detail record for the call, recording endpoint information and Connect and Release times for example GATEKEEPER OPERATIONS

38 38 H.323v2 Features Related to Gatekeeper Authentication Framework –Tokens (password or certificate based) for RAS –TLS (certificate based) for Q.931 –Negotiated H.245 security –H.323 defines the framework - need profiles to nail down specific choices of algorithms Mechanism to specify alternative gatekeepers to endpoints Registration “keep alive” similar to conference IRR “keep alive” H.323v2 and Gatekeepers

39 39 H.323v2 Features Related to Gatekeeper RAS Transport Improvements –IRR ACK/NAK –Request In Progress (RIP) to ask for more time Signalling changes –Excuse endpoints from Admission Requests –Fast call setup / tunneled H.245 –Gatekeeper can request Q.931 information be forwarded to it on direct routed calls H.450 Services –Call transfer and call forwarding H.323v2 and Gatekeepers

40 40 Beyond H.323v2: Network Management Definition of Management Information Bases (MIB) for H.323 protocols and devices under development Gatekeepers can provide large amount of centralized management information and control Beyond H.323v2 Network Management Station GatekeeperGateway MCU and others SNMP/ CMIP

41 41 Beyond H.323v2: Inter-gatekeeper Communication Current H.323 standards do not provide an inter- zone model that scales well for large networks Inter-gatekeeper protocols being discussed to enable gatekeepers to efficiently locate one another to route calls to non-local address Hierarchical arrangements with “clearinghouse” gatekeepers have been proposed Beyond H.323v2

42 42... integrating voice, fax, data and video Internet Multimedia Communications Software For information on elemedia’s H.323 Gateway Toolkits and H.323 Gatekeeper Toolkits, please contact us at: elemedia ( ) (U.S. and Canada)


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