联通培训-H323原理.ppt

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1、H.323原理,教学目标,理解H323的概念掌握H323的组成及其特点掌握主要的呼叫控制信令,教学内容,什么是H323？H323的组成及特点H323区域H323协议集,What Is H.323?,International standard for conferencing over packet-based networksInteroperability standard for network-,ISDN-,and telephony-based conferencing systemsSingle standard for network,video,and telephony pr

2、oducts to interoperate,H.323,Technology for the transmission of real-time audio,video,and data communications over packet-based networksSpecifies the components,protocols,and procedures providing multimedia communication over packet-based networks H.323 can be applied in a variety of mechanismsAudio

3、 only(IP telephony)Audio and video(videotelephony)Audio and dataAudio,video,and dataCan also be applied to multipoint-multimedia communications,H.323 Standard,ITU RecommendationV1 approved in 1996,v2 in January 1998Defines multimedia applications over packet based networksLeverages existing standard

4、sWide market acceptanceFacilitates interoperability between vendorsCisco VoIP solutions are H.323 compliant,6,0573_01F9_c2,1998,Cisco Systems,Inc.,H323标准是H32X家族的一部分，家族中其他的协议定义了基于不同网络的多媒体通信服务基于SCN的H324基于ISDN的H320基于B-ISDN的H321和H310基于能提供QOS的LAN的H322,H.324Terminal,H.323Gatekeeper,Packet Network,H.323Ter

5、minal,H.323Gateway,H.323MCU,Scope of H.323,PSTN,ISDN,V.70Terminal,SpeechTerminal,H.320Terminal,SpeechTerminal,H.323 Components,V,GK,H323终端,主要是IP电话和PC机，而非普通的电话，PC包括：一个网络接口音视频编解码器H323软件必须支持G.711 和H.261必须支持H245、H225、RAS、RTP/RTCP,终端：参考结构,Video I/O Equipment,Audio I/O Equipment,Video CodecH.261,H.263,Aud

6、io CodecG.711,G.723.1,ReceivePathDelay,User Data App.T.120,SystemControlUser Interface,System Control,H.245 Control,Call ControlH.225.0,RAS ControlH.225.0,H.225.0Layer,LANInterface,H323网关,转换协议转换信息格式传递信息,H323关守,地址转换控制许可带宽控制和管理区域管理其他可选的功能-呼叫控制信令-呼叫授权-呼叫管理,MCU-多点控制单元,提供3个或多点间的会议服务MCU管理各点间的会议资源和协商包括两个功能

7、部件：MC（多点控制器）进行会议控制以决定信息流的流向MP（多点处理器）负责组合、交换和处理信息流,MCU,本地服务：MCU：参考模型,MC,Ref:H.323v2,MCU应用案例,H.323 层次结构图,H.323 Zones,H.323 Gatekeeper B,Gatekeeper Zone B,Local PSTN,H.323 Gatekeeper A,Gatekeeper Zone A,H.323Client,Local PSTN,H.323GW,QoS WAN,Local PSTN,Local PSTN,H323 ZONE,由关守管理的所有终端、网关、MCU的集合一个区域至少包括一

8、个终端一个区域只有一个关守,H.235,H.323 Protocol Stack,TCP,UDP,IP,RTCP,RAS,Audio orVideoControl,H.225(Q.931),Call Control Data,T.120,H.245,Payload,Header,G.7xx,H.26x,RTP,Audio Video,H323定义的协议,Audio CODECSVideo CODECSH.225 Call Control(ISDN Q.931)H.245 System ControlReal-Time Protocol(RTP)for media streamsRegistra

9、tion,Admission,Status(RAS)Messages for gatekeeper to endpoint communications,Audio CODEC,发起端音频CODEC对模拟话音进行编码，转换成数字信号在网络里传输；接收端对数字信号进行解编码，把它还原成模拟的语音信号。-采样-量化-编码-压缩所有H323终端必须支持语音CODECITU-T建议使用G711,Video CODEC,发起端视频CODEC把从摄象机获取的图象进行编码，转换成数字信号在网络里进行传输；在接收端，视频CODEC把数字信号进行解码，把它输出到视频显示器上H323定义视频CODEC作为可选项提

10、供视频通信的终端必须支持视频CODECITU-T建议使用H261,H.225 Call Control(ISDN Q.931),SetupIncoming callCall ProceedingAlertingPhone is ringingConnectMedia cut through(used for billing)Release/Release CompleteTear down call,Capabilities ExchangeCODEC negotiation-Transmitter/Receiver capabilitiesMode Request-Request speci

11、fic transmission formatMaster/Slave DeterminationOpen Logical Channel/AckCreate new audio/video/T.120 streamCommands and IndicationsFrame flow control,camera control,etc.,H.245 System Control,RTP/RTCPRFCs 1889/1890,End-to-end network transport function Sequence numberingTime StampingDelivery monitor

12、ingPayload type identification-Voice,Video,Compression TypeRTCP(Real-Time Control Protocol)provides feedback on the quality of the distribution,Example:Call Signaling Between Two Endpoints,Media(UDP)Cisco Implementation Note:UDP ports 16384 thru 16384+(4 x the number of channels on the device),RTP S

13、tream,RTCP Stream,H.323Endpoint A,H.245(TCPDynamic Port),Open Logical Channel,H.225(TCP Port 1720),Setup,Alerting/Connect,Open Logical Channel Acknowledge,Capabilities Exchange/MSD,RTP Stream,H.323Endpoint B,V,V,H.323v1(5/96)-7 or 8 Round TripsH.323v2(2/98)-2 Round Trips,Assumes Endpoints(Clients)kn

14、ow each others IP addresses,GRQ/GCF/GRJ(Discovery)Unicast-MulticastFind a gatekeeperRRQ/RCF/RRJ(Registration)Endpoint alias/IP address bindingEndpoint authenticationARQ/ACF/ARJ(Admission)Destination Address ResolutionInitial bandwidth requestCall RoutingCall Authorization,RAS Messages,DRQ/DCF/DRJ(Di

15、sconnect)Get rid of call stateLRQ/LCF/LRJ(Location)Stateless name-IP address resolutionInter gatekeeper communicationIRQ/IRR(Information Request)Ping during active callsResource information for gatewaysBRQ/BCF/BRJ(Bandwidth)Ask for more/less bandwidth during callURQ/UCF/URJ(Unregistration)Get rid of

16、 registration state,RAS Messages(cont.),RAS Message Exchange,Gatekeeper A,Gatekeeper B,RRQ/RCF,ARQ,RRQ/RCF,ARQ/ACF,LRQ,IP Network,Phone A,Phone B,Gateway A,Gateway B,H.225(Q.931)Setup,H.225(Q.931)Connect,H.245,RTP,ACF,LCF,V,V,Gatekeeper Discovery,H.323 Endpoints/GWs attempt to discover a GK(their zo

17、ne)via RASUnicast discoveryGK will explicitly reply with a GCF,or GRJGK-GW relationship is deterministicMulticast discoveryGK will explicitly reply with a GCF,or remain silentGK can be configured as to which subnets to respond toIf GW requests an explicit GK name,only that one will respond determini

18、stic If not,the first GK to respond will become the GWs GK non-deterministicIf a GK is not available,the GW will periodically attempt to rediscoverIf GW discovers GK has gone off-line,it will stop accepting new calls,attempt to rediscover a GK.Active calls are not affected.,Seq NumberH.225 Protocol

19、IdentifierrasAddessendpointTypegatekeeperID.,Selected Message Fields,Registration Message Sequence,H.323 Client learns of GK via Static configuration or dynamic DiscoveryRegistration with an H.323 ID,or an E.164 addressH323 ID:E.164 address:4085551212Every E.164 address can be registered only onceRe

20、gistration expires after keepalive(30 seconds)Unregister messages(URQ/UCF)to de-register from GKEvery GW can register with only one GKOnly one GK per zoneMultiple zones,or logical GKs,per physical machine,Seq NumberH.225 Protocol IdentifiercallSignalAddressrasAddressterminalTypeterminalAliasgatekeep

21、erIDtimeToLivekeepaliveendpointID.,Selected Message Fields,Intra-Zone Call Set-up,GK1,1)Terminal A dials the phone number 408-667-1111 for Terminal B2)GWA sends GK1 an ARQ,asking permission to call Terminal B3)GK1 does a look-up and finds Terminal B registered;returns an ACF with the IP address of G

22、WB4)GWA sends a Q.931 Call-Setup to GWB with Terminal Bs phone number5)GWB sends GK1 an ARQ,asking permission to answer GWAs call6)GK1 returns an ACF with the IP address of GWA7)GWB sets up a POTS call to Terminal B at 408-667-11118)When Terminal B answers,GWB sends Q.931 Connect to GWA,Terminal A41

23、5-557-1111,Inter-Zone Call Set-up,1)Terminal A dials the phone number 408-667-1111 for Terminal B2)GWA sends GK1 an ARQ,asking permission to call Terminal B3)GK1 does a look-up and does NOT find Terminal B registered;GK1 does a prefix look-up and finds a match with GK2;GK1 sends an LRQ to GK24)GK2 d

24、oes a look-up and finds Terminal B registered;returns an LCF with the IP address of GWB5)GK1 returns an ACF with the IP address of GWB6)GWA sends a Q.931 Call-Setup to GWB with Terminal Bs phone number7)GWB sends GK2 an ARQ,asking permission to answer GWAs call8)GK2 returns an ACF with the IP addres

25、s of GWA9)GWB sets up a POTS call to Terminal B at 408-667-111110)When Terminal B answers,GWB sends Q.931 Connect to GWA,Inter-Zone Call Set-up:Directory Gatekeeper,1)Terminal A dials the phone number 408-667-1111 for Terminal B2)GWA sends GK1 an ARQ,asking permission to call Terminal B3)GK1 does a

26、look-up and does NOT find Terminal B registered;GK1 does a prefix look-up and finds a wildcard match with Dir-GK;GK1 sends LRQ to Dir-GK4)Dir-GK does a prefix look-up and finds GK2;Forwards the LRQ to GK25-11)Same as steps 4-10 in previous scenario,Call Disconnect,Terminals A and B are in active con

27、versation.1)Terminal B hangs up2)GWB sends DRQ to GK2,disconnecting the call between Terminals A and B.A DCF is received some time later.3)GWB sends a Q.931 Release Complete to GWA4)GWA sends DRQ to GK1,disconnecting the call between Terminals A and B.A DCF is received some time later.5)GWA signals

28、a call disconnect to the voice network(the mechanism differs depending on the trunk used on GWA.If it is a phone set(FXS),then there is no mechanism to signal the disconnect.,Real-Time Transport Protocol(RTP),Works with UDP to provide transport-protocol functionalityProvides end-to-end delivery serv

29、ices of real-time audio and videoRTP provides payload-type identification,sequence numbering,timestamping,and delivery monitoringUDP provides multiplexing and checksum servicesCan be used with other transport protocols,H.323 Proxy,Conceals identities of endpointsGW A never knows the IP address of GW

30、 BProxy relays all call signaling and media streamsAbility to provide a RAS interface to non-RAS clients.,GK A-Direct,GK B-Proxied,LRQ/LCF,ARQ/ACF,H.225/H.245/RTP,GW A,GW B,Proxies,Proxies are used for:Security(hiding the identity of the true end-point)Quality of serviceApplication Specific Routing(

31、ASR)SecurityProxy inside the FirewallProxy in Co-Edge ModeProxy Outside the FirewallProxies and Network Address Translation(NAT)12.0(3)T does not support a single proxy per calldual proxy or directthe destination GK makes the decision to assign a proxy or notUse“zone access”command to instruct GK to

32、 assign proxyDetermination to use proxy made by the terminating GKThe originating GK will assign a proxy if the terminating GK is using a proxy,Inter-Zone Call Set-up with Proxies,1)Terminal A dials Terminal B2)GWA sends ARQ to GK13)GK1 sends LRQ to GK24)GK2 returns Proxy-Bs address,hiding GWBs iden

33、tity5)GK1 knows to get to Proxy-B,it must go through Proxy-A,so GK1 returns Proxy-As address to GWA6)GWA calls Proxy-A7)Proxy-A consults GK1 to find the true destination,GK1 tells it to call Proxy-B8)Proxy-A calls Proxy-B9)Proxy-B consults GK2 for the true destination,which is GWB;GK2 gives GWBs add

34、ress to Proxy-B10)Proxy-B completes the call to GWBFrom here the call proceeds as before.,Limitations and Guidelines,Zone prefixes per Directory GK:10,000 for dedicated Dir-GK2,000 for any GK managing local zonesLRQ hopsMax hop-count of 5Cisco-specific feature;LRQs from non-Cisco gear and pre-12.0(3

35、)T Cisco gear will not be forwardedActive RegistrationsTerminals are low-maintenance,but GWs are highTarget of 100 GWs per GK(keep call traffic in mind)Local zones per GK:100Remote zones per GK:100 for H.323 ID destinationsless impacting for E.164 destinationsTech Prefixes:50 per GK,Components of Qu

36、ality,DSPsCODECs,Carrier-Class Voice Quality,End-to-End NetworkingQoS Service Elements,DSPsCODECs,QoS WAN,Gateway LatencyCoding Quality,Network LatencyJitter Control,Cisco AS5300,Silence Suppression/VAD,Essential Components22%,Pauses56%,Repetitive22%,Over half of the typical voice call is silence!VA

37、D removes silence from data stream.Comfort noise during silent periods.,RTP Header Compression,20ms8kb/s yields 20 byte payloadIP header 20;UDP header 8;RTP header 122X payload!Header compression 40Bytes to 2-4 much of the timeHop-by-Hop Slow Links,Overhead,Version,IHL,Type of Service,Total Length,I

38、dentification,Flags,Fragment Offset,Header Checksum,Protocol,Time to Live,Source Address,Destination Address,Padding,Options,Source Port,Destination Port,Checksum,Length,PT,M,CC,X,P,V=2,Sequence Number,Timestamp,Synchronization Source(SSRC)Identifier,H323应用案例,VOIP,Case-1：不经过关守的配置,网关配置（无关守）,基本配置Route

39、r#conf terminalRouter(config)#hostname bj-gw 定义主机名接口配置Bj-gw#conf terminalBj-gw(config)#int fastethernet0/0Bj-gw(config-if)#ip addr 10.1.1.1 255.255.255.0Bj-gw(config-if)#no shut,拨号对等体的配置本地（LOCAL）对等体配置Bj-gw(config)#dial-peer voice 10 potsBj-gw(config)#destination-pattern 010114Bj-gw(config)#port 1/0/

40、0网络端的对等体配置 Bj-gw(config)#dial-peer voice 20 voipBj-gw(config)#destination-pattern 021114Bj-gw(config)#session tartget ipv4:10.1.1.2,Case-2：经过一个关守的配置,网关配置（有关守）,基本配置Router#conf terminalRouter(config)#hostname bj-gw 定义主机名接口配置Bj-gw#conf terminalBj-gw(config)#int fastethernet0/0Bj-gw(config-if)#ip addr 1

41、0.1.1.1 255.255.255.0Bj-gw(config-if)#no shutBj-gw(config-if)#h323-gateway voip interface（与VOIP相连接口）Bj-gw(config-if)#h323-gateway voip id gk-bj ipaddr 192.168.1.1 1719（指向关守的IP地址）Bj-gw(config-if)#h323-gateway voip h323-id beijing-gw（本网关的别名）Bj-gw(config-if)#h323-gateway voip tech-prefix 1#（注明身份类型）,关守配

42、置,配置本地和远端的区域名Gk(config)#gatekeeper#zone local gk-bj#zone local.#zone remote 配置区域前缀（区号）#zone prefix gk-bj 010*#zoen prefix gk-sh 021*#zone prefix,关守配置（续）,配置缺省的技术前缀及其它Gw-type-prefix 1#default-technologyArq reject-unknown-prefixLrq reject-unknown-prefixNo shut,Case study,gw-bj1 1#,gw-bj2 2#,gw-bj3 3#,g

43、w-sh1 1#,gw-sh2 2#,gw-sh3 3#,gk-bj,gk-sh,Beijing:zone local gk-bjzone remote gk-shzone prefix gk-bj 010*zone prefix gk-sh 021*gw-type-prefix 5#hopoff gk-HKTELgw-type-prefix 1#default-technologyArq reject-unknown-prefixLrq reject-unknown-prefixLrq forward-queries,Shanghai:zone local gk-shzone remote

44、gk-bjzone prefix gk-bj 010*zone prefix gk-sh 021*gw-type-prefix 5#hopoff gk-HKTELgw-type-prefix 1#default-technologyArq reject-unknown-prefixLrq reject-unknown-prefixLrq forward-queries,Scene 1:2#02112345678,从北京网关发起呼叫,落地网关:,gw-sh2,Scene 2:02112345678,Scene 3:5#0085212345678,Scene 4:02912345678,gw-sh

45、1,gw-bj1?,interface Ethernet0/0 h323-gateway voip tech-prefix 1#,dial-peer voice 101 voip destination-pattern 021T tech-prefix 2#session target ras,interface Ethernet0/0 h323-gateway voip tech-prefix 2#,interface Ethernet0/0 h323-gateway voip tech-prefix 3#,dial-peer voice 102 voip destination-patte

46、rn 021T session target ras,dial-peer voice 103 voip destination-pattern 00852T tech-prefix 3#session target ras,dial-peer voice 104 voip destination-pattern 029T session target ras,H323应用案例,COIP,Scenario 0:Point to Point A/V/D with No Gatekeeper,呼叫流程,Endpoint A calls Endpoint B*:Endpoint A sends SET

47、UP to Endpoint B Endpoint B sends CALL PROCEEDING to Endpoint A(optional).Endpoint B sends ALERTING to Endpoint A Endpoint B sends CONNECT to Endpoint A.Endpoints terminate call Endpoint A sends RELEASE COMPLETE to Endpoint B.,Scenario 1:Point to point A/V/D call within Single Zone,H.323 EP,“A-2”,H.

48、323 GK,“A”,Single Zone,H.323 EP,“A-1”,呼叫流程,Endpoints perform discovery/registration using alias.Endpoint A1 calls Endpoint A2 Endpoint A1-sends ARQ to Gatekeeper with alias.Endpoint A1 receives ACF with IP address and contacts Endpoint A2 or GK.Endpoint A2 sends ARQ to Gatekeeper and receives ACF.Ga

49、tekeeper has call active.,Endpoints terminate call Both endpoints send DRQ to Gatekeeper.Both endpoints receive DCF.Gatekeeper has call cleared.,Scenario 2:Point to point A/V/D call between multiple zones,H.323 EP,“A-2”,H.323 GK,“A”,Zone“A”,H.323 GK,“B”,H.323 EP,“B-2”,Zone“B”,H.323 EP,“A-1”,H.323 EP

50、,“B-1”,Inter-zone Calls,呼叫流程,Endpoints perform discovery/registration using aliasEndpoint A1 calls Endpoint B1 Endpoint A1 sends ARQ to Gatekeeper A Gatekeeper A issues LRQ(uni/multicast)to Gatekeeper B Gatekeeper A returns ACF Gatekeeper A has call active Endpoint B1 performs ARQ/ACF sequence,retur