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 networks Interoperability standard for network-, ISDN-, and telephony-based conferencing systems Single standard for network, video, and t

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

3、 mechanisms Audio only (IP telephony) Audio and video (videotelephony) Audio and data Audio, video, and data Can also be applied to multipoint-multimedia communications,H.323 Standard,ITU Recommendation V1 approved in 1996, v2 in January 1998 Defines multimedia applications over packet based network

4、s Leverages existing standards Wide market acceptance Facilitates interoperability between vendors Cisco 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.324 Terminal

5、,H.323 Gatekeeper,Packet Network,H.323 Terminal,H.323 Gateway,H.323 MCU,Scope of H.323,PSTN,ISDN,V.70 Terminal,Speech Terminal,H.320 Terminal,Speech Terminal,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 Equ

6、ipment,Audio I/O Equipment,Video Codec H.261,H.263,Audio Codec G.711,G.723.1,Receive Path Delay,User Data App. T.120,System Control User Interface,System Control,H.245 Control,Call Control H.225.0,RAS Control H.225.0,H.225.0 Layer,LAN Interface,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

7、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.323 Client,Local PST

8、N,H.323 GW,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 or Video Control,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 CODECS Video CODECS H.225 Call

9、Control (ISDN Q.931) H.245 System Control Real-Time Protocol (RTP) for media streams Registration, 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CODEC ITU-T建议使用G711,Vi

10、deo 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 提供视频通信的终端必须支持视频CODEC ITU-T建议使用H261,H.225 Call Control (ISDN Q.931),Setup Incoming call Call Proceeding Alerting Phone is ringing Connect Media cut through (used for billing) Release/Release Comple

11、te Tear down call,Capabilities Exchange CODEC negotiation - Transmitter/Receiver capabilities Mode Request - Request specific transmission format Master/Slave Determination Open Logical Channel/Ack Create new audio/video/T.120 stream Commands and Indications Frame flow control, camera control, etc.,

12、H.245 System Control,RTP/RTCPRFCs 1889/1890,End-to-end network transport function Sequence numbering Time Stamping Delivery monitoring Payload type identification - Voice, Video, Compression Type RTCP (Real-Time Control Protocol) provides feedback on the quality of the distribution,Example: Call Sig

13、naling Between Two Endpoints,Media (UDP) Cisco Implementation Note: UDP ports 16384 thru 16384 + (4 x the number of channels on the device),RTP Stream,RTCP Stream,H.323 Endpoint A,H.245 (TCP Dynamic Port),Open Logical Channel,H.225 (TCP Port 1720),Setup,Alerting / Connect,Open Logical Channel Acknow

14、ledge,Capabilities Exchange / MSD,RTP Stream,H.323 Endpoint B,V,V,H.323v1 (5/96) - 7 or 8 Round Trips H.323v2 (2/98) - 2 Round Trips,Assumes Endpoints(Clients) know each others IP addresses,GRQ/GCF/GRJ (Discovery) Unicast - Multicast Find a gatekeeper RRQ/RCF/RRJ (Registration) Endpoint alias/IP add

15、ress binding Endpoint authentication ARQ/ACF/ARJ (Admission) Destination Address Resolution Initial bandwidth request Call Routing Call Authorization,RAS Messages,DRQ/DCF/DRJ (Disconnect) Get rid of call state LRQ/LCF/LRJ (Location) Stateless name - IP address resolution Inter gatekeeper communicati

16、on IRQ/IRR (Information Request) Ping during active calls Resource information for gateways BRQ/BCF/BRJ (Bandwidth) Ask for more/less bandwidth during call URQ/UCF/URJ (Unregistration) Get rid of registration state,RAS Messages (cont.),RAS Message Exchange,Gatekeeper A,Gatekeeper B,RRQ / RCF,ARQ,RRQ

17、 / 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 zone) via RAS Unicast discovery GK will explicitly reply with a GCF, or GRJ GK - GW relationshi

18、p is deterministic Multicast discovery GK will explicitly reply with a GCF, or remain silent GK can be configured as to which subnets to respond to If GW requests an explicit GK name, only that one will respond deterministic If not, the first GK to respond will become the GWs GK non-deterministic If

19、 a GK is not available, the GW will periodically attempt to rediscover If GW discovers GK has gone off-line, it will stop accepting new calls, attempt to rediscover a GK. Active calls are not affected.,Seq Number H.225 Protocol Identifier rasAddess endpointType gatekeeperID .,Selected Message Fields

20、,Registration Message Sequence,H.323 Client learns of GK via Static configuration or dynamic Discovery Registration with an H.323 ID, or an E.164 address H323 ID: E.164 address: 4085551212 Every E.164 address can be registered only once Registration expires after keepalive (30 seconds) Unregister me

21、ssages (URQ / UCF) to de-register from GK Every GW can register with only one GK Only one GK per zone Multiple zones, or logical GKs, per physical machine,Seq Number H.225 Protocol Identifier callSignalAddress rasAddress terminalType terminalAlias gatekeeperID timeToLive keepalive endpointID .,Selec

22、ted Message Fields,Intra-Zone Call Set-up,GK1,1) Terminal A dials the phone number 408-667-1111 for Terminal B 2) GWA sends GK1 an ARQ, asking permission to call Terminal B 3) GK1 does a look-up and finds Terminal B registered; returns an ACF with the IP address of GWB 4) GWA sends a Q.931 Call-Setu

23、p to GWB with Terminal Bs phone number 5) GWB sends GK1 an ARQ, asking permission to answer GWAs call 6) GK1 returns an ACF with the IP address of GWA 7) GWB sets up a POTS call to Terminal B at 408-667-1111 8) When Terminal B answers, GWB sends Q.931 Connect to GWA,Terminal A 415-557-1111,Inter-Zon

24、e Call Set-up,1) Terminal A dials the phone number 408-667-1111 for Terminal B 2) GWA sends GK1 an ARQ, asking permission to call Terminal B 3) 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 GK2 4) GK2 does a look

25、-up and finds Terminal B registered; returns an LCF with the IP address of GWB 5) GK1 returns an ACF with the IP address of GWB 6) GWA sends a Q.931 Call-Setup to GWB with Terminal Bs phone number 7) GWB sends GK2 an ARQ, asking permission to answer GWAs call 8) GK2 returns an ACF with the IP addres

26、s of GWA 9) GWB sets up a POTS call to Terminal B at 408-667-1111 10) 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 B 2) GWA sends GK1 an ARQ, asking permission to call Terminal B 3)

27、 GK1 does a 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-GK 4) Dir-GK does a prefix look-up and finds GK2; Forwards the LRQ to GK2 5-11) Same as steps 4-10 in previous scenario,Call Disconnect,Terminals A and

28、B are in active conversation. 1) Terminal B hangs up 2) 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 GWA 4) GWA sends DRQ to GK1, disconnecting the call between Terminals A and B. A DCF is received

29、 some time later. 5) GWA signals 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 function

30、ality Provides end-to-end delivery services of real-time audio and video RTP provides payload-type identification, sequence numbering, timestamping, and delivery monitoring UDP provides multiplexing and checksum services Can be used with other transport protocols,H.323 Proxy,Conceals identities of e

31、ndpoints GW A never knows the IP address of GW B Proxy relays all call signaling and media streams Ability 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

32、 end-point) Quality of service Application Specific Routing (ASR) Security Proxy inside the Firewall Proxy in Co-Edge Mode Proxy Outside the Firewall Proxies and Network Address Translation (NAT) 12.0(3)T does not support a single proxy per call dual proxy or direct the destination GK makes the deci

33、sion to assign a proxy or not Use “zone access” command to instruct GK to assign proxy Determination to use proxy made by the terminating GK The 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 B 2) GWA sends A

34、RQ to GK1 3) GK1 sends LRQ to GK2 4) GK2 returns Proxy-Bs address, hiding GWBs identity 5) GK1 knows to get to Proxy-B, it must go through Proxy-A, so GK1 returns Proxy-As address to GWA 6) GWA calls Proxy-A 7) Proxy-A consults GK1 to find the true destination, GK1 tells it to call Proxy-B 8) Proxy-

35、A calls Proxy-B 9) Proxy-B consults GK2 for the true destination, which is GWB; GK2 gives GWBs address to Proxy-B 10) Proxy-B completes the call to GWB From here the call proceeds as before.,Limitations and Guidelines,Zone prefixes per Directory GK: 10,000 for dedicated Dir-GK 2,000 for any GK manag

36、ing local zones LRQ hops Max hop-count of 5 Cisco-specific feature; LRQs from non-Cisco gear and pre-12.0(3)T Cisco gear will not be forwarded Active Registrations Terminals are low-maintenance, but GWs are high Target of 100 GWs per GK (keep call traffic in mind) Local zones per GK: 100 Remote zone

37、s per GK: 100 for H.323 ID destinations less impacting for E.164 destinations Tech Prefixes: 50 per GK,Components of Quality,DSPs CODECs,Carrier-Class Voice Quality,End-to-End NetworkingQoS Service Elements,DSPs CODECs,QoS WAN,Gateway Latency Coding Quality,Network Latency Jitter Control,Cisco AS530

38、0,Silence Suppression / VAD,Essential Components 22%,Pauses 56%,Repetitive 22%,Over half of the typical voice call is silence! VAD removes silence from data stream. Comfort noise during silent periods.,RTP Header Compression,20ms8kb/s yields 20 byte payload IP header 20; UDP header 8; RTP header 12

39、2X payload! Header compression 40Bytes to 2-4 much of the time Hop-by-Hop Slow Links,Overhead,Version,IHL,Type of Service,Total Length,Identification,Flags,Fragment Offset,Header Checksum,Protocol,Time to Live,Source Address,Destination Address,Padding,Options,Source Port,Destination Port,Checksum,L

40、ength,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 Router#conf terminal Router(config)#hostname bj-gw 定义主机名 接口配置 Bj-gw#conf terminal Bj-gw(config)#int fastethernet0/0 Bj-gw(config-if)#ip addr 10.1.1.1 255.255.255.0

41、Bj-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 pots Bj-gw(config)#destination-pattern 010114 Bj-gw(config)#port 1/0/0 网络端的对等体配置 Bj-gw(config)#dial-peer voice 20 voip Bj-gw(config)#destination-pattern 021114 Bj-gw(config)#session tartget ipv4:10.1.1.2,Case-2：经过一个关守的

42、配置,网关配置（有关守）,基本配置 Router#conf terminal Router(config)#hostname bj-gw 定义主机名 接口配置 Bj-gw#conf terminal Bj-gw(config)#int fastethernet0/0 Bj-gw(config-if)#ip addr 10.1.1.1 255.255.255.0 Bj-gw(config-if)#no shut Bj-gw(config-if)#h323-gateway voip interface （与VOIP相连接口） Bj-gw(config-if)#h323-gateway voip i

43、d 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

44、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-technology Arq reject-unknown-prefix Lrq reject-unknown-prefix No shut,Case study,gw-bj1 1#,gw-bj2 2#,gw-bj3 3#,gw-sh1 1#,gw-sh2 2#,gw-sh3 3#,gk-bj,gk-sh,Beijing: zone local gk-bj zone remote gk-sh zone prefix gk-bj 010* zone pre

45、fix gk-sh 021* gw-type-prefix 5# hopoff gk-HKTEL gw-type-prefix 1# default-technology Arq reject-unknown-prefix Lrq reject-unknown-prefix Lrq forward-queries,Shanghai: zone local gk-sh zone remote gk-bj zone prefix gk-bj 010* zone prefix gk-sh 021* gw-type-prefix 5# hopoff gk-HKTEL gw-type-prefix 1#

46、 default-technology Arq reject-unknown-prefix Lrq reject-unknown-prefix Lrq 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-sh1,gw-bj1?,interface Ethernet0/0 h323-gateway voip tech-prefix 1#,dial-peer voice 101 voip

47、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-pattern 021T session target ras,dial-peer voice 103 voip destination-pattern 00852T tech-prefi

48、x 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 SETUP to Endpoint B Endpoint B sends CALL PROCEEDING to Endpoint A (optional). Endpoint B

49、 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.323 GK,“A”,Single Zone,H.323 EP,“A-1”,呼叫流程,Endpoints perform discovery/registratio

50、n 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. Gatekeeper has call active.,Endpoints terminate call Both endpoints send DRQ to