聯(lián)通培訓(xùn)H323原理

1、1h.323原理原理2教學(xué)目標(biāo)教學(xué)目標(biāo) 理解理解h323的概念的概念 掌握掌握h323的組成及其特點(diǎn)的組成及其特點(diǎn) 掌握主要的呼叫控制信令掌握主要的呼叫控制信令3教學(xué)內(nèi)容教學(xué)內(nèi)容 什么是什么是h323？ h323的組成及特點(diǎn)的組成及特點(diǎn) h323區(qū)域區(qū)域 h323協(xié)議集協(xié)議集4what is h.323? international standard for conferencing over packet-based networks interoperability standard for network-, isdn-, and telephony-based conferencing

2、 systems single standard for network, video, and telephony products to interoperate5h.323technology 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-bas

3、ed networks h.323 can be applied in a variety of mechanismsaudio only (ip telephony)audio and video (videotelephony)audio and dataaudio, video, and datacan also be applied to multipoint-multimedia communicationsh.323 standarditu recommendationv1 approved in 1996, v2 in january 1998defines multimedia

4、 applications over packet based networksleverages existing standardswide market acceptancefacilitates interoperability between vendorscisco voip solutions are h.323 compliant60573_01f9_c2 1998, cisco systems, inc. 7 h323標(biāo)準(zhǔn)是標(biāo)準(zhǔn)是h32x家族的一部分，家族中家族的一部分，家族中其他的協(xié)議定義了基于不同網(wǎng)絡(luò)的多媒體其他的協(xié)議定義了基于不同網(wǎng)絡(luò)的多媒體通信服務(wù)通信服務(wù) 基于基于s

5、cn的的h324 基于基于isdn的的h320 基于基于b-isdn的的h321和和h310 基于能提供基于能提供qos的的lan的的h3228packet networkscope of h.323pstnisdnh.323 componentsevgk9h323終端終端 主要是主要是ip電話和電話和pc機(jī)，而非普通的電話，機(jī)，而非普通的電話，pc包括包括：一個(gè)網(wǎng)絡(luò)接口一個(gè)網(wǎng)絡(luò)接口音視頻編解碼器音視頻編解碼器h323軟件軟件 必須支持必須支持g.711 和和h.261 必須支持必須支持h245、h225、ras、rtp/rtcp10終端：參考結(jié)構(gòu)終端：參考結(jié)構(gòu)video i/o equipm

6、entaudio i/o equipmentvideo codech.261,h.263audio codecg.711,g.723.1receivepathdelayuser data app.t.120systemcontroluser interfacesystem controlh.245 controlcall controlh.225.0ras controlh.225.0h.225.0layerlaninterface11h323網(wǎng)關(guān)網(wǎng)關(guān) 轉(zhuǎn)換協(xié)議轉(zhuǎn)換協(xié)議 轉(zhuǎn)換信息格式轉(zhuǎn)換信息格式 傳遞信息傳遞信息12h323關(guān)守關(guān)守 地址轉(zhuǎn)換地址轉(zhuǎn)換 控制許可控制許可 帶寬控制和管理帶寬控制和

7、管理 區(qū)域管理區(qū)域管理 其他可選的功能其他可選的功能 -呼叫控制信令呼叫控制信令 -呼叫授權(quán)呼叫授權(quán) -呼叫管理呼叫管理13mcu-多點(diǎn)控制單元多點(diǎn)控制單元 提供提供3個(gè)或多點(diǎn)間的會(huì)議服務(wù)個(gè)或多點(diǎn)間的會(huì)議服務(wù) mcu管理各點(diǎn)間的會(huì)議資源和協(xié)商管理各點(diǎn)間的會(huì)議資源和協(xié)商 包括兩個(gè)功能部件：包括兩個(gè)功能部件：mc（多點(diǎn)控制器）進(jìn)行會(huì)議控制以決定信息流的多點(diǎn)控制器）進(jìn)行會(huì)議控制以決定信息流的流向流向mp（多點(diǎn)處理器）負(fù)責(zé)組合、交換和處理信息流多點(diǎn)處理器）負(fù)責(zé)組合、交換和處理信息流14mcu本地服務(wù)：mcu：參考模型mcmp(audio)mp(video)mp(data)callaudiodatavi

8、deoref: h.323v215mcu應(yīng)用案例應(yīng)用案例16h.323 層次結(jié)構(gòu)圖層次結(jié)構(gòu)圖rtprtcpterminal to gatekeeper signalingh.225.0ras信信道道h.225.0 信號(hào)呼叫信號(hào)呼叫信道信道unreliable transport (udp)physical layerlink layerg.7xxdata appav apph.26xnetwork layer (ip)h.245控制控制信道信道terminal control and managementreliable transport (tcp)t.12017 h.323 zonesh.

9、323 gatekeeper bgatekeeper zone blocal pstnvh.323 gatekeeper agatekeeper zone ah.323clientlocal pstnvh.323gwqos wangkgklocal pstnvlocal pstnv18 19h323 zone 由關(guān)守管理的所有終端、網(wǎng)關(guān)、由關(guān)守管理的所有終端、網(wǎng)關(guān)、mcu的的集合集合 一個(gè)區(qū)域至少包括一個(gè)終端一個(gè)區(qū)域至少包括一個(gè)終端 一個(gè)區(qū)域只有一個(gè)關(guān)守一個(gè)區(qū)域只有一個(gè)關(guān)守20h.235h.323 protocol stacktcpudpiprtcprasaudio orvideocontro

10、l h.225(q.931)call control datat.120h.245payloadheaderg.7xxh.26xrtpaudio video21h323定義的協(xié)議定義的協(xié)議 audio codecs video codecs h.225 call control (isdn q.931) h.245 system control real-time protocol (rtp) for media streams registration, admission, status (ras) messages for gatekeeper to endpoint communica

11、tions22audio codec 發(fā)起端音頻發(fā)起端音頻codec對(duì)模擬話音進(jìn)行編碼，轉(zhuǎn)換對(duì)模擬話音進(jìn)行編碼，轉(zhuǎn)換成數(shù)字信號(hào)在網(wǎng)絡(luò)里傳輸；接收端對(duì)數(shù)字信號(hào)成數(shù)字信號(hào)在網(wǎng)絡(luò)里傳輸；接收端對(duì)數(shù)字信號(hào)進(jìn)行解編碼，把它還原成模擬的語(yǔ)音信號(hào)。進(jìn)行解編碼，把它還原成模擬的語(yǔ)音信號(hào)。 -采樣采樣 -量化量化 -編碼編碼 -壓縮壓縮 所有所有h323終端必須支持語(yǔ)音終端必須支持語(yǔ)音codec itu-t建議使用建議使用g71123video codec 發(fā)起端視頻發(fā)起端視頻codec把從攝象機(jī)獲取的圖象進(jìn)行把從攝象機(jī)獲取的圖象進(jìn)行編碼，轉(zhuǎn)換成數(shù)字信號(hào)在網(wǎng)絡(luò)里進(jìn)行傳輸；在編碼，轉(zhuǎn)換成數(shù)字信號(hào)在網(wǎng)絡(luò)里進(jìn)行傳輸；

12、在接收端，視頻接收端，視頻codec把數(shù)字信號(hào)進(jìn)行解碼，把把數(shù)字信號(hào)進(jìn)行解碼，把它輸出到視頻顯示器上它輸出到視頻顯示器上 h323定義視頻定義視頻codec作為可選項(xiàng)作為可選項(xiàng) 提供視頻通信的終端必須支持視頻提供視頻通信的終端必須支持視頻codec itu-t建議使用建議使用h26124h.225 call control (isdn q.931) setupincoming call call proceeding alertingphone is ringing connectmedia cut through (used for billing) release/release comp

13、letetear down call25 capabilities exchangecodec negotiation - transmitter/receiver capabilitiesmode request - request specific transmission format master/slave determination open logical channel/ackcreate new audio/video/t.120 stream commands and indicationsframe flow control, camera control, etc.h.

14、245 system control26rtp/rtcprfcs 1889/1890 end-to-end network transport function sequence numberingtime stampingdelivery monitoringpayload type identification - voice, video, compression type rtcp (real-time control protocol) provides feedback on the quality of the distributionrtp timestampsynchroni

15、zation source (ssrc) id4bytes4bytes4bytessequence numberpayload typemccver27example: call signaling between two endpointsmedia (udp)cisco implementation note:udp ports 16384 thru 16384 + (4 x the number of channels on the device)h.323endpoint ah.245 (tcpdynamic port)open logical channelh.225 (tcp po

16、rt 1720)setupalerting / connectopen logical channel acknowledgecapabilities exchange / msdh.323endpoint bvvh.323v1 (5/96) - 7 or 8 round tripsh.323v2 (2/98) - 2 round tripsassumes endpoints(clients) know each others ip addresses28 grq/gcf/grj (discovery)unicast - multicastfind a gatekeeper rrq/rcf/r

17、rj (registration)endpoint alias/ip address bindingendpoint authentication arq/acf/arj (admission)destination address resolutioninitial bandwidth requestcall routingcall authorizationras messages29 drq/dcf/drj (disconnect)get rid of call state lrq/lcf/lrj (location)stateless name - ip address resolut

18、ioninter gatekeeper communication irq/irr (information request)ping during active callsresource information for gateways brq/bcf/brj (bandwidth)ask for more/less bandwidth during call urq/ucf/urj (unregistration)get rid of registration stateras messages (cont.)30ras message exchangegatekeeper agatek

19、eeper brrq / rcfarqrrq / rcfarq / acflrqip networkphone aphone bgateway agateway bh.225 (q.931) setuph.225 (q.931) connecth.245rtpacflcfvv31gatekeeper 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 rel

20、ationship 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-determin

21、istic if 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.gatekeepergateway agateway bvvgrq (unicast)grq (multicast)gcfgcf seq number h.225 protocol

22、identifier rasaddess endpointtype gatekeeperid.selected message fields32registration 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 on

23、ly once registration expires after keepalive (30 seconds) unregister messages (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 machinegatekeepergateway agateway bvvrrqrrqrcfrcf seq number h.225 protocol identi

24、fier callsignaladdress rasaddress terminaltype terminalalias gatekeeperid timetolive keepalive endpointid.selected message fields33intra-zone call set-upgk11) 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-

25、up and finds terminal b registered; returns an acf with the ip address of gwb4) 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 4

26、08-667-11118) when terminal b answers, gwb sends q.931 connect to gwaterminal a415-557-1111gwagwbterminal b408-667-11112345681734inter-zone call set-up1) 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 an

27、d 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 does 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 w

28、ith terminal bs phone number7) gwb sends gk2 an arq, asking permission to answer gwas call8) gk2 returns an acf with the ip address 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 gwagk1gwagwb61019257834gk2terminal a415-557-1111te

29、rminal b408-667-111135inter-zone call set-up: directory gatekeeper1) 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 wildcard

30、 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 scenario711110268935gwbgwagk1gk2dir-gk4terminal a415-557-1111terminal b408-667-111136call disconnect terminals a and b are in active conversation.1) t

31、erminal 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 a cal

32、l 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.gk1gwagwb23132gk2terminal a415-557-1111terminal b408-667-111137real-time transport protocol (rtp) works with udp to provide tra

33、nsport-protocol functionality provides end-to-end delivery services 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 protocols38h.323 proxy co

34、nceals identities of endpointsgw a never knows the ip address of gw bproxy relays all call signaling and media streams ability to provide a ras interface to non-ras clients.vvgk a - directgk b - proxiedlrq/lcfarq/acfh.225 / h.245 / rtpgw agw b39proxies proxies are used for:security (hiding the ident

35、ity of the true end-point)quality of serviceapplication specific routing (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 t

36、he decision to assign a proxy or not use “zone access” command to instruct gk to assign proxydetermination to use proxy made by the terminating gkthe originating gk will assign a proxy if the terminating gk is using a proxy40inter-zone call set-up with proxies1) terminal a dials terminal b2) gwa sen

37、ds arq to gk13) gk1 sends lrq to gk24) gk2 returns proxy-bs address, hiding gwbs identity5) 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

38、calls proxy-b9) proxy-b consults gk2 for the true destination, which is gwb; gk2 gives gwbs address to proxy-b10) proxy-b completes the call to gwbfrom here the call proceeds as before.gk2gk1gwagwb6125934terminal a415-557-1111terminal b408-667-1111proxy-aproxy-b781041limitations and guidelines zone

39、prefixes per directory gk:10,000 for dedicated dir-gk2,000 for any gk managing local zones lrq hopsmax hop-count of 5cisco-specific feature; lrqs from non-cisco gear and pre-12.0(3)t cisco gear will not be forwarded active registrationsterminals are low-maintenance, but gws are hightarget of 100 gws

40、 per gk (keep call traffic in mind) local zones per gk: 100 remote zones per gk: 100 for h.323 id destinationsless impacting for e.164 destinations tech prefixes:50 per gk42components of qualitycarrier-class voice qualityqos wancisco as5300vv43silence suppression / vadpauses56%repetitive22% over hal

41、f of the typical voice call is silence! vad removes silence from data stream. comfort noise during silent periods.44rtp header compression 20ms8kb/s yields 20 byte payload ip header 20; udp header 8; rtp header 12 header compression 40bytes to 2-4 much of the time slow linksoverheadversionihltype of

42、 servicetotal lengthidentificationflagsfragment offsetheader checksumprotocoltime to livesource addressdestination addresspaddingoptionssource portdestination portchecksumlengthptmccxpv=2sequence numbertimestampsynchronization source (ssrc) identifier45h323應(yīng)用案例應(yīng)用案例 voip46case-1 ：不經(jīng)過關(guān)守的配置：不經(jīng)過關(guān)守的配置 12

43、3456789*8#123456789*8#routerbjroutership cloud port1/0/0 port1/0/010.1.1.110.1.1.247網(wǎng)關(guān)配置（無關(guān)守）網(wǎng)關(guān)配置（無關(guān)守） 基本配置基本配置router#conf terminalrouter(config)#hostname bj-gw 定義主機(jī)名定義主機(jī)名 接口配置接口配置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 s

44、hut48 撥號(hào)對(duì)等體的配置撥號(hào)對(duì)等體的配置本地（本地（local）對(duì)等體配置對(duì)等體配置bj-gw(config)#dial-peer voice 10 potsbj-gw(config)#destination-pattern 010114bj-gw(config)#port 1/0/0網(wǎng)絡(luò)端的對(duì)等體配置網(wǎng)絡(luò)端的對(duì)等體配置 bj-gw(config)#dial-peer voice 20 voipbj-gw(config)#destination-pattern 021114bj-gw(config)#session tartget ipv4:10.1.1.249case-2：經(jīng)過一個(gè)關(guān)守的

45、配置經(jīng)過一個(gè)關(guān)守的配置123456789*8#123456789*8#shrouterip cloud port1/0/1 port1/0/1h.323 gatekeeper10.1.1.110.1.1.2 192.168.1.1 bj router50網(wǎng)關(guān)配置（有關(guān)守）網(wǎng)關(guān)配置（有關(guān)守） 基本配置基本配置router#conf terminalrouter(config)#hostname bj-gw 定義主機(jī)名定義主機(jī)名 接口配置接口配置bj-gw#conf terminalbj-gw(config)#int fastethernet0/0bj-gw(config-if)#ip addr

46、10.1.1.1 255.255.255.0bj-gw(config-if)#no shutbj-gw(config-if)#h323-gateway voip interface （與與voip相連接口）相連接口）bj-gw(config-if)#h323-gateway voip id gk-bj ipaddr 192.168.1.1 1719 （ 指向關(guān)守的ip地址）bj-gw(config-if)# h323-gateway voip h323-id beijing-gw （本網(wǎng)關(guān)的別名）bj-gw(config-if)# h323-gateway voip tech-prefix 1

47、# （注明身份類型）51關(guān)守配置關(guān)守配置 配置本地和遠(yuǎn)端的區(qū)域名配置本地和遠(yuǎn)端的區(qū)域名gk(config)#gatekeeper #zone local gk-bj #zone local. #zone remote 配置區(qū)域前綴（區(qū)號(hào)）配置區(qū)域前綴（區(qū)號(hào)） #zone prefix gk-bj 010* #zoen prefix gk-sh 021* #zone prefix52關(guān)守配置（續(xù)）關(guān)守配置（續(xù)） 配置缺省的技術(shù)前綴及其它配置缺省的技術(shù)前綴及其它gw-type-prefix 1# default-technologyarq reject-unknown-prefixlrq reje

48、ct-unknown-prefixno shut53 case study54 gw-bj1 1# gw-bj2 2# gw-bj3 3# gw-sh1 1# gw-sh2 2# gw-sh3 3# gk-bj gk-shbeijing: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

49、-unknown-prefixlrq forward-queriesshanghai:zone local gk-shzone remote 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-queries55scene 1: 2#02112345678 從北京網(wǎng)關(guān)發(fā)起呼叫從北京網(wǎng)關(guān)發(fā)起呼

50、叫落地網(wǎng)關(guān)落地網(wǎng)關(guān): gw-sh2 scene 2: 02112345678scene 3: 5#0085212345678scene 4: 02912345678 gw-sh1 gw-bj1?interface ethernet0/0 h323-gateway voip tech-prefix 1#dial-peer voice 101 voip destination-pattern 021t tech-prefix 2# session target rasinterface ethernet0/0 h323-gateway voip tech-prefix 2#interface et

51、hernet0/0 h323-gateway voip tech-prefix 3#dial-peer voice 102 voip destination-pattern 021t session target rasdial-peer voice 103 voip destination-pattern 00852t tech-prefix 3# session target rasdial-peer voice 104 voip destination-pattern 029t session target ras56h323應(yīng)用案例應(yīng)用案例 coip57scenario 0: poin

52、t to point a/v/d with no gatekeeper ip networkh.323 endpoint ah.323endpoint b58呼叫流程呼叫流程 endpoint a calls endpoint b*: endpoint a sends setup to endpoint b endpoint b sends call proceeding to endpoint a (optional). endpoint b sends alerting to endpoint a endpoint b sends connect to endpoint a. endpoi

53、nts terminate call endpoint a sends release complete to endpoint b. 59scenario 1: point to point a/v/d call within single zoneh.323 ep“a-2”h.323 gk“a”single zoneh.323 ep“a-1”60呼叫流程呼叫流程 endpoints perform discovery/registration using alias. endpoint a1 calls endpoint a2 endpoint a1- sends arq to gatek

54、eeper 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. 61 endpoints terminate call both endpoints send drq to gatekeeper.both endpoints receive dcf.gatekeeper has call cleared.62scenari

55、o 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“b-1”inter-zone calls63呼叫流程呼叫流程 endpoints perform discovery/registration using alias endpoint a1 calls endpoint b1 endpoint a1 sends arq to gatekeeper a gateke

56、eper a issues lrq (uni/multicast) to gatekeeper b gatekeeper a returns acf gatekeeper a has call active endpoint b1 performs arq/acf sequence, returns connect gatekeeper b has call active 64 endpoints terminate callboth endpoints send drq to gatekeeper. both endpoints receive dcf. gatekeepers have c

57、alls cleared. 65scenario 3: multi-point a/v/d call between multiple zones inter-zone callsh.323 mcuh.323 ep“a-1”h.323 gk“a”h.323 ep“a-2”zone “a”h.323 gk“b”h.323 ep“b-2”zone “b”h.323 ep“b-1”66呼叫流程呼叫流程 endpoints perform discovery/registration using alias. mcu registers (rrq) h323-id for conference ali

58、as at gatekeeper, gets rcf the mcu will establish a g.711 & h.261 cif centralized conference. 67 endpoint a1 calls mcu endpoint a1 sends arq to gatekeeper with conference alias.endpoint a1 receives acf with ip address and contacts mcu. mcu sends arq to gatekeeper and receives acf the mcu sends m

59、ultipointconference indication to a1. a1 shall wait for communicationmode command. the mcu will send communicationmode command with the conference mode.68 mcu and endpoint a1 open audio, video and data channels according to communicationmode command. endpoint a2 calls mcu (to join conference) endpoi

60、nt a2 sends arq to gatekeeper with conference alias.endpoint a2 receives acf with ip address and contacts mcu.mcu sends arq to gatekeeper and receives acf69 the mcu sends multipointconference indication to a2. a2 shall wait for communicationmode command. the mcu will send communicationmode command wit