مقایسه تکنیک های پیاده سازی انتقال Audio and Video Streaming در سیستم های موبایل
اسلاید 1: بررسی و مقایسه تکنیک های پیاده سازی انتقال Audio & Video Streaming در سیستم های موبایل مبتنی بر p2p1امید رضا باقریدانشگاه امیرکبیر
اسلاید 2: فهرست مطالبمقدمهآشنایی با اصطلاحات مورد استفاده در مقالهآشنایی اجمالی با ساختار شبکه موبایلساختار NATبررسی تجربی یک آزمایشارزیابی و مقایسه چند نرم افزار در استفاده از روش P2P در انتقال ویدئو و صدا2
اسلاید 3: آشنایی با ساختار کلی شبکه موبایل و پروتکلهای آننسل های موبایل1G2G2.5 G2.75G3G3G-324M3G/UMTS3GPPETSI4Gنحوه انتقال صدا و داده در موبایل3
اسلاید 4: 3G Compared to 2G and 2.5G services, 3G allows simultaneous use of speech and data services and higher data rates (up to 14.4 Mbit/s on the downlink and 5.8 Mbit/s on the uplink with HSPA+). To support mobile multimedia applications,3G had to deliver packet-switched data with better spectral efficiency, at far greater speeds3G networks offer a greater degree of security than 2G predecessors. 3G networks use the KASUMI block crypto instead of the older A5/1 stream cipher.4
اسلاید 5: 3G-324M3G-324M is the 3GPP umbrella protocol for video telephony in 3G mobile networks.The 3G-324M protocol operates over an established circuit switched connection between two communicating peers. 3G-324M is an umbrella specification to enable conversational multimedia communication over Circuit Switched (CS) networks and has been adopted by the 3GPP. 3G-324M is based on the ITU-T H.3245
اسلاید 6: 3G-324M Sub protocolsITU-T H.245 for call control ITU-T H.223 for bit streams to data packets multiplexer/demultiplexer ITU-T H.223 Annex A and B for error handling of low and medium BER detection, correction and concealment ITU-T H.324 with Annexes A and C for operating in wireless environment 6
اسلاید 7: Scope of 3G-324M7
اسلاید 8: 3G-324M UsagesThe 3G-324M specification using the Circuit switched network allows delay sensitive conversational multimedia services such as:Video Conferencing for personal and business use Multimedia entertainment services Telemedicine Surveillance Live Video Broadcasting– Cable TV On-the-Go Video-on-demand (movies, news clips) 8
اسلاید 9: 3G-UMTSUMTS is one of the third-generation (3G) mobile telecommunications technologies, which is also being developed into a 4G technology. It is specified by 3GPP and is part of the global ITU IMT-2000 standardThe most common form of UMTS uses W-CDMA (IMT Direct Spread) as the underlying air interface but the system also covers TD-CDMA and TD-SCDMA (both IMT CDMA TDD).UMTS also covers the radio access network (UMTS Terrestrial Radio Access Network; UTRAN), the core network (Mobile Application Part; MAP) as well as authentication of users via USIM cards (Subscriber Identity Module).9
اسلاید 10: 3G-UMTSUMTS, using W-CDMA, supports maximum theoretical data transfer rates of 21 Mbit/s (with HSDPA),although at the moment users in deployed networks can expect a transfer rate of up to 384 Kbit/s for R99 handsets, and 7.2 Mbit/s for HSDPA handsets in the downlink connection. This is still much greater than the 9.6 Kbit/s of a single GSM error-corrected circuit switched data channel or multiple 9.6 Kbit/s channels in HSCSD (14.4 Kbit/s for CDMAOne), and—in competition to other network technologies such as CDMA2000, PHS or WLAN—offers access to the World Wide Web and other data services on mobile devices.10
اسلاید 11: 3G-UMTS11
اسلاید 12: UMTS Transmitter12
اسلاید 13: Radio Network Controller(RNC)The RNC is a governing element in the UMTS radio access network (UTRAN) and is responsible for control the Node Bs that are connected to it.The RNC connects to the Circuit Switched Core Network through Media Gateway (MGW) and to the SGSN (Serving GPRS Support Node) in the Packet Switched Core Network.13
اسلاید 14: RNC InterfacesThe logical connections between the network elements are known as interfaces.14
اسلاید 15: عملکرد تکنولوژی NATNAT چیست؟انواع NATNAT TraversalUDP Hole punchingTraversal Using relay NAT (TURN)Simple Traversal of UDP over NATs (STUN)مزایا و معایب15
اسلاید 16: NAT Traversal by Relaying TURN16
اسلاید 17: NAT Traversal by Connection STUN17
اسلاید 18: IP Addressing در شبکه موبایلPublic IP AddressDynamic IP AddressPrivate IP Address18
اسلاید 19: Public and private IP address domains19
اسلاید 20: NAPTNetwork Address Port Translation20
اسلاید 21: نمایی از پورت های محدود شده در NATClientServer1Server2RequestResponse123421
اسلاید 22: What is UDP Hole Punching ?In computing, UDP hole punching is a commonly used NAT traversal technique.Network address translation (NAT) traversal through User Datagram Protocol (UDP) hole punching is a method for establishing bidirectional UDP connections between Internet hosts in private networks using NAT. It does not work with all types of NATs as their behavior is not standardized.Each host behind a NAT contacts a third, well-known server (usually a STUN server) in the public address space and then, once the NAT devices have established UDP state information, switches to direct communication hoping that the NAT devices will keep the states despite the packets coming from a different host.UDP hole punching will not work with a Symmetric NAT (also known as bi-directional NAT) which tend to be found inside large corporate networks. With Symmetric NAT, the IP address of the well known server is different from that of the endpoint, and therefore the NAT mapping the well known server sees is different from the mapping that the endpoint would use to send packets through to the client. For details on the different types of NAT, see network address translation.A somewhat more elaborate approach is where both hosts will start sending to each other, using multiple attempts. On a Restricted Cone NAT, the first packet from the other host will be blocked. After that the NAT device has a record of having sent a packet to the other machine, and will let any packets coming from these IP address and port number through.The technique is widely used in peer-to-peer software and Voice over Internet Protocol telephony. It is one of the methods used in Skype to bypass firewalls and NAT devices. It can also be used to assist the establishment of virtual private networks operating over UDP.The same technique is sometimes extended to Transmission Control Protocol (TCP) connections, albeit with much less success.22
اسلاید 23: UDP Hole PunchingAlgorithmLet A and B be the two hosts, each in its own private network; N1 and N2 are the two NAT devices; S is a public server with a well-known globally reachable IP address.A and B each begin a UDP conversation with S; the NAT devices N1 and N2 create UDP translation states and assign temporary external port numbers S relays these port numbers back to A and B A and B contact each others NAT devices directly on the translated ports; the NAT devices use the previously created translation states and send the packets to A and B23
اسلاید 24: UDP Hole Punching Process behind Common NAT24
اسلاید 25: UDP Hole Punching, Peers Behind Different NATs25
اسلاید 26: UDP Hole Punching, Peers Behind Multiple Levels of NAT26
اسلاید 27: Experimental ProceduresInitial ValuesInitial ValuesInterval of Connecting10 times (In each half an hour)Download Speed234kbpsNum of packets sent50Access Point Type Nokia Indoor MicrocellOperatorOrange with 2 Mbps (E1)27
اسلاید 28: Experimental Procedures28
اسلاید 29: Technology EvaluationP2P Arrangements :Direct P2P Advantages : no intermediary node is neededDisadvantages : critical traffic in 3G network, bring security (each nodes should handle security by itself)Indirect P2P Advantages : Security control bye middle nodes, communicate with public and private IP over other nodesDisadvantages : Authentication is required by the applications to eliminate such unexpected traffic29
اسلاید 30: Sections Describes the Outcomes of the P2P Tests QnextYahoo MessengerGoogle TalkMSN MessengerSkypeSightSpeed(v6)Real Networks30
اسلاید 31: Qnext (ver. 3.0)Specifications : Java-based Software ApplicationCould not Establish a Direct P2P SessionStream all Traffic via a Common Central NodeUse TCP Protocol instead of UDP for all usageAnalysis : ( on 10-based LAN & direct p2p & UDP)Unacceptable for real-time mobile video applicationsUDP hole punching process over the orange NAT Failed31
اسلاید 32: Yahoo Messenger (ver. 8.1)Specifications :Call setup through implementing SIP & LaboratoryStreams Audio & Video via a Central Node over TCPAnalysis : (over 3G network)Poor overall performance including Video Delays of Approximately 7 sec ‘glitchy’ & pixilated32
اسلاید 33: Google Talk (beta)Specifications : Streamed Directly from P2P & over the UDPExtensible Messaging & Presence Protocol (XMPP)Audio & video Delay 3 secAnalysis : Incoming & Outgoing Packets and Transmission was effectively SymmetricalAverage Data Rates received is 13kbps33
اسلاید 34: 34
اسلاید 35: MSN Messenger (ver. 8.1)Specifications : Bidirectional Video StreamingSIP SupportMSNMS Protocol over TCP to gather IP & Port detailsBi-directional Video Streaming & Direct P2PAnalysis : 1sec Delay56kbps Data Rates 35
اسلاید 36: Skype (ver. 3.0)Specifications : No CostP2p Video Calls with millisecond over 3GUse Proprietary ProtocolsTransmission via Public IP addressAnalysis : Data rate of 3-16kbpsAverage 58kbps on Upload pathAverage 195bytes packet size during video call36
اسلاید 37: SightSpeed (ver. 6)Specifications : Use H.263 video codecBi-directional video streaming performance1sec direct P2P delayAnalysis : Average packet size of 380 bytes (double than Skype)4 times delay more than SkypeHigher quality picture than SKype37
اسلاید 38: Real NetworksFree source software :Drawing Streaming ServerHelix ServerReal Network products:Helix Mobile producerHelix ServerReal Player38
اسلاید 39: AlternativesMobile MonitorIMS ( IP Multimedia Subsystem)39
اسلاید 40: ConclusionSightspeed & Skype gave acceptable streaming performance in for (near) real-time video applicationsSightspeed & Skype overcome the NAT issues involved and implemented a direct based P2P, bidirectional video streamingMobile application designer can improve performance with suitable and tailored encoding and streaming formats such as MPEG4-part10(H264) & ACC CODECSProve the feasibility of such mobile applications40
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