COST Action 272 Packet-Oriented Service Delivery via Satellite

Transcription

1 COST Action 272 Packet-Oriented Service Delivery via Satellite CNES CNIT Cooperation within COST 272 TD P Author(s) Franco Davoli, Erina Ferro, Luca Simone Ronga 1

2 The following information is related to the co-operation between the two experimental satellite networks of CNES (F) and CNIT (I), within the COST Action 272 framework. The first Section of this document directly refers to the message sent by Robert Rumeau to Franco Davoli, reported in Annex A. The second Section describes a possible second step to be implemented after the three alternatives indicated by Robert Rumeau have been implemented and tested. I. SECTION Point 1) Applications The Teledottorato projects employ a subset of MBONE Tools, exactly: VIC v2.8 (Video, H261, Hardware Encoded via BT848 based acquisition board) RAT v4.2.4 (Audio) SDR v3.0 (Session Announcement) MPPT v1.3 (Microsoft Power Point Multicast Transmission Plug.In) The first 3 applications are available for the major platforms; MPPT is only available for the Microsoft Windows one. Point 2) Traffic Rates The Teacher Originated flows are dimensioned as follows: Audio RTP Flow on IP Multicast: 64 kbps Video RTP Flow on IP Multicast: 256 kbps (@15 fps) MPPT ECSRM/FCAST Reliable Multicast with bursts <= 128 kbps In total the teacher flow require a sustained rate of 384 kbps with bursts of 512 kbps (more or less) The Students Originated flows are: For Iron sites: Audio RTP Flow on IP Multicast : 64 kbps (muted during the lesson) For Gold Sites Audio RTP Flow on IP Multicast : 64 kbps Video RTP Flow on IP Multicast : 128 kbps (@15 fps) Only a limited number of Gold sites are allowed for each session, depending on the size of the minimum link of the heterogeneous network. As regards checking a traceroute between Toulouse and Naples, the right IP address is NOT , which corresponds to the University of Genoa on the Italian Research Network (GARR). The CNIT network address that can be used is , corresponding to the main Naples router (CISCO 7513). As contact person for Naples, reference can be made to Franco Davoli (phone: ; franco@dist.unige.it) or to Stefano Vignola 2

3 (phone: ; who is the senior research scientist in the CNIT multimedia communication laboratory. Point 3) Application Level Gateway Proposals The basic connection that could be set up is IP-IP Tunnelling with Multicast enabled. This could be achieved with: ISDN Aggregation of 4 Basic Rate Accesses between one of the CNIT sites and CNES. To obtain this, a 4 BRI port Router is necessary at CNES, along with 4 ISDN accesses. The advantage is the link level guaranteed bandwidth, at the expense of 8 long distance Italy-France telephone calls. Internet quality IP tunnelling between Neaples (CNIT) and CNES. We agree on the concerns about the availability of a sufficiently good Internet link across countries, quick tests to evaluate the connectivity between any CNIT site and CNES could be performed. Once obtained IP level connectivity we can apply one of the three -very interesting!-, or all the three, service trans-coding modes, as described by Robert: TV Mode H263 to MPEG2 trans-coding via composite video analog signal MPEG4/IP Mode H263 to MPEG4/IP transcoding via composite video analog signal Transparent Mode IP level routing between Ka CNIT and DVB-S platform II. SECTION The interconnection of the two networks is foreseen in two steps. Initially, a remote IP-IP tunnelling is tested, where the two networks are interconnected via standard European terrestrial lines, without the movement of a Ku band earth station from the CNES network to Italy. Let s call this phase remote-tunnelling configuration, RTC. Subsequently, a Ku band earth station is moved from France to one of the Italian Ka band sites, and interconnected, via a dedicated terrestrial line, with the Ka band earth station of CNIT selected to route the data to the CNES Ku band earth station, which, at its turn, will retransmit them to France. Let s call this phase co-located station configuration, CSC. Both these phases are interesting in order to compare the results of measures performed in different conditions on the same amount of traffic. During the RTC phase, additional errors and/or other congestion problems can be introduced by the long terrestrial link, thus affecting the end-to-end delay, and the packet loss. In the MSC phase, the dedicated terrestrial link is completely transparent, but the station working in Ku band (CNES) will be affected by the same weather conditions as the station working in Ka band (CNIT). In this particular situation, in addition to the same measures of the RTC phase, it becomes interesting to compare in Italy and in France the quality of the transmission in Ka band and in Ku band of the same data, both in subjective way and and in objective way. For the subjective measurement, the mean opinion score (MOS) is generally calculated from the ratings given by a sample of human observers, under controlled conditions, who judge the image quality. The reference measures used for an objective video quality assessment are the mean squared error (MSE), calculated on the difference signal between the original and the coded sequence, and the peak signal to noise ratio (PSNR). 3

4 These measures are not necessarily a good quality index of the subjective assessment due to a human perception. This is expecially true when considering an error-prone environment, where the channel error effects can be limited to a relatively small portion of the image, causing some very annoying artefacts not highlighted from the mean MSE. For this reason we could use another objective video quality assessment system, that emulates the HVS (Human Visual System), where a linear combination is calculated of three complementary video quality measurements, based on spatial and temporal distortion. We hope to realize the CLC phase before the end of this year. 4

5 Annex A [ ] 1) Applications: Can you provide details about the kind of "multimedia applications" you are using? Expected answers could be: - Mbone tools (VIC, RAT, SDR, WB,...) - Real technology - Windows Media technology - Quick Time technology - Proprietary "home made" software - Other... 2) Traffic rates: What kind of "IP traffic rate" are we talking about? Expected answers could be: - less than 100 Kbit/sec (sustained) - less than 200 Kbit/sec (sustained) - less than 300 Kbit/sec (sustained) Above this rate, we think that a France-Italy "long distance" connection over the public European Internet is, unfortunately, pure utopia. A good starting point could be to check a trace-route between Toulouse and Naples to measure how many hops are necessary. For multimedia datagram, hazardous areas are the internal buffers of crossed routers seems to be your mail originating address. Can you confirm if x.x is your Naples Class B network address. Can you provide a reactive IP address for tracerouting? 3) Application level gateway questions: If we consider a "live conference" (for instance, a teacher lecture "IP flow" coming from/via any of your 4 Italian ground stations), we identify 3 possible types of "gateways" between CNIT and CNES systems. 3.a) TV-mode: By running (in Toulouse) one of your IP client software (through the Toulouse-Naples Internet ground link), Toulouse could temporarily become a member of your learning community in the same conditions (except Internet loss of packets?) than a local Napolitan pupil. If so, we convert (here in Toulouse) from VGA to PAL (audio and video), encode into MPEG2/DVB and provide a European digital TV program that could be somehow similar to what we can see today on "Nettuno channels". For this kind of "application level" gateway, IP tunnelling between Naples and Toulouse is not necessary. Toulouse terminal shows up like a standard "external ground terminal" and IP traffic can be unicast. Ku receiving device on your side could be: - an IRD + TV box - or a TV/DVB-S PC board (example: "Hauppauge Win-TV DVB-S" works fine) - an antenna pointing Eutelsat 13 E, freq= 12,558 Ghz, Pol=Vertical, Channel name: CNES- Toulouse 5

6 3.b) MPEG4/IP mode: This mode is similar to TV-mode for connecting Toulouse terminal to Naples access point. The difference comes when we encode PAL signals into space channel. Instead of MPEG2/DVB, we encode through a Windows Media MPEG4/IP encoder (a rate of Kbits/sec is enough for evaluation tests). Space generated stream is multicast and we provide.asx and.nsc Windows Media ancillary files to decode and display this multimedia stream. Receiving device on your side could be: - an IP/DVB router - or a IP/DVB PC board (example: "Hauppauge Win-TV DVB-S" works fine) Note: "Hauppauge WinTV DVB-S" PC board can do at the same time TV decoding/display and IP processing. 3.C) IP "Pass-thru mode" In this mode, Ka/Ku gateway is done at IP level. It is a kind of "IP level inter satellite bridging". Toulouse receives IP packets from Naples. Toulouse does not have any "application level understanding" of the syntax/semantic of the incoming traffic. Toulouse just encapsulates received IP datagrams into Ku DVB-S channel and broadcast over Europe. This "pass-thru" mode has two major constraints: - IP traffic *MUST* be natively multicast. Natively means "from originating Italian applications" - So, to "crawl" from Naples to Toulouse through the ground public Internet (which is not multicast aware), this multicast traffic *HAS* to be tunnelled into unicast IP datagrams. Distinct flavours of IP tunnelling are possible: a) Router level tunnelling b) Application level tunnelling We can come back later to those distinct options. I propose to start this "international cooperating game" by just trying the "TV mode". It is "not too complex" to generate and a simple low cost "digital IRD + TV box" is enough to receive. 6

7 Annex B The CNIT Italian Satellite Network is constituted by 3 active earth stations (+ 4 soon available ) operating in the Ka Band (20-30 GHz) on the Italsat satellite. The active stations are located in: Genoa, Florence (Prato), and Naples. The four on going operative stations will be located in Pisa, Catania and Padova. Each station is connected to a CNIT laboratory where a number of instruments, PCs and various network devices are available for traffic emulation and field trials of satellite data services. The CNIT laboratories are also connected to ISDN and Internet through routers and dedicated firewalls. Satellite Earth Station Each CNIT earth station is equipped with a Terrestrial Testbed The CNIT terrestrial LANs provide a comprehensive testbed for experiments over a broad range of topics. Linux and Microsoft platforms are used as experimental network nodes for conducting field trial tests on: - IP connectivity through satellite - DiffServ and IntServ QoS support - Dynamic Resource allocation strategies - TCP friendly scheduling techniques over satellite links - IP Multicast support by link-level Satellite broadcast m Ka outdoor unit (Antenna, LNB, SSPA) - Modem ABCS SkyWan (by Nortel Dasa) - CISCO 36x0 Router (w. IOS version The earth station provides full meshed IP connectivity through the satellite segment via MF- TDMA access methods, regulated by DAMA. Modulation type is QPSK, with convolutional FEC (possible data coding rates are 1/2, 3/4 and 7/8, a- priori selectable). The system is configured to provide 2 x 2 Mbps shared capacity to the stations with two different access modes: 1) Dynamic MAC level channel assignment for Ethernet packets directly captured from terrestrial LAN 2) 512 Kbps Frame Relay VP regulated by a QoS compliant access routers (CISCO) 36x0) 7

8 Software Tools and Applications The CNIT Satellite network permits to build different topologies: Point-to point Point to multipoint Broadcast Fully meshed In order to fully exploit the operational capabilities of the network, IP-multicast based software tools are employed. In particular: MBONE Tools for Audio/Video conferencing on multicast IP; MPPT for Multicast Delivery of PowerPoint Slides; MDP for multicast delivery of general data and images; Netference (by Darim) MPEG1 Videoconferencing system. The platform is currently supporting a number of experimental CNIT projects and services. Among others, a notable service is within the framework of the "Teledottorato" project, which is aimed at creating and delivering a number of short courses (10 hours each, in English) on various advanced subjects in Telecommunications for Ph.D. students to CNIT sites located all over Italy. The delivery is fully interactive, with QoSguaranteed multicast audio, video and slides over the Internet Protocol Suite, and exploites the mixed satellite and terrestrial (ADSL and ISDN access) CNIT network. For additional information contact: Dr. Luca Simone Ronga luca.ronga@cnit.it 8