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Piccola presentazioni sulla mia tesi, quello che ho fatto e quello che farò

Piccola presentazioni sulla mia tesi, quello che ho fatto e quello che farò

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    gio's tesi gio's tesi Presentation Transcript

    • IP – FLOW IP FLows over Optical and Wireless FL Milan testbed – Politecnico di Milano Milano - Fri. 18 may 2007 Università degli studi di Trento Politecnico di Torino
    • Introduction - The need of QoS IP-FLOW project Nowadays the need of real-time sessions is growing more and more. The current data network are divided in two categories: • Circuit – switched Well suited for transporting CBR real-time traffic. They may be highly inefficient for carrying bursty data traffic. • Packet – switched Designed for high resource utilization exploiting the statistical-multiplexing capability. Trade off between efficiency and capacity Politecnico di Milano 01 Dipartimento di Elettronica ed Informazione
    • How it works - properties IP-FLOW project TDP: Time Driven Priority The TDP packet – scheduling technique combines the statistical multiplexing and the predictability. How does it works? It gives higher priority to real time traffic in a periodic fashion, only to packets arrived in the previous time interval. It leads to these properties: • Bounded delay • Constant bound on the jitter • Deterministic loss-free And all these properties are guaranteed even if there is a congestion inside the network and de-allocating reserved resources when it isn’t necessary. Politecnico di Milano 02 Dipartimento di Elettronica ed Informazione
    • How it works - principles IP-FLOW project All the TDP network elements must be synchronized (ex. with a common reference like GPS) in order to switch the packets correctly. The global time is divided in Time Frame (TF), usually derived as a fraction of UTC. A certain number of TF is grouped in Time Cycle (TC). TFs are partially or totally reserved during the resource reservation procedure. TFs are also used for implementing switching time-based. Politecnico di Milano 03 Dipartimento di Elettronica ed Informazione
    • How it works - principles IP-FLOW project Periodic Forwarding The basic TDP operation is regulated by two simple rules: I. All packets that must be sent in TF t by a node must be in its output ports’ buffers by the end of TF t-1 II. A packet p transmitted in TF t by a node n must be transmitted in TF t + dp by node n+1, where dp is an integer constant called forwarding delay that must be large enough to satisfy (1) Best effort traffic can be transmitted during any unused portion of a TF. Politecnico di Milano 04 Dipartimento di Elettronica ed Informazione
    • How it works - network elements – TDP Router IP-FLOW project In a real network not any element could be synchronized with a common reference time. We need some devices that can interface the synchronized TDP network with the asynchronous world, this device is the TDP Router. No signaling protocol implemented, at the moment, between any TDP Router. The implementation needs: • Ethernet NICs, optical and CAT-5 • GPS - Symmetricomm PCI card that generates an interrupt every n us (n could be ≈ 125-250 us) in order to divide the TFs Politecnico di Milano 05 Dipartimento di Elettronica ed Informazione
    • How it works - network elements – TDP Router IP-FLOW project Router Input Processing Each router must know in which TF is the incoming packet. This could be achieved in different ways: I. Attaching a sort of timestamp to each packet II. Including a TF delimiter III. Precisely measuring propagation delay and arrival time Router Output Processing Considering d as the maximum forwarding delay (in TFs) there are nbuf = d + 1 queues at each output interface, each having capacity Tf x C, where Tf is the TF duration. Pakets arriving at the output interface are enqueued in a buffer determined as a function of forwarding TF (TFout), current TF (TFcurr), the number of TFs per TC (nTF) and the buffer currently in use (bufcurr) The buffers are simply FIFO queues. Politecnico di Milano 06 Dipartimento di Elettronica ed Informazione
    • How it works - network elements – TDP Switch IP-FLOW project Another network element is the TDP Switch (TDS) that is also synchronized as the TDP Router. The functionality of the switch is simple. It’s a time-division commutating matrix. In the testbed is implemented as an optic / electric switch, that change is matrix depending on the current TF Politecnico di Milano 07 Dipartimento di Elettronica ed Informazione
    • Milan Testbed IP-FLOW project The testbed is at the Lambrate laboratory: Politecnico di Milano 08 Dipartimento di Elettronica ed Informazione
    • Milan Testbed – Local Area Tests (LAT) IP-FLOW project Till now the studies about the IP-FLOW project were only theoretical without any practical application in the real world. So the next step was to make real what was only theory, the born of the Milan test bed. We decided some local test in order to prove the implementation issues of this system. The local environment is necessary to prove the system in the ideal condition: no jitter, no packet loss, short propagation delay and high bit-rate capacity Politecnico di Milano 09 Dipartimento di Elettronica ed Informazione
    • Milan Testbed – Local Area Tests (LAT) IP-FLOW project twelve Local Area test to implement Name depend A Single Loop - B Single Destination - C Loop + Different Destination A-B D Fork A-B E Fork + 1_Loop D-C F Source + Destination B G Source + Destination + 1_Loop C H Source + Destination + Back_Loop D I Source + Destination + Forward_Loop E J Source + Double Destination H K Src + Double Dest + 1_Loop (after Fork) H-E L Src + Double Dest + 1_Loop (befor Fork) H-E Politecnico di Milano 10 Dipartimento di Elettronica ed Informazione
    • Milan Testbed – Wide Area Tests (WAT) IP-FLOW project Another type of test must be the so called Wide Area Tests. These tests are oriented to prove the system connecting the three local testbeds (Trento, Torino and Milano) through the Internet network WAT has different aims: • Test the system with the maximum possible jitter. • The Interconnection of the common asynchronous network to the IP-FLOW (synchronous) system. • Test the system in the case of very huge delay. Politecnico di Milano 11 Dipartimento di Elettronica ed Informazione
    • Milan Testbed – Wide Area Tests (WAT) IP-FLOW project Nowadays we had some test only to prove the configuration of the routers and to test the interconnectivity of the three testbeds through the establishment of VPN. No TDP Switch were used in order to simplify the WAT tests. Problems found: • Configuration • Sending of TF delimiter the now needs to use virtual IF • Synchronization between TDP Routers. Politecnico di Milano 12 Dipartimento di Elettronica ed Informazione
    • Milan Testbed – Wide Area Tests (WAT) IP-FLOW project Nowadays we implemented four WAT tests: Session Aim Results Multimedia session TN to MI Test the first WAT Not good: wireshark configuration analysis: BAD UDP LENGTH 28 feb 2007 1324 (later we discovered that gif1 and gif2 had mtu at 1350). Multimedia session MI to TO First test with two TDP TDPs not working when both Router synchronized syn. 01 mar 2007 Delimgen unavailable because of the use of virtual interfaces. Synchronization MI and TO Use of new Delimigen The two TDP were synchronized but no traffic 22 mar 2007 flow initialized. Multimedia session TO to MI Multimedia session with two Packets trunk by the virtual TDP synchronized Interface in Milan. 29 mar 2007 Politecnico di Milano 13 Dipartimento di Elettronica ed Informazione
    • Milan Testbed – Wide Area Tests (WAT) IP-FLOW project Next step: Introducing TDP Switch Problems of introducing TDP Switch: • We have more complex topology of the network • Different problems due to the propagation of delimiter packets throughout the switch: we cannot use null packets in order to maintain synchronized the TDP Routers. • Multiple destinations allowed and enhanced switching required in order to implement the more complex networks Politecnico di Milano 14 Dipartimento di Elettronica ed Informazione
    • Critical issues IP-FLOW project Doing the implementation of the IP-FLOW system some critical issues appears: • Problems in Delimiters receiving • Efficiency of mono-processor PC • Signaling protocol • Synchronization to the reference time Of course, the major problem is the last one. GPS-based synchronization is a point of weakness: • Need of a system for receiving the GPS signal (antenna + card) • Dependency from the GPS system Politecnico di Milano 15 Dipartimento di Elettronica ed Informazione
    • Synchronization Issues IP-FLOW project Another fact is that we don’t need to know the perfect time in every moment. It’s only necessary that the difference of phase between the clocks of the network elements remains constant. it could be interesting to use a local clock that generates interrupts every n usec. With a PLL (software) device that can adjust it. The local clock shouldn’t be the PC clock because it’s difficult to generate interrupts in sw mode, it’s surely simpler generating them with an hardware PCI card or similar. Next Step: It’s to evaluate synchronization errors Politecnico di Milano 16 Dipartimento di Elettronica ed Informazione
    • Synchronization Issues IP-FLOW project The evaluation of synchronization errors can be done in different ways: • Through a theoretical analysis and models. • Simulation tool written using Omnetpp libraries. • Experiments on the real system. I found three aim for this issue: • How synchronization errors can affect the system. • Which is the maximum jitter allowed in the syn network. • How to design a new Common Time Reference Network- distribution. a) Externally distributed reference b) Network-distributed Politecnico di Milano 17 Dipartimento di Elettronica ed Informazione
    • Synchronization Issues – The Simulator IP-FLOW project Simulating the real network is essential in understanding the functionality of the system. The simulator is designed in order to have a simple way to introduce statistical error in the common (simulated) time reference. A node represent the GPS device the distributes the reference. In the ideal case the syn message reaches all the TDP Router at the same simulated time. We can add statistical phase delay simply changing the sending time of the syn message or the propagation delay of the syn link. Politecnico di Milano 18 Dipartimento di Elettronica ed Informazione
    • Synchronization Issues – The Simulator IP-FLOW project Next steps for the Simulator: • Finding the network topology we want to simulate. • Understanding what happens if the TF are not aligned: some documents say that at the current TF the buffer used is completely flushed and the incoming packets must be queued to the next reserved buffer available (at maximum the time- delay is one TC). • Implementing the synchronization error delays in the simulated network. • Evaluating the effects of synchronization in the network throughput. • Evaluating the maximum jitter allowed. Politecnico di Milano 19 Dipartimento di Elettronica ed Informazione
    • Summary IP-FLOW project What is done: • Study of the system IP-FLOW • Implementing the testbed in Milan • First phase of WAT tests • First release of the TDP simultator Which are the next steps: • LAT tests • Second step of WAT tests: • Introducing the switch • Different topology and routing • Multiple clients and server media flow during each test • Study about the introduction of synchronization errors • Simulation of synchronization errors • Implementation of a sustainable network-based synchronization system Politecnico di Milano 20 Dipartimento di Elettronica ed Informazione
    • References IP-FLOW project References: • http://dit.unitn.it/ip-flow/index.html Project Website • http://netgroup.polito.it/TDP/ FreeBSD TDP kernel sources Politecnico di Milano 21 Dipartimento di Elettronica ed Informazione