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Communication networks, a ctive network ing and reliable multicast

Communication networks, a ctive network ing and reliable multicast. C. PHAM Mardi 12 juin , 200 1. Outline. Introduction Nowadays network technologies Active networking Application: Active Reliable Multicast Conclusions. Outline. Introduction Nowadays network technologies

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Communication networks, a ctive network ing and reliable multicast

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  1. Communication networks, active networking and reliable multicast C. PHAM Mardi 12 juin, 2001

  2. Outline • Introduction • Nowadays network technologies • Active networking • Application: Active Reliable Multicast • Conclusions

  3. Outline • Introduction • Nowadays network technologies • Active networking • Application: Active Reliable Multicast • Conclusions

  4. The need for communication

  5. Internet The way people are communicating…

  6. Something really fast ?? Internet 2, NG 2000 ATM, QoS, RVSP, DiffServ, IPv6, MPLS… Internet as you know it 1995 1990 ANSNET from MERIT, MCI, IBM 1983 ARPANET has 200 transit nodes 1974 TCP/IP for internetworking 1969 ARPANET was born with 4 transit nodes 1968 First transit node by BBN on DDP 316 1960 DoD project for a reliable, flexible network Internet milestone

  7. User perspective of the Internet from UREC, http://www.urec.fr

  8. What it is in reality… from UREC, http://www.urec.fr

  9. Outline • Introduction • Nowadays network technologies • Active networking • Application: Active Reliable Multicast • Conclusions

  10. Links: the basic element for networking • Backbone links • optical fibers • 10 to 160 GBits/s with DWDM techniques • End-user access • V.90 56KBits/s modem on twisted pair • 512Kbits/s to 2MBits/s with xDSL modem • 1Mbits/s to 10Mbits/s Cable-modem • 64Kbits/s to 1930KBits/s ISDN access • 9.6KBits/s (GSM) to 2MBits/s (UMTS)

  11. Routers: key elements of internetworking • Routers • run routing protocols and build routing table, • receive data packets and perform relaying, • may have to consider Quality of Service constraints for scheduling packets, • are highly optimized for packet forwarding functions.

  12. General architecture of an IP router • receives input packets, • sends packets to output buffers, • transmits packets (with QoS?).

  13. Desires put on the general Internet • High-bandwidth • for bandwidth-consuming applications • Ubiquity of the network access (wireless, RTC, xDSL, mobile…) • for remaining connected everywhere • Quality of Service • for high-quality multimedia reception • Dynamicity, adaptability • to take into account recent technologies

  14. Challenges for the Internet • high-speed www • video-conferencing • video-on-demand • interactive TV programs • tele-medecine • high-performance computing, grids • virtual reality, immersion systems • distributed interactive simulations • remote archival systems…

  15. The reality…(1) • High-bandwidth accesses are not available for everybody • high-bandwidth is achievable in the core network with optical fibers and DWDM techniques but, • most end-users have an access ranging from 56Kbits/s to 2Mbits/s and, • it will be the case for many years!

  16. The reality…(2) • An ubiquitous network access • generally implies heterogeneity and asymmetric performances, • how to take into account this heterogeneity? • The heterogeneity of bandwidth makes QoS • a difficult quest on an end-to-end basis, • seems that QoS is the networking forever Graal…

  17. The reality…(3) • New technologies require years to be deployed • need for standardization • IPv6, MPLS • new services and protocols are costly to deploy • many proprietary implementations, no interoperability of services and new technologies • DiffServ, TagSwitching, LabelSwitching…

  18. Towards a better Internet… • Interoperability of systems • Rapid deployment of new services, accelerating infrastructure innovation • Take into account the heterogeneity of needs and network accesses • Customization of services, application-oriented processing features

  19. Towards the concept of… • Introduction • Nowadays network technologies • Active networking • Application: Active Reliable Multicast • Conclusions

  20. What is active networks? • Programmable nodes/routers • Customized computationson packets • Standardized execution environment and programming interface • No killer applications, only a different way to offer high-value services, in an elegant manner • However, adds extra processing cost

  21. Motivations behind Active Networking • From the user perspective • applications can specify, implement, and deploy (on-the-fly) customized services and protocols • From the operator perspective • reduce the latency/cost for new services deployment/management • From the network perspective • globally better performances by reducing the amount of traffic

  22. Active networks implementations • Discrete approach (operator's approach) • Adds dynamic deployment features in nodes/routers • New services can be downloaded into router's kernel • Integrated approach • Adds executable code to data packets • Capsule = data + code • Granularity set to the packets

  23. A1 active code A1 active code A2 A2 Data Data The discrete approach • Separates the injection of programs from the processing of packets

  24. data data data data code data code The integrated approach • User packets carry code to be applied on the data part of the packet • High flexibility to define new services data

  25. AL packet An active router some layer for executing code. Let's call it Active Layer

  26. Interoperability with legacy routers APPLI APPLI traditional IP routing AL AL AL AL TCP/UDP TCP/UDP TCP/UDP TCP/UDP IP IP IP IP IP IP

  27. Some open problems… • Security and integrity • how to be sure that user code are safe? • Performances • how to add active computation without weeping out performances? • Standardization of programming interface • How to bill the CPU time?

  28. Some active network applications • Customization of services • Web-caching, on-the-fly compression/encryption • Filtering • Auction, Distributed Interactive Simulations, HLA • Firewall • Congestion control • QoS • Network management • Reliable multicast • Middleware collective operation

  29. Where to put active components? • In the core network? • routers already have to process millions of packets per second • gigabit rates make additional processing difficult without a dramatic slow down • At the edge? • to efficiently handle heterogeneity of user accesses • to provide QoS, implement intelligent congestion avoidance mechanisms…

  30. ISDN xDSL PSTN GSM, UMTS 10Mbits/s core network Gbits/s Server 100Mbits/s wireless LAN 1Mbits/s, 10MBits/s visio-conferencing

  31. Outline • Introduction • Nowadays network technologies • Active networking • Application: Active Reliable Multicast • Conclusions

  32. Unicast Sender • Problem • Sending same data to many receivers via unicast is inefficient • Example • Popular WWW sites become serious bottlenecks data data data data data data Receiver Receiver Receiver

  33. What is multicast? Sender • Not n-unicast from the sender perspective • Efficient one to many data distribution data data data data Receiver Receiver Receiver

  34. Multicast • History • Long history of usage on shared medium networks • Data distribution • Resource discovery: ARP, Bootp, DHCP • Ethernet • Broadcast (software filtered) • Multicast (hardware filtered) • Multiple LAN multicast protocols • DECnet, AppleTalk, IP from Gordon Chafee, http://bmrc.berkeley.edu/people/chaffee

  35. IP Multicast Introduction • Efficient one to many data distribution • Tree style data distribution • Packets traverse network links only once • Location independent addressing • IP address per multicast group • Receiver oriented service model • Applications can join and leave multicast groups • Senders do not know who is listening • Similar to television model • Contrasts with telephone network, ATM from Gordon Chafee, http://bmrc.berkeley.edu/people/chaffee

  36. IP Multicast • Service • All senders send at the same time to the same group • Receivers subscribe to any group • Routers find receivers • Unreliable or reliable delivery • Reserved IP addresses • 224.0.0.0 to 239.255.255.255 reserved for multicast • Static addresses for popular services (e.g. SAP) from Gordon Chafee, http://bmrc.berkeley.edu/people/chaffee

  37. Example: video-conferencing from UREC, http://www.urec.fr

  38. video-conferencing (2) 224.2.0.1 Multicast address group 224.2.0.1 from UREC, http://www.urec.fr

  39. Multicast difficulties • At the routing level • management of the group address (IGMP) • dynamic nature of the group membership • construction of the multicast tree (pruning…) • multicast packet forwarding • At the transport level • reliability, loss recovery strategies • flow control • congestion avoidance

  40. Reliable multicast • What is the problem of loss recovery? • feedback (ACK or NACK) implosion • replies/repairs duplications • adaptability to dynamic membership changes • Design goals • reduces recovery latencies • reduces the feedback traffic • improves recovery isolation

  41. Reliable multicast: a big win for grids!! SDSC IBM SP 1024 procs 5x12x17 =1020 data & program distribution collective & gather operations synchronization barriers 224.2.0.1 NCSA Origin Array 256+128+128 5x12x(4+2+2) =480 CPlant cluster 256 nodes application user Multicast address group 224.2.0.1

  42. Solutions • Traditional • end-to-end retransmission schemes • scoped retransmission with the TTL fields • receiver-based local NACK suppression • Active contributions • cache of data to allow local recoveries • feedback aggregation • subcast

  43. A step toward active services: LBRM

  44. NACK4 Active local recovery • routers perform cache of data packets • repair packets are sent by routers, when available data data data5 data1 data2 data1 data3 data2 data4 data3 data5 data4 data5 data4 data1 data2 data3 data5

  45. NACK4 NACK4 data4 NACK4 NACK4 only one NACK is forwarded to the source by the router: global NACK suppression NACK4 Active feedback aggregation • Routers aggregate feedback packets

  46. data4 NACK4 data4 NACK4 data4 data4 data4 NACK4 data4 data4 NACK4 data4 data4 data4 data4 Active subcast features • Send repair packet only to the relevant set of receivers

  47. Active Reliable Multicast Mechanisms • Answer general questions such as • is active networking beneficial for multicast? • where active components should be placed? • in what proportion? • how fast do they need to be? • Answer specific questions such as • what mechanisms (global vs local NAK suppression, subcast facilities) for what performance? • scalabity of the proposed solutions? • Design of new multicast protocols

  48. Network model F active routers among N. B receivers in a local group 2 kinds of receivers: linked and free M. Maimour & C. Pham

  49. Benefit of global aggregation on throughput M. Maimour & C. Pham

  50. Benefit of the source subcast facility M. Maimour & C. Pham

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