Push Technology Push by rt3463df

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									Push Technology

Humie Leung
Annabelle Huo
   Push technology is a set of technologies used to send information to a client
    without the client requesting it
   Push versus Pull
      Pull technology is based on the traditional request/reply model. It requires that
       users know a priori where and when to look for data. It suffers from transmission
       latency and duplicate data traffic.
      Push technology allows users to get information as soon as it become available
       and users do not have any knowledge about virtual information servers. This
       transfer of control from users to providers is a potential problem.
   Focus is on Multicast-base push protocols
   Multicasting is a 1-to-n form of communication for transmitting packets
    from one host to a set of member hosts in the same group
 Continuous Multicast Push - CMP
 Issues on Push using IP multicasting
 Proposed Solution
   Reliable Multicast Transport Protocol -
     Continuous Multicast Push                                                        1 (1998)

        Comparison of CMP and AMP (Asynchronous
         Multicast Push 2)

      CMP Framework
      Problems with using CMP and solutions
      Issues of the Use of IP Multicast for Push

1.   P. R. Rodriguez, E. W. Biersack, Continuous Multicast Push of Web Documents over the Internet
2.   J. Nonnenmacher, E. W. Biersack, Asynchronous Multicast Push: AMP
AMP & CMP: Push Categories

                Non-periodic                      Periodic

   Unicast    Multicast   Broadcast          Unicast   Multicast    Broadcast

Email Lists     Asynchronous                            Multicast
(Individual     Multicast Push                         Push (CMP)
unicast             (AMP)
to multiple
CMP: Framework
   CMP
       Cyclically deliver a site’s most frequently changing and heavily
        requested documents on the same multicast address
       Based on raw IP multicasting
       Reliability is basically achieved through simply repetitive, cyclic

   Web server
                                                UDP/IP multicasting
       Monitor documents
       Transmission

   Clients
       Subscribe interested information
            how to join the multicast group
                                              1. Advertise Information

5. Push Info to G1 (Eg.

                                                             2. Look up services
                                         3.. Return multicast address and port number

                              4.. Send IGMP message to tell local router to join the group


                                           IGMP: Internet Group Membership Protocol
CMP: Problems and Solutions
   Server End
      Problem: How to monitor the number of requests for a document at any moment,
       based on that to decide whether the document is popular or not
      Solution: Polling the multicast channel periodically for the feedback but have to
       avoid the feedback implosion

   Reliability
        Forward Error Correction Code (FEC)

   Client End
      Problem: repeatedly receive the same information or mixed new and old
       information on a same channel because of the cyclically delivery
      Solution: Layered Multicasting
    Issues on the Use of IP-Multicast for Push
   Need routers to support multicasting
      Tunneling: encapsulate multicast IP packets in Unicast IP packets. MBone the
         multicast backbone is spammed in this way connecting islands with native
         multicast support
   Session Servers or Session Mechanism
      Session Description Protocol /Session Announcement Protocol, or use a function
         to map the document’s URL to the multicast address
   Address Assignment Mechanism
      Two types of groups: permanent with an permanently assigned address and
         transient which group gets a multicast address only as long as they have
   Difficult to specify the recipients
      Host membership is dynamic meaning that hosts can enter and leave a group
         whenever they wish
      The number of hosts in a multicast group is not limited                                                     RTMP
      A host can send multicast datagram to a multicast group without being a member
         of that group
   Reliability: UDP is used without any control functions
   Without concerning about the content or structure of the information being
      Multiple groups corresponding to different information sources
      Content-Based Multicast3 Extra content filtering is performed at the interior node
         of the IP multicast tree

3. R. Shah, R. Jain, F. Anjum, Efficient Dissemination of Personalized Information Using Content-Based Multicast
RMTP – Intro and Features
   A protocol that uses IP multicasting for the reliable
    delivery of data from a sender to a group of receivers
   Emphasis is on (1) reliability (2) scalability (3)
       Reliability – RMTP compensates for the reliability shortcomings
        of IP multicasting by monitoring ACKs responses from clients
       Scalability – (1) independent state information (2) uses a
        receiver-driven approach (3) groups receivers into local regions
       Heterogeneity – RMTP handles receivers in heterogeneous
        network environments in an efficient manner
RMTP - Entities
   Three main entities: (1) Sender, (2) Receiver and (3) Designated
    Receiver (DR)
      Sender
         divides data into fixed-size packets

      Receiver
         periodically sends ACK packets to sender/DR

      DR
         assists processing ACKs and in retransmitting data

         Alleviates ack-implosion problem

         Data Cache - needs to buffer entire data file
RMTP – Protocol Description

                  Router                      Router

        Router             Router                      Router

                 Router             Router
RMTP – Protocol Description

               Router                      Router

     Router             Router                      Router

              Router             Router
RMTP – Protocol Description
                                Sender             Designated

             Router                      Router

   Router             Router                      Router

            Router             Router
RMTP – Protocol Description
             ACK                Sender             Designated

             Router                      Router

   Router             Router                      Router

            Router             Router
RMTP - Performance

 CMP  - Continuous Multicast Push
 RMTP - Reliable Multicast

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