cs221 20070427 multicast

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Published on November 28, 2007

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Slide1:  Christophe Jelger Post-doctoral researcher Christophe.Jelger@unibas.ch IP Multicasting and Mobile IP Plan:  Plan IP Multicast General concept Subscriptions (IGMP, MLD) Multicast routing Shared trees Source-based trees Mobile IP General concept Mobile IPv4 Mobile IPv6 Slide3:  IP Multicast Group communications at the network layer IP Multicast Mobile IP Slide4:  Unicast streaming Slide5:  Multicast streaming Multicast Tree Slide6:  IPv4 Class-D addresses: 224.0.0.0 to 239.255.255.255 (224.0.0.0/28, or 16 Class-A networks !) Some special addresses … 224.0.0.1 = all multicast-capable hosts 224.0.0.2 = all multicast routers 224.0.0.13 = all PIM routers IPv6 ff0x::/8 where x is the scope (2=local, 5=site, e=global) Some special addresses … ff02::1 all nodes on link, ff02::2 all routers on link ff02::16 all MLDv2 multicast routers ff02::d all PIM multicast routers IP Multicast: address range (see http://www.iana.org) Slide7:  IPv4 Ethernet multicast (first 24 bits): 01:00:5E + 0 for 25th bit  23 bits available to map the IPv4 address to an Ethernet address  the least significant bits are mapped Ex: 224.129.47.23  01:00:5E:01:2F:17 IPv6 Ethernet multicast (first 16 bits): 33:33  32 bits available to map the IPv6 address  the least significant bits are mapped Ex: ff05::207:85ff:fe92:7ff8  33:33:fe:92:7f:f8 In both cases, the Ethernet layer acts as an imperfect filter IP Multicast: IP to Ethernet mapping Slide8:  IPv4 : Internet Group Membership Protocol (IGMP) IPv6 : Multicast Listener Discovery (MLD) Objective: a multicast router must periodically discover nodes that want to join a certain group The router can then join the appropriate multicast delivery tree The router only needs to know if there is some interest for a group: it does not need to know exactly how many nodes are interested There exists different versions of IGMP and MLD: the main difference is the ability to perform "source-filtering" (so that only the traffic sent by a (some) given source(s) is received) IP Multicast: Step 1  group subscription Slide9:  IP Multicast: group subscription with MLD (subscription with IGMP is similar) Group: ff0e::1234:5678/64  MAC : 33:33:12:34:56:78 MLD Query Multicast router MLD Report ff0e::1234:5678 JOIN multicast group ff0e::1234:5678 Multicast DATA sent to 33:33:12:34:56:78 / ff0e::1234:5678 Slide10:  Objective is to build the multicast delivery tree(s) Two families of trees: Shared-trees (*,G): the tree is shared by all (*) multicast sources sending to group G Source-based trees (S,G): only a given source S can send multicast data on the delivery tree for group G There has been many protocols for multicast routing, but today the only protocol deployed is PIM: Protocol Independent Multicast PIM-SM: Sparse-Mode (shared trees) PIM-SSM: Source-Specific Multicast (source-based trees) IP Multicast: Step 2  Multicast routing Slide11:  1 4 3 2 5 6 7 1 Shared tree (PIM-SM) IP Multicast: Step 2  Multicast routing 1 4 3 2 5 6 7 1 Source-based tree (PIM-SSM) Source S1 PIM router with group member(s) PIM JOIN message Source S1 Source S2 Rendez-Vous Point Slide12:  IP Multicast is very suitable for Group communications with multiple sources and receivers (shared tree): known as N-to-M communication Video-conferencing, network games Group communications with one source and multiple receivers (source-based tree): known as 1-to-M communication TV and radio streaming, content distribution Current deployment of IP Multicast is not large Lack of security: a misbehaving user can create forwarding states by joining hundreds of groups Billing: who should pay for what ? Source discovery accross AS (Autonomous Systems) is complex IP Multicast: some conclusions Slide13:  Mobile IP Adding mobility at the network layer IP Multicast Mobile IP Slide14:  Users are becoming mobile World-wide availability of popular wireless communication technologies More and more portable wireless devices are also available, and they become really powerful Slide15:  Problems introduced by mobility When a mobile node moves to a visited network, how is it possible to reach it again ? What about current on-going connections ? (with TCP, IP addresses partly identifies a connection) Objectives of Mobile IP To permit that a mobile node becomes reachable when it is in a visited network To allow on-going connections to be maintained when the mobile node is moving Mobile IP Slide16:  Mobile IPv6: basic mechanisms Home network Internet Binding Update Message (H@  CoA) Visited network Home agent Correspondant Sending to H@ Access point The mobile node main address is the home address (H@) The mobile node obtains an address in the visited network: the care-of address (CoA) Slide17:  Mobile IPv6: route optimization Home network Internet Visited network Home agent Correspondant Access point Correspondant Sending to H@ via CoA Binding Update Message (H@  CoA) Slide18:  IPv4: tunneling A packet sent by or to the mobile node's home address is encapsulated in another packet sent by or to the CoA IPv6: routing header and home address option Via the home agent, tunneling is used With route optimization, a packet sent to the mobile node's home address is replaced by a packet sent to the CoA which also contains a routing header equal to the H@ A packet sent by the mobile node always uses the CoA as source address, and it contains a home address option equal to H@ Mobile IP: maintaining TCP connections Slide19:  Deployment Mobile IP has failed to be widely deployed because until recently it suffered from serious security problems: authentication is indeed critical so that a malicious user cannot register a bogus CoA with a home agent Usage The "always-on" paradigm is not a reality yet The need for Mobile IP is not mature enough Mobile IP: some conclusions

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