ip_multicast

ip_multicast - An Introduction to An IP Multicast The...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: An Introduction to An IP Multicast The Problem The It’s election night 2056 at RepubliCrat It’s National Headquarters. Results are pouring in from all over the country for aggregation on a CORBA.NET server. By 7pm, 50 million voters have activated their Election Results Page using an ASP.NET client on their PC, and all 50 million clients want instantaneous updates from that single server… server… Presentation Overview Presentation This presentation provides a technical This introduction to IP Multicast concepts and technical features. technical It discusses the requirements for IP It Multicast delivery, addressing, host group management, and some approaches to multicast routing. multicast IP Multicast Background IP IP Multicast is a bandwidth-conserving IP technology that reduces network traffic technology Simultaneously deliver a single stream of Simultaneously information to thousands of recipients information – Corporate and homes It does not add any additional burden on the It source or receivers while using the least network bandwidth network IP Multicast Background, contd. IP Multicast packets are replicated in the Multicast network by routers enabled with Protocol Independent Multicast (PIM) and other supporting multicast protocols supporting This configuration is the most efficient This delivery of data to multiple receivers delivery Suitable Applications Suitable Video conferencing Corporate communications Distance learning Stock quotes Software distribution News Three forms of ‘casting Three Unicasting: point-to-point Three forms of ‘casting Three Unicasting: point-to-point Broadcasting: everyone on a subnet Three forms of ‘casting Three Unicasting: point-to-point Broadcasting: everyone on a subnet Multicasting: one-to-many or many-to-many The Multicast Concept The Receivers join a particular multicast host Receivers group group The Multicast Concept The Receivers join a particular multicast host Receivers group group Traffic is delivered to all members of that Traffic group by the network infrastructure group The Multicast Concept The Receivers join a particular multicast host Receivers group group Traffic is delivered to all members of that Traffic group by the network infrastructure group The sender does not need to maintain a list The of receivers of The Multicast Concept The Receivers join a particular multicast host Receivers group group Traffic is delivered to all members of that Traffic group by the network infrastructure group The sender does not need to maintain a list The of receivers of Only one copy of a multicast message will Only pass over any link in the network. pass Multicast Requirements Multicast Support for Multicast in the TCP/IP stack Multicast Requirements Multicast Support for Multicast in the TCP/IP stack Support for IGMP to communicate requests Support to join multicast groups and receive traffic to Multicast Requirements Multicast Support for Multicast in the TCP/IP stack Support for IGMP to communicate requests Support to join multicast groups and receive traffic to NICs which understand Multicast addresses Multicast Requirements Multicast Support for Multicast in the TCP/IP stack Support for IGMP to communicate requests Support to join multicast groups and receive traffic to NICs which understand Multicast addresses IP Multicast-capable network routers Multicast Requirements Multicast Support for Multicast in the TCP/IP stack Support for IGMP to communicate requests Support to join multicast groups and receive traffic to NICs which understand Multicast addresses IP Multicast-capable network routers Firewalls which permit IP Multicast traffic Multicast Requirements Multicast Support for Multicast in the TCP/IP stack Support for IGMP to communicate requests Support to join multicast groups and receive traffic to NICs which understand Multicast addresses IP Multicast-capable network routers Firewalls which permit IP Multicast traffic IP Multicast application software Multicast-enabled components Multicast-enabled IP Multicast Addressing IP Class D: 1110 as high-order four bits IP Multicast Addressing IP Class D: 1110 as high-order four bits 256 million IP Multicast addresses IP Multicast Addressing IP Class D: 1110 as high-order four bits 256 million IP Multicast addresses 224.0.0.0 to 239.255.255.255 IP Multicast Addressing IP Class D: 1110 as high-order four bits 256 million IP Multicast addresses 224.0.0.0 to 239.255.255.255 Some permanent addresses, such as Some 224.0.0.1 (“all hosts group” on LAN). 224.0.0.1 IP Multicast Addressing IP Class D: 1110 as high-order four bits 256 million IP Multicast addresses 224.0.0.0 to 239.255.255.255 Some permanent addresses, such as Some 224.0.0.1 (“all hosts group” on LAN). 224.0.0.1 Some reserved, such as 224.0.0.0 to Some 224.0.0.255 for routing protocols 224.0.0.255 IP Multicast Addressing IP Class D: 1110 as high-order four bits 256 million IP Multicast addresses 224.0.0.0 to 239.255.255.255 Some permanent addresses, such as 224.0.0.1 (“all Some hosts group” on LAN). hosts Some reserved, such as 224.0.0.0 to 224.0.0.255 Some for routing protocols for – – Automatic routing discovery Exchange link state information Rest are dynamically assigned as needed Receiving Multicast Datagrams Receiving Application requests membership in the Application group associated with a particular multicast group Receiving Multicast Datagrams Receiving Application requests membership in the Application group associated with a particular multicast group Request is communicated to the LAN router Receiving Multicast Datagrams Receiving Application requests membership in the Application group associated with a particular multicast group Request is communicated to the LAN router Request may be forwarded to intermediate Request WAN routers between sender and receiver WAN Receiving Multicast Datagrams Receiving Application requests membership in the Application group associated with a particular multicast group Request is communicated to the LAN router Request may be forwarded to intermediate Request WAN routers between sender and receiver WAN NIC starts filtering for multicast packets Receiving Multicast Datagrams Receiving Application requests membership in the Application group associated with a particular multicast group Request is communicated to the LAN router Request may be forwarded to intermediate Request WAN routers between sender and receiver WAN NIC starts filtering for multicast packets WAN routers deliver Multicast packets to WAN LAN router, which maps to MAC address LAN Binding Binding IP unicast address is statically bound to a IP single NIC on a single IP network. single Binding Binding An IP unicast address is statically bound to a An single NIC on a single IP network single An IP host group address is dynamically An bound to a set of NICs on a set of IP networks bound Binding Binding An IP unicast address is statically bound to a An single NIC on a single IP network single An IP host group address is dynamically An bound to a set of NICs on a set of IP networks bound An IP host group address is not bound to a set An not of IP unicast addresses of Binding Binding An IP unicast address is statically bound to a An single NIC on a single IP network single An IP host group address is dynamically An bound to a set of NICs on a set of IP networks bound An IP host group address is not bound to a set An not of IP unicast addresses of Multicast routers only need to know the Multicast groups for which there is one member on the subnetwork subnetwork IGMP IGMP The Internet Group Management Protocol is The used by multicast routers to learn the existence of host group members on their directly attached subnets. directly IGMP Messages IGMP To determine if any hosts on a local subnet To belong to a multicast group, one multicast router per subnet periodically sends a hardware (data link layer) IGMP Host Membership Query to all IP end nodes on its LAN, asking them to report back on the host groups memberships of their processes. This query is sent to the all-hosts group (224.0.0.1). (224.0.0.1). IGMP Messages (continued) IGMP IGMP Messages (continued) IGMP To avoid network congestion, each host To delays it’s report by a random interval if it has not seen a report for the same group from another host. As a result, only one report is sent in response for each active group address per subnet, although many hosts may have memberships. hosts IGMP Messages (continued) IGMP IGMP updates are used by multicasting IGMP routers to communicate host group memberships to neighboring routers, propagating group information through the internet. internet. Routing Routing Multicast routers interact with each other to Multicast exchange information about neighboring routers. To avoid duplication of effort, a single router is selected (via IGMP) as the Designated Router for each physical network. network. Spanning Trees Spanning For efficient transmission, Designated For Routers construct a spanning tree that spanning connects all members of an IP Multicast group. group Minimal number of edges (transmission Minimal links) to guarantee delivery of source data packets to receivers packets Spanning Trees (continued) Spanning “Dense-mode” Multicasting The first approach is based on the assumption that The the multicast group members are densely distributed throughout the network and bandwidth is plentiful, is – i.e., almost all hosts on the network belong to the group. group. So-called “dense-mode” multicast routing So-called protocols rely on periodic flooding of the network with multicast traffic to set up and maintain the spanning tree. spanning “Sparse-mode” Multicasting The second approach to multicast routing is based The on the assumption that the multicast group members are sparsely distributed throughout the network and bandwidth is not necessarily widely available available – for example across many regions of the Internet Hence, ``sparse-mode'' multicast routing protocols Hence, must rely on more selective techniques to set up and maintain multicast trees. and Conclusion Conclusion IP Multicast enables many new types of IP applications and reduces network congestion and server loads. congestion Advances are being made in areas such as Advances reliable multicasting and real-time applications support. ...
View Full Document

Ask a homework question - tutors are online