Anycast & Multicast


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Unit 4 Of ACN

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Anycast & Multicast

  1. 1. Anycast address overview <ul><li>A new type in IPv6. Not defined for IPv4 </li></ul><ul><li>It is assigned to more than one interface </li></ul><ul><li>Refers to one among many address </li></ul><ul><ul><li>A packet sent to an anycast address is routed to the nearest interface with that address. </li></ul></ul><ul><ul><ul><li>Unicast – one to one </li></ul></ul></ul><ul><ul><ul><li>Multicast – one to many </li></ul></ul></ul><ul><ul><ul><li>Broadcast – one to all </li></ul></ul></ul><ul><ul><ul><li>Anycast – one to one of many </li></ul></ul></ul>
  2. 2. Anycast address & use <ul><li>Allocated from unicast address space </li></ul><ul><ul><li>Link local, site local, global </li></ul></ul><ul><li>It is an unicast address assigned to many interfaces </li></ul><ul><li>Nodes with anycast address must be explicitly configured to receive anycast packets. </li></ul><ul><li>Used to identify </li></ul><ul><ul><li>a set of routers of an ISP </li></ul></ul><ul><ul><li>a set of routers in a subnet </li></ul></ul><ul><ul><li>A set of routers providing entry to a routing domain </li></ul></ul>
  3. 3. Anycast address restrictions <ul><li>Cannot be used as a source address </li></ul><ul><li>Cannot be assigned to a host </li></ul><ul><li>May be assigned to a router only </li></ul>
  4. 4. Multicasting <ul><li>One to many addressing </li></ul><ul><li>Delivery of packets to many destinations </li></ul><ul><ul><li>Interactive conferencing </li></ul></ul><ul><ul><li>Dissemination of mail </li></ul></ul><ul><ul><li>News to multiple recepients </li></ul></ul><ul><ul><li>Webcasts to multiple registered recipients </li></ul></ul><ul><ul><li>Location of servers by clients </li></ul></ul>
  5. 5. Multicast address
  6. 6. IPv4 multicast address Class D <ul><li>Range from through </li></ul><ul><li>A set of hosts listening to a IP multicast address is called a host group </li></ul><ul><li>A host group can span multiple networks </li></ul><ul><li>Membership to a host group is dynamic </li></ul><ul><li>No restriction on number of hosts to a group </li></ul><ul><li>Non member can send a message to a group </li></ul>1 1 1 0 28 bit multicast gp ID
  7. 7. Special multicast addresses <ul><li> Reserved; not used </li></ul><ul><li> All devices on the subnet </li></ul><ul><li> All routers on the subnet </li></ul><ul><li> Mobile agents (for Mobile IP) </li></ul><ul><li> DHCP Server / Relay Agent </li></ul>
  8. 8. Ethernet Multicast address <ul><li>Host group to multicast source </li></ul><ul><ul><li>IP : group IP address </li></ul></ul><ul><ul><li>MAC : next hop address </li></ul></ul><ul><li>Multicast source to Host group </li></ul><ul><ul><li>IP : group IP address </li></ul></ul><ul><ul><li>MAC : Ethernet multicast address </li></ul></ul>
  9. 9. IPv6 Multicast address <ul><li>Format prefix : FF </li></ul><ul><li>Flags: 000T </li></ul><ul><ul><li>T= 0: well known permanent </li></ul></ul><ul><ul><li>T=1: temporary </li></ul></ul><ul><li>Scope: 0 to 15 </li></ul><ul><ul><li>0: reserved </li></ul></ul><ul><ul><li>1: interface local </li></ul></ul><ul><ul><li>2: link local </li></ul></ul><ul><ul><li>3 : reserved </li></ul></ul><ul><ul><li>4 : admin local </li></ul></ul><ul><ul><li>5 : site local </li></ul></ul><ul><ul><li>8 : org local </li></ul></ul><ul><ul><li>E : global </li></ul></ul><ul><ul><li>F : reserved </li></ul></ul>Multicast address structure
  10. 10. IPv6 Multicast address <ul><li>Group ID – Identifies the multicast group and is unique within the scope </li></ul><ul><ul><li>Two well known group IDs </li></ul></ul><ul><ul><ul><li>1 : all nodes </li></ul></ul></ul><ul><ul><ul><li>2 : all routers </li></ul></ul></ul><ul><li>Examples: </li></ul><ul><ul><li>FF01::1 (interface-local scope all-nodes multicast address) </li></ul></ul><ul><ul><li>FF02::1 (link-local scope all-nodes multicast address) </li></ul></ul><ul><ul><li>FF01::2 (interface-local scope all-routers multicast address) </li></ul></ul><ul><ul><li>FF02::2 (link-local scope all-routers multicast address) </li></ul></ul><ul><ul><li>FF05::2 (site-local scope all-routers multicast address) </li></ul></ul>
  11. 11. Mapping IPv6 Multicast Addresses to Ethernet Addresses When sending IPv6 multicast packets on an Ethernet link, the corresponding destination MAC address is 33-33-mm-mm-mm-mm where mm-mm-mm-mm is a direct mapping of the last 32 bits of the IPv6 multicast address, as shown in Figure above
  12. 12. Solicited node multicast address <ul><li>Format: FF02:0:0:0:0:1:FFXX:XXXX </li></ul><ul><li>It is formed by taking the lower order 24 bits of ( unicast or anycast ) </li></ul><ul><li>When A node n1 which wants to find MAC address of node n2, it will send neighbor solicitation message with solicited multicast address to n2. </li></ul><ul><li>Node n2 will reply with neighbor advertisement message </li></ul>
  13. 13. A Node’s multi cast addresses <ul><li>For example, a host with the Ethernet MAC address of 00-AA-00-3F-2A-1C (link-local address of FE80::2AA:FF:FE3F:2A1C) registers the following multicast MAC addresses with the Ethernet adapter: </li></ul><ul><li>          The address of 33-33-00-00-00-01, which corresponds to the link-local scope all-nodes multicast address of FF02::1. </li></ul><ul><li>          The address of 33-33-FF-3F-2A-1C, which corresponds to the solicited-node address of FF02::1:FF3F:2A1C. Remember that the solicited-node address is the prefix FF02::1:FF00:0/104 and the last 24-bits of the unicast IPv6 address. </li></ul>
  14. 14. Mapping of class D IP address into Ethernet Multicast Address <ul><li>IANA has allotted 01:00:5e:00:00:00 through 01:00:5e:7f:ff:ff for multicast </li></ul><ul><li>Lower order 23 bits if gp id copied to ethernet address </li></ul><ul><li>Eg1: (hex e0.80.40.20) maps to hex 01:00:5e:00:40:20 </li></ul><ul><li>Eg2 : (hex e0.00.40.20) also maps to hex 01:00:5e:00:40:20 </li></ul>IEEE 802 address