Anycast & Multicast
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Anycast & Multicast



Unit 2 Of ACN

Unit 2 Of ACN



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    Anycast & Multicast Anycast & Multicast Presentation Transcript

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