IPv6 (from ch 4 of Computer Networking by Jim Kurose and Keith Ross, 2002.

1. IPv6 (from ch 4 of Computer Networking by Jim Kurose and Keith Ross, 2002. • Changes in IPv6 • Expanded addressing capabilities (32 to 128 bits), anycast address • A streamlined 40-byte header • Flow labeling and priority • Fig 4.44

2. IPv4 • Fig 5-45

3. IPv6 vs IPv4 • Fragmentation/reassembly: IPv6 does not allow for fragmentation and reassembly at intermediate routers. • Header checksum: IPv4 header checksum needed to be recomputed at every router. • Options: next headers pointer in IPv6 • ICMP for IPv6 • Packet too big, unrecognized IPv6 options error codes • IGMP • Transitioning from IPv4 to IPv6 • Flag day • Dual-stack: DNS to determine whether another node is IPv6 or IPv4 • Tunneling

4. Fig 4.45 • Fig 4.46

5. Multicast routing • Unicast vs multicast • The sending of a packet from one sender to multiple receivers with a single send operation. • Network-layer aspects of multicast • Handle multicast groups • One-to-all unicast • Application-level multicast • Explicit multicast at the network layer • How to identify the receivers of a multicast datagram? • Address indirection: a single identifier is used for the group of receivers -> class D • How to address a datagram sent to these receivers?

6. Fig 4.47

7. Fig 4.48

8. IGMP • Group membership protocol • Locally between a host and an attached router • Means for a host to inform its attached router that an application running one the host wants to join a specific multicast group • Joining a multicast group is receiver-driven • Network-layer multicast algorithms (PIM, DVMRP, MOSPF) • Coordinate the multicast routers so that multicast datagrams are routed to their final destinations • Table 4.4

9. Fig 4.50(IGMP member query and membership report)

10. Fig 4.51

11. Multicast routing: the general case • The goal of multicast routing is to find a tree of links that connects all of the routers that have attached hosts belonging to the multicast group. • Fig 4.52

12. Two approaches: whether a single “group-shared” tree is used to distribute the traffic for all senders in the group, or whether a source-specific routing tree is constructed for each individual sender. • Fig 4.53

13. Multicast routing using a group-shared tree • Fig 4.54 • Steiner tree problem: None of the existing Internet multicast routing algs has been based on this approach: information about all links is needed, rerun whenever link costs change, and performance. • Center-based approach: center node, rendezvous point or core: how to select the center

14. Multicast routing using a source-based tree • Reverse path forwarding (RPF) • Fig 4.56 • If there were thousands of routers downstream from D, … -> pruning

15. Multicast routing in the Internet • DVMRP: Distance Vector Multicast Routing Protocol • Source-based trees with reverse path forwarding and pruning • Small fraction of the Internet routers are multicast-capable -> Tunneling, e.g., Mbone • Fig 4.57

16. Multicast routing in the Internet • PIM: Protocol Independent Multicast • Dense mode: a flood-and-prune reverse path forwarding • Sparse mode: a center-based approach • The ability to switch from a group-shared tree to a source-specific tree after joining the rendezvous point. • UUNet • Multicast Open Shortest Path First (MOSPF) • DVMRP has been the de facto inter-AS multicast routing protocol