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

2. 2  Fig 5-45 IPv4

3. 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. 4  Fig 4.45  Fig 4.46

5. 5  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? Multicast routing

6. 6  Fig 4.47

7. 7  Fig 4.48

8. 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. 9  Fig 4.50(IGMP member query and membership report)

10. 10  Fig 4.51

11. 11  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 Multicast routing: the general case

12. 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. 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. 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. 15  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 Multicast routing in the Internet

16. 16  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 Multicast routing in the Internet