1. 1 o Two issues in practice – Scale – Administrative autonomy o Autonomous system (AS) or region o Intra autonomous system routing protocol o Gateway routers o Inter-autonoumous system routing protocol Hierarchical routing

2. 2 o Fig 4.11

3. 3 o Fig 4.13 o IPv4, IP version 6 o Internet Control Message Protocol (ICMP) The Internet Protocol (IP)

4. 4 o IPv4 addressing – An IP address is associated with an interface rather than with the host or router containing the interface. – 32 bits long – Dotted-decimal notation (pp. 322) – Fig 4.14 – 223.1.1.0/24 where /24 -> a network mask, network prefix, an IP network, a network

5. 5 o Fig 4.15

6. 6 o Classful addressing: A, B, C, D o Fig 4.17 o Classless Interdomain Routing (CIDR): e.g., a.b.c.d/21 for 2000 hosts o Corporation for Assigned Names and Numbers (ICANN) – Allocate IP address – Manage the DNS root servers – Assign domain names – Resolve domain name disputes

7. 7 o Obtaining a host address – Manual configuration – Dynamic Host Configuration Protocol (DHCP)

8. 8

9. 9 o Fig 4.21 Addressing, Routing, and Forwarding

10. 10 o Fig 4.22

11. 11 o Fig 4.23 o Type of service: differentiated service (e.g., Cisco) o IPv6: no fragmentation at routers o Why does TCP/IP perform error checking at the both layers? o IP options were dropped in the IPv6 header. IPv4 datagram format

12. 12 o MTU(max transfer unit): max amount of data that a link-layer packet can carry, e.g., 1,500 bytes for Ethernet, 576 bytes for wide-area links o Fragment o The designers of IPv4 decided to put the job of datagram reassembly in the end systems rather than in network routers. IP datagram fragmentation

13. 13 o Fig 4.24

14. 14 o Table 4.3

15. 15 o Error reporting o Above IP o Fig 4.25 ICMP

16. 16 o For a newly arriving host, the DHCP does – DHCP server discovery: broadcasting – DHCP server offer(s): the proposed IP address for the client, the network mask, and an IP address lease time – DHCP request – DHCP ACK o From a mobility aspect, how about DHCP? DHCP

17. 17 o Fig 4.27

18. 18 o The NAT-enabled router does not run an Inter-AS routing protocol. o The NAT-enabled router behaves to the outside world as a single device with a single IP address. (port numbers) o Fig 4.28 Network Address Translators (NATs)

19. 19 o Intra-AS routing: RIP and OSPF o Routing Information Protocol – Distance vector protocol – Hop count as a cost metric – Max cost of a path: 15 – Every 30 seconds for RIP advertisements o Open Shortest Path First – Link state protocol – Once every 30 minutes – Adv.: security, multiple same-cost paths, integrated support for unicast and multicast routing, and support for hierarchy within a single routing domain. Routing in the Internet

20. 20 o Fig 4.35

21. 21 o Inter-AS routing: BGP – Path vector protocol – Exchange path information than cost information – Routing policy – On TCP

22. 22 o Fig 4.38 (router arch) o Fig 4.39 (input port) Router

23. 23 o Given the need to operate at today’s high link speeds, a number of ways to find out an appropriate forwarding table entry. – A linear search – Store the forwarding table entries in a tree data structure – Content addressable memories – Forwarding table entries in a cache

24. 24 o Fig 4.40 (switching fabric)

25. 25 o Fig 4.41 (output ports) o Packet queues at both the input ports and the output ports -> packet loss depending on the traffic load, the relative speed of the switching fabric, and the line speed.

26. 26 o Fig 4.42 o Packet scheduler: choose one packet among queued for transmission – First-come-first-served (FCFS) scheduling – Weighted fair queueing (WFQ) – Important for quality-of-service guarantees.

27. 27 o Drop a packet before the buffer is full in order to provide a congestion signal to the sender -> active queue management (Random Early Detection (RED)) o Head-of-the-line (HOL) blocking in an input-queued switch o Fig 4.43

28. 28 o 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

29. 29 o 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 o ICMP for IPv6 – Packet too big, unrecognized IPv6 options error codes – IGMP o Transitioning from IPv4 to IPv6 – Flag day – Dual-stack: DNS to determine whether another node is IPv6 or IPv4 – Tunneling

30. 30 o Fig 4.45 o Fig 4.46

31. 31 o Unicast vs multicast o The sending of a packet from one sender to multiple receivers with a single send operation. o Network-layer aspects of multicast o Handle multicast groups – One-to-all unicast – Application-level multicast – Explicit multicast at the network layer o How to identify the receivers of a multicast datagram? – Address indirection: a single identifier is used for the group of receivers -> class D o How to address a datagram sent to these receivers? Multicast routing

32. 32 o Fig 4.47

33. 33 o Fig 4.48

34. 34 o 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 o Network-layer multicast algorithms (PIM, DVMRP, MOSPF) – Coordinate the multicast routers so that multicast datagrams are routed to their final destinations o Table 4.4

35. 35 o Fig 4.50

36. 36 o Fig 4.51

37. 37 o 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. o Fig 4.52 Multicast routing: the general case

38. 38 o 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. o Fig 4.53

39. 39 o 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

40. 40 o Multicast routing using a source-based tree – Reverse path forwarding (RPF) – Fig 4.56 – If there were thousands of routers downstream from D, … -> pruning

41. 41 o 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

42. 42 o 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 o Multicast Open Shortest Path First (MOSPF) o DVMRP has been the de facto inter-AS multicast routing protocol Multicast routing in the Internet

43. 43 o An Internet application needs to know the IP address and port number of the remote entity with which it is communicating. o Fig 4.58 o Ad hoc networking Mobility and the Network layer

44. 44 o Figure 4.59

45. 45 o Indirect routing to a mobile node – Triangle routing problem – Encapsulation/decapsulation = tunneling – Fig 4.60

46. 46 – Fig 4.61 – The occasional datagram loss within a connection when a node moves between networks.

47. 47 o Direct routing to a mobile node – Fig 4.62 – GSM

48. 48 o Agent discovery, registration with the home agent, and indirect routing of datagram o Security: authentication o An agent receiving the solicitation will unicast an agent advertisement directly to the mobile node. o Fig 4.63 Mobile IP

49. 49 – Fig 4.64