Copyright 2002, S.D. Personick. All Rights Reserved.1 Telecommunications Networking II Topic 19 Internetworking Protocol (IP) (continued) Ref: Tanenbaum pp Dr. Stewart D. Personick Drexel University

Copyright 2002, S.D. Personick. All Rights Reserved.2 IP- Multicasting Uses a special “Class D” IP address: 1110XXXX + 3 bytes ( ) There are some permanent group addresses: e.g., => all hosts on a LAN Temporary group addresses are created to form ad-hoc groups

Copyright 2002, S.D. Personick. All Rights Reserved.3 IP- Multicasting A protocol called the Internet Group Management Protocol (IGMP) is used by special routers, called multicast routers, to determine which hosts on the LANs connected to those routers wish to belong to one or more multicast groups. I.e., you elect to join a multicast group Multicast routers form “spanning trees” to distribute multicast packets

Copyright 2002, S.D. Personick. All Rights Reserved.4 Spanning Tree

Copyright 2002, S.D. Personick. All Rights Reserved.5 Spanning Tree

Copyright 2002, S.D. Personick. All Rights Reserved.6 IP- Multicasting IP multicasting is used to broadcast audio and audio-visual programs (MBONE) over the Internet

Copyright 2002, S.D. Personick. All Rights Reserved.7 Mobile IP How to accommodate Internet hosts that move away from their “home location” Solution: Reinvent “call forwarding” (with a twist) and cellular roaming -Networks that support mobile IP provide “home agents” and “foreign agents” -Hosts that arrive at a foreign network register with the local foreign agent

Copyright 2002, S.D. Personick. All Rights Reserved.8 Mobile IP The local foreign agent contacts the visitor’s home agent, and provides a “forwarding address” (usually the IP address of the foreign agent) Datagrams sent to the mobile host’s normal IP address are picked up by the mobile host’s home agent…and forwarded inside of another IP datagram (tunneling) to the forwarding address

Copyright 2002, S.D. Personick. All Rights Reserved.9 Tunneling IP Datagram IP Header Foreign Agent IP Address Original IP Address

Copyright 2002, S.D. Personick. All Rights Reserved.10 Mobile IP The home agent also sends a datagram to the sender of the original packet, providing the forwarding address…so that future datagrams can be sent directly to the foreign agent The foreign agent receives the forwarded datagram, takes it out of its IP wrapper, and delivers the unwrapped datagram to the mobile host

Copyright 2002, S.D. Personick. All Rights Reserved.11 Mobile IP Issues: -How does the home agent know that a forwarding request is legitimate? (solution: cryptographic authentication) -How to delete registrations at foreign agents when mobile (visiting) hosts leave without de-registering (solution: timeout)

Copyright 2002, S.D. Personick. All Rights Reserved.12 Classless InterDomain Routing CIDR Problem: the original scheme of assigning IP addresses, Class A, Class B and Class C, results in very inefficient use of the total address space. -Class A: 127 possible (each has 256 x 256 x 256 possible host addresses) Too few -Class B: 64 x 256 possible (each has 256 x 256 possible host addresses) Too few

Copyright 2002, S.D. Personick. All Rights Reserved.13 Classless InterDomain Routing CIDR Problem (continued) -Class C: 32 x 256 x 256 possible (each has only 256 possible host addresses) -Router tables (in backbone routers) need to store and manage all network address-route pairs (~2 million possible Class C network addresses)

Copyright 2002, S.D. Personick. All Rights Reserved.14 CIDR Solution -Assign networks multiples of adjacent Class C addresses to provide for N x 256 hosts -Backbone routers need only store one network address-route pair for each block on contiguous Class C addresses assigned to the same network (not obvious)