Other Routing Protocols Outline Multicast Routing Mobile IP Ad-hoc Networks

Multicast Routing Methods of sending message to a subset of nodes in the network Unicast to each member in the group or broadcast can be used but inefficient. Multicast

Components of Multicast Routing Group management: mechanism for nodes to create, destroy, join, and leave a group. Routers need to know which host belongs to which group. Multicast routing: form multicast trees to reach every members in the group, can be done in different ways.

Components of Multicast Routing One tree per source per group. Each router computes a spanning tree. When a host sends a multicast message, the first router encountered pruned the tree to keep only the branches that reach one or more members One tree per group (core-based tree): all members of a group share the same spanning tree rooted at the center of the group, hosts send multicast messages to the tree, which are distributed along the tree. Less memory usage but nonoptimal paths for some members.

Pruning Multicast Tree (a) A network. (b) A spanning tree for the leftmost router. (c) A multicast tree for group 1. (d) A multicast tree for group 2.

Methods for Pruning Multicast Tree When link state routing is used, routers have the complete topology of the network, and pruning can be done starting from the leaves toward the root of the tree. When distance vector routing is used, reverse path forwarding is used, a router with no host belonging to a group and not connected to routers that have hosts belonging to the group responds a prune message to a multicast message, pruning is done recursively.

Internet Multicasting IP supports multicast using class D addresses. Each class D address (28 effective bits) identifies a multicast group. Groups can be permanent or temporary. Permanent groups are always there and need no setup, some examples are 224.0.0.1 all systems on a LAN 224.0.0.2 all routers on a LAN 224.0.0.5 all OSPF routers on a LAN 224.0.0.6 all designated routers on a LAN

Internet Multicasting Temporary groups must be created before being used. Hosts can join and leave a group dynamically. Multicast is implemented by multicast routers, i.e., routers with multicast software, which need not be omnipresent for multicast to work. Tunneling is used bypass routers that do not run multicast software, e.g., Mbone.

Internet Multicasting Multicast routers know about the group membership by running IGMP (internet group management protocol, defined in RFC1112), IGMP has two types messages: query and reply. Query is periodically sent out by multicast routers to the machines on the LAN asking which group they belong using L2 multicast (224.0.0.1). Reply messages give the answers.

Routing for Mobile Hosts Mobile hosts pose unique challenge for routing, since, in addiction to finding the path to reach the host, its location needs to be discovered first.

Mobile IP Each mobile host has a home location (e.g., a home LAN), a permanent address (e.g., cell phone number), and a home agent that forwards the message destined for the mobile host to its current location. Each location has a foreign agent that keep track all visiting mobile hosts. When a mobile host visits a foreign location, it must register with the foreign agent telling its home address, current link address, and security info. The foreign agent then informs the mobile host’s home agent, which now knows the location of the mobile host.

Routing for Mobile Hosts

Routing for Mobile Hosts When a packet is sent to the mobile host, it is first routed to its home LAN and is intercepted by its home agent, which looks up the mobile host’s current foreign agent. The home agent then encapsulates the packet in another packet and sends it to the foreign host (tunneling), and tells the sender to henceforth send packets (also encapsulated) directly to the foreign agent.

Routing for Mobile Hosts There are variants differing in the following ways. Partition functionality between routers and hosts, if hosts, which layers. In some schemes, routers along the way can cache the addresses and intercept, redirect traffic before it even gets to the home location. In some schemes, each visitor gets a unique temporary address, in others, all visitors share one temporary address. To redirect traffic, some schemes directly change the header address field, others encapsulate the packet in another one. Different schemes have different security measures.

Routing in Ad Hoc Networks Routing in ad hoc networks is different form mobile IP in that there are no fixed router infrastructure, mobile hosts are themselves routers. Mobile ad hoc networks (MANET) have the following scenarios: Military vehicles on battlefield with no infrastructure. A fleet of ships at sea. All moving all the time Emergency works at earthquake: The infrastructure destroyed. A gathering of people with notebook computers: In an area lacking 802.11. Proactive and Reactive protocols AODV, DSR, DSDV.