Quick announcements CSE 123b Communications Software z Spring 2004 z Lecture 9 Mobile Networking Typo in problem 1 of HW 2 fixed as of 1pm yesterday Please consider chapter 4 3 4 3 3 to be part of the assigned reading for the midterm this was the reading related to Inter domain routing Stefan Savage May 9 2004 Last class z z z One to many Publish and subscribe model receiver based z Per source tree routing z RPF RPB RPM Builds Efficient trees S G state explosion for large networks groups May 9 2004 z Unicast to rendezvous point More complex fragile hard to manage Trees inefficient by as much as 2x Only requires G state on routers CSE 123b Lecture 8 IP Multicast 3 The Mobility Problem z z May 9 2004 CSE 123b Lecture 8 IP Multicast 4 z How does a mobile host get a local IP address IP routing breaks if addresses change location Why Unfortunately the buying public likes mobility z z z May 9 2004 Mobile IP Johnson96 TCP Migrate Snoeren et al00 Problems Implicit assumption that Internet hosts are fixed Remember routing It doesn t work anymore Problem review Design issues Case studies Shared tree What are implications of hosts that move Routing protocols 2 Today s issues Multicast communications CSE 123b Lecture 8 IP Multicast CSE 123b Lecture 8 IP Multicast 5 How do you know which IP address to use when sending to a mobile host If a host moves during communication how do you know how to migrate state to the new IP address Backwards compatibility higher layer state caching May 9 2004 CSE 123b Lecture 8 IP Multicast 6 1 Application demands z Some simple solutions Geographic scope z Rate of change z Continuity z Interactivity z Remote accessibility May 9 2004 z Switching 802 11 LANs at UCSD vs visiting IBM in Zurich Cell phone in airplane vs hotel room dialin z State associated with session e g ordering plane tickets Dynamic Host Configuration Protocol DHCP Request IP address dynamically special broadcast address How do you get contacted at new IP address One solution dynamic DNS Cell phone handoff Authentication issues who can use 802 11 in AP M Pro Great over longer time scales Con What happens if you move during a session Client vs Server CSE 123b Lecture 8 IP Multicast 7 May 9 2004 Dates back to research in the early 90s IPv4 RFC 2002 IPv6 version is roughly the same z Mobile Host MH has two addresses z Home address Design constraints Network layer solution Only requires changes to mobile hosts Stationary hosts oblivious to mobility Incrementally deployable z Care of address Will change perhaps frequently In foreign network Related to current location IP routing gets it to the right place May 9 2004 CSE 123b Lecture 8 IP Multicast 9 Home and Foreign Agents z May 9 2004 CSE 123b Lecture 8 IP Multicast 10 Mobile IP MH at Home Home agent HA implements level of indirection between the mobile host and correspondents 8 Never changes uniquely identifies the host In home network Correspondent host CH addresses all packets to the home address z CSE 123b Lecture 8 IP Multicast Mobile IP Approach Current IETF proposed standard for mobility Wireless learning bridges CMU campus solution Transparently update MAC layer mappings in access points Pro transparent to all higher layers Con Local scope only Mobile IP Johnson96 z Datalink layer mobility Correspondent Host CH Packet Accepts traffic sent to home address What about requests from home network z Tunnels traffic to the mobile host using care of address And vice versa correspondent none the wiser Internet Foreign agent FA represents mobile in foreign network Mobile host does not need its own address in foreign network Potential advantage deal with local mobility locally May 9 2004 CSE 123b Lecture 8 IP Multicast Visiting Location Home Foreign agent can be care of address Mobile Host MH 11 May 9 2004 Home Agent HA CSE 123b Lecture 8 IP Multicast 12 2 Mobile IP MH Moving Mobile IP MH Away Packet Packet Correspondent Host CH Correspondent Host CH Mobile Host MH Mobile Host MH Internet Internet Register MH is now with me Home Home Agent HA May 9 2004 Encapsulated Visiting Location Home Agent HA Foreign Agent FA CSE 123b Lecture 8 IP Multicast 13 Mobile IP Issues z May 9 2004 z z z 15 z Agents multicast agent advertisements locally Mobile can also multicast an agent solicitation Why does multicast work here z So that the home agent knows where to tunnel packets Registration needs to be updated when location changes z 16 z 17 Came from mobile host authenticity Has not been altered integrity Is not a replay of a previous registration freshness Mechanisms Registrations have TTLs Hey send all the mobile s traffic to me now Need to authenticate that a registration Registration requests first go to foreign agent then to home agent which replies to foreign agent which forwards back to the mobile CSE 123b Lecture 8 IP Multicast CSE 123b Lecture 8 IP Multicast Registration requests can be used by attackers to hijack tunnels from home agent May 9 2004 Beacons that tell the mobile who it can hear Start in network A move to network B Lack of A s beacons and presence of B s tells mobile it has switched networks Registration Authentication Lifetimes To find a foreign agent to register with May 9 2004 Multiple steps Mobiles must register care of addresses with their home agents To notice when it changes networks To notice when it is home again Registration z z 14 When home take down the tunnel z CSE 123b Lecture 8 IP Multicast CSE 123b Lecture 8 IP Multicast Agent discovery enables a mobile host Discovering agents Registering addresses with agents establishing bindings Authentication Tunneling Performance May 9 2004 Foreign Agent FA Agent Discovery To make all this happen a number of issues have to be addressed Visiting Location Home May 9 2004 Shared keys mobile and home are from same admin domain MD5 digests Nonces or timestamps CSE 123b Lecture 8 IP Multicast 18 3 Tunneling z Home agent and mobile communicate using a tunnel z Correspondent address src mobile home address dest Gets sent to home agent z Encapsulates original packet Home agent src care of address dest Gets sent to foreign agent or mobile depending on care of Mobile can respond back directly which source address z CSE 123b Lecture 8 IP Multicast 19 Route optimization shortcuts the triangle May 9 2004 Correspondents can learn and use mobile care of addresses Tunnel packets directly to care of address skip home agent Requires changes to correspondents Same goals z Different approach z Issues Binding