Internet Mobility Presented by Nitin Bahadur Nitin Bahadur Distributed Systems Spring 2000 1 References Mary Baker Xinhua Zhao Stuart Cheshire Jonathan Stone Supporting mobility in Mosquitonet Proceedings of USENIX Technical Conference 1996 Stuart Cheshire and Mary Baker Internet Mobility 4x4 SIGCOMM 96 Kevin Lai Mema R Diane Tang Xinhua Zhao Mary Baker Experiences with a Mobile Testbed Proceedings of WWCA 98 Nitin Bahadur Distributed Systems Spring 2000 2 References C Perkins IP Mobility Support for IPv4 Internet Draft draft ietf mobileip rfc2002 bis 01 txt Jan 2000 C Perkins Route optimization in Mobile IP Internet Draft deaft ietf mobileip opim 09 txt Feb 2000 David Maltz Pravin Bhagwat MSOCKS An Architecture for transport layer mobility IEEE INFOCOM 98 Nitin Bahadur Distributed Systems Spring 2000 3 Outline Motivation and Challenges Some proposed solutions IP Mobility Routing Optimizations Security Issues Recent Extensions Conclusions Nitin Bahadur Distributed Systems Spring 2000 4 Motivation Ubiquitous connectivity continuous connectivity Ability to maintain current conversations connections during movement Move from one kind of network to another Move to networks that do NOT provide support for mobility Nitin Bahadur Distributed Systems Spring 2000 5 Challenges Movement causes change in IP address Problems with TCP connections Maintaining transparency Efficient routing to new location of mobile host Security issues Nitin Bahadur Distributed Systems Spring 2000 6 Some Solutions Use Host specific routes possible with IPv6 Link Layer solutions Limited to a single medium A new solution for every medium Compatibility issues with other mediums Use extended DNS to register COA with DNS Information propagation time Global change in DNS Nitin Bahadur Distributed Systems Spring 2000 7 Basic Terminology Mobile Host MH Correspondent Host CH Home Agent HA Foreign Agent FA Care of Address COA Internet CH HA Nitin Bahadur FA Distributed Systems MH Spring 2000 8 Split TCP Two TCP connections CH HA MH Transport Layer mechanism TCP I Internet HA CH TCP II Nitin Bahadur Distributed Systems Spring 2000 9 Split TCP Two TCP connections instead of one Changed end points HA acks packets to CH even before MH has received them Home agent is responsible for final packet delivery Multiple traversal through the TCP protocol stack HA needs to maintain a TCP connection for every TCP connection of all its mobile hosts Nitin Bahadur Distributed Systems Spring 2000 10 TCP Splicing Two TCP connections CH HA MH Transport Layer mechanism Acks are sent on TCP I to CH only when MH sends them on TCP II TCP I Internet HA CH TCP II Nitin Bahadur Distributed Systems Spring 2000 11 TCP Splicing The scheme works like 1 TCP connection Location transparency is maintained Multiple traversal through the TCP protocol stack HA still needs to maintain a TCP connection for every TCP connection of all its mobile hosts Nitin Bahadur Distributed Systems Spring 2000 12 Mobility using Foreign Agent MH obtains COA from FA FA discovery using Agent Advertisement or Agent Solicitation messages MH host registers COA with HA through FA HA intercepts packets for MH HA encapsulates and sends packets to FA FA decapsulates packets and sends it to MH Everything done at IP level no TCP Same mechanism in the reverse direction This is called Bidirectional tunneling Nitin Bahadur Distributed Systems Spring 2000 13 Mobility using Foreign Agent Internet HA CH FA Nitin Bahadur Distributed Systems Spring 2000 14 Encapsulation IP in IP Source CH Destn MH DATA Source HA Destn COA HA Source CH Destn MH FA Source CH Destn MH DATA DATA Encapsulation maintains consistency in Source and Destination address fields Allows MH to receive packets as it moves from network to network Nitin Bahadur Distributed Systems Spring 2000 15 Encapsulation Issues IP encapsulation and automatic decapsulation is dangerous How can one verify if the inner packet has a source address if claims to be Encapsulation can cause packet fragmentation TCP breaks data in chunks of 1460 bytes and gives it to IP Encapsulation will automatically lead to packet fragmentation in such cases So extra overhead Nitin Bahadur Distributed Systems Spring 2000 16 Mobility without Foreign Agent MH obtains a COA using DHCP MH registers COA with HA directly MH performs encapsulation and decapsulation Internet HA Nitin Bahadur CH Distributed Systems Spring 2000 17 Implementation in MosquitoNet Altered the route lookup function ip rt route Mobile Policy Table helps in combination with ip rt route is used for making routing decisions Nitin Bahadur Distributed Systems Spring 2000 18 Home Agent Functionality Maintaining information about MH s current location Acting as an ARP proxy for MH ARP to get link layer address for an IP address Proxy ARP done to answer a new ARP request on behalf on MH Gratuitous ARP done to update ARP information of MH in all nodes Forwarding packets to CH and MH Nitin Bahadur Distributed Systems Spring 2000 19 Movement of MH away from home network Detection by MH received a different agent advertisement message stopped receiving agent advertisement messages Disable ARP Register with FA or HA HA performs Gratuitous ARP on behalf of MH Nitin Bahadur Distributed Systems Spring 2000 20 Movement of MH to home network Re enable ARP De register itself with HA HA performs Gratuitous ARP on behalf of MH Nitin Bahadur Distributed Systems Spring 2000 21 Advantages of using Foreign Agent No need for a temporary COA for every MH If MH leaves foreign network then Inflight packets can de directed by FA to new location of MH Less packet loss Less complexity in MH Nitin Bahadur Distributed Systems Spring 2000 22 Advantages of NOT using Foreign Agent MH can visit networks without a foreign agent FA is not a bottleneck or single point of failure No need for a FA on each network Nitin Bahadur Distributed Systems Spring 2000 23 Triangular Routing Proposed by Mobile IP working group CH sends packets to HA which forwards it to MH MH sends directly packets to CH CH MH Internet HA CH HA COA CH MH Nitin Bahadur MH CH Distributed Systems Spring 2000 24 Problems with Routing Techniques Bidirectional tunneling and Triangular routing Inefficient increase in RTT increase in path length HA is a bottleneck and a single point of failure Source address filtering problem with triangular routing Nitin Bahadur Distributed Systems Spring 2000 25 Source Address Filtering Problem Foreign network might not allow transit