06/11/12 With the Internet explosion, everyone wants to or has to be connected. Mobile IP provides the required solution for hosts to stay mobile.
06/11/12 mobile host/node : A node that can change its link-level point of attachment from one IP subnet to another, while still being reachable via its home address. home address : An IP address assigned to a mobile node within its home subnet. The network prefix in a mobile node's home address is equal to the network prefix of the home subnet. home net (subnet) : The IP subnet indicated by a mobile node's home address. Standard IP routing mechanisms will deliver packets destined for a mobile node's home address to its home subnet. home agent : A router on a mobile node's home subnet with which the mobile node has registered its current care-of address. While the mobile node is away from home, the home agent intercepts packets on the home subnet destined to the mobile node's home address, encapsulates them, and tunnels them to the mobile node's registered care-of address. care-of address : An IP address associated with a mobile node while visiting a foreign subnet, which uses the network prefix of that foreign subnet. Among the multiple care-of addresses that a mobile node may have at a time (e.g., with different network prefixes), the one registered with the mobile node's home agent is called its &quot;primary” care-of address.
Mobile IP 2
Background• With new applications developing at a rapid pace, and advancements in Mobile Computing technology, the number of users replacing their desktop PCs with super- portable laptops is on the up.
Topics covered• Simple overview : Mobile IP• Tunneling• TCP Comparison• Route Optimization• Mobile IP in IPv6
Design Goals : Mobile IP• Make size and frequency of routing updates as small as possible.• Software level : Simplicity in implementation• Allow mobile nodes to operate with on one IP address, instead of a spool of addresses.
Terminology• Mobile Node• Home Address, Home Link, and Home Agent.• Care-of Address, Foreign Link, and Foreign Agent.
Components : Mobile IP• Agent Discovery : Provides information about home and foreign agents to the mobile node.• Registration : Mobile node requests services from its foreign agent.• Mobile IP defines the rules for routing any type of packet - unicast, multicast, and broadcast.
Overview of Operation• When a mobile host moves out of its home site, it contacts the closest foreign agent.• Registration takes place.• Previous foreign(local) agent if any are notified regarding the change.• Communication starts. (also known as triangle routing).
Overview of OperationFigure 1 :CN sending data to MN at home Correspondent node bulk data acknowledgements Home agent Foreign agentbulk adv acknowledgements Scenario A: Mobile node No tunnelling No fragmentation No dogleg route
Overview of Operation Figure 2:MN sending data to CN from home Correspondent node acknowledgements bulk data Home agent Foreign agentacknowledgements adv Scenario B: bulk No tunnelling Mobile node No fragmentation No dogleg route
Overview of OperationFigure 3:CN sending data to MN through Foreign Agent Correspondent node bulk data acknowledgements tunnelled bulk data Home agent Foreign agent bulk data Scenario C: adv MTU is 1500 bytes acknowledgements Tunnelling of bulk data Fragmentation Mobile node Dogleg route
Overview of OperationFigure 4:MN sending data to CN via Foreign Agent Correspondent node acknowledgements bulk data tunnelled acknowledgements Foreign agent Home agent acknowledgements Scenario D: adv No tunnelling of data bulk data Tunnelling of acks No fragmentation Mobile node Dogleg route
Scenario 1: Correspondent node bulk data acknowledgements Home agent Foreign agent bulk adv acknowledgements Scenario A: Mobile node No tunnelling No fragmentation No dogleg routeFig. 1 - Mobile node is receiving bulk data from thecorrespondent node while the mobile node is at home. MTUis 1500 bytes
Scenario 2: Correspondent node acknowledgements bulk data Home agent Foreign agent acknowledgements adv Scenario B: bulk No tunnelling Mobile node No fragmentation No dogleg routeFig. 2 - Mobile node is sending bulk data to thecorrespondent node while the mobile node is at home. MTUis 1500 bytes
Scenario 3: Correspondent node bulk data acknowledgements tunnelled bulk data Home agent Foreign agent bulk data Scenario C: adv MTU is 1500 bytes acknowledgements Tunnelling of bulk data Fragmentation Mobile node Dogleg routeFig. 3 - Mobile node is receiving bulk data from thecorrespondent node while the mobile node is at a foreignnetwork. MTU is 1500 bytes
Scenario 4: Correspondent node acknowledgements bulk data tunnelled acknowledgements Foreign agent Home agent acknowledgements Scenario D: adv No tunnelling of data bulk data Tunnelling of acks No fragmentation Mobile node Dogleg routeFig. 4 - Mobile node is sending bulk data to thecorrespondent node while the mobile node is at a foreignnetwork. MTU is 1500 bytes
Scenario 5: Correspondent node bulk data acknowledgements tunnelled bulk data Home agent Foreign agent bulk data adv acknowledgements Scenario E: MTU is 1450 bytes Mobile node Tunnelling of bulk data No fragmentation Dogleg routeFig. 5 - Mobile node is receiving bulk data from thecorrespondent node while the mobile node is at a foreignnetwork. MTU is 1450 bytes
Comparisons: Differences in Setup Scenario : Sender of the Location of MTU (in file mobile node bytes) A CN At home 1500 B MN At home 1500 C CN At foreign 1500 D MN At foreign 1500 E CN At foreign 1450Table 1 - Differences in setup between the five different scenario
Comparisons: Presence of tunneling, fragmentation and dogleg routeScenario : Tunnelling Fragmentation Dogleg route overhead overhead overhead present? present? present?A No No NoB No No NoC Yes Yes YesD Yes No NoE Yes No Yes
Test Details• MTU in scenario 5 was reduced solely to prevent fragmentation.• Comparison using FTP file transfer, 30.2 MB file ≈ 241.6 Mbits• Repeated 20 times• Throughput = file size / mean transfer time• % throughput = throughput / maximum capacity of link
Comparisons: Mean transfer time and standard deviation for FTP file transferScenario : Mean transfer Standard Throughput time (s) deviation (s) (Mbit/s)A 41.21 1.81 5.86B 43.30 1.04 5.58C 78.22 1.43 3.09D 46.17 1.14 5.23E 75.62 1.33 3.19
Evaluations• File transfer takes 90% more time to complete, with all 3 overheads.• Encapsulation and Decapsulation of bulk data or acknowledgments takes the same time• The longer route results in a higher delay before the packets reach the mobile node• Link usage will increase if the IP packet and its encapsulated form both use the same link while being routed to the destination• The tunneling overhead causes the file transfer to take about 7% more time to complete
Evaluations• Fragmentation overhead causes the file transfer to take about 6% more time to complete• The dogleg route overhead obtained using this method causes the file transfer to take about 80% more time to complete• The handover overhead will depend on the TCP handover latency, the frequency of handoffs, the duration of the TCP connection and the agent advertisement interval• The TCP handover latency is about 60% more than the MIP network handover latency
Evaluations• The handover overhead is about 13%.• Two ways of reducing the handover overhead: – reduce the retransmission timer value – reduce the agent advertisement interval. • Tradeoff: bandwidth consumption
Route Optimization and Authentication• The paper describes the Internet Mobile Host Protocol with the following features: – route optimization – authentication of management packets – performance and operational transparency to the user.
IMHP Architecture Entities• Mobile host – unique home address• Local Agent – helps mobile host register, provides care- off address – maintains a visitor list • lists all the mobile hosts • needs to be refreshed
IMHP Architecture Entities• Cache Agent – Maintains the location cache – using cache entry the data packet is “tunneled” to the mobile host. • Done by including a small IMHP header • adds 8 or 12 bytes of overhead to each packet
IMHP Architecture Entities• Home Agent – maintains a home list – special case: home agent maintains a visitor entry for mobile host – must also be a cache agent for its mobile hosts
Authentication• Basically required to authenticate binding and management packets.• MH to HA : by including an authenticator based on a shared secret• General Authentication: node sends a request for binding with random number and gets reply with the same number.
Authentication• Use of route flag in management packet to enforce normal IP routing of packet.• Local agent authenticates visitor list entries from the home agent.• All entries into lists are timer based.
Optimization• special tunnel packet - destination of tunnel is same as destination of packet.• Specified as a set of forwarding rules for the IMHP entities.
Rules for forwarding• Node receives tunneled packet with its own destination address.• Node receives a non-tunneled packet with its own destination address
Rules: Home Agent• HA receives an IMHP management packet with route flag set.• HA receives a special tunnel packet.• HA receives packet for one of its mobile hosts – HA has a visitor entry for the host. – HA does not have a visitor entry.
Rules: Home Agent• HA never tunnels a packet back to a node that has just tunneled the packet to it.
Rules: Other Agents• Receives special tunnel packet with route flag set.• LA receives a tunneled packet for host in visitor list.• LA receives a regular packet for host in visitor list• CA receives a packet and has an entry in its location cache.
Rules: Other Agents• Receives packet that was tunneled directly to this node, and the agent is unable to forward it further. – Solution : special tunnel
Bindings• Binding notifications: – MH notifies HA and previous LA about “change of address”. – Any node can notify any other node about wrong binding information stored by it. – Notification Back-off
IMHP : Other Issues• restrictions on advertising bindings - use of private flag.• MH in Popup Mode – requires facilities such as DHCP – acts as its own local agent. – Binding should be kept private• Performance of MH at home should be like a stationary host.
Mobility Support in IPv6• IPv6: – 128 bit address space – link local addresses• Extension headers : Destination Options header, hop-by-hop header, routing header and an authentication header.
Overview of Mobile IPv6• All packets carrying information must be authenticated.• Avoid “remote redirection” attacks• Allows MH to allow more than one care-of addresses at a time, but registers only one of its bindings.• Allows CH to dynamically learn the MH’s binding. In this case it uses the Routing header but does not encapsulate.
Overview of Mobile IPv6• Reasonable to expect all the IPv6 nodes to have caching capabilities.• Implementation of the Binding Updates and Binding Acknowledgments - the key to reliability and optimization.
Binding Update Option• Provides optimization and performance in IPv6• Used by mobile host to: – notify home agent of its primary care-of address – notify correspondent nodes of its current binding• Binding Updates should always be authenticated.
Binding Update Format• Lifetime:time duration for which the binding remains valid.• Identification: To ensure in order processing of updates.• Care-of address: Holds the current care of address
Binding Update Format• Flags: – H: Destination requested to serve as home agent. – A: Acknowledgment expected – L:Link Local address present• Updates could be retransmitted if there is no acknowledgment.
Binding Acknowledgment Format• Code: indicates whether binding update was accepted or rejected. – < 128 update accepted – >= 128 update rejected• Lifetime: during for which node will retain the binding.• Refresh: time interval for sending updates• Identification: Same number as the update.
Sending Updates• First update sent to home agent to register the new care-of address. – From another foreign network – From the home network• Can be included in a regular packet or sent alone.• Only the mobile node can send its own binding updates.
Movement detection• Neighbor Discovery protocol including Router Discovery and Neighbor Unreachability Detection to create list• Selects the default router from the list• configures its care-off address
Unreachability• detecting unreachability – using the Neighbor Unreachability detection – using the higher layers – using the lower layers. – When not receiving packets
Smooth Handoffs• Using overlapping cells - accept packets at multiple addresses for a short while.• Router Assisted - Previous router can forward packets to new local router.• Renumbering the home network
CH & HA Operations• Sending packet to MH• Handling ICMP error messages• Home agent discovery
More information on Mobile IP• National University of Singapore• Carnegie Mellon University• Columbia University
• Presentation based on the reading list sent out earlier.All diagrams and tables have been included from the reading list research papers.
Mobile IP Prashant BhargavaCS 599 : Wireless Communications and Mobile Computing 602 08 8857