IPv 6 Multihoming Support in the Mobile Internet

IPv 6 Multihoming Support in the Mobile Internet Presented by Paul Swenson CMSC 681, Fall 2007 Article by M. Bagnulo et. al. and published in the October 2007 issue of IEEE Wireless Communications

Mobile Device Networking Support • Modern “fourth-generation” (or 4 G) mobile devices support multiple network interfaces – Today, in the US, can buy advanced PDA phones that can speak both 802. 11 g (Wi-fi) and 1 x. RTT/EV-DO for data service. – Carriers will soon be rolling out 802. 16 Wi. MAX networks in the 2. 5 GHz and 700 MHz bands (pending FCC auctioning of the new wireless spectrum). – Mobile phones of tomorrow will support these technologies and more for accessing Internet resources.

Benefits of Multiple Physical Interfaces • By providing multiple redundant data interfaces, • roaming capabilities are greatly enhanced Multiple path technology would allow for fault tolerance in data connections – Preservation of established communications through outages of service or requisite roaming from one service to another • Ability to route flow of data based on predefined quantifiers such as cost of access or quality of the connection

Problems with Current Implementations • None of the currently-available mobility protocols • • support those advanced features Current mobile devices support different interfaces, but switching is far from seamless, mostly a manual process right now In order to fully realize the possibilities of modern mobile networks, a mechanism to provide mobile host multihoming support is required

Mobile IPv 6 and SHIM 6 • The paper’s proposed solution to this problem is a combined Mobile IPv 6 (MIPv 6) and SHIM 6 -based approach – Backwards-compatible with existing transport protocols/applications – Any existing TCP or UDP-based protocols will benefit from the enhanced fault tolerance provided – Works around limitations inherent to MIPv 6

Mobile IPv 6 Multihoming Support • Mobile IPv 6 supports multihoming natively • • without any extra help Requires the client to send a special “Binding Update” MIPv 6 message that it is going to be changing its active interface from the home address Packets then are redirected to the “Mobile Node” until another “Binding Update” redirects them back to the home address

Disadvantages to this Approach • If the connection between the handset and the • • home network is broken, there is no automatic failover to the mobile node Connections established while connected to the home network or one of the mobile nodes must be re-established, no automatic failover Requires the home agent (a server running on the home network) to be available even when roaming as a mobile node for traffic to get through

Why IPv 6? • IPv 6 provides any-to-any route optimization support allowing packets to flow across whichever route is best suited (or available) to carry the flow of information • Allow direct communication between the mobile node and the remote server w/out depending on the home agent

SHIM 6 and Multihoming • SHIM 6 handles the case where you have a host A with n distinct addresses wanting to communicate with a host B with m distinct addresses. – A and B should be able to communicate across any of the addresses to any of the other addresses and all packets should make it to their destination w/out any input from the protocol layer

SHIM 6 and Multihoming (2) • Within the SHIM 6 scheme, host A will do a DNS • • lookup, obtaining a subset of the addresses for host B. SHIM 6 will then use the RFC 3484 address selection process for IPv 6 to choose one of the addresses of B to contact it on. Now, as part of the SHIM 6 negotiation, the two peers exchange alternate locators so that in the event that one of the links fails, each end of the communication will know all possible ways to reach the other host.

SHIM 6 and Multihoming (3) • IPv 6 Reachability Protocol (REAP) is then used to verify that the currently used path is functioning. • Special keepalive packets are sent when data has not been transmitted after a certain amount of time in order to allow REAP to detect an outage based on time since last packet received

SHIM 6 and Failures • When a failure is detected by one of the hosts, that host • • enters an “exploratory phase” in which special probe packets are sent to each of the known addresses on the other end of the link (and using multiple interfaces on that host’s side) Based upon the received responses the communications channel is redirected over links that were successful in reaching the other host, thus preserving the information flow (be it connection-oriented or connection-less). Thanks to SHIM 6 and MIPv 6, packets end up going to the target system, not a specific IP address on that system.

Security in SHIM 6 • SHIM 6 protects against redirection attacks using Cryptographically Generated Addresses (CGA) – CGAs are regular unicast IPv 6 addresses that are signed with the interface identifier, a public key and the prefix of the address • This allows a host to claim ownership over a specific CGA since it owns the private key

Architecture (MIPv 6 and SHIM 6) • The SHIM 6 layer is considered to be on top (it is what applications interact with) • The Mobile IPv 6 layer is then situated below that in a block diagram • The IP forwarding sublayer is then below the MIPv 6 layer

Conclusions • Article provides an architecture for providing • • • multihoming + failover support to 4 G wireless nodes that will be capable of multiple simultaneous network links Makes use of standard Mobile IPv 6 and overlays SHIM 6 on top to provide advanced failure detection using REAP and recovery support thanks to SHIM 6 Works without any modifications to the Mobile IPv 6 protocol, making use of a standards-compliant multihoming mechanism layered on top of it. Minimizes changes required to existing protocols (they should be able to function with little or no change and without being aware of the SHIM 6 layer at all).