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Preserving Established Communications in IPv6 Multi-homed Sites with MEX

Preserving Established Communications in IPv6 Multi-homed Sites with MEX. Juan F. Rodríguez, Marcelo Bagnulo, A. García-Martínez, I. Soto, A. Azcorra. Dept. de Ingeniería Telemática Universidad Carlos III de Madrid. Index. Introduction Multihoming through Extension Headers (MEX).

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Preserving Established Communications in IPv6 Multi-homed Sites with MEX

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  1. Preserving Established Communications in IPv6 Multi-homed Sites with MEX Juan F. Rodríguez, Marcelo Bagnulo, A. García-Martínez, I. Soto, A. Azcorra. Dept. de Ingeniería Telemática Universidad Carlos III de Madrid

  2. Index • Introduction • Multihoming through Extension Headers (MEX). • MEX Walkthrough • Normal Operation. • Fault Tolerance Support. • MEX Requirements • Conclusions.

  3. Provider-A Introduction • Multihoming usually means “more than one provider”. • Host multihomed: • More than one address. • More than one link. Provider-B Multi-homed Site

  4. <P.I. addr. block> Site reachability information Site addr.block Provider-A Introduction • IPv4 Multihoming announces specific routes Default Free Zone <ISP-B addr. block> <ISP-A addr. block> Provider-B Multi-homed Site

  5. Introduction • Routing table scalability issue: • CIDR: • Aggregates routes. • IPv4 Multihoming: • Advertises more specific routes. • Expected growth will be driven by: • The number of providers. • The number of multihomed-sites. • IPv4 multihoming doesn’t scale well.

  6. Introduction • IPv6 routing architecture is stiffer: • ISPs don’t announce other ISP’s prefixes. • Addresses are aggregated by providers. • Some IPv6 Multihoming goals: • Scalability. • Interoperability with legacy IPv6 hosts. • Transport-Layer Survivability • Fault detection • Recovery process

  7. MEX • Extends the IPv6 protocol to: • Share reachability information end-2-end. • Communicate alternative paths to the routing system. • Host based solution (active): • Stores different prefixes for a given destination. • Sends information to the routing system. • Router based solution (passive): • The routing system takes over the recovery process.

  8. Opt. Type Opt. Length Reserved Alternative Prefix 1 … Alternative Prefix N Segments Left Next Hdr Hdr Ext Len Reserved Reserved Alternative Prefix 1 … Alternative Prefix N MEX • Alternative Prefix Destination Option: • It informs the peer about the alternative prefixes. • Alternative Prefix Extension Header: • It Informs the routers how to re-route packets if there’s no route to the destination.

  9. Normal Operation ISP-B ISP-A ISP-C DNS “Host A” (addrA1, addrA2) “Host B” (addrB1, addrB2) IPv6 header, dst = <addrB1> IPv6 Ext. Header with <prefixB2> IPv6 Dst. Opt. w/ <prefixA1,prefixA2> Upper Layer Protocol

  10. Fault Tolerance support • MEX capable router (MEX-R): • It understands the MEX Ext. Header. • It’s able to attract packets when there’s a black-hole. • MEX-R walkthrough: • It looks for the MEX Ext. Header. • It swaps dest. prefix with one of the alternative prefixes. • It looks at his routing table to forward the packet.

  11. Fault Tolerance support MEX-R ISP-B ISP-A Default Free Zone Host 1 ISP-D ISP-C Host 2 (PA:PC:….::/64) (PB:PD:….::/64)

  12. MEX Requirements • Changes on hosts: • It requires upgrades on hosts to achieve multihoming benefits. • Changes on routers: • Only some routers should be upgraded per ISP. • “Normal” routers shouldn’t discard packets with the new Extension Header.

  13. Conclusion • Reduce Packet Loss. • It doesn’t pollute the IPv6 routing system. • Incremental Deployment. • Compatible with unmodified hosts. • Transparent to upper layers. • Peers don’t realize of the addr. swapping. • Established communications are preserved. • Implemented on a FreeBSD-4.5 kame release.

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