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Multihoming in IPV6
Habib Naderi
Department of Computer ScienceUniversity of Auckland
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Definition of Multihoming• Having connection to the Internet through
more than one provider
Provider1Provider2
Internet
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Multihoming Benefits
• Redundancy: having backup links to protect against failures.
• Traffic engineering: distributing traffic on different links to achieve better performance.
• Policy selection: assigning different traffics to different links based on site’s policies (cost, commercial reasons, ...).
• Around 60 % of stub networks are multihomed and this number is growing.
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How Multihoming Is Achieved in the Current Internet
• The site acquires its own address block, can be Provider Independent or Provider Aggregatable, and announces that through all its providers.
Provider1Provider2
Internet
169.254.187.0/2420.0.123.0/24
20.0.0.0/8169.254.187.0/24
30.0.0.0/8169.254.187.0/2420.0.123.0/24
PI addressPA address
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Is Current Solution deployable in IPV6?
• Scalability concerns: each MH site inserts new routing entries in global BGP routing tables.
• As the number of MH sites grows, the routing table size will cause a big problem. It needs more memory and processing power.
• Current studies show a growth of about 25% per annum in routing table. 20% of the entire size is related to multi-homing prefixes.
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Solutions for IPV6
• Router based: routing system should provide the MH functionality
- MH with BGP: like ipv4- MH using cooperation between providers- MH support at site exit router
• Middle Box: a box between multihomed hosts and Internet provides MH functionality.
- NAT- Multihoming Aliasing Protocol- Multihoming Translation Portocol
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Solutions for IPV6
• Host Centric: multihomed hosts with multiple prefixes provide MH
functionality.- HIP- SHIM6
- SCTP- multihomed TCP...
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Shim6
• Shim6 is a host centric solution, chosen by IETF, for providing MH in IPV6 Internet (RFC 5533).
• It inserts a shim layer between IP and transport layer which switches between different IP addresses transparently.
Transport (TCP, UDP, ...)
IP routing sub-layer
Shim6
IP endpoint sub-layer (Frag/Reass, Dst opts)
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Shim6
• To be transparent to the transport layer, shim6 uses the concept of ID/Locator separation.
• Transport layer uses one of the host’s IPV6 addresses , which is called ULID, for establishing connection. This ID will not change during the connection life.
• When a failure happens, shim6 will pick one of other host’s addresses, which are called set of locators, and switch to that. Switching is completely transparent to the transport layer.
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Shim6
• One important part of shim6 is failure detection and recovery mechanism.
• A protocol called REAchability Protcol (REAP) has been designed for this purpose.
• RFC 5534
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Failure Detection in REAP
• REAP uses FBD (Force Bidirectional Detection) for verifying reachability.
• When there is a traffic in one direction, there should be also traffic in the other direction.
• REAP sends KEEP_ALIVE messages in the case that there is no data to be sent.
• So, when there is an outgoing traffic but no return traffic, it’s a sign of failure.
• REAP employs two timers (send timer and keep alive timer) to manage this process.
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Recovery Mechanism in REAP
• When a failure is detected, REAP starts the exploration process to find a working pair of locators.
• A set of locator pairs are built using host and peer locator sets. The set is pruned and ordered using DAS rules(RFC 3484).
• Then REAP starts to send probe messages for each member of the resulting set to test its reachability. This process finishes when an operational address pair is found.
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An Example
B1B2
A1A2
A1, B1A1, B2A2, B1A2, B2
Candidate Set
B1B2
A1A2
B1B2
A1A2
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Our Current Research Topic
• Analyzing the behaviour of the REAP in large sites to answer the following questions:
- If the REAP is deployed in future internet what will happen if a failure happens in a site with thousands of hosts?
- How much traffic will be generated? - How long the recovery process will take?
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Our Current Research Topic
• To answer these questions, we have built and simulated a model of the REAP by using Möbius modeling tool.
• We have performed some experiments with 3000 instances of the REAP to measure the generated traffic and recovery time.
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Some Preliminary results• Delay: Normal• No congestion• Mean= 0.08, 0.09, 0.1, 0.11, 0.12 sec Variance=0.04 • Number of shim6 contexts: 3000 Send timer = 10 sec
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Some Preliminary Results
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Some Preliminary Results(including congestion)
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Some Preliminary Results(including congestion)
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Some Preliminary Results(more congestion)
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Some Preliminary Results(more congestion)
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Research Areas in Networking Field in the Department of Computer Science
• DNS History Database– Tracks FQDNs and their IP addresses, keeping first and last
appearance dates– Started in 2006, now10 collectors world-wide– Around 750 million entries overall– Current Auckland research on tracking Fast Flux Networks (Leo)– Working on a web site for the project!
Traffic Flow measurements (DongJin, Jerry)• DNS RTT: long-term measurements (Nevil)• Performance Measurements of NZ ISPs (Nevil)• For more details contact Nevil Brownlee at
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Research Areas in Networking Field in the Department of Computer Science
• Routing issues • IPv6 deployment • For more details contact Brian Carpenter at