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230:(PI) is available in IPv6. This technique has the advantage of working like IPv4, supporting traffic balancing across multiple providers, and maintaining existing TCP and UDP sessions through cut-overs. Critics say that the increased size of routing tables needed to handle multi-homing in this way will overwhelm current router hardware. Proponents say that new hardware will be able to handle the increase due to cheaper memory, which drops in price according to
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However, from a pragmatic perspective, allocating a /32 is equivalent in global address space cost to allocating a single IPv4 address, and this may be acceptable if, as seems to be likely for the foreseeable future, the number of multihomed sites can be numbered only in the millions, as opposed to the many billions of non-multihomed endpoints which are anticipated to comprise the vast majority of IPv6 endpoints. Some
35:
A typical host or end-user network is connected to just one network. Connecting to multiple networks can increase reliability because if one connection fails, packets can still be routed through the remaining connection. Connecting to multiple networks can also improve performance because data can be
241:
Because many ISPs filter out route announcements with small prefixes, this will generally require a large "ISP-sized" IP allocation, such as a /32, to ensure global reachability. Using such large prefixes is an inefficient use of IPv6's address space; there are only about 4 billion /32 prefixes.
169:
must be positioned such that no single piece of network hardware controls all network access to a given host. In particular, it is not uncommon to see multiple
Internet uplinks all converge on a single edge router. In such a configuration, the loss of that single router disconnects the Internet
206:
While multihoming with multiple addresses has been implemented for IPv4, it is not generally used, as host implementations do not deal well with multiple addresses per interface which requires the use of "virtual interfaces". It is also possible to implement multihoming for IPv4 using multiple
279:
Automated renumbering. If one uplink goes down, all addresses in the network will be renumbered into a new /48 subnet. DNS and firewall records must be updated to redirect traffic to a different /48 subnet. This renumbering will break live TCP and UDP
150:
providers. Furthermore, to lessen the possibility of simultaneous damage to all upstream links, the physical location of each of these upstream links should be physically diverse: far enough apart that a piece of machinery (such as a
190:
to that server be functional. For example, if the failure of a single element blocks users from properly resolving the DNS name of that server, then the server is effectively inaccessible, despite its otherwise connected
110:
Multihoming with multiple addresses is cheaper than classic multihoming, and can be used without any cooperation from the providers (e.g. in a home network) but requires additional technology in order to perform routing:
180:, each connected to a separate router or switch. Alternatively, and preferably, the function of a given host could be duplicated across multiple computers, each of which is connected to a different router or switch.
88:, which announces the network's address range to all providers. If one of the links fails, the dynamic routing protocol recognizes the failure within seconds or minutes and reconfigures its
107:
In this approach, the network is connected to multiple providers, and assigned multiple address ranges, one for each provider. Hosts are assigned multiple addresses, one for each provider.
246:(RIR) such as RIPE have started to allocate /48 from a specific prefix for this purpose. RIPE allocates IPv6 provider-independent address spaces /48 or shorter from 2001:0678::/29.
254:
Multihoming with multiple addresses has been implemented for IPv6. For outgoing traffic, this requires support on the host, either protocol agnostic (
186:: Not only must a host be accessible, but in many cases it must also be "referenced" to be useful. For most servers, this means in particular that the
560:
203:
Classic multihoming is the dominant technique for IPv4. This requires that a network have its own public IP address range and a public AS number.
195:
By increasing the number of interfaces and links being used and making routing less deterministic, multihoming complicates network administration.
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99:(AS) number, and a dynamic routing protocol. Since multihomed address space cannot be aggregated, it causes growth of the global routing table.
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must be used to route packets through the correct provider, and reasonable source address selection policies must be implemented by hosts.
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philosophy supports the idea that it is better to deploy an imperfect solution now than a perfect solution after it is too late.
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283:
76:
In classic multihoming, a network is connected to multiple providers and uses its own range of addresses (typically from a
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Proceedings of the 2003 conference on
Applications, technologies, architectures, and protocols for computer communications
473:
Problem
Statement for Default Address Selection in Multi-Prefix Environments: Operational Issues of RFC 3484 Default Rules
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Akella, A.; Maggs, B.; Seshan, S.; Shaikh, A. & Sitaraman, R. (2003). "A measurement-based analysis of multihoming".
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A single host may be connected to multiple networks. For example, a mobile phone might be simultaneously connected to a
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Classic multihoming is costly, since it requires the use of address space that is accepted by all providers, a public
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and, depending on the destination, it may be more efficient to route through one network or the other.
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to more than one network. This can be done in order to increase reliability or performance.
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8:
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68:. A multihomed host usually is assigned multiple addresses, one per connected network.
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Both classic multihoming and multihoming with multiple addresses may be used in IPv6.
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When multihoming is used to improve reliability, care must be taken to eliminate any
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transmitted and received through the multiple connections simultaneously multiplying
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731:"Multihoming, content delivery networks, and the market for Internet connectivity"
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80:(PI) range). The network's edge routers communicate with the providers using a
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network, and a desktop computer might be connected to both a home network and a
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Sample
Configuration for BGP with Two Different Service Providers (Multihoming)
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166:
25:
713:
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255:
89:
16:
Practice of connecting a host or a computer network to more than one network
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234:. Proponents also say this is the only viable solution right now, and the
146:: A given network operations center must have multiple upstream links to
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De
Launois, C.; Bagnulo, M. (2006). "The paths toward IPv6 multihoming".
349:
509:
Matthieu
Boutier; Juliusz Chroboczek (2015), "Source-specific routing",
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593:"Provider Independent (PI) IPv6 Assignments for End User Organisations"
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115:
for incoming traffic, hosts must be associated with multiple A or AAAA
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637:
482:
449:
354:
730:
176:: A "reliable" host must be connected to the network over multiple
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Atkinson, Randall; Carpenter, Brian E.; Flinck, Hannu (May 2010).
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508:
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uplink, despite the fact that multiple ISPs are otherwise in use.
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728:
267:
541:
Winter, Rolf; Faath, Michael; Ripke, Aneas (21 March 2016).
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Scalable
Support for Multi-homed Multi-provider Connectivity
155:) won't accidentally sever all connections at the same time.
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57:
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There are several different ways to perform multihoming.
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to use the remaining links, transparently to the hosts.
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61:
102:
543:"Multipath TCP Support for Single-homed End-systems"
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729:Hau, T.; Burghardt, D. & Brenner, W. (2011).
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119:so that they are reachable through all providers;
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605:
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606:Lamparter, David; Smirnov, Anton (2 May 2016).
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702:IEEE Communications Surveys & Tutorials
122:for outgoing traffic, a technique such as
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636:
518:
481:
448:
222:
360:Site Multihoming by IPv6 Intermediation
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336:Locator/Identifier Separation Protocol
284:Locator/Identifier Separation Protocol
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325:Identifier/Locator Network Protocol
250:Multihoming with multiple addresses
103:Multihoming with multiple addresses
51:
13:
656:
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266:, etc.) or specific to IPv6 (e.g.
228:Provider Independent Address Space
14:
785:
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24:is the practice of connecting a
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1:
384:A look at multihoming and BGP
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747:10.1016/j.telpol.2011.04.002
628:Renumbering Still Needs Work
608:"Destination/Source Routing"
244:regional Internet registries
7:
290:
43:
10:
790:
511:Proc. IFIP Networking 2015
342:Media-independent handover
130:
735:Telecommunications Policy
714:10.1109/COMST.2006.315853
214:
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137:single point of failure
124:source-specific routing
381:Iljitsch van Beijnum,
319:Host Identity Protocol
769:Internet architecture
674:10.1145/863955.863995
144:Upstream connectivity
667:. pp. 353–364.
184:Referencing entities
84:protocol, typically
78:Provider Independent
529:2014arXiv1403.0445B
223:Classic multihoming
72:Classic multihoming
178:network interfaces
595:. 6 January 2011.
420:. Bgp.potaroo.net
346:vertical handover
174:Host connectivity
97:Autonomous System
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638:10.17487/RFC5887
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52:Host multihoming
30:computer network
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657:Further reading
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236:worse is better
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188:name resolution
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82:dynamic routing
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741:(6): 532–542.
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562:Vector Routing
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90:routing tables
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60:network and a
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684:1-58113-735-4
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575:on 2013-05-17
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418:"BGP Reports"
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391:on 2010-07-06
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708:(2): 38–51.
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664:
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611:
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577:, retrieved
570:the original
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422:. Retrieved
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389:the original
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34:
21:
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764:Multihoming
350:IEEE 802.21
232:Moore's law
148:independent
117:DNS records
22:Multihoming
758:Categories
579:2012-01-07
424:2022-08-17
368:References
314:Dual-homed
211:gateways.
38:throughput
520:1403.0445
355:Mobile IP
280:sessions.
722:37377959
291:See also
167:switches
139:(SPOF):
44:Variants
774:Routing
693:1801040
525:Bibcode
362:(SHIM6)
163:Routers
159:Routers
153:backhoe
131:Caveats
720:
691:
681:
338:(LISP)
327:(ILNP)
286:(LISP)
191:state.
718:S2CID
689:S2CID
573:(PDF)
566:(PDF)
515:arXiv
321:(HIP)
268:SHIM6
28:or a
679:ISBN
646:5887
612:IETF
547:IETF
491:5220
458:2260
264:QUIC
260:SCTP
215:IPv6
199:IPv4
165:and
58:WiFi
26:host
743:doi
710:doi
669:doi
643:RFC
633:doi
488:RFC
478:doi
455:RFC
445:doi
348:in
344:or
270:).
209:NAT
86:BGP
66:VPN
760::
739:35
737:.
733:.
716:.
704:.
687:.
677:.
641:.
631:.
610:.
545:.
523:,
513:,
499:^
486:.
476:.
453:.
443:.
262:,
258:,
161::
62:3G
749:.
745::
724:.
712::
706:8
695:.
671::
648:.
635::
614:.
549:.
527::
517::
493:.
480::
460:.
447::
427:.
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
