Site Multihoming by IPv6 Intermediation (shim6)

Last modified: 2011-08-02


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Description of Working Group:

Earlier efforts in this working group completed the Shim6 protocol specification, documented in RFCs 5533 through 5535. This protocol is a layer 3 shim for providing locator agility with failover capabilities for IPv6 nodes. Hosts that employ Shim6 use multiple IPv6 address prefixes and setup state with peer hosts. This state can later be used to failover to a different set of locators, should the original locators stop working.

The Shim6 approach has a number of advantages, such as enabling small sites to be multihomed without requiring a provider independent IPv6 address prefix for the site. But the approach has also been criticized, e.g., for the operational impacts that the use of multiple prefixes causes. At this time there is no clear view on how well Shim6 works in practice. Implementation and deployment in select networks is needed to determine its true characteristics.

The Shim6 working group is chartered to track the implementation and testing or deployment efforts. The group is also expected to shepherd to completion a few remaining informational documents that complement the existing protocol specifications.

The specific work items of the group are:

  • Write an implementation and/or deployment experience report.
  • Specify socket API extensions. This API enables interactions between applications and the Shim6 layer for advanced locator management, and access to information about failure detection and path exploration. It also enables some applications to turn Shim6 off.
  • Complete the work on the applicability draft. This draft explains in detail in which types of networks Shim6 is applicable, and what its advantages and disadvantages are. The draft will also explain how firewalls are impacted by the use of Shim6. Finally, the draft will also explain how Shim6 can be used in situations where native IPv6 connectivity is not available, such as using Shim6 over 6to4.

The group will also work in co-operation with the 6MAN working group as they continue their efforts in improving IPv6 address selection mechanisms.

The group shall not work on extensions to the Shim6 protocol itself at this time. However, new work items can be added through rechartering as others get completed.

Goals and Milestones

Done First draft of architectural document
Done First draft of protocol document
Done First draft on cryptographic locators, if required
Done First draft on multi-homing triggers description
Done First draft on applicability statement document
Done WG last-call on protocol document
Done WG last-call on cryptographic locators, if required
Done WG last-call on multihoming triggers description
Done Submit document on cryptographic locators to the IESG, if required
Done Submit protocol document to the IESG
Done Submit draft on multihoming triggers description to the IESG
Sep 2009 Next revision of the API document
Nov 2009 First WG draft on an implementation report
Jan 2010 Submit API document to IESG for publication as Informational RFC
Jan 2010 Next revision of the applicability document
Dec 2010 Submit implementation report to IESG for publication as Informational RFC
Dec 2010 Submit applicability document to IESG for publication as Informational RFC
Dec 2010 Close or re-charter

No Internet-Drafts

Request for Comments

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