Large-scale Autorenumbering in IPv6

Allison Mankin

USC Information Sciences Institute

Table of Contents

• Stan Barber's Notes
• February 1996 NANOG Home Page

Stan Barber's Notes

Auto-address configuration

Forming a Link-Local Address

Sites consisting of machine attached to a single link should not require a presence of router or stateful address server. In simplest and common case, the IEEE 802 address prefixed with a large number of zeros (to full the 128 bits)

Duplicate Address Detection

Can be disabled if administrator prefers
This is used in both stateless address auto configuration and other address acquitions.
For stateless autoaddresses, DAD is performed only on link-local addresses, thus is not in critical path in large-scale-renumbering.
Address is TENTAIVE until DAD complete

Routable Addresses

These may be site and/or global. A router is required to configure these types of addresses. Periodically, routers advertise themselves. Configuration flags in the router advertisment message. If autoconfiguring, a prefix information message is used to provide basic data for forming the address prefix. These addresses all have specific lifetimes. Addresses start being tentative, then preferred (valid), deprecated (still valid), and finally invalid.

Large-scale Auto-renumbering

Basic scaling

1. NS sent to small number of hosts on a link, Solicited-Node-Multicast
2. RS sent to All-Routers-Multicast
3. RA sent to All-Nodes-Multicast, if unsolicited

Router Advertisement(stateless) mechanism facilitates

Rapid segment-by-segment node renumberings. Lazy reconfiguration, as the router prefix addition (and expiry of the old) needed as well for global routing

Coexistence of depreciated and new preferred addresses facilitates

modification/removal of embedded literal addresses
graceful termination
PIER

Comparision with IPv4 renumbering

• DHCP is available for IPv4. It is elective and not implemented in all hosts.
• IPv6 renumbering is available in all implementations and not elective.
• Domain Name Systems issues are the same for both.
• IPv6 addressessing has built-in leasing.
• IPv6 has built in private address spaces (that are easily filtered).
• IPv4 compatible addresses could be converted fairly easily to regular IPv6 addresses overtime.
• It is easy to move things around and change things in IPv6.

Security Considerations

Open Issues

• How consistent can we make NBMA adaptations of addrconf and Neighbor Discovery?
• Someone should simulate time-scales and sizes of segments and make sure we have good paramenters for large segments,outages?
• What running applications should presist through a renumbering?
• Are rehomable-TCP and other transport identifier schemes very important?
• How do we add(very needed) service location in the link-local domain?