IPv6 Site-Local Discussion Bob Hinden & Margaret Wasserman IETF 56 San Francisco March 2003

Goals for Site-Local Discussion Analyze options available for site-local usage and reach consensus on an approach Chairs both believe that it is more important to make a decision and move forward than it is to pursue any particular approach Chairs will both support any proposal that reaches WG consensus

Range of Use Cases No site-local addresses Only on disconnected networks (“limited”) Nodes exclusively global or site-local –Nodes do not have both global & SL addresses No multi-sited nodes (“moderate”) –A node may be in, at most, one site Full usage, including site-border nodes

Current Documents “Limited” usage document in SL impact appendix “Exclusive” model is not documented “Moderate” usage proposal “Full” usage documented in scoped addressing architecture (WG I-D) –Site local impact draft documents issues with “full” usage -- no longer directly applicable –Already have WG consensus not to support

“Limited” Model Site-locals used only on disconnected sites –Non-Internet connected sites –Sites behind NAT IPv4 IPv6, IPv6 IPv6 Site-locals treated exactly like globals Transition from disconnected to connected requires renumbering

“Exclusive” Model Site-local and global addresses are never configured on the same node –Nodes must be explicitly configured to use site-locals Simplifies address selection –Use what you have Specifies rules for simple SBRs and firewalls to enforce site boundaries –Requires “no site” concept, similar to “moderate” proposal Site-local addresses not in global DNS Eliminates possibility of hosts leaking site-locals globally

“Moderate” Model Site-local addresses must be explicitly configured –In Router Advertisements and DNS Nodes may have site-local and/or global addresses No requirement for nodes to be multi-sited Specifies rules for simple SBRs and firewalls to enforce site boundaries –Introduces “no site” concept –No routing protocol changes required Prefer global over site-local in address selection Site-local addresses not in global DNS Only create site-local address using Autoconf or Privacy

“Limited” Model Benefits Addressing for disconnected sites Addressing behind NATs

“Exclusive” Model Benefits “Limited” model benefits, plus: Stable addressing for local nodes –Global nodes do not have stable addresses in newly connected, intermittently connected or renumbered networks –Connections between local nodes survive address prefix changes Prevents global access to/from local nodes and services

“Moderate” Model Benefits “Exclusive” model benefits, plus: Stable addressing –Site-local addresses remain stable in newly connected, intermittently connected or renumbered networks Potential for applications to choose site-local addressing to allow local connections to survive address prefix changes

Issues List IP Layer Address Leaking DNS Address Leaking Address Leaking by Upper-Layers Routing Protocol Issues Forwarding Table Issues Mobile IP Issues

IP Layer Address Leaking Site-local IP source/destination addresses leaking outside of the site None of the proposals have this problem –“Limited” proposal doesn’t send packets outside the site (isolated) –“Exclusive” and “Moderate” enforce at site boundaries

IP Address Selection Issues Changes required to existing IPv6 address selection rules and implementations “Limited” and “Exclusive” do not require changes “Moderate” requires change to prefer global over site-local

DNS Address Leaking Need to keep site-local addresses out of the global DNS “Limited” proposal doesn’t have this problem because there is no global DNS access “Exlusive” and “Moderate” require some mechanism to enforce (i. e. split DNS)

Address Leaking by Upper-Layers Addresses leaked by application, session and transport layer protocols that exchange addresses with other nodes “Limited” doesn’t have problem “Exclusive” eliminates problem because global nodes don’t have local addresses to leak “Moderate” requires upper layers to have address selection rules

Routing Protocol Issues Routing protocols shouldn’t exchange site- local routes across site boundaries All of the proposals eliminate this problem –“Limited” doesn’t connect to outside routers –“Exclusive” and “Moderate” introduce “no site” concept at site borders and BGP filters

Forwarding Table Issues Need to maintain multiple site-local forwarding table and select between them All proposals eliminate this problem –None support nodes in more than one site

Mobile IP Issues Nodes may move between sites –Site local addresses from the first site are not valid (and may be ambiguous) in the new site “Limited” doesn’t have problem “Exclusive” and “Moderate” requires mobile nodes to use only global addresses

Major Differences Differences between “Exclusive” and “Moderate”: –“Exclusive” does not require address selection in upper- layer protocols nor at IP layer –“Exclusive” does not require changes to IPv6 address selection rules and implementations “Limited” proposal eliminate all issues and virtually all benefits

Moving Forward Can we reach consensus on an approach to pursue? –Do we have enough information to decide? –“Limited”, “Exclusive” or “Moderate” If not, can we progress parts of Scoped Addressing Architecture without site-local? –Multicast and link-local