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