Routing IPv4-Embedded IPv6 Packets
draft-cheng-ospf-ipv4-embedded-ipv6-routing-01
Dean Cheng ([email protected])
Mohamed Boucadair ([email protected])
79th IETF Beijing
Some Terminologies

IPv4-Embedded IPv6 address
 Denotes an IPv6 address which contains an embedded 32-bit IPv4
address constructed according to the rules defined in:
draft-ietf-behave-address-format-10

IPv4-Embedded IPv6 packets
 IPv6 packets with destination addresses as IPv4-Embedded IPv6
addresses

AFBR
 Address Family Border Router (RFC5565)
 Refers to a border router which is located at the boundary of an IPv6only network and an IPv4-only network
The Problem
IPv4
AFBR
IPv6
IPv6
?
AFBR
?
IPv6 backbone
?
ASBR
AFBR
IPv4
IPv4
IPv6
ASBR
Softwire Mesh (RFC5565) Approach
IPv4
AFBR
IPv6
IPv6
IPv6 backbone
ASBR
AFBR
AFBR
IPv4
IPv4
IPv6
ASBR
•AFTRs exchange IPv4 reachability using BGP-MP
•Tunnels established between AFTRs full-mesh
•IPv4 packets transported in tunnels
OSPFv3 MT/MI Approach
IPv4
AFBR
IPv6
IPv6
IPv6 backbone
AFBR
AFBR
ASBR
IPv4
IPv4
IPv6
ASBR
•AFBRs advertise IPv4-Embedded IPv6
addresses into the partial IPv6 backbone
•A separate routing table for routing IPv4Embedded IPv6 packets.
Scenarios where OSPFv3 approach useful

Running BGP not feasible on some AFTRs.

Tunnel based forwarding not feasible
CPE
IPv6
DS-Lite
CPE
AFTR
ICXF
IPv4
CPE
CPE
AFTR
ICXF
IPv6 Network
IPv4
CPE
AFTR
ICXF
CPE
IPv4
CPE
DualStack
IPv6
http://tools.ietf.org/html/draft-boucadair-dslite-interco-v4v6-04
Mechanisms for separate routing table

Use OSPFv3 multi-instance mechanism

Reference: RFC5838

Instantiate a separate instance for IPv4-Embedded unicast IPv6
routing

Use OSPFv3 multi-topology mechanism

Reference: http://tools.ietf.org/html/draft-ietf-ospf-mt-ospfv3-03.txt

Configure interfaces for IPv4-Embedded unicast IPv6 routing
Advertising IPv4-Embedded IPv6 Routes

IPv4-Embedded IPv6 addresses would be advertised by AFBR
into IPv6 network as AS External LSA per OSPFv3(RFC5340)

A single OSPFv3 AS External LSA carries one or more IPv4Embedded IPv6 addresses and prefixes

By default, the metric is type-1 metric

Added to the intra-AS path for OSPFv3 routes calculation

May also be set to type-2 metric (by provisioning at AFBR)

External metric may be exact the same unit as in IPv4 network
Forwarding IPv4-Embedded IPv6 Packets

Arriving packets with IPv4-Embedded IPv6 addresses are
forwarded along on IPv4-Embedded IPv6 topology.

Packet header translation
 According to http://tools.ietf.org/html/draft-ietf-behave-v6v4-xlate-23

Address translation
 According to draft-ietf-behave-address-format-10
 IPv6 prefix
Well known IPv6 prefix 64::FF9B::/96, or
ISP-specific IPv6 prefix

MTU handling
 Recommendation – AFTR to run PMTU (RFC1981.txt)
An issue for discussion

In Section 2.6 of RFC5838
 IPv4 address is located in the first 32-bit of the Forwarding Address
field in AS-external LSA, with the remaining bits set to zero.

In this draft
 IPv4-Embedded IPv6 address encoded according to:
draft-ietf-behave-address-format-10

Question for the WG:
 How to resolve this issue?
Next Step …

Authors would like to solicit comments with discussion on
mailing list at this time

If there is enough interest, we’ll propose to move this I-D as
a working group document