draft-ietf-ospf-transition-to-ospfv3-07.txt   draft-ietf-ospf-transition-to-ospfv3-08.txt 
Internet Draft I. Chen Internet Draft I. Chen
<draft-ietf-ospf-transition-to-ospfv3-07.txt> Ericsson <draft-ietf-ospf-transition-to-ospfv3-08.txt> Ericsson
Intended Status: Standards Track A. Lindem Intended Status: Standards Track A. Lindem
Updates: 5838 Cisco Updates: 5838 Cisco
R. Atkinson R. Atkinson
Consultant Consultant
Expires in 6 months May 24, 2016 Expires in 6 months June 13, 2016
OSPFv3 over IPv4 for IPv6 Transition OSPFv3 over IPv4 for IPv6 Transition
<draft-ietf-ospf-transition-to-ospfv3-07.txt> <draft-ietf-ospf-transition-to-ospfv3-08.txt>
Status of this Memo Status of this Memo
Distribution of this memo is unlimited. Distribution of this memo is unlimited.
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
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The mechanism takes advantage of the fact that OSPFv2 and OSPFv3 The mechanism takes advantage of the fact that OSPFv2 and OSPFv3
share the same IP protocol number, 89. Additionally, the OSPF packet share the same IP protocol number, 89. Additionally, the OSPF packet
header for both OSPFv2 and OSPFv3 includes the OSPF header version header for both OSPFv2 and OSPFv3 includes the OSPF header version
(i.e., the field that distinguishes an OSPFv2 packet from an OSPFv3 (i.e., the field that distinguishes an OSPFv2 packet from an OSPFv3
packet) in the same location (i.e., the same offset from the start of packet) in the same location (i.e., the same offset from the start of
the header). the header).
If the IPv4 topology and IPv6 topology are not identical, the most If the IPv4 topology and IPv6 topology are not identical, the most
likely cause is that some parts of the network deployment have not likely cause is that some parts of the network deployment have not
yet been upgraded to support both IPv4 and IPv6. In situations where yet been upgraded to support both IPv4 and IPv6. In situations where
the IPv4 deployment is a proper superset of the IPv6 deployment, it the IPv4 deployment is a superset of the IPv6 deployment, it is
is expected that OSPFv3 packets would be transported over IPv4, until expected that OSPFv3 packets would be transported over IPv4, until
the rest of the network deployment is upgraded to support IPv6 in the rest of the network deployment is upgraded to support IPv6 in
addition to IPv4. In situations where the IPv6 deployment is a addition to IPv4. In situations where the IPv6 deployment is a
proper superset of the IPv4 deployment, it is expected that OSPFv3 superset of the IPv4 deployment, it is expected that OSPFv3 would be
would be transported over IPv6. transported over IPv6.
Throughout this document, OSPF is used when the text applies to both Throughout this document, OSPF is used when the text applies to both
OSPFv2 and OSPFv3. OSPFv2 or OSPFv3 is used when the text is OSPFv2 and OSPFv3. OSPFv2 or OSPFv3 is used when the text is
specific to one version of the OSPF protocol. Similarly, IP is used specific to one version of the OSPF protocol. Similarly, IP is used
when the text describes either version of the Internet protocol. when the text describes either version of the Internet protocol.
IPv4 or IPv6 is used when the text is specific to a single version of IPv4 or IPv6 is used when the text is specific to a single version of
the Internet protocol. the Internet protocol.
2. Terminology 2. Terminology
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For OSPFv3 over IPv4, the source address is the primary IPv4 For OSPFv3 over IPv4, the source address is the primary IPv4
address for the interface over which the packet is transmitted. address for the interface over which the packet is transmitted.
All OSPFv3 routers on the link SHOULD share the same IPv4 subnet All OSPFv3 routers on the link SHOULD share the same IPv4 subnet
for IPv4 transport to function correctly. for IPv4 transport to function correctly.
While OSPFv2 operates on a subnet, OSPFv3 operates on a link While OSPFv2 operates on a subnet, OSPFv3 operates on a link
[RFC5340]. Accordingly, an OSPFv3 router implementation MAY [RFC5340]. Accordingly, an OSPFv3 router implementation MAY
support adjacencies with OSPFv3 neighbors on different IPv4 support adjacencies with OSPFv3 neighbors on different IPv4
subnets. If this is supported, the IPv4 data plane MUST resolve subnets. If this is supported, the IPv4 data plane MUST resolve
the layer-2 address using Address Resolution Protocol (ARP) on IPv4 addresses to layer-2 addresses using Address Resolution
multi-access networks and point-to-point over LAN [RFC5309] for Protocol (ARP) on multi-access networks and point-to-point over LAN
direct next-hops on different IPv4 subnets. [RFC5309] for direct next-hops on different IPv4 subnets.
3.2. Destination Address 3.2. Destination Address
As defined in OSPFv2, the IPv4 destination address of an OSPF As defined in OSPFv2, the IPv4 destination address of an OSPF
protocol packet is either an IPv4 multicast address or the IPv4 protocol packet is either an IPv4 multicast address or the IPv4
unicast address of an OSPFv2 neighbor. Two well-known link-local unicast address of an OSPFv2 neighbor. Two well-known link-local
multicast addresses are assigned to OSPFv2, the AllSPFRouters multicast addresses are assigned to OSPFv2, the AllSPFRouters
address (224.0.0.5) and the AllDRouters address (224.0.0.6). The address (224.0.0.5) and the AllDRouters address (224.0.0.6). The
multicast address used depends on the OSPF packet type, the OSPF multicast address used depends on the OSPF packet type, the OSPF
interface type, and the OSPF router's role on multi-access interface type, and the OSPF router's role on multi-access
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endpoint. Because IPv6 is the presumed Internet protocol and an endpoint. Because IPv6 is the presumed Internet protocol and an
IPv4 destination is not routable, the OSPFv3 address family IPv4 destination is not routable, the OSPFv3 address family
extension [RFC5838] specifies that only IPv6 address family virtual extension [RFC5838] specifies that only IPv6 address family virtual
links are supported. links are supported.
As illustrated in Figure 1, this document specifies OSPFv3 As illustrated in Figure 1, this document specifies OSPFv3
transport over IPv4. As a result, OSPFv3 virtual links can be transport over IPv4. As a result, OSPFv3 virtual links can be
supported with IPv4 address families by simply setting the IPv4 supported with IPv4 address families by simply setting the IPv4
destination address to a reachable IPv4 unicast address for the destination address to a reachable IPv4 unicast address for the
virtual link endpoint. Hence, the restriction in Section 2.8 of virtual link endpoint. Hence, the restriction in Section 2.8 of
RFC 5838 [RFC5838] is removed. If IPv4 transport, as specified RFC 5838 [RFC5838] is relaxed since virtual links can now be
herein, is used for IPv6 address families, virtual links cannot be supported for IPv4 address families as long as the transport is
supported. Hence, it is RECOMMENDED to use the IP transport also IPv4. If IPv4 transport, as specified herein, is used for
matching the address family in OSPF routing domains requiring IPv6 address families, virtual links cannot be supported. Hence, it
virtual links. is RECOMMENDED to use the IP transport matching the address family
in OSPF routing domains requiring virtual links.
4. IPv4-only Use Case 4. IPv4-only Use Case
OSPFv3 only requires IPv6 link-local addresses to form adjacencies, OSPFv3 only requires IPv6 link-local addresses to form adjacencies,
and does not require IPv6 global-scope addresses to establish an IPv6 and does not require IPv6 global-scope addresses to establish an IPv6
routing domain. However, IPv6 over Ethernet [RFC2464] uses a routing domain. However, IPv6 over Ethernet [RFC2464] uses a
different EtherType (0x86dd) from IPv4 (0x0800) and the Address different EtherType (0x86dd) from IPv4 (0x0800) and the Address
Resolution Protocol (ARP) (0x0806) [RFC826] used with IPv4. Resolution Protocol (ARP) (0x0806) [RFC826] used with IPv4.
Some existing deployed link-layer equipment only supports IPv4 and Some existing deployed link-layer equipment only supports IPv4 and
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optional OSPFv3 Authentication Trailer. optional OSPFv3 Authentication Trailer.
6. IANA Considerations 6. IANA Considerations
No actions are required from IANA as result of the publication of No actions are required from IANA as result of the publication of
this document. this document.
7. Acknowledgments 7. Acknowledgments
The authors would like to thank Alexander Okonnikov for his thorough The authors would like to thank Alexander Okonnikov for his thorough
review and valuable feedback. review and valuable feedback. The authors would also like to thank
Wenhu Lu for acting as document shepherd.
8. References 8. References
8.1. Normative References 8.1. Normative References
[RFC791] Postel, J., "Internet Protocol", STD 5, RFC 791, September [RFC791] Postel, J., "Internet Protocol", STD 5, RFC 791, September
1981. 1981.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998. (IPv6) Specification", RFC 2460, December 1998.
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