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Simple Failover Mechanism for Lightweight 4over6

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Presentation on theme: "Simple Failover Mechanism for Lightweight 4over6"— Presentation transcript:

1 Simple Failover Mechanism for Lightweight 4over6
draft-lee-softwire-lw4over6-failover-01 Qi Sun (Presenter)

2 Background lw4over6 is a softwire based IPv6 transition technology
lw4over6 is a stateful technology lwAFTR maintains a per-subscriber binding table When the Primary lwAFTR fails, the Backup lwAFTR may not have the necessary state to provide softwire service for the lwB4. This draft discusses lw4over6 failover design.

3 Use Case Assumptions A set of lwAFTRs using the same IPv6 Anycast address IPv4 provisioning used by lwB4 is dynamic (via dhcpv4 over dhcpv6 or pcp) Primary lwAFTR creates the dynamic binding upon successful lwB4 provisioning IPv4 address used by the lwB4 either static or dynamic either full or port-restricted Shared address cannot be interface addr. ARP static configuration for address prefix in enterprise case

4 Typical Failover Use Case
Primary lwAFTR fails lwB4 continues to send packets to the anycast address Backup lwAFTR receives the packets, then what to do? Backup lwAFTR Primary lwAFTR lwB4 IPv6 anycast

5 We propose two mechanisms
ICMPv6 Trigger Failover Backup lwAFTR Primary lwB4 Characteristics Modify lwB4 Original connections would fail lwAFTRs can advise different v4 prefixes Comms not needed between lwAFTRs IPv4-in-IPv6 packet When lwAFTR receives a packet with an unknown IPv6 source address, it will send an ICMPv6 Error Message which will trigger the lwB4 to re-send IPv4 provisioning message to create the binding in the Backup lwAFTR Unknown Source IPv6 ICMPv6 Error Message Restart IPv4 provisioning Create binding table IPv4-in-IPv6 packets

6 We propose two mechanisms
Data Packet Trigger Failover Backup lwAFTR Primary lwB4 Characteristics Not modify lwB4 Original connections would not fail lwAFTRs advise the same v4 prefixe Require additional validation method(s) IPv4-in-IPv6 packet When lwAFTR receives a packet with an unknown IPv6 source address, lwAFTR will extract the IPv4 address and validate the IPv4 authentication (e.g., lease query). Upon successful authentication, the Backup lwAFTR will create the binding Unknown Source IPv6 Validate the IPv4 authentication; Create binding IPv4-in-IPv6 packets

7 Comparison with two mechanisms
Control Message Trigger Data Packet Trigger Address pool Configuration Primary and Backup lwAFTR may use the same address pool or different IPv4 address pools Primary and Backup lwAFTR must use the same IPv4 address pool Impact on applications PCP: No guarantee same public v4 addr; can not be used for external-initiated applications. DHCP: Can use same public v4 addr; also can be used for external-initiated applications. Use the same public IPv4 address. It can also be used for external-initiated applications. Implementation requirement Implement the ICMP mechanism in lwB4 and lwAFTR Require an interface between lwAFTR and the supporting system to check the validity of the binding.

8 Next Step Comments? Any interest to continue the work?

9 Backup: Some Considerations
Backup lwAFTR Discovery Use Anycast Recommend to hash the outer v6 header for ECMP lwAFTR must stop announcing the anycast addr when offline lwB4 IPv4 Prefix Announcement on lwAFTR Management Dynamic IPv4 address No special action. Each lwAFTR advertises its own IPv4 prefix. Different IPv4 prefixes Static IPv4 address Primary and Backup lwAFTRs will announce the same IPv4 prefix given that the Backup lwAFTR will use a lower matrix lwB4 Address Provisioning DHCPv4 over DHCPv6 DHCP server: Centralized lwAFTRs: DHCPv6 relay, unicast to DHCP server PCP PCP server: Collocate with lwAFTR Use IPv4-in-IPv6 tunnel; hash on the outer IPv6 header if ECMP is used IPv6 address is 4 times longer than IPv4 address, it guarantees way better uniqueness for the hash. lwB4 v4 prefix management (static): run dynamic routing protocol 1. Primary and Backup lwAFTRs are running dynamic routing protocol 2. Primary lwAFTR set the routing matrix higher than the Backup lwAFTR does for the serving IPv4 prefix 3. When Primary detects problem, it stops advertising the IPv4 prefix 4. Routing protocol converges and the Backup lwAFTR is the router announcing the IPv4 prefix


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