OSPF WG – IETF 63 OSPFv3 Graceful Restart Padma Pillay-Esnault Cisco Systems

OSPF WG – IETF 62 Agenda  Common methodology between the OSPFv2 and OSPFv3 Graceful Restart  OSPFv3 specificities and considerations  OSPFv3 Grace LSA  Going forward  Questions ?

OSPF WG – IETF 62 OSPFv2/v3 Graceful Restart (1) Most of the methodology described in RFC 3623 are applicable both OSPFv2 and OSPFv3.  Grace LSA is used as a link local signaling mechanism for a router to announce it intention to undergo restart  Grace LSA contains information about the duration of the graceful restart from the restarting router and the reason for restart  LSA generation suppression during graceful restart

OSPF WG – IETF 62 OSPFv2/v3 Graceful restart (2)  OSPF in FULL state are preserved/faked by the helper neighbors  Restarting router criteria to abort graceful restart  Helpers criteria to abort graceful restart  LSA changes strict checking or not

OSPF WG – IETF 62 OSPFv3 GR specificities (1)  In OSPFv2 neighbors are identified either by their router-id or their interface address on the broadcast, NBMA and P2MP. Hence, the Grace LSA in OSPFv2 carry the router-interface address. In OSPFv3, neighbors are solely identified by their router-id.  Hence the router-address TLV is not used.  The interface-id must be preserved across reboot.

OSPF WG – IETF 62 OSPFv3 GR specificities (2)  In OSPFv2, the LSA ID of a summary network LSA (type 3) and an external LSA (type 5) reflects the prefix being advertised. Hence, in OSPFv2, the LSA ID is preserved by the semantic of the LSA header.  In OSPFv3, the LSA ID does not have the same semantics as in OSPFv2. The inter-area prefix and the external prefix LSAs merely use a 32 bit number with no correlation with the prefix they advertise in their body. Hence, to prevent network churn and premature abort, the restarting router should preserve the correspondence of LSA-ID and prefix advertised

OSPF WG – IETF 62 OSPFv3 Grace LSA Header  A Grace LSA is link local scope LSA with LS type 0x00B  The U-bit is set to 0 for link local scope  The S1-bit and S2-bit are also set to 0 to indicate link local scope  The LSA ID is the interface ID on which the Grace LSA is originated on

OSPF WG – IETF 62 OSPFv3 Grace LSA  The Grace period TLV (type 1, length 4) Value - number of seconds for graceful restart  The reason TLV (type 2, length 4) Values 0 : unknown 1 : software restart 2 : software reload/upgrade 3 : switch to redundant control processor

OSPF WG – IETF 62 Going forward  Proposed Standard  Two implementations

OSPF WG – IETF 62 Questions ? Thank You.