Technique for restoring adjacencies in OSPF in a non-stop forwarding intermediate node of a computer network

An apparatus for restoring an adjacency between a router and its neighbor during reload of routing software on the router, the apparatus comprising:

• an interface adapted for placement into a predetermined state that enables the router to receive an incoming Hello packet from the neighbor over a computer network;
• a processor coupled to the interface;
• and
• a unicast Hello packet created by the processor in response to receiving an incoming Hello packet from the neighbor, the unicast Hello packet sent to the neighbor to thereby prevent the neighbor from dropping the adjacency with the router.

Apparatus for restoring an adjacency between a router and its neighbor during reload of routing software on the router, the apparatus comprising:

• means for placing an interface of the router in a predetermined state that enables the router to receive incoming Hello packets from its neighbors over a computer network;
• means for creating a unicast Hello packet in response to receiving an incoming Hello packet from each neighbor;
• and
• means for sending the unicast Hello packet to each neighbor from whom it has received an incoming Hello packet to thereby prevent the neighbor from dropping its adjacency with the router.

A computer readable medium containing executable program instructions for restoring adjacencies between a router and its neighbors during reload of routing software on the router, the executable program instructions comprising program instructions for:

• placing an interface of the router in a predetermined state that enables the router to receive incoming Hello packets from its neighbors over a computer network;
• creating a unicast Hello packet in response to receiving an incoming Hello packet from each neighbor;
• and
• sending the unicast Hello packet to each neighbor from whom it has received an incoming Hello packet to thereby prevent the neighbor from dropping its adjacency with the router.

A method for restoring adjacencies between a router and its neighbors during reload of routing software on the router, the method comprising the steps of:

• determining if a neighbor data structure exists for each neighbor from which an incoming Hello packet was received;
• if not, creating a neighbor data structure for each neighbor from which an incoming Hello packet was received;
• placing an interface of the router in a predetermined state that enables the router to receive incoming Hello packets from its neighbors over a computer network;
• creating a unicast Hello packet in response to receiving an incoming Hello packet from each neighbor and in response to the created neighbor data structure and the predetermined state;
• and
• sending the unicast Hello packet to each neighbor from whom it has received an incoming Hello packet to thereby prevent the neighbor from dropping its adjacency with the router.

A method for restoring adjacencies between a router and its neighbors during reload of routing software on the router, the method comprising the steps of:

• placing an interface of the router in a predetermined state that enables the router to receive incoming Hello packets from its neighbors over a computer network;
• creating a unicast Hello packet in response to receiving an incoming Hello packet from each neighbor;
• sending the unicast Hello packet to each neighbor from whom it has received an incoming Hello packet to thereby prevent the neighbor from dropping its adjacency with the router;
• in response to the step of placing, sending an empty link state Update packet from the router over the interface to a selected neighbor;
• receiving the empty link state Update packet at the selected neighbor;
• and
• in response to the step of receiving, resetting an inactivity timer for the router at the selected neighbor to thereby prevent the selected neighbor from resetting its adjacency with the router before the router sends the unicast Hello packet.

Apparatus for restoring an adjacency between a router and its neighbor during reload of routing software on the router, the apparatus comprising:

• means for determining if a neighbor data structure exists for each neighbor from which an incoming Hello packet was received;
• means for creating a neighbor data structure for each neighbor from which an incoming Hello packet was received, if the neighbor data structure does not exist;
• means for placing an interface of the router in a predetermined state that enables the router to receive incoming Hello packets from its neighbors over a computer network;
• means for creating a unicast Hello packet in response to receiving an incoming Hello packet from each neighbor and in response to the created neighbor data structure and the predetermined state;
• and
• means for sending the unicast Hello packet to each neighbor from whom it has received an incoming Hello packet to thereby prevent the neighbor from dropping its adjacency with the router.

Apparatus for restoring an adjacency between a router and its neighbor during reload of routing software on the router, the apparatus comprising:

• means for placing an interface of the router in a predetermined state that enables the router to receive incoming Hello packets from its neighbors over a computer network;
• means for creating a unicast Hello packet in response to receiving an incoming Hello packet from each neighbor;
• and
• means for sending the unicast Hello packet to each neighbor from whom it has received an incoming Hello packet to thereby prevent the neighbor from dropping its adjacency with the router;
• means for sending an empty link state Update packet from the router over the interface to a selected neighbor;
• and
• means for the selected neighbor to reset an inactivity timer for the router in response to receiving the empty link state Update packet, the reset inactivity timer preventing the selected neighbor from resetting its adjacency with the router before the router sends the unicast Hello packet.

Apparatus for restoring an adjacency between a router and its neighbor during reload of routing software on the router, the apparatus comprising:

• an interface adapted for placement into a predetermined state that enables the router to receive an incoming Hello packet from the neighbor over a computer network;
• a processor;
• a memory coupled to the processor,
• a neighbor data structure stored in the memory, the neighbor data structure containing information pertinent to the adjacency formed between the router and neighbor;
• and
• a unicast Hello packet created by the processor in response to receiving an incoming Hello packet from the neighbor, the unicast Hello packet sent to the neighbor to thereby prevent the neighbor from dropping the adjacency with the router.

Apparatus for restoring an adjacency between a router and its neighbor during reload of routing software on the router, the apparatus comprising:

• an interface adapted for placement into a predetermined state that enables the router to receive an incoming Hello packet from the neighbor over a computer network;
• a processor;
• an empty link state Update packet created by the processor and multicasted over the network in response to placement of the interface into a Waiting state during the reload of routing software;
• the empty link state Update packet received at a neighbor;
• and
• an inactivity timer for the router at the neighbor, the inactivity timer reset in response to receiving the empty link state Update packet to thereby prevent the neighbor from resetting its adjacency with the router before the router sends the unicast Hello packet.

A computer readable medium containing executable program instructions for restoring adjacencies between a router and its neighbors during reload of routing software on the router, the executable program instructions comprising program instructions for:

• determining if a neighbor data structure exists for each neighbor sending an incoming Hello packet;
• if not, creating a neighbor data structure for each neighbor sending the incoming Hello packet;
• placing an interface of the router in a predetermined state that enables the router to receive incoming Hello packets from its neighbors over a computer network;
• creating a unicast Hello packet in response to receiving an incoming Hello packet from each neighbor and in response to the created data structure and predetermined state;
• and
• sending the unicast Hello packet to each neighbor from whom it has received an incoming Hello packet to thereby prevent the neighbor from dropping its adjacency with the router.

A computer readable medium containing executable program instructions for restoring adjacencies between a router and its neighbors during reload of routing software on the router, the executable program instructions comprising program instructions for:

• placing an interface of the router in a predetermined state that enables the router to receive incoming Hello packets from its neighbors over a computer network;
• creating a unicast Hello packet in response to receiving an incoming Hello packet from each neighbor;
• and
• sending the unicast Hello packet to each neighbor from whom it has received an incoming Hello packet to thereby prevent the neighbor from dropping its adjacency with the router;
• in response to the step of placing, sending an empty link state Update packet from the router over the interface to a selected neighbor;
• receiving the empty link state Update packet at the selected neighbor;
• and
• in response to the step of receiving, resetting an inactivity timer for the router at selected neighbor to thereby prevent the selected neighbor from resetting its adjacency with the router before the router sends the unicast Hello packet.

A method for maintaining adjacencies between a router and its neighbors, the method comprising the steps of:

• placing an interface of the router in a predetermined state that enables the router to receive incoming Hello packets from its neighbors over a computer network;
• creating an outgoing Hello packet by the interface and in response to receiving an incoming Hello packet from each neighbor;
• and
• sending the outgoing Hello packet to each neighbor from whom it has received an incoming Hello packet to thereby prevent the neighbor from dropping its adjacency with the router.

Apparatus for maintaining an adjacency between a router and its neighbor, the apparatus comprising:

• means for placing an interface of the router in a predetermined state that enables the router to receive incoming Hello packets from its neighbors over a computer network;
• means for creating an outgoing Hello packet by the interface and in response to receiving an incoming Hello packet;
• and
• means for sending the outgoing Hello packet to each neighbor from whom it has received an incoming Hello packet to thereby prevent the neighbor from dropping its adjacency with the router.

A computer readable medium containing executable program instructions for maintaining adjacencies between a router and its neighbors, the executable program instructions comprising program instructions for:

• placing an interface of the router in a predetermined state that enables the router to receive incoming Hello packets from its neighbors over a computer network;
• creating an outgoing Hello packet by the interface and in response to receiving an incoming Hello packet from each neighbor;
• and
• sending the outgoing Hello packet to each neighbor from whom it has received an incoming Hello packet to thereby prevent the neighbor from dropping its adjacency with the router.

A method for restoring adjacencies between a router and its neighbors during reload of routing software on the router, the method comprising the steps of:

• placing an interface of the router in a predetermined state that enables the router to receive incoming Hello packets from its neighbors over a computer network;
• creating a unicast Hello packet by the interface, the unicast Hello packet in response to receiving an incoming Hello packet from a neighbor;
• and
• sending the unicast Hello packet by the interface to each neighbor from whom it has received an incoming Hello packet.

An apparatus for restoring adjacencies between a router and its neighbors during reload of routing software on the router, the apparatus comprising:

• means for placing an interface of the router in a predetermined state that enables the router to receive incoming Hello packets from its neighbors over a computer network;
• means for creating a unicast Hello packet by the interface, the unicast Hello packet in response to receiving an incoming Hello packet from each neighbor;
• and
• means for sending the unicast Hello packet by the interface to each neighbor from whom it has received an incoming Hello packet to thereby prevent the neighbor from dropping its adjacency with the router.

An Apparatus for restoring an adjacency between a router and its neighbor during reload of routing software on the router, the apparatus comprising:

• an interface adapted for placement into a predetermined state that enables the router to receive an incoming Hello packet from the neighbor over a computer network;
• a processor coupled to the interface on a line card;
• and
• a unicast Hello packet created by the processor in response to receiving an incoming Hello packet from the neighbor, the unicast Hello packet sent to the neighbor.

A method for restoring adjacencies between a router and its neighbors during reload of routing software on the router, the method comprising the steps of:

• placing an interface of the router in a predetermined state that enables the router to receive incoming Hello packets from its neighbors over a computer network;
• creating a unicast Hello packet by the interface, the unicast Hello packet in response to receiving an incoming Hello packet from a neighbor;
• sending the unicast Hello packet by the interface to each neighbor from whom it has received an incoming Hello packet;
• and
• in response to a neighbor router receiving the Hello packet, preventing the neighbor router from dropping its adjacency with the router.

An apparatus for restoring adjacencies between a router and its neighbors during reload of routing software on the router, the method comprising the steps of:

• means for placing an interface of the router in a predetermined state that enables the router to receive incoming Hello packets from its neighbors over a computer network;
• means for creating a unicast Hello packet by the interface, the unicast Hello packet in response to receiving an incoming Hello packet from a neighbor;
• means for sending the unicast Hello packet by the interface to each neighbor from whom it has received an incoming Hello packet;
• and
• in response to a neighbor router receiving the Hello packet, means for preventing the neighbor router from dropping its adjacency with the router.

An Apparatus for restoring an adjacency between a router and its neighbor during reload of routing software on the router, the apparatus comprising:

• an interface adapted for placement into a predetermined state that enables the router to receive an incoming Hello packet from the neighbor over a computer network;
• a processor coupled to the interface on a line card;
• and
• a unicast Hello packet created by the processor in response to receiving an incoming Hello packet from the neighbor, the unicast Hello packet sent to a neighbor router;
• the neighbor router, in response to the Hello packet, is prevented from dropping the adjacency with the router.