Detecting unavailable network connections

• US 20060159011A1
• Filed: 01/14/2005
• Published: 07/20/2006
• Est. Priority Date: 01/14/2005
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Ramaiah, Anantha, Appanna, Chandrashekhar, Kapoor, Ruchi, Dalal, Mitesh
• Granted Patent: US 7,903,546 B2
• Time in Patent Office: Days
• US Class Current: 370/220
• CPC Class Codes: H04J 3/14 Monitoring arrangements for SDH/SONET rings H04J3/085
• CPC Class Codes: H04L 1/187 Details of sliding window management
• CPC Class Codes: H04L 45/02 Topology update or discovery
• CPC Class Codes: H04L 45/033 by updating distance vector protocols
• CPC Class Codes: H04L 45/22 Alternate routing
• CPC Class Codes: H04L 45/243 using M+N parallel active paths
• CPC Class Codes: H04L 45/28 using route fault recovery
• CPC Class Codes: H04L 45/586 of virtual routers
• CPC Class Codes: H04L 67/104 Peer-to-peer [P2P] networks
• CPC Class Codes: H04L 67/1048 Departure or maintenance mechanisms
• CPC Class Codes: H04L 67/1095 Replication or mirroring of data, e.g. scheduling or transport for data synchronisation between network nodes
• CPC Class Codes: H04L 67/14 Session management for real-time applications in data packet communications networks H04L65/1066
• CPC Class Codes: H04L 69/14 Multichannel or multilink protocols
• CPC Class Codes: H04L 69/16 Implementation or adaptation of Internet protocol [IP], of transmission control protocol [TCP] or of user datagram protocol [UDP]
• CPC Class Codes: H04L 69/40 for recovering from a failure of a protocol instance or entity, e.g. service redundancy protocols, protocol state redundancy or protocol service redirection management of faults, events, alarms or notifications in data switching networks H04L41/06

Abstract

A method for detecting unavailable network connections comprises, at a first data processing node that is hosting a transport protocol connection that uses a plurality of sequence values to identify messages sent to a peer node, wherein the first node is communicatively coupled to a second data processing node serving as a redundant backup, periodically sending a checkpoint sequence value to the second node; detecting that either the transport protocol connection or a process using the transport protocol connection is unavailable, without use of a timeout; and in response thereto, sending a notification to the peer node, wherein the notification includes the checkpoint sequence value. One embodiment provides for rapidly detecting and responding to failure of a TCP process without using long timeouts as conventionally provided in long-lived applications that run on top of TCP.

Claims

1. A method, comprising:

at a first data processing node that is hosting a transport protocol connection that uses a plurality of sequence values to identify messages sent to a peer node, wherein the first node is communicatively coupled to a second data processing node serving as a redundant backup, periodically sending a checkpoint sequence value to the second node;

detecting that either the transport protocol connection or a process using the transport protocol connection is unavailable, without use of a timeout; and

in response thereto, sending a notification to the peer node, wherein the notification includes the checkpoint sequence value.

2. A method as recited in claim 1, wherein the checkpoint sequence value is initially set equal to a maximum sequence value allowed for a window of sequence values associated with the transport protocol connection.

3. A method as recited in claim 1, further comprising:

determining that a sent-unacknowledged sequence value identifying a lowest sequence value of data sent on the transport protocol connection but unacknowledged by the peer node is greater than the checkpoint sequence value;

only in response thereto, updating the checkpoint sequence value to a then-current maximum sequence value allowed for a window of sequence values associated with the transport protocol connection, and sending the updated checkpoint sequence value to the second node.

4. A method as recited in claim 1, wherein the transport protocol connection is a Transmission Control Protocol (TCP) connection, and wherein the process using the transport protocol connection is a Border Gateway Protocol (BGP) process.

5. A method as recited in claim 4, further comprising:

determining that a SND.UNA value is greater than the checkpoint sequence value;

in response thereto, updating the checkpoint sequence value is updated to a SND.MAX value associated with the transport protocol connection

6. A method as recited in claim 4, wherein sending a notification comprises sending a TCP RST segment from the second node to the peer node, wherein the TCP RST segment includes the checkpoint sequence value as the sequence value of the TCP RST segment.

7. A method as recited in claim 1, wherein the detecting step is performed at the second node by periodically sending heartbeat messages from the second node to the first node.

8. A method as recited in claim 1, wherein the first node hosts a plurality of transport protocol connections, and wherein the steps of claim 1 are performed only for one or more of the transport protocol connections that are marked for a fast notification capability.

9. A method as recited in claim 1, wherein sending a checkpoint sequence value to the second node further comprises sending a source network address value, source port value, destination address value, and destination port value in association with the checkpoint sequence value to the second node.

17. A method as recited in claim 10, wherein the first node hosts a plurality of TCP connections, and wherein the steps of claim 1 are performed only for one or more of the TCP connections that are marked for a fast notification capability.

10. A method, comprising:

at a first data processing node that is hosting a Transport Control Protocol (TCP) connection that uses sequence numbers to identify messages sent to a peer node, wherein the first node is communicatively coupled to a second data processing node serving as a redundant backup, setting a checkpoint sequence number equal to a maximum sequence number allowed for a window of sequence number associated with the transport protocol connection;

periodically sending a checkpoint sequence number to the second node;

detecting that either the TCP connection or a process using the TCP connection is unavailable, without use of a timeout;

in response thereto, sending a notification to the peer node, wherein the notification includes the checkpoint sequence number;

determining that a sent-unacknowledged sequence number identifying a lowest sequence number of data sent on the TCP connection but unacknowledged by the peer node is greater than the checkpoint sequence number;

only in response thereto, updating the checkpoint sequence number to a then-current maximum sequence number allowed for a window of sequence numbers associated with the TCP connection, and sending the updated checkpoint sequence number to the second node.

11. A method as recited in claim 10, wherein the process using the transport protocol connection is any long-lived application running over TCP.

12. A method as recited in claim 10, wherein the process using the transport protocol connection is a Border Gateway Protocol (BGP) process.

13. A method as recited in claim 10, wherein the process using the transport protocol connection is a Label Distribution Protocol (LDP) process.

14. A method as recited in claim 10, further comprising:

determining that a SND.UNA number is greater than the checkpoint sequence number;

in response thereto, updating the checkpoint sequence number is updated to a SND.MAX number associated with the transport protocol connection

15. A method as recited in claim 10, wherein sending a notification comprises sending a TCP RST segment from the second node to the peer node, wherein the TCP RST segment includes the checkpoint sequence number as the sequence number of the TCP RST segment.

16. A method as recited in claim 10, wherein the detecting step is performed at the second node by periodically sending heartbeat messages from the second node to the first node.

18. A method as recited in claim 10, wherein sending a checkpoint sequence number to the second node further comprises sending a source network address value, source port value, destination address value, and destination port value in association with the checkpoint sequence number to the second node.

19. A method as recited in claim 18, wherein sending a checkpoint sequence number to the second node further comprises sending any of an acknowledgment value and application-specific information in association with the checkpoint sequence number to the second node.

20. A computer-readable medium carrying one or more sequences of instructions, which instructions, when executed by one or more processors, cause the one or more processors to carry out the steps of:

at a first data processing node that is hosting a transport protocol connection that uses a plurality of sequence values to identify messages sent to a peer node, wherein the first node is communicatively coupled to a second data processing node serving as a redundant backup, periodically sending a checkpoint sequence value to the second node;

detecting that either the transport protocol connection or a process using the transport protocol connection is unavailable, without use of a timeout; and

in response thereto, sending a notification to the peer node, wherein the notification includes the checkpoint sequence value.

21. An apparatus, comprising:

means, at a first data processing node that is hosting a transport protocol connection that uses a plurality of sequence values to identify messages sent to a peer node, wherein the first node is communicatively coupled to a second data processing node serving as a redundant backup, for periodically sending a checkpoint sequence value to the second node;

means for detecting that either the transport protocol connection or a process using the transport protocol connection is unavailable, without use of a timeout; and

means for sending, in response thereto, a notification to the peer node, wherein the notification includes the checkpoint sequence value.

22. An apparatus for creating and storing troubleshooting information for diagnosing one or more problems experienced in one or more completed voice calls that are carried by a packet-switched data network, comprising:

a network interface that is coupled to the data network for receiving one or more packet flows therefrom;

a processor;

one or more stored sequences of instructions which, when executed by the processor, cause the processor to carry out the steps of;

at a first data processing node that is hosting a transport protocol connection that uses a plurality of sequence values to identify messages sent to a peer node, wherein the first node is communicatively coupled to a second data processing node serving as a redundant backup, periodically sending a checkpoint sequence value to the second node;

detecting that either the transport protocol connection or a process using the transport protocol connection is unavailable, without use of a timeout; and

in response thereto, sending a notification to the peer node, wherein the notification includes the checkpoint sequence value.