Session load balancing and use of VIP as source address for inter-cluster traffic through the use of a session identifier

• US 20060080446A1
• Filed: 11/30/2005
• Published: 04/13/2006
• Est. Priority Date: 11/01/2000
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Bahl, Pradeep
• Granted Patent: US 7,483,992 B2
• Time in Patent Office: Days
• US Class Current: 709/227
• CPC Class Codes: H04L 67/1001 for accessing one among a plurality of replicated servers
• CPC Class Codes: H04L 67/1023 based on a hash applied to IP addresses or costs
• CPC Class Codes: H04L 67/1034 Reaction to server failures by a load balancer
• 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 69/163 In-band adaptation of TCP data exchange; In-band control procedures
• CPC Class Codes: H04L 9/40 Network security protocols

Abstract

A method and system for enhancing a load balancing network'"'"'s ability to load balance sessions is presented. A session identifier is placed within the TCP packet to enable a new mechanism of load distribution and connection grouping within a load balancing system. Specifically, TCP is invoked by a user application to obtain a unique session identifier value. TCP places the session identifier as a sender session identifier within the OPTIONS field of the TCP header. As an alternative, a session identifier can be placed within a session header that is attached to the TCP packet. On receiving such a packet, the destination load balancing system hashes over at least the session identifier value, and the node corresponding to the results of the hash algorithm acquires the packet. This method of hashing ensures that the same node acquires all subsequently received TCP packets possessing the same session identifier regardless of the source IP address or source port information. The node then places an identical session identifier value in the form of a response session identifier in its TCP response packet. When the TCP packet with response session identifier is received at a load balancing system, the node whose session identifier matches the response session identifier acquires it. This ensures that a response to a node assigned to a virtual IP address is received by the proper node, thus preventing other member nodes assigned to the same VIP address from picking up the packet instead.

Claims

1. A method for enabling sessions established between a client and a server to be uniquely defined to enhance the performance of a load balancing system, the method comprising the steps of:

receiving a packet from a client connected to a network, the packet including a sender session identifier;

parsing the packet to obtain the sender session identifier;

hashing over at least the sender session identifier to determine which node within the load balancing system will acquire the packet; and

acquiring the packet by a single determinant node based on the results of the hashing step.

2. The method of claim 1, wherein:

the packet is a TCP packet having a TCP header and an OPTIONS field; and

the sender session identifier is specified in the OPTIONS field of the TCP header or in a session header that is attached to the TCP header.

3. The method of claim 1, wherein the step of acquiring further comprises procuring all subsequently received packets carrying the same sender session identifier by the same determinant node.

4. The method of claim 1, wherein the determinant node'"'"'s protocol stack stores the sender session identifier in a TCP control block as a response session identifier, and passes the packet up the protocol stack to a specified application.

5. The method of claim 1, wherein the step of acquiring further comprises associating the sender session identifier with a connection descriptor created to describe a connection associated with the session.

6. The method of claim 1, further comprising the step of transmitting a second packet to the client, the second packet including a response session identifier that is identical to the sender session identifier.

7. The method of claim 6, wherein:

the packet is a TCP packet having a TCP header and an OPTIONS field; and

the sender session identifier is associated with the OPTIONS field of the TCP header.

8. The method of claim 1, further comprising the step of transmitting a second TCP packet having a TCP header to the client, wherein the second packet includes a session header attached to the TCP header and the session header contains a response session identifier and original destination port information.

9. The method of claim 8, wherein the session header specifies a destination port that is an assigned port of the load balancing system located at a destination IP address to which the second packet is to be transmitted.

10. The method of claim 1, further comprising:

establishing a connection between a source IP address associated with the client and a destination IP address associated with the server by allocating a TCP control block for the connection wherein the TCP control block contains a second session identifier identical to the session identifier of the packet.

11. The method of claim 1, further comprising:

establishing a connection between a source IP address associated with the client and a destination IP address associated with the server by allocating a TCP control block for the connection;

associating the session identifier with a connection descriptor created to describe the connection; and

completing a three-way-handshake.

12. A method for enabling sessions established between a client and a server to be uniquely defined to enhance the performance of a load balancing system, the method comprising the steps of:

invoking client-side TCP executable instructions;

identifying an available sender session identifier for uniquely identifying a session between the client and the server;

forming a packet to be transmitted over a network to a destination IP address, the packet containing information that includes the sender session identifier; and

transmitting the packet to the destination IP address.

13. The method of claim 12, wherein a second sender session identifier associated with each subsequent packet formed during the session is identical to the sender session identifier.

14. The method of claim 12, wherein the step of identifying further comprises at least one of the following:

invoking the TCP executable instructions to obtain the sender session identifier from a first session identifier pool of available session identifiers;

using an application that invoked the TCP executable instructions to automatically assign the sender session identifier; and

querying a service that resides on a node to obtain the sender session identifier from a second session identifier pool of available session identifiers.

15. The method of claim 14, wherein the first session identifier pool and the second session identifier pool contain a range of unique session identifiers that are distributed amongst one or more nodes within the load balancing system such that each node has its own pool.

16. The method of claim 12, wherein:

the packet is a TCP packet having a TCP header and an OPTIONS field; and

the step of forming further comprises associating the sender session identifier with the OPTIONS field of the TCP header.

17. The method of claim 12, wherein:

the packet is a TCP packet having a TCP header; and

the step of forming further comprises associating the sender session identifier and the destination port with a session header that is attached to the TCP header.

18. The method of claim 12, wherein:

the packet is a TCP packet having a TCP header; and

the step of forming further comprises associating the sender session identifier and the destination port with a session header that is attached to the TCP header, wherein the session header is attached to the packet by an interception shim that operates within a protocol stack of the client.

19. The method of claim 12, wherein:

the packet is a TCP packet having a TCP header; and

the step of forming further comprises changing a destination port associated with the TCP header to an assigned port number of the load balancing system located at the destination IP address.

20. One or more computer-readable media containing computer-executable instructions that, when executed, implement a computer process for enhancing the performance of a load balancing system, the computer process comprising:

receiving a TCP packet having a TCP header and an OPTIONS field from a computing device associated with a source IP address, the packet including a session identifier;

parsing the packet to identify the session identifier;

hashing over at least the session identifier to determine which node within the load balancing system will acquire the packet;

acquiring the packet by a single determinant node based on results of the hashing step, wherein all subsequently received packets carrying the same session identifier are acquired by the same determinant node; and

establishing a connection between the source IP address and a destination IP address associated with a second computing device by allocating a TCP control block for the connection.