Load balancing

• US 20020103846A1
• Filed: 02/06/2001
• Published: 08/01/2002
• Est. Priority Date: 07/15/1998
• Status: Active Grant

• Current Assignee: Radware Limited
• Original Assignee: Radware Limited
• Inventors: Zisapel, Roy, Peless, Amir
• Granted Patent: US 6,718,359 B2
• Time in Patent Office: Days
• US Class Current: 718/105
• CPC Class Codes: G06F 9/505 considering the load
• CPC Class Codes: H04L 61/4511 using domain name system [DNS]
• CPC Class Codes: H04L 67/1001 for accessing one among a plurality of replicated servers
• CPC Class Codes: H04L 67/1006 with static server selection, e.g. the same server being selected for a specific client
• CPC Class Codes: H04L 67/1008 based on parameters of servers, e.g. available memory or workload monitoring of computer activity G06F11/30
• CPC Class Codes: H04L 67/101 based on network conditions
• CPC Class Codes: H04L 69/32 Architecture of open systems interconnection [OSI] 7-layer type protocol stacks, e.g. the interfaces between the data link level and the physical level

Abstract

A method for load balancing requests on a network, the method including receiving a request from a requester having a requestor network address at a first load balancer having a first load balancer network address, the request having a source address indicating the requestor network address and a destination address indicating the first load balancer network address, forwarding the request from the first load balancer to a second load balancer at a triangulation network address, the request source address indicating the requester network address and the destination address indicating the triangulation network address, the triangulation network address being associated with the first load balancer network address, and sending a response from the second load balancer to the requestor at the requester network address, the response having a source address indicating the first load balancer network address associated with the triangulation network address and a destination address indicating the first requester network address.

Claims

1. A method for load balancing requests on a network, the method comprising:

receiving a request from a requestor having a requestor network address at a first load balancer having a first load balancer network address, said request having a source address indicating said requestor network address and a destination address indicating said first load balancer network address;

forwarding said request from said first load balancer to a second load balancer at a triangulation network address, said request source address indicating said requestor network address and said destination address indicating said triangulation network address, said triangulation network address being associated with said first load balancer network address; and

sending a response from said second load balancer to said requester at said requestor network address, said response having a source address indicating said first load balancer network address associated with said triangulation network address and a destination address indicating said first requestor network address.

2. A method according to claim 1 and further comprising:

maintaining said association between said triangulation network address and said first load balancer network address at either of said load balancers.

3. A method according to claim 1 and further comprising:

maintaining said association between said triangulation network address and said first load balancer network address at said second load balancer; and

communicating said association to said first load balancer.

4. A method according to claim 1 and further comprising:

directing said request from said second load balancer to a server in communication with said second load balancer;

composing said response at said server; and

providing said response to said second load balancer.

5. A method for load balancing requests on a network, the method comprising:

determining the network proximity of a requester with respect to each of at least two load balancers;

designating a closest one of said load balancers by ranking said load balancers by network proximity; and

directing requests from said requester to said closest load balancer.

6. A method according to claim 5 and further comprising directing requests from any source having a subnet that is the same as the subnet of said requester to said closest load balancer.

7. A method according to claim 5 and further comprising:

monitoring the current load of each of said load balancers; and

performing said directing step wherein the current load of said closest load balancer is less than the current load of every other of said load balancers.

8. A method according to claim 5 wherein said determining step comprises periodically determining.

9. A method according to claim 5 wherein said determining step comprises determining at at least one fixed time.

10. A method according to claim 5 wherein said determining step comprises polling said requester to yield at least two attributes selected from the group consisting of:

latency, relative TTL, and number of hops to requester.

11. A method according to claim 5 wherein said determining step comprises polling said requester using at least two polling methods selected from the group consisting of:

pinging, sending a TCP ACK message to said requestor'"'"'s source address and port, sending a TCP ACK message to said requestor'"'"'s source address and port 80, and sending a UDP request to a sufficiently high port number as to elicit an “

ICMP port unreachable”

reply.

12. A method according to claim 5 wherein said designating step comprises designating a closest one of said load balancers by ranking said load balancers by network proximity and either of current load and available capacity.

15. A system according to claim 14 wherein either of said load balancers is operative to maintain a table of said association between said triangulation network address and said first load balancer network address.

16. A system according to claim 14 wherein said second load balancer is operative to maintain a table of said association between said triangulation network address and said first load balancer network address and communicate said association to said first load balancer.

17. A system according to claim 14 and further comprising a server in communication with said second load balancer, wherein said second load balancer is operative to direct said request from said second load balancer to said server, and wherein said server is operative to compose said response and provide said response to said second load balancer.

19. A system according to claim 18 wherein said load balancers are operative to poll said requestor to yield at least two attributes selected from the group consisting of:

latency, relative TTL, and number of hops to requestor.

20. A system according to claim 18 wherein said load balancers are operative to poll said requestor using at least two polling methods selected from the group consisting of:

pinging, sending a TCP ACK message to said requestor'"'"'s source address and port, sending a TCP ACK message to said requestor'"'"'s source address and port 80, and sending a UDP request to a sufficiently high port number as to elicit an “

ICMP port unreachable”

reply.

21. A system according to claim 18 wherein said at least one of said load balancers is operative to designate said closest one of said load balancers by ranking said load balancers by network proximity and either of current load and available capacity.

13. A method for determining network proximity, the method comprising:

sending from each of at least two servers a UDP request having a starting TTL value to a client at a sufficiently high port number as to elicit an “

ICMP port unreachable”

reply message to at least one determining one of said servers indicating said UDP request'"'"'s TTL value on arrival at said client;

determining a number of hops from each of said servers to said client by subtracting said starting TTL value from said TTL value on arrival for each of said servers; and

determining which of said servers has fewer hops of said client; and

designating said server having fewer hops as being closer to said client than the other of said servers.

14. A network load balancing system comprising:

a network;

a first load balancer connected to said network and having a first load balancer network address;

a second load balancer connected to said network and having a triangulation network address, said triangulation network address being associated with said first load balancer network address; and

a requestor connected to said network and having a requestor network address,

wherein said requester is operative to send a request via said network to said first load balancer, said request having a source address indicating said requestor network address and a destination address indicating said first load balancer network address, wherein said first load balancer is operative to forward said request to said second load balancer at said triangulation network address, said request source address indicating said requestor network address and said destination address indicating said triangulation network address, and wherein said second load balancer is operative to send a response to said requester at said requestor network address, said response having a source address indicating said first load balancer network address associated with said triangulation network address and a destination address indicating said first requestor network address.

18. A network load balancing system comprising:

a network;

at least two load balancers connected to said network; and

a requester connected to said network,

wherein each of said at least two load balancers is operative to determine the network proximity of said requester, and wherein at least one of said load balancers is operative to designate a closest one of said load balancers by ranking said load balancers by network proximity and direct requests from either of said requester and a subnet of said requester to said closest load balancer.