Browse Prior Art Database

METHOD OF PROVIDING HIGH AVAILABILITY FOR TCP-BASED SERVICES

IP.com Disclosure Number: IPCOM000030404D
Original Publication Date: 2004-Aug-11
Included in the Prior Art Database: 2004-Aug-11
Document File: 3 page(s) / 153K

Publishing Venue

IBM

Abstract

A method of providing high availability for TCP based services in disclosed, according to which the next incoming TCP connection request is forwarded to a plurality of hardware servers; however, only one of the servers’ responses will be allowed to be delivered to the TCP connection originator. This is achieved by assigning the same IP address and the same MAC address to the front end network interface cards (NICs) of all the servers comprising the highly available service, and by specifying the routing tables on those servers so that all the IP addressing space is divided among those servers in a way where for any given valid IP address there is only one routing table (on one of the servers) which provides for successful routing of IP packets to that address.

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METHOD OF PROVIDING HIGH AVAILABILITY FOR TCP-BASED SERVICES

A method of providing high availability for TCP based services in disclosed, according to which the next incoming TCP connection request is forwarded to a plurality of hardware servers; however, only one of the servers' responses will be allowed to be delivered to the TCP connection originator. This is achieved by the following means:
(a) Forwarding the TCP connection request to all the servers is achieved via assigning the same IP address and the same MAC address to the front end network interface cards (NICs) of all the servers comprising the highly available service,
(b) Preventing all but one servers to respond to the connection request is achieved via specifying the routing tables on those servers so that all the IP addressing space is divided among those servers in a way where for any given valid IP address there is only one routing table (on one of the servers) which provides for successful routing of IP packets to that address. All other routing tables the IP packet destined to the given IP address will be delivered to a router which quietly, or otherwise, discards all the packets accepted.

In the exemplary embodiment of the Highly Available system(see Fig.1), three servers are set up. It is understood that the number of servers can be any desired number more or equal 2 while the number three has been chosen here for illustrative purposes only.

These servers share both the IP address (32.12.1.5) and MAC address (00:06:1a:fe:c5:12) for the network interfaces that receive packets from the Internet through the Inbound Router. The routing tables on these servers are set up in such a way that all the outbound traffic is routed through the segment 10.1.1.0/24. In one exemplary embodiment, the Discarding Router quietly drops all IP packets it receives. In another embodiment, that Discarding Router replies with a TCP RST packet with the source IP address set to the IP address of the client, destination IP address set to the originating IP address of the server (in our example, 32.12.1.5), and the destination MAC address set to the originating MAC address (in our example, 00:06:1a:fe:c5:14), thus notifying the replying server that the TCP connection has been terminated.

Outbound router is an ordinary IP router forwarding packets to the Internet. Each of the servers 1-3 has a routing table that is unique for this HA group of servers. The purpose of the routing tables on the serv...