Methods for providing a reliable server architecture using a multicast topology in a communications network
View Patent ↗Multi cast techniques are employed to provide host computer elements access to multiple redundant servers of a communication network in such a way that the hosts need not know which of the servers is active. In one embodiment, the servers provide a gateway function between an Ethernet LAN and an external network. The Ethernet LAN comprises one or more hosts connected to one or more switches, the switches connected to corresponding servers defining an active/standby pair. The servers are connected to an external network by corresponding active/standby links. The hosts send messages directed to a multicast address to at least one of the switches. The switches forward the messages on ports according to a multicast routing topology having been determined by performing IGMP “snooping” of messages issued from the servers. Both the active and standby servers receive the messages; and the active server sends the messages to the external network. In case the active server fails or is removed from service, the standby server is promoted to active server and assumes the role of the formerly active server without necessitating any communication to the hosts to inform them of the change in status of the active server.
1. In a communication network including a host interconnected via a switching element to an active and standby server, the switching element comprising a first and second switch and including a plurality of ports, the first switch connected to the active server and the second switch connected to the standby server, a method comprising:
defining a multicast routing topology associated with a multicast address, the multicast routing topology identifying which ports of the plurality of ports are to be used for forwarding messages directed to the multicast address;
sending a message from the host to one of the first and second switches directed to the multicast address;
sending the message from the one of the first and second switches to the other of the first and second switches, from the first switch to the active server and from the second switch to the standby server according to the multicast routing topology; and
processing the message by the active server.
2. The method of claim 1 , wherein the step of sending a message from the host is accomplished without the host having knowledge of which one of the active and standby servers is active.
3. The method of claim 1 , further comprising:
changing state of the active and standby servers, the active server becoming a formerly active server and the standby server becoming a new active server, the step of processing the message comprising processing the message by the new active server without informing the host of the changing state.
4. The method of claim 1 , wherein the communication network comprises an Ethernet LAN and the switching element comprises first and second Ethernet switches.
5. The method of claim 4 , wherein the active and standby server provide a gateway between the Ethernet LAN and an external network, the step of processing the message comprising sending the message from the active server to the external network.
6. The method of claim 4 , wherein the active and standby server provide a gateway between the Ethernet LAN and an external network, the step of processing the message comprising:
converting the message to a format associated with the external network, yielding a converted message; and
sending the converted message from the active server to the external network.
7. The method of claim 6 , wherein the external network comprises an ATM/SONET network, the step of converting the message comprising converting the message from a format associated with the Ethernet LAN to a format associated with the ATM/SONET network.
8. The method of claim 1 , wherein the step of defining a multicast topology comprises:
receiving, by the switching element, commands issued by the active and standby servers indicating a desire of the servers to receive messages addressed to the multicast address;
identifying ports on which the commands were received; and
mapping the multicast address to the ports, thereby forming the multicast routing topology.
9. The method of claim 8 wherein the step of receiving the commands comprises receiving IGMP Join messages.
10. The method of claim 8 wherein the step of defining a multicast topology further comprises provisioning ports on the switching element for forwarding packets directed to the multicast address.
11. The method of claim 10 wherein the step of provisioning ports comprises provisioning one or more ports independent of the commands issued by the active and standby servers.
12. In a communication network including a switching element comprising at least a first and second switch connected to N+K servers, N defining a number of active servers and K defining a number of standby servers, wherein N and K are integers, a method comprising:
receiving, by the first switch, a message directed to a multicast address;
forwarding the message according to a multicast routing topology that includes routing the message from the first switch to the second switch, the multicast routing topology defined by at least one of: Internet Group Management Protocol (IGMP) snooping of messages issued by the N+K servers and provisioning of ports independent of IGMP snooping;
receiving the message by the N+K servers; and
processing the message by the N active servers.
13. The method of claim 12 , wherein the step of receiving a message by the switching element comprises receiving the message from a host having no knowledge of which servers of the N+K servers are active servers.
14. The method of claim 13 , further comprising:
changing state of at least a portion of the N+K servers, a number of the N active servers becoming formerly active servers and a number of the K standby servers becoming new active servers, the step of processing the message comprising processing the message by the new active servers without informing the host of the changing state.