Simplified packet routing
A method for communication, includes routing unicast data packets among nodes in a network using respective Layer-3 addresses that are uniquely assigned to each of the nodes. Respective Layer-2 unicast addresses are assigned to the nodes in accordance with an algorithmic mapping of the respective Layer-3 addresses. The unicast data packets are forwarded within subnets of the network using the assigned Layer-2 addresses.
1. A method for communication, comprising:
receiving in an integrated router including routing logic and a plurality of layer-2 switches, multicast data packets, each having a Layer-3 multicast destination address and a Layer-2 multicast destination address corresponding to the Layer-3 multicast address in all of a plurality of subnets serviced by the integrated router and layer-2 switches;
for at least one of the multicast data packets received by the integrated router:
identifying, in accordance with a single lookup operation, a plurality of layer-2 output ports through which the at least one multicast data packet is to be forwarded by the integrated router, wherein the single lookup operation includes the integrated router looking up the Layer-2 multicast destination address only once and determining two or more subnets corresponding to the plurality of layer-2 output ports; and
forwarding the at least one multicast data packet from the integrated router to the identified plurality of layer-2 output ports in the two or more subnets without changing the Layer-2 multicast destination address of the at least one multicast packet,
wherein the forwarding of the at least one of the multicast data packets through at least one of the plurality of layer-2 output ports includes updating a time to live (TTL) value of the forwarded multicast data packet.
2. The method according to claim 1 ,
wherein the Layer-2 multicast destination address is derived by applying an algorithmic mapping function to the corresponding Layer-3 multicast address.
3. The method according to claim 1 ,
wherein the plurality of layer-2 output ports identified in the single lookup operation for the at least one of the multicast data packet comprises both a first port in a source subnet of the multicast data packet and a second port in another of the subnets, other than the source subnet, to which the router is connected for forwarding of the at least one multicast data packet.
4. The method according to claim 3 ,
wherein the forwarding comprises forwarding the at least one of the received multicast data packet via the first port without modification and via the second port with an updated layer 2 header and an updated TTL value.
5. The method according to claim 1 ,
wherein the single lookup operation comprises
deriving respective subnet mask vectors for the subnets, and selecting the output ports of the router through which the at least one multicast data packet is to be transmitted using the subnet mask vectors.
6. The method according to claim 1 , and comprising, upon receiving the forwarded multicast data packet at a host in the network, filtering the data packet in a network interface controller of the host, by comparing the Layer-3 multicast address of the data packet to a list of layer-3 multicast addresses of multicast groups to which the host is registered.
7. The method according to claim 1 , wherein the forwarding is performed without a lookup based on layer-3 information.
8. An apparatus for communication, implementing an integrated router including layer-2 switches, comprising:
a plurality of layer-2 ports, which are configured to receive multicast data packets,
wherein the received multicast data packets have a Layer-3 multicast destination address, and a Layer-2 multicast destination address corresponding to the Layer-3 address in all of a plurality of subnets serviced by the integrated router;
a multicast forwarding table indicating for multicast addresses, through which of the plurality of ports packets directed to the multicast address are to be forwarded; and
routing logic configured to:
identify, in accordance with a single lookup operation, a plurality of layer-2 output ports through which at least one of the received multicast data packets is to be forwarded by the integrated router, wherein the single lookup operation includes the integrated router looking up the Layer-2 multicast destination address only once and determining two or more subnets corresponding to the plurality of layer-2 output ports;
forward the at least one of the received multicast data packets from the integrated router to the identified plurality of layer-2 output ports in the two or more subnets without changing the Layer-2 multicast destination address of the at least one received multicast packet; and
update a time to live (TTL) value of the forwarded multicast data packet when forwarding the packet through at least one of the plurality of layer-2 output ports.
9. The apparatus according to claim 8 ,
wherein the Layer-2 multicast addresses of the multicast packets are derived by applying an algorithmic mapping function to the corresponding Layer-3 multicast addresses of the packets.
10. The apparatus according to claim 8 ,
wherein the routing logic is configured to apply respective subnet mask vectors for the subnets in order to select the ports through which the at least one of the received multicast data packet is to be transmitted to each of the determined two or more subnets.