Method of shrinking a data loss window in a packet network device
View Patent ↗A packet network device includes a control module, one or more line cards each one or which includes a plurality of ingress and egress ports, and each of the ingress and egress ports are connected to external network links. The line cards maintain forwarding tables and include functionality that employs information in the forwarding tables to determine how incoming packets of information should be forwarded. The control module includes functionality that operates to learn reachability information about other devices connected to the network that are and to use this reachability information to update forwarding tables maintained on the line cards. The control module also includes an enhance ARP functionality that operates in cooperation with standard ARP functionality and other network protocols included on the control module to diminish the amount of data lost in the event that a link connected to one of the egress ports fails.
1. A method for diminishing data lost at a packet network device as the result of a failed communication link, comprising:
detecting a failure of a communication link to which a first egress port in a packet network device is connected;
in response to the detected failure, disabling the first egress port and enabling a second egress port on the packet network device that was previously blocked and that is a member of the same VLAN as the first egress port;
using an address resolution protocol cache flush disable function to temporarily inhibit a standard address resolution protocol function from removing layer-3 forwarding table entries associated with the disabled first egress port while updated layer-3 forwarding information for the second egress port is learned;
identifying one or more layer-3 table entries associated with the disabled first egress port and using a layer-3 forwarding table update function to replace a portion of each of the one or more layer-3 forwarding table entries with a multicast identity of the VLAN such that traffic destined for the disabled first egress port is temporarily flooded to a plurality of ports that are members of the VLAN; and
updating the one or more layer-3 forwarding table entries to replace the multicast identity of the VLAN with the learned layer-3 forwarding information for the second egress port.
2. The method of claim 1 wherein the failure of the communication link is manifested by the inability of the packet network device to successfully forward data over the first egress port.
3. The method of claim 1 wherein the packet network device is a network switch, a network router or both a switch and a router.
4. The method of claim 1 wherein each of the one or more layer-3 forwarding table entries are comprised of an IP address, a medium access control address, a VLAN identity and an egress port identity.
5. The method of claim 1 wherein address resolution protocol cache flush disable function, the standard address resolution protocol function, and the layer-3 forwarding table update function are included in an enhanced address resolution protocol function provided by a layer-3 route processor module.
6. The method of claim 1 wherein the second port was previously blocked according to the spanning tree protocol.
7. The method of claim 1 wherein the update layer-3 forwarding information is comprised of a medium access control (MAC) address and an identity of a port over which the MAC address is learned.
8. The method of claim 1 wherein the portion of the layer-3 table entry that is replaced with the multicast identity of the VLAN includes an egress port identity.
9. The method of claim 1 wherein the multicast identity of the VLAN includes the identity of two or more egress ports that are members of the VLAN.
10. The method of claim 1 wherein the updating all of the layer-3 forwarding table entries associated with the second port to replace the multicast identity of the VLAN with the learned layer-3 forwarding information for the second egress port includes replacing one or more of an IP address, a medium access control address and a port identity.
11. A packet network device, comprising:
a control module that is operable to run layer-2 and layer-3 network protocols and to run an enhanced address resolution protocol function that includes a standard address resolution protocol function, an address resolution protocol cache flush disable function, and a layer-3 forwarding table update function;
one or more line cards each of which includes a packet processor, a port manager, memory to store one or more forwarding tables, and a plurality of ingress and egress ports connected to external network communication links, wherein the control module and the one or more line cards cooperate in the event of a link failure that effects a first of the plurality of egress ports to:
disable the first of the plurality of egress ports and enable a second of the plurality of the egress ports that was previously blocked and that is a member of the same VLAN as the first of the plurality of egress ports;
use the address resolution protocol cache flush disable function to temporarily inhibit the standard address resolution protocol function from removing layer-3 forwarding table entries associated with the disabled first of the plurality of the egress ports while layer-3 update forwarding information is learned for the second of the plurality of egress ports;
identify one or more layer-3 forwarding table entries associated with the disabled first of the plurality of the egress ports and use the layer-3 forwarding table update function to replace a portion of each of the one or more layer-3 forwarding table entries with a multicast identity of the VLAN such that traffic destined for the disabled first of the plurality of egress ports is temporarily flooded to a plurality of egress ports that are members of the VLAN; and
update the one or more layer-3 forwarding table entries to replace the multicast identity of the VLAN with the learned layer-3 forwarding information for the second egress port.
12. The packet network device of claim 11 , wherein the control module and the one or more line cards are included in a network switch, a network router, or a combined network switch and network router.
13. The packet network device of claim 11 , wherein the control module is comprised of a layer-2 route processor module and a layer-3 route processor module.
14. The packet network device of claim 13 wherein the layer-2 route processor module is comprised of layer-2 network protocols, layer-2 switching tables, VLAN information, a layer-2 manager and a link state database, and the layer-3 route processor module is comprised of layer-3 network protocols, layer-3 routing tables, the enhanced address resolution protocol function, and a layer-3 routing table manager.
15. The packet network device of claim 11 wherein the packet processor operates to examine a received packet of information to determine how to forward the packet over the network.
16. The packet network device of claim 11 wherein the port manager operates to disable and enable any one of the plurality of the egress ports.