Source: https://patents.google.com/patent/US6751191B1/en
Timestamp: 2019-08-24 04:58:18
Document Index: 326987900

Matched Legal Cases: ['application No. 09', 'application No. 09', 'application No. 09', 'application No. 09', 'application No. 09', 'application No. 09', 'application No. 10', 'application No. 09', 'application No. 09']

US6751191B1 - Load sharing and redundancy scheme - Google Patents
Load sharing and redundancy scheme Download PDF
US6751191B1
US6751191B1 US09/342,859 US34285999A US6751191B1 US 6751191 B1 US6751191 B1 US 6751191B1 US 34285999 A US34285999 A US 34285999A US 6751191 B1 US6751191 B1 US 6751191B1
US09/342,859
Jonathan Davar
1999-06-29 Application filed by Cisco Technology Inc filed Critical Cisco Technology Inc
1999-06-29 Priority to US09/342,859 priority Critical patent/US6751191B1/en
1999-06-29 Assigned to CISCO TECHNOLOGY, INC. reassignment CISCO TECHNOLOGY, INC. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: DAVAR, JONATHAN, KANEKAR, BHUSHAN MANGESH, RAJENDRAN, SARAVANAKUMAR
2004-06-15 Publication of US6751191B1 publication Critical patent/US6751191B1/en
Now, suppose that the host 112 wishes to send a message to a corresponding node 120. A message from the host 112 is then packetized and forwarded through the appropriate routers and to the corresponding node 120, as indicated by dotted line “packet from host” 122, according to a standard protocol. If the corresponding node 120 wishes to send a message to the host 112—whether in reply to a message from the host 112 or for any other reason—it addresses that message to the IP address of the host 112 on the network segment 114. The packets of that message are then forwarded to router R1 116 and ultimately to the host 112 as indicated by dotted line “packet to host” 124.
FIG. 3 is a general block diagram illustrating routers that share a single set of interfaces according to in embodiment of the invention.
Packets received at the shared interfaces may be forwarded in hardware via the forwarding engine or in software. However, packets must be encapsulated in the same manner regardless of whether the packets are forwarded in hardware or software. Thus, similarly to the information maintained by the routing processor and switching processor, the forwarding engines maintain layer 2 and layer 3 tables, as will be shown and described. with reference to FIGS. 13A and 13B. As shown at block 1210 of FIG. 12A, the forwarding engine tables of the slave are modified after failure of the master to enable packets to be accurately forwarded by the slave. One method of modifying the forwarding engine tables of the slave after failure of the master is presented in FIG. 12C. The process begins at block 1230. In the absence of a layer 3 entry for a particular flow, a packet following this flow is sent via software. In order to determine the router used to send the packet, the layer 2 table is used to match the destination MAC address of the packet and therefore must contain updated information. Thus, at block 1232, entries in the slave's layer 2 table that are associated with the master are modified or replaced such that the resulting entries are mapped to the slave rather than the master. Once modified, the slave's layer 2 table may be used to determine the appropriate router to forward packets in the absence of an entry in the slave's layer 3 table. During forwarding of a packet, if there is no layer 3 entry, an entry in the layer 2 table associated with the destination MAC address of the packet is identified. The router identified in this layer 2 table entry is then used to forward the packet in software until a layer 3 entry for this flow is created.
a second router having a second processor and a second memory associated therewith, the first router and the second router having a shared set of interfaces, the shared set of interfaces enabling the first router and the second router to share forwarding data for forwarding packets on the shared set of interfaces and to share updates including at least one of synchronized state information indicating states of ports associated with the set of interfaces and VLAN membership.
2. The device as recited in claim 1, wherein the first router and the second router are provided in a single device, thereby enabling communication between the first router and the second router, wherein the communication occurs in a backplane of the device such that the first router replaces the second router upon detection of failure of the second router.
3. The device as recited in claim 1, wherein
the first memory includes a first set of forwarding data associated with the first router; and
the second memory includes a second set of forwarding data associated with the second router, the first set of forwarding data and the second set of forwarding data comprising layer 2 protocol information and layer 3 protocol information for forwarding packets;
wherein the first set of forwarding data associated with the first router includes forwarding data updates sent from the second router to the first router prior to the failure of the second router.
5. The device as recited in claim 3, wherein the first set of forwarding data associated with the first router further includes data obtained by the first router from the shared set of interfaces prior to the failure of the second router.
7. The device as recited in claim 1, further comprising a memory coupled to at least one of the routers, the memory storing a set of configuration information for configuring the first router and the second router.
8. The system as recited in claim 7, wherein the set of configuration information comprising a number of ports associated with both the first router and the second router, a type of the ports associated with both the first router and the second router, and a single set of security information associated with both the first router and the second router.
9. A method of forwarding packets in a network, comprising:
providing a first router;
providing a second router, the first router and the second router sharing a single set of interfaces;
sending synchronized state information indicating states of ports associated with the set of interfaces and VLAN membership information via the set of interfaces; and
detecting a failure of the second router such that the first router forwards packets received at the single set of interfaces in response to the detection of failure of the second router.
10. The method as recited in claim 9, further including
providing the first router and the second router in a single device, wherein the failure is detected through a signal sent within the device from the second router to the first router.
maintaining a first set of forwarding data associated with the first router;
maintaining a second set of forwarding data associated with the second router, the first set of forwarding data and the second set of forwarding data comprising layer 2 protocol information and layer 3 protocol information for forwarding packets;
sending forwarding data updates from the second router to the first router prior to the failure of the second router; and
updating the first set of forwarding data associated with the first router with the forwarding data updates sent from the second router.
12. The method as recited in claim 11, wherein the forwarding data updates include layer 2 protocol updates.
obtaining data from the shared set of interfaces by the first router prior to the failure of the second router; and
incorporating the obtained data in the first set of forwarding data.
14. The method as recited in claim 13, wherein the data obtained by the first router includes one or more shortcuts established by the second router, the one or more shortcuts specifying layer 3 forwarding information.
assigning a shared IP address and shared MAC address to the first router and the second router;
assigning a first MAC address to the first router;
assigning a second MAC address to the second router; and
configuring a default gateway such that a default gateway IP address is associated with the shared IP address.
associating the shared IP address with the first MAC address.
associating the shared IP address with the second MAC address in response to a failure of the first router.
18. The method as recited in claim 15, wherein configuring a default gateway includes configuring a first default gateway and a second default gateway, the method further comprising:
associating a first host with a first default gateway; and
associating a second host with a second default gateway, wherein the first default gateway and the second default gateway are identified with at least one of the first router and the second router, thereby enabling a packet to be forwarded via the first or the second default gateway when at least one of the source and destination of the packet identifies the first host or the second host.
19. The method as recited in claim 9, further comprising:
determining whether the first router or the second router functions as a master router.
20. The method as recited in claim 19, wherein determining whether the first router or the second router functions as a master router comprises:
ascertaining from priorities assigned to the first router and the second router which of the first router and the second router functions as the master router.
21. The method as recited in claim 19, wherein determining comprises:
receiving a signal at the first router from the second router;
ascertaining whether the signal asserts that the second router is the master router;
reading a configuration file for configuration information for both the first router and the second router, wherein at least some of the configuration information is identical for the first router and the second router.
23. In a master router, a method of forwarding packets received at a set of interfaces, the method comprising:
running a protocol;
updating a database in the master router with updates, the updates including at least one of synchronized state information indicating states of ports associated with the set of interfaces and VLAN membership of the master router; and
sending the updates to a slave router, thereby enabling the slave router to forward packets received at the set of interfaces using the updates received from the master router.
24. The method as recited in claim 23, wherein the protocol is a layer 2 protocol and the updates include layer 2 protocol updates, wherein sending the updates comprises:
sending synchronized state information from the master router to the slave router to synchronize states of ports associated with the set of interfaces.
25. The method as recited in claim 23, wherein the updates do not include information associated with the routing table maintained by the master router, wherein sending the updates comprises:
sending VLAN membership of the master router to the slave router such that the slave has access to each VLAN associated with the master router upon failure of the master router.
26. The method as recited in claim 23, wherein sending the updates comprises:
sending synchronized state information from the master router to the slave router to synchronize states of ports associated with the set of interfaces; and
using the synchronized state information on the slave router in response to a detection of failure of the master router.
sending forwarding engine information from the master router to the slave router such that the second forwarding engine is initialized; and
sending hardware information from the master router to the slave router, the hardware information including at least one of temperature and indication of power supply failure.
29. In a slave router, a method of forwarding packets received at a set of interfaces, the method comprising:
receiving updates from a master router running a protocol, the updates including at least one of synchronized state information indicating states of ports associated with the set of interfaces and VLAN membership of the master router; and
30. The method as recited in claim 29, wherein the protocol is a layer 2 protocol and the updates include layer 2 protocol updates.
31. The method as recited in claim 29, wherein the updates do not include information associated with a layer 3 protocol.
detecting a failure of the master router; and
running the protocol on the slave router.
sending acknowledgement of the updates from the slave router to the master router.
34. A method of forwarding packets in a switching system, the system comprising a master router and a slave router having a shared set of interfaces, the method comprising:
maintaining a first set of forwarding data for the master router and a second set of forwarding data for the slave router;
sending forwarding data updates from the master router to the slave router;
sending at least one of synchronized state information indicating states of ports associated with the set of interfaces and VLAN membership of the master router to the slave router;
obtaining packet header data from the shared set of interfaces; and
updating the second set of forwarding data with the forwarding data updates sent from the master router and the packet header data obtained from the shared set of interfaces.
35. The method as recited in claim 34, wherein obtaining packet header data from the shared set of interfaces is performed with the slave router.
36. The method as recited in claim 34, wherein the forwarding data updates include layer 2 protocol updates and the packet header data obtained from the shared set of interfaces includes one or more shortcuts established by the master router, the one or more shortcuts specifying layer 3 forwarding information.
37. The method as recited in claim 34, further comprising:
maintaining a first routing table associated with the master router; and
maintaining a second routing table associated with the slave router.
38. The method as recited in claim 37, wherein the second routing table associated with the slave router is not recalculated in response to a failure of the master router.
39. The method as recited in claim 34, further comprising:
updating the second set of forwarding data in response to a failure of the master router.
40. The method as recited in claim 39, wherein updating the second set of forwarding data comprises:
invalidating one or more shortcuts established by the master router, the one or more shortcuts specifying layer 3 forwarding information.
41. In a system including a first router and a second router having a shared set of interfaces, a first forwarding engine coupled to the set of interfaces and the first router, the first forwarding engine being associated with a first set of forwarding engine tables for facilitating forwarding of packets in hardware, and a second forwarding engine coupled to the set of interfaces and the second router, the second forwarding engine being associated with a second set of forwarding engine tables for facilitating forwarding of packets in hardware, a method of forwarding a packet received at the set of interfaces comprising:
sending at least one of synchronized state information indicating states of ports associated with the set of interfaces and VLAN membership of the first router to the second router;
observing the packet at the set of interfaces to obtain information from the packet; and
updating the first and second sets of forwarding engine tables with the obtained information such that the packet is associated with at least one of the first router and the second router, thereby enabling the first router and the second router to forward a packet using the obtained information.
42. The method as recited in claim 41, wherein the first forwarding engine has an associated layer 2 table and layer 3 table, and the second forwarding engine has an associated layer 2 table and layer 3 table, wherein the layer 2 tables each associate one or more MAC addresses with the first router or the second router, and wherein the layer 3 tables each specify one or more shortcuts including layer 3 forwarding information, each one of the shortcuts being associated with a flow associated with a source IP address and destination IP address, the method further comprising:
updating entries in the layer 2 table associated with the slave router such that each one of the entries is mapped to the slave router rather than the master router.
removing selected entries in the layer 3 table associated with the slave router, the selected entries specifying shortcuts associated with the master router, thereby enabling replacement entries to be created upon forwarding of packets such that the replacement entries specify shortcuts associated with the slave router.
forwarding a packet via the second forwarding engine.
45. The method as recited in claim 41, wherein the first router has an associated first routing table for facilitating forwarding of packets in software and the second router has an associated second routing table for facilitating forwarding of packets in software, the method further comprising:
running a first routing protocol on the first router and a second routing protocol on the second router; and
separately building the first routing table and the second routing table.
46. The method as recited in claim 45, wherein the first routing protocol and the second routing protocol are different.
47. The method as recited in claim 45, wherein the first routing protocol and the second routing protocol are identical.
48. The method as recited in claim 15, wherein a plurality of VLANs are coupled to the set of interfaces.
performing load distribution among the first router and the second router based upon a source of incoming packets.
associating the plurality of VLANs with one or more default gateways.
51. The method as recited in claim 48, further comprising:
associating one or more of the plurality of VLANs with the default gateway.
52. The method as recited in claim 15, further comprising:
associating one or more of the set of interfaces with the default gateway.
53. The method as recited in claim 49, wherein the source is one of the plurality of VLANS.
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US09/342,859 US6751191B1 (en) 1999-06-29 1999-06-29 Load sharing and redundancy scheme
US10/723,371 US7006431B1 (en) 1999-06-29 2003-11-26 Load sharing and redundancy scheme
US11/190,696 US8077604B1 (en) 1999-06-29 2005-07-26 Load sharing and redundancy scheme
US13/300,377 US9276834B2 (en) 1999-06-29 2011-11-18 Load sharing and redundancy scheme
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US13/300,377 Active 2020-06-22 US9276834B2 (en) 1999-06-29 2011-11-18 Load sharing and redundancy scheme
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