Load sharing and redundancy scheme

Details Load sharing and redundancy scheme Load sharing and redundancy scheme

1999-06-29

2004-06-15

Rao, Seema S. (Department: 2666)

Multiplex communications

Fault recovery

Bypass an inoperative switch or inoperative element of a...

C370S219000, C370S469000, C370S392000, C370S401000, C709S249000

Reexamination Certificate

active

06751191

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to networking technology. More particularly, the present invention relates to providing load sharing and redundancy in a network through a master router and a slave router having a shared set of interfaces in a single device.
2. Description of the Related Art
Networks are commonly used by organizations for a variety of purposes. For instance, through the use of networks, resources such as programs and data may be shared by users of the network. In addition, a computer network can serve as a powerful communication medium among widely separated users.
Communication among hosts and users of a network is often facilitated through connection to one or more routers. As shown in
FIG. 1
, a host
112
normally resides on a network segment
114
that enables its network entities to communicate with other entities or networks. Note that the host
112
need not directly connect to the entities or networks with which it communicates. For example, as shown in
FIG. 1
, the host
112
may be connected through a router R
1
116
. The router R
1
116
may, in turn, connect one or more other routers such as router R
2
118
with selected entities or networks.
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 R
1
116
and ultimately to the host
112
as indicated by dotted line “packet to host”
124
.
As described above, packets sent to and from the host
112
are forwarded via the router R
1
116
. As shown, the router R
1
116
is the only route to and from the host
112
. Thus, if the router R
1
116
fails, communication with the host
112
becomes impossible. Accordingly, the reliability of the network as well as the routers in the network is of utmost importance.
As networks become a critical resource in many organizations, it is important that the networks are reliable. One way of achieving reliability is through redundancy. As described above, a single router failure may prevent communication to and from each host and user connected to the router. In many networks, it is common to provide redundancy through the use of multiple routers such that a backup router functions in the event of failure of a primary router. However, when the primary router fails, there is typically a “switchover time” that is required for the backup router to take over the functions of the primary router. As a result, such attempts to provide redundancy in switches suffer from a large switchover time. Accordingly, it would be beneficial if such redundancy could be provided with a reduction in the switchover time from a non-functional to a functional router.
In addition to reliability, it is often desirable to improve performance within a given network. In order to achieve this improvement, load sharing is often preferable. For instance, various users of a network may have a higher traffic level than other users of the network. It would therefore be desirable if performance could be achieved through the distribution of traffic among multiple routers.
In view of the above, it would be desirable if a redundancy and load sharing scheme could be implemented to reduce the switchover time upon failure of a router while implementing a load sharing scheme among multiple routers operating in a single device.
SUMMARY OF THE INVENTION
An invention is described herein that provides load sharing and redundancy in a network. This is accomplished, according to one embodiment, through the use of a master router and a slave router operating in the same chassis and having a shared set of interfaces. Prior to failure of the master router, the master router communicates shared state information to the slave router. In addition, the slave router operates in “standby mode” to obtain information from the shared set of interfaces. In this manner, the switchover time required to switch from the master router to the slave router upon failure of the master router is significantly reduced.
According to one aspect of the invention, a default gateway is associated with both the master router and the slave router. This is accomplished by assigning a shared IP address and a shared MAC address to both a first router and a second router so that the shared IP and MAC addresses are shared between the first router and the second router. Additionally, a first MAC address is assigned to the first router and a second MAC address is assigned to the second router. The default gateway is configured on the hosts such that a default gateway IP address is associated with the shared IP address. The shared IP and MAC addresses are associated with one of the routers (e.g., the first router or master router). When the master fails, the slave takes over both the shared IP address and the shared MAC address.
In order to route traffic, there are three layers of protocol: a physical layer, a data link layer, and a network layer. The data link layer is often referred to as “layer
2
” while the network layer is often referred to as “layer
3
.” The responsibility of the data link layer is to transmit chunks of information across a link. The responsibility of the network layer is to enable systems in the network to communicate with each other. Thus, the network layer finds a path or “shortcut” through a series of connected nodes that must forward packets in the specified direction.
According to another aspect, the master and the slave each includes a switching processor to switch packets in hardware and a routing processor to enable packets to be routed in software. The switching processor is adapted for running a layer
2
protocol (e.g., spanning tree) and the routing processor is adapted for running a layer
3
routing protocol. In addition, the master and the slave each maintains its own forwarding data. More particularly, the master and the slave each maintain a layer
2
database associated with the layer
2
protocol and a routing table associated with the layer
3
routing protocol. Both the master and the slave independently run its own layer
3
routing protocol and maintain its own routing table. However, only the master runs the layer
2
protocol. More particularly, the master saves the layer
2
protocol information in a layer
2
protocol database (e.g., spanning tree database) and sends layer
2
protocol updates to the slave so that it may similarly store the layer
2
protocol updates in its own layer
2
protocol database. When the master fails, the slave then runs the layer
2
protocol and accesses its own layer
2
protocol database. Since the slave maintains its own layer
2
protocol database and layer
3
routing table, switchover time upon failure of the master is minimized.
According to another aspect, prior to failure of the master, the slave receives updates from the master in order to synchronize operation of the two routers. For instance, the master maintains the hardware information for both the master and the slave. Therefore, in addition to sending layer
2
protocol updates, the master also sends other information related to the hardware shared by the two routers. As one example, multicast group membership for the shared ports is sent by the master to the slave. As another example, hardware information such as temperature and information related to the power supply is sent by the master to the slave.
According to yet another aspect, the master and the slave each include a forwarding engine in addition to the routing processor and the switching processor. The forwarding engines are adapted for forwarding packet

Affiliated with

Also associated with

Rating

Load sharing and redundancy scheme does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Load sharing and redundancy scheme, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Load sharing and redundancy scheme will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3359618