Multiplex communications – Data flow congestion prevention or control – Flow control of data transmission through a network
Reexamination Certificate
2003-02-07
2004-08-10
Marcelo, Melvin (Department: 2663)
Multiplex communications
Data flow congestion prevention or control
Flow control of data transmission through a network
C370S252000, C370S352000
Reexamination Certificate
active
06775235
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to computer network data transmission, and more particularly relates to tools and techniques for communications using disparate parallel networks, such as a virtual private network (“VPN”) or the Internet in parallel with a point-to-point, leased line, or frame relay network, in order to help provide benefits such as load balancing across network connections, greater reliability, and increased security.
TECHNICAL BACKGROUND OF THE INVENTION
Organizations have used frame relay networks and point-to-point leased line networks for interconnecting geographically dispersed offices or locations. These networks have been implemented in the past and are currently in use for interoffice communication, data exchange and file sharing. Such networks have advantages, some of which are noted below. But these networks also tend to be expensive, and there are relatively few options for reliability and redundancy. As networked data communication becomes critical to the day-to-day operation and functioning of an organization, the need for lower cost alternatives for redundant back-up for wide area networks becomes important.
Frame relay networking technology offers relatively high throughput and reliability. Data is sent in variable length frames, which are a type of packet. Each frame has an address that the frame relay network uses to determine the frame's destination. The frames travel to their destination through a series of switches in the frame relay network, which is sometimes called a network “cloud”; frame relay is an example of packet-switched networking technology. The transmission lines in the frame relay cloud must be essentially error-free for frame relay to perform well, although error handling by other mechanisms at the data source and destination can compensate to some extent for lower line reliability. Frame relay and/or point-to-point network services are provided or have been provided by various carriers, such as AT&T, Qwest, XO, and MCI WorldCom.
Frame relay networks are an example of a network that is “disparate” from the Internet and from Internet-based virtual private networks for purposes of the present invention. Another example of such a “disparate” network is a point-to-point network, such as a T
1
or T
3
connection. Although the underlying technologies differ somewhat, for purposes of the present invention frame relay networks and point-to-point networks are generally equivalent in important ways, such as the conventional reliance on manual switchovers when traffic must be redirected after a connection fails, and their implementation distinct from the Internet. A frame relay permanent virtual circuit is a virtual point-to-point connection. Frame relays are used as examples throughout this document, but the teachings will also be understood in the context of point-to-point networks.
A frame relay or point-to-point network may become suddenly unavailable for use. For instance, both MCI WorldCom and AT&T users have lost access to their respective frame relay networks during major outages. During each outage, the entire network failed. Loss of a particular line or node in a network is relatively easy to work around. But loss of an entire network creates much larger problems.
Tools and techniques to permit continued data transmission after loss of an entire frame relay network that would normally carry data are discussed in U.S. patent application Ser. No. 10/034,197 filed Dec. 28, 2001 and incorporated herein. The '197 application focuses on architectures involving two or more “private” networks in parallel, whereas the present application focuses on architectures involving disparate networks in parallel, such as a proprietary frame relay network and the Internet. Note that the term “private network” is used herein in a manner consistent with its use in the '197 application (which comprises frame relay and point-to-point networks), except that a “virtual private network” as discussed herein is not a “private network”. Virtual private networks are Internet-based, and hence disparate from private networks, i.e., from frame relay and point-to-point networks. To reduce the risk of confusion that might arise from misunderstanding “private network” to comprise “virtual private network” herein, virtual private networks will be henceforth referred to as VPNs. Other differences and similarities between the present application and the '197 application will also be apparent to those of skill in the art on reading the two applications.
Various architectures involving multiple networks are known in the art. For instance,
FIG. 1
illustrates prior art configurations involving two frame relay networks for increased reliability; similar configurations involve one or more point-to-point network connections. Two sites
102
transmit data to each other (alternately, one site might be only a data source, while the other is only a data destination). Each site has two border routers
105
. Two frame relay networks
106
,
108
are available to the sites
102
through the routers
105
. The two frame relay networks
106
,
108
have been given separate numbers in the figure, even though each is a frame relay network, to emphasize the incompatibility of frame relay networks provided by different carriers. An AT&T frame relay network, for instance, is incompatible—in details such as maximum frame size or switching capacity—with an MCI WorldCom frame relay network, even though they are similar when one takes the broader view that encompasses disparate networks like those discussed herein. The two frame relay providers have to agree upon information rates, switching capacities, frame sizes, etc. before the two networks can communicate directly with each other.
A configuration like that shown in
FIG. 1
may be actively and routinely using both frame relay networks A and B. For instance, a local area network (LAN) at site
1
may be set up to send all traffic from the accounting and sales departments to router A
1
and send all traffic from the engineering department to router B
1
. This may provide a very rough balance of the traffic load between the routers, but it does not attempt to balance router loads dynamically in response to actual traffic and thus is not “load-balancing” as that term is used herein.
Alternatively, one of the frame relay networks may be a backup which is used only when the other frame relay network becomes unavailable. In that case, it may take even skilled network administrators several hours to perform the steps needed to switch the traffic away from the failed network and onto the backup network, unless the invention of the '197 application is used. In general, the necessary Private Virtual Circuits (PVCs) must be established, routers at each site
102
must be reconfigured to use the correct serial links and PVCs, and LANs at each site
102
must be reconfigured to point at the correct router as the default gateway.
Although two private networks are shown in
FIG. 1
, three or more such networks could be employed, with similar considerations coming into play as to increased reliability, limits on load-balancing, the efforts needed to switch traffic when a network fails, and so on. Likewise, for clarity of illustration
FIG. 1
shows only two sites, but three or more sites could communicate through one or more private networks.
FIG. 2
illustrates a prior art configuration in which data is normally sent between sites
102
over a private network
106
. A failover box
202
at each site
102
can detect failure of the network
106
and, in response to such a failure, will send the data instead over an ISDN link
204
while the network
106
is down. Using an ISDN link
204
as a backup is relatively easier and less expensive than using another private network
106
as the backup, but generally provides lower throughput. The ISDN link is an example of a point-to-point or leased line network link.
FIG. 3
illustrates prior art configurations involving two private networks for increased relia
Bhaskar Ragula
Datta Sanchaita
Marcelo Melvin
Ragula Systems
Thorpe North & Western LLP
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