Multiplex communications – Network configuration determination
Reexamination Certificate
2001-03-01
2004-11-30
Pham, Chi (Department: 2667)
Multiplex communications
Network configuration determination
C370S255000, C370S258000, C370S406000
Reexamination Certificate
active
06826158
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to broadband communication services, and more particularly to network configuration of metropolitan area communication networks laid out in rings managed according to a spanning tree protocol.
2. Description of Related Art
In a metropolitan area, fiber optic cables are typically installed in rings to provide an alternate route diverse path in the case of physical failure or interruption of a fiber optic link. Some of the fiber or fiber transmission capacity in each ring is reserved for use in the face of such a failure. The rules used by the networking equipment to react to such failures are usually governed by protocols that assume that the network is configured as a ring or as a set of interconnected rings.
In an enterprise data network, fiber optic connections between packet switches are usually made point to point in a ‘redundant, dual-homed, tree like’ topology to facilitate rapid reconfiguration with the minimum loss of service. The revised spanning tree protocol under standardization in IEEE 802.1 is a suitable protocol for establishing the failover rules in the network. The recently completed link aggregation standard, IEEE Std. 802.3ad, is another—providing for resiliency of parallel links.
A leading protocol deployed in metropolitan area networks is SONET (Synchronous Optical NETwork). SONET is a digital transmission technology that provides high availability communication between switching nodes. In networks comprising communicating switching nodes connected by fiber links in a ring topology, SONET provides protection against the loss of communications between any pair of nodes due to failure of links or intervening nodes by using the alternate path in the ring topology.
While other network topologies, e.g. meshes, are capable of providing high availability through redundancy, fiber rings are especially important because (a) their simple topology lends itself to simple fast protection switching arrangements (b) wide deployment of SONET means fiber is often available and operationally configured in ring topologies.
Unfortunately deployment of SONET in a network comes at the expense of fully half the potential bandwidth of the fiber ring. An alternative would be to use only the fiber between a pair of nodes to support communication between them. This permits ‘serial reuse’ of the fiber ring to carry communication between other nodes. Such an approach is particularly attractive when data traffic is being carried. Unlike telephone traffic, data traffic, particularly that generated by TCP in the TCP/IP protocol suite, will adjust to increases or decreases in available transmission capacity. Serial reuse thus makes best use of the available resources in the normal case when failure has not occurred, while allowing the redundant connectivity of the ring to protect against failure.
The problem to be solved, then, is to make the best use of fiber rings for carrying IP (Internet Protocol) data traffic between nodes on the rings while retaining the benefits of the present SONET arrangements, notably (a) very rapid failover to backup links and switches typically within 50 milliseconds of a failure (b) timely delivery of traffic.
One available protocol is known as SRP (Serial Reuse Protocol) developed by Cisco Systems, Inc., San Jose, Calif., to support packet services on fiber rings. SRP is new media access protocol, providing mechanisms for ‘healing’ the ring in cases of failure, for determining where nodes (identified by their media access (MAC) address) are on the ring, and for confining traffic between the nodes to just that portion of the ring to allow reuse. Part of the operation of SRP gives priority to traffic already circulating on the ring (as opposed to traffic joining the ring) to ensure timeliness of delivery. Other organizations and individuals have also proposed similar services, introducing new protocols to provide frame relay like services on fiber rings. These solutions have the disadvantage that it is necessary to build special purpose hardware to support them.
Some proposals only work in ring topologies, or at least in topologies of interconnected rings. Growing the bandwidth of such a network beyond that naturally provided by a single ring typically involves the development of additional equipment supporting the specialized hardware, and may not be possible without disrupting the service provided by the ring.
It is desirable therefore to provide a network topology that is scalable and efficient as uses of networking are expanding, and which takes advantage of the existing deployed media arranged for ring based protocols in metropolitan area networks.
SUMMARY
This invention comprises a method for configuring a network, and a network configured according to such method, in which a communication links laid out in a ring in a metropolitan area are partitioned into link segments, and managed according to a spanning tree protocol. In various embodiments, the switches are configured according to the methods described above, establishing unique, mesh or tree type network configurations suitable for application to communication media arranged to support ring based protocols.
The method is used for connecting communication links arranged in a plurality of rings, which traverse a plurality of collocation sites in a metropolitan area. The method comprises configuring switches in the plurality of collocation sites to partition rings in the plurality of rings into a plurality of link segments providing point to point paths between switches at collocation sites in the plurality of collocation sites. The switches and link segments are managed according to a spanning tree protocol.
In one embodiment of the invention, the configuring of switches includes allocating a first set of the link segments as a first ring and a second set of the link segments as a second ring, breaking the first and second rings by blocking transmission on a link segment in the first ring between the first pair of collocation sites, and by blocking transmission on a link segment in the second ring between a second pair of collocation sites. In addition, the method includes cross-connection the first and second rings by a communication link. The communication link used for cross-connection in various embodiments is not part of the first and second rings, but consists of additional lengths of communication medium which extend between collocation sites in the first and second rings, such as other link segments of the same type of media, or other kinds of communication channels, such as high bandwidth wireless connections, or others. In one embodiment, the collocation sites in the first and second rings which are coupled by said communication link consists of collocation sites in which the first and second rings are broken. An ideogram illustrating this concept for heuristic purposes is shown in FIG.
2
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In one embodiment, the method includes aggregating a plurality of link segments between switches in different collocation sites to provide a single logical link with higher bandwidth between the collocation sites.
According to another embodiment of the invention, a metropolitan area network is provided. The metropolitan area network comprises a plurality of communication links, such as fiber-optic cable, arranged in a plurality rings which traverse a plurality of collocation sites in the metropolitan area. A plurality of switches is provided in the plurality of collocation sites, which are configured to partition rings in the plurality of rings into a plurality of link segments providing point to point paths between switches at the collocation sites. The plurality of switches and communication links is managed according to a spanning tree protocol.
According to one aspect of the invention, a communication system is provided using technology that has been developed within the communications, enterprise data networking, electronic commerce, and carrier service provider industries to provide service in new ways particularl
Jain Vipin
Seaman Michael J.
Haynes Beffel & Wolfeld LLP
Ly Anh Vu H
Onfiber Communications, Inc.
Pham Chi
LandOfFree
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