Multiplex communications – Fault recovery – Bypass an inoperative switch or inoperative element of a...
Reexamination Certificate
1998-05-28
2001-07-31
Kizou, Hassan (Department: 2662)
Multiplex communications
Fault recovery
Bypass an inoperative switch or inoperative element of a...
C370S216000, C370S218000, C370S219000, C370S220000, C370S221000, C370S242000, C370S248000
Reexamination Certificate
active
06269076
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to data communication networks and more particularly relates to a method of creating and resolving split VLANs utilizing a NMS.
BACKGROUND OF THE INVENTION
Currently, there is a growing trend to make Asynchronous Transfer Mode (ATM) networking technology the basis of future global communications. ATM has already been adopted as a standard for broadband communications by the International Telecommunications Union (ITU) and by the ATM Forum, a networking industry consortium.
Asynchronous Transfer Mode
ATM originated as a telecommunication concept defined by the Comite Consulatif International Telegraphique et Telephonique (CCITT), now known as the ITU, and the American National Standards Institute (ANSI) for carrying user traffic on any User to Network Interface (UNI) and to facilitate multimedia networking between high speed devices at multi-megabit data rates. ATM is a method for transferring network traffic, including voice, video and data, at high speed. Using this connection oriented switched networking technology centered around a switch, a great number of virtual connections can be supported by multiple applications through the same physical connection. The switching technology enables bandwidth to be dedicated for each application, overcoming the problems that exist in a shared media networking technology, like Ethernet, Token Ring and Fiber Distributed Data Interface (FDDI). ATM allows different types of physical layer technology to share the same higher layer—the ATM layer.
More information on ATM networks can be found in the book “ATM: The New Paradigm for Internet, Intranet and Residential Broadband Services and Applications,” Timothy Kwok, Prentice Hall, 1998.
ATM uses very short, fixed length packets called cells. The first five bytes, called the header, of each cell contain the information necessary to deliver the cell to its destination. The cell header also provides the network with the ability to implement congestion control and traffic management mechanisms. The fixed length cells offer smaller and more predictable switching delays as cell switching is less complex than variable length packet switching and can be accomplished in hardware for many cells in parallel. The cell format also allows for multi-protocol transmissions. Since ATM is protocol transparent, the various protocols can be transported at the same time. With ATM, phone, fax, video, data and other information can be transported simultaneously.
ATM is a connection oriented transport service. To access the ATM network, a station requests a virtual circuit between itself and other end stations, using the signaling protocol to the ATM switch. ATM provides the User Network Interface (UNI) which is typically used to interconnect an ATM user with an ATM switch that is managed as part of the same network.
The current standard solution for routing in a private ATM network is described in Private Network Node Interface (PNNI) Phase
0
and Phase
1
specifications published by ATM Forum. The previous Phase
0
draft specification is referred to as Interim Inter-Switch Signaling Protocol (IISP). The goal of the PNNI specifications is to provide customers of ATM network equipment some level of multi-vendor interoperability.
Lan Emulation
Today, most data traffic in existing customer premises networks travels over legacy LANs. It is desirable to permit these legacy LANs and their embedded infrastructure to operate with new ATM networks currently being deployed. To enable an easier migration path to ATM, the ATM Forum has defined the LAN Emulation (LANE) specification which allows ATM networks to coexist with legacy systems. The LANE specification defines a way for an ATM network to emulate a logical Ethernet or Token Ring segment, these currently being the most popular LAN technologies.
LANE service provides connectivity between ATM capable devices and legacy LAN capable devices across an ATM network. Since LANE connectivity is defined at the MAC layer, the upper protocol layer functions of LAN applications can continue to function unchanged after the device joins an emulated LAN. This important feature protects corporate investments in legacy LAN applications. An ATM network can support multiple independent emulated LAN (ELAN) networks. A network may have one or more emulated LANs wherein each emulated LAN is separate and distinct from the others. Emulated LANs communicate via routers and bridges just as they do in legacy LANs. The emulated LAN provides communication of user data frames between its users just as in an actual legacy LAN.
Emulation over ATM networks, the LANE Version 1.0 standard drafted by the ATM Forum and incorporated herein by reference, defines the LANE architecture and a set of protocols used by the LANE entities. LANE uses a client/server model to provide its services. A diagram illustrating an example ATM network having a plurality of nodes, LESs, LECSs and LECs is shown in FIG.
1
. The network, generally referenced
10
, comprises an ATM network cloud
19
which includes a plurality of nodes (switches)
12
connected by one or more links. A plurality of edge devices
16
, which include LECs, labeled LEC #
1
through LEC #
6
are connected to the switches. A plurality of LESs labeled LES #
1
and LES #
2
are also connected to switches. In addition, a plurality of LECSs
14
labeled LECS #
1
and LECS #
2
are also connected to switches.
The entities defined by the LANE architecture include LAN Emulation Clients (LECs), a LAN Emulation Server (LES), a Broadcast and Unknown Server (BUS) and LAN Emulation Configuration Server (LECS). The LES, BUS and LECS constitute what is known as the LANE Service.
The LAN Emulation Clients (LECs) represent a set of users, as identified by their MAC addresses. A LEC emulates a LAN interface that communicates with higher layer protocols such as IP, IPX, etc. that are used by these users. To achieve this task, the LEC communicates with the LANE Services and to other LECs. LECs communicate with each other and to the LANE Services via ATM Virtual Channel Connections (VCCs). The VCCs are typically Switched Virtual Circuits (SVCs), but Permanent Virtual Connections (PVCs) might also be used for this purpose.
In order for a LEC to participate in an emulated LAN, the LEC may first communicate with an LECS. It may utilize a specific ATM address of the LECS if it knows it, or, as it typically the case, may use the well known address of the LECS to establish communications.
As described previously, the LANE Service comprises several entities: LANE Server (LES), a Broadcast and Unknown Server (BUS) and LAN Emulation Configuration Server (LECS). The LES provides Joining, Address Registration and Address Resolution services to the LECs. Note that a given LES serves only a single emulated LAN.
The LANE BUS is responsible for the distribution of the Broadcast, Multicast and unknown traffic to the LECs which is typically sent by a LEC before the ATM address has been resolved. Note that a given BUS serves only one emulated LAN.
The LECS contains the database used in determining which emulated LAN a LEC belongs to. Each LEC consults the LECS once, at the time it requests to join an emulated LAN, to determine which emulated LAN it should join. The LECS assigns the LEC to a given emulated LAN by giving the LEC the ATM address of the LES associated with that particular emulated LAN. Different policies may be utilized by the LECS in making the assignment. The assignment may be based on the LEC ATM address, the ELAN name, the LEC MAC address or any other suitable criteria. Note that the LECS serves all the emulated LANs defined for the given administrative ATM network domain.
The straightforward implementation of the LANE Version 1.0 specification includes a single LECS for the entire administrative domain and a single LES per emulated LAN. A disadvantage of this implementation is that it suffers from a single point of failure for both the LECS and the LES. Failure of the LECS prevents LE
Barkai Sharon
Shamir Yoram
Shani Sarit
3Com Corporation
Kizou Hassan
Logsdon Joe
McDonnell & Boehnen Hulbert & Berghoff
Zaretsky Howard
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