Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
2001-10-09
2003-04-22
Ton, Dang (Department: 2666)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
Reexamination Certificate
active
06553030
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method and apparatus for data communication in a network.
BACKGROUND OF THE INVENTION
Conventionally, integrating different network protocols or media types is complex and difficult. Routers and gateways may be used for protocol conversion and for managing quality of services. However, these techniques and devices tend to be complex, resource intensive, difficult and time consuming to implement and slow in operation.
In conventional high speed networks, data is typically transmitted in a single format, e.g., ATM, frame relay, PPP, Ethernet, etc. Each of these various types of formats generally requires dedicated hardware and communication paths along which to transmit the data. The principle reason for this is that the communication protocols and signaling techniques tend to be different for each format. For example, in a transmission using an ATM format, data cells are sent from a source to a destination along a predetermined path. Headers are included with each cell for identifying the cell as belonging to a set of associated data. In such a transmission, the size of the data cell being sent is known, as well as the beginning and end of the cell. In operation, cells are sent out, sometimes asynchronously, for eventual reassembly with the other associated data cells of the set at a destination. Idle times may occur between transmissions of data cells.
For a frame relay format, communications are arranged as data frames. Data is sent sometimes asynchronously for eventual reassembly with other associated data packets at a destination. Idle time may occur between the transmissions of individual frames of data. The transmission and assembly of frame relay data, however, is very different from that of ATM transmissions. For example, the frame structures differ as well as the manner in which data is routed to its destination.
Some network systems require that connections be set up for each communication session and then be taken down once the session is over. This makes such systems generally incompatible with those in which the data is routed as discrete packets. A Time Division Multiplex (TDM) system, for example, requires the setting up of a communication session to transmit data. While a communication session is active, there is no time that the communication media can be considered idle, unlike the idle periods that occur between packets in a packet-based network. Thus, sharing transmission media is generally not possible in conventional systems. An example of this type of protocol is “Point-to-Point Protocol” (PPP). Internet Protocol (IP) is used in conjunction with PPP in manner known as IP over PPP to forward IP packets between workstations in client-server networks.
It would be useful to provide a network system that allows data of various different formats to be transmitted from sources to destinations within the same network and to share transmission media among these different formats.
As mentioned, some network systems provide for communication sessions. This scheme works well for long or continuous streams of data, such as streaming video data or voice signal data generated during real-time telephone conversations. However, other network systems send discrete data packets that may be temporarily stored and forwarded during transmission. This scheme works well for communications that are tolerant to transmission latency, such as copying computer data files from one computer system to another. Due to these differences in network systems and types of data each is best suited for, no one network system is generally efficient and capable of efficiently handling mixed streams of data and discrete data packets.
Therefore, what is needed is a network system that efficiently handles both streams of data and discrete data packets.
Further, within conventional network systems, data packets are received at an input port of a multi-port switch and are then directed to an appropriate output port based upon the location of the intended recipient for the packet. Within the switch, connections between the input and output ports are typically made by a crossbar switch array. The crossbar array allows packets to be directed from any input port to any output port by making a temporary, switched connection between the ports. However, while such a connection is made and the packet is traversing the crossbar array, the switch is occupied. Accordingly, other packets arriving at the switch are blocked from traversing the crossbar. Rather, such incoming packets must be queued at the input ports until the crossbar array becomes available.
Accordingly, the crossbar array limits the amount of traffic that a typical multi-port switch can handle. During periods of heavy network traffic, the crossbar array becomes a bottleneck, causing the switch to become congested and packets lost by overrunning the input buffers.
An alternate technique, referred to as cell switching, is similar except that packets are broken into smaller portions called cells. The cells traverse the crossbar array individually and then the original packets are reconstructed from the cells. The cells, however, must be queued at the input ports while each waits its turn to traverse the switch. Accordingly, cell switching also suffers from the drawback that the crossbar array can become a bottleneck during periods of heavy traffic.
Another technique, which is a form of time-division multiplexing, involves allocating time slots to the input ports in a repeating sequence. Each port makes use of the crossbar array during its assigned time slots to transmit entire data packets or portions of data packets. Accordingly, this approach also has the drawback that the crossbar array can become a bottleneck during periods of heavy traffic. In addition, if a port does not have any data packets queued for transmission when its assigned time slot arrives, the time slot is wasted as no data may be transmitted during that time slot.
Therefore, what is needed is a technique for transmitting data packets in a multi-port switch that does not suffer from the afore-mentioned drawbacks. More particularly, what is needed is such a technique that avoids a crossbar array from becoming a traffic bottleneck during periods of heavy network traffic.
Under certain circumstances, it is desirable to send the same data to multiple destinations in a network. Data packets sent in this manner are conventionally referred to as multi-cast data. Thus, network systems must often handle both data intended for a single destination (conventionally referred to as uni-cast data) and multi-cast data. Data is conventionally multi-cast by a multi-port switch repeatedly sending the same data to all of the destinations for the data. Such a technique can be inefficient due to its repetitiveness and can slow down the network by occupying the switch for relatively long periods while multi-casting the data.
Therefore, what is needed is an improved technique for handling both uni-cast and multi-cast data traffic in a network system.
Certain network protocols require that switching equipment discover aspects of the network configuration in order to route data traffic appropriately (this discovery process is sometimes referred to as “learning”). For example, an Ethernet data packet includes a MAC source address and a MAC destination address. The source address uniquely identifies a particular piece of equipment in the network (i.e. a network “node”) as the originator of the packet. The destination address uniquely identifies the intended recipient node (sometimes referred to as the “destination node”). Typically, the MAC address of a network node is programmed into the equipment at the time of its manufacture. For this purpose, each manufacturer of network equipment is assigned a predetermined range of addresses. The manufacturer then applies those addresses to its products such that no two pieces of network equipment share an identical MAC address.
A conventional Ethernet switch must learn the MAC addresses of the nodes in the network an
Gyllenhammer Carl
Kothary Piyush
Kottapalli Sreenivas
Ku Ed
Yarlagadda Ramesh
Harper Kevin C.
Maple Optical Systems Inc.
Stevens David R.
Ton Dang
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