Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
2001-05-15
2004-02-24
Ton, Dang (Department: 2666)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S389000, C370S395700, C370S471000, C370S476000
Reexamination Certificate
active
06697368
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to network switches.
2. Background Art
A network switch is a device that provides a switching function (i.e., determines a physical path) in a data communications network. Switching involves transferring information, such as digital data packets or frames, among entities of the network. Typically, a switch is a computer having a plurality of circuit cards coupled to a backplane. In the switching art, the circuit cards are typically called “blades.” The blades are interconnected by a “switch fabric.” Each blade includes a number of physical ports that couple the switch to the other network entities over various types of media, such as Ethernet, FDDI (Fiber Distributed Data Interface), or token ring connections. A network entity includes any device that transmits and/or receives data packets over such media.
The switching function provided by the switch typically includes receiving data at a source port from a network entity and transferring the data to a destination port. The source and destination ports may be located on the same or different blades. In the case of “local” switching, the source and destination ports are on the same blade. Otherwise, the source and destination ports are on different blades and switching requires that the data be transferred through the switch fabric from the source blade to the destination blade. In some case, the data may be provided to a plurality of destination ports of the switch. This is known as a multicast data transfer.
Switches operate by examining the header information that accompanies data in the data frame. The header information includes the international standards organization (ISO) 7-layer OSI (open-systems interconnection model). In the OSI model, switches generally route data frames based on the lower level protocols such as Layer 2 or Layer 3. In contrast, routers generally route based on the higher level protocols and by determining the physical path of a data frame based on table look-ups or other configured forwarding or management routines to determine the physical path (i.e., route).
Ethernet is a widely used lower-layer network protocol that uses broadcast technology. The Ethernet frame has six fields. These fields include a preamble, a destination address, source address, type, data and a frame check sequence. In the case of an ethernet frame, the digital switch will determine the physical path of the frame based on the source and destination addresses. Standard Ethernet operates at a ten Mbit/s data rate. Another implementation of Ethernet known as “Fast Ethernet” (FE) has a data rate of 100 Megabits/s. Yet another implementation of FE operates at 10 Gigabits/sec.
A digital switch will typically have physical ports that are configured to communicate using different protocols at different data rates. For example, a blade within a switch may have certain ports that are 10 Mbit/s, or 100 Mbit/s ports. It may have other ports that conform to optical standards such as SONET and are capable of such data rates as 10 gigabits per second.
A performance of a digital switch is often assessed based on metrics such as the number of physical ports that are present, and the total bandwidth or number of bits per second that can be switched without blocking or slowing the data traffic. A limiting factor in the bit carrying capacity of many switches is the switch fabric. For example, one conventional switch fabric was limited to 8 gigabits per second per blade. In an eight blade example, this equates to 64 gigabits per second of traffic. It is possible to increase the data rate of a particular blade to greater than 8 gigabits per second. However, the switch fabric would be unable to handle the increased traffic.
It is desired to take advantage of new optical technologies and increase port densities and data rates on blades. However, what is needed is a switch and a switch fabric capable of handling higher bit rates and providing a maximum aggregate bit carrying capacity well in excess of conventional switches.
BRIEF SUMMARY OF THE INVENTION
The present invention provides a high-performance network switch. Serial link technology is used in a switching fabric. Serial data streams, rather than parallel data streams, are switched in a switching fabric. Blades output serial data streams in serial pipes. A serial pipe can be a number of serial links coupling a blade to the switching fabric. The serial data streams represent an aggregation of input serial data streams provided through physical ports to a respective blade. Each blade outputs serial data streams with in-band control information in multiple stripes to the switching fabric.
In one embodiment, the serial data streams carry packets of data in wide striped cells across multiple stripes. Wide striped cells are encoded. In-band control information is carried in one or more blocks of a wide cell. For example, the initial block of a wide cell includes control information and state information. Further, the control information and state information is carried in each stripe. In particular, the control information and state information is carried in each subblock of the initial block of a wide cell. In this way, the control information and state information is available in-band in the serial data streams (also called stripes). Control information is provided in-band to indicate traffic flow conditions, such as, a start of cell, an end of packet, abort, or other error conditions.
A wide cell has one or more blocks. Each block extends across five stripes. Each block has a size of twenty bytes made up of five subblocks each having a size of four bytes. In one example, a wide cell has a maximum size of eight blocks (160 bytes) which can carry a 148 bytes of payload data and 12 bytes of in-band control information. Packets of data for full-duplex traffic can be carried in the wide cells at a 50 Gb/sec rate in each direction through one slot of the digital switch. According to one feature, the choice of maximum wide cell block size of 160 bytes as determined by the inventors allows a 4×10 Gigabit/sec Ethernet (also called 4×10 GE) line rate to be maintained through the backplane interface adapter. This line rate is maintained for Ethernet packets having a range of sizes accepted in the Ethernet standard including, but not limited to, packet sizes between 84 and 254 bytes.
In one embodiment, a digital switch has a plurality of blades coupled to a switching fabric via serial pipes. The switching fabric can be provided on a backplane and/or one or more blades. Each blade outputs serial data streams with in-band control information in multiple stripes to the switching fabric. The switching fabric includes a plurality of cross points corresponding to the multiple stripes. Each cross point has a plurality of port slices coupled to the plurality of blades. In one embodiment five stripes and five five cross points are used. Each blade has five serial links coupled to each of the five cross points respectively. In one example implementation, the serial pipe coupling a blade to switching fabric is a 50 Gb/s serial pipe made up of five 10 Gb/s serial links. Each of the 10 Gb/s serial links is coupled to a respective cross point and carries a serial data stream. The serial data stream includes a data slice of a wide cell that corresponds to one stripe.
In one embodiment of the present invention, each blade has a backplane interface adapter (BIA). The BIA has three traffic processing flow paths. The first traffic processing flow path extends in traffic flow direction from local packet processors toward a switching fabric. The second traffic processing flow path extends in traffic flow direction from the switching fabric toward local packet processors. A third traffic processing flow path carried local traffic from the first traffic processing flow path. This local traffic is sorted and routed locally at the BIA without having to go through the switching fabric.
The BIA includes one or more receivers, wide cell
Chang Andrew
Patel Ronak
Wong Ming G
Foundry Networks Inc.
Hom Shick
Sterne Kessler Goldstein & Fox PLLC
Ton Dang
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