This invention relates to computer networking equipment, and more particularly to stackable repeaters for dual-speed networks.
Local-Area Networks (LAN""s) using the Ethernet standard can be found in many offices today. The original 10 Mbps (10M) Ethernet standard has been extended to create the Fast Ethernet standard, operating at 100 Mbps (100M). While newly-installed network adapters usually can operate at 100M, much older equipment remains that still operates at the lower 10M speed. Thus mixed-speed networks are common as networks gradually replace older 10M equipment with 100M equipment.
To reduce the cost and ease the transition to higher-speed LAN""s, dual-speed network equipment is available. Low-speed equipment can be connected to dual-speed network equipment and still operate at the lower 10M speed, while high-speed equipment operates at the higher 100M speed.
FIG. 1 shows a dual-speed network with an external network switch. Repeaters 10, 12, 14 are stackable repeaters that are stacked together. Two separate network busses 15, 17 connect repeaters 10, 12, 14. One network bus 15 operates at 10 Mbps, while the other network bus 17 operates at 100 Mbps. The network busses 15, 17 are stackable busses such as chassis backplane buses or stacking cables.
Repeaters 10, 12, 14 are dual-speed repeaters. Each repeater 10, 12, 14 contains two independent repeater circuitsxe2x80x94one that operates at 10M, and the other operating at 100M. Ports operating at 10M connect only to the 10M-repeater circuitry and the 10M stacking network bus 15, while ports operating at 100M connect only to the 100M-repeater circuitry and the 100M stacking network bus 17.
Each repeater has four ports that connect to dual-speed 10/100M stations, 10M-only stations, or 100M-only stations. These are shown as stations S1-S10. Stations can be client machines, servers, gateways, and other network devices. Network-management software can set the speed of each repeater port to either 10M or 100M, or N-way auto-negotiation is used to sense the speed of the attached station and configure the port accordingly. N-way auto-negotiation is defined by the 100Base-T standard.
When any of the 10M stations connected to repeaters 10, 12, 14 send a packet, the data is repeated to all other ports on repeaters 10, 12, 14 that are also configured for 10M. Data is sent over the 10M stackable network bus 15 coupled to repeaters 10, 12, 14. Likewise, when any of the 100M stations connected to repeaters 10, 12, 14 send a packet, the data is repeated to all other ports on repeaters 10, 12, 14 that are also configured for 100M. However, data sent from a 10M port is not repeated to any of the 100M ports, and data sent from a 100M port is not repeated to any 10M port by the repeaters. Repeaters 10, 12, 14 essentially act as two independent, isolated networks, one at 10M, the other at 100M.
Data from the 10M network must be sent over a network bridge or switch to the 100M network since it is not directly transferred by repeaters 10, 12, 14. Network switch 16 connects to a port of repeater 10 that is configured for 10M operation. Network switch 16 also connects to a 100M-configured port of repeater 12. Network switch 16 stores incoming packets received from one side of the network and forwards (transmits) the stored packets to the other side of the network. Data cannot simply be repeated since the two sides of the network operate at different speeds. Entire packets are buffered.
Only one network switch or bridge can connect the 10M side of the network to the 100M side. If two bridges were connected between the same 10M and 100M sides, then a loop would occur. Data packets could be sent around endlessly in such as loop. A spanning-tree algorithm is sometimes used by network-management software to detect and break such loops.
FIG. 2 shows an internal bridge for connecting 10M and 100M networks. Rather than using the ports of repeater 10, bridge 18 connects directly to stackable network busses 15, 17, the backplane buses of a stack of repeaters. Bridge 18 is a 2-port network switch that stores entire packets received from either bus 15 or bus 17, and re-transmits the packets to the other stackable network bus 17 or 15. Bridge 18 is contained within stackable-repeater unit 20 that includes repeater 10.
FIG. 3 shows an internal bridge connected to bridging ports of repeaters. Stackable repeater unit 22 contains repeaters 10, 12, and bridge 18. Stackable repeater unit 22 can be connected to other repeater units in a stack through stackable network busses 15, 17. Each repeater 10, 12 connects with up to four stations that are each configured for either 10M or 100M operation as described for FIG. 1. However, each repeater 10, 12 also contains an additional bridge port that connects to internal bridge 18. The bridge port on repeater 10 is configured for 10M operation, and is connected to 10M bus 15 by repeater 10, while the bridge port on repeater 12 is connected to 100M bus 17 by repeater 12.
Bridge 18 can be directly connected to repeaters 10, 12 using a digital connection. No long cables need to be driven, so large analog line drivers and receivers are not necessary as with bridge 18 of FIG. 2. Bridge 18 can be connected to repeaters 10, 12 at the controller level rather than the physical layer. This reduces cost.
While such an internal bridge is useful and more cost-effective than an external bridge, repeater units are no longer identical. Only one repeater unit in the stack with the internal bridge can be used; otherwise loops can occur. Other repeater units in the stack must not contain bridges. Having the repeater units in a stack be non-identical is problematic and causes confusion for network administrators and technicians. Simply disabling the bridge for the other repeater units is wasteful.
What is desired is a stackable repeater unit that can operate at two network speeds. A 10M/100M dual-speed repeater is desired. It is desired to have identical repeater units in a stack while still providing only one bridge between the 10M and 100M networks. It is desired to operate disabled bridges in repeater units for other useful purposes rather than simply disabling them to avoid looping.
A dual-speed stackable repeater unit has a first connection to a first stacking bus that operates at a first network speed and a second connection to a second stacking bus that operates at a second network speed. A plurality of ports connect to network stations. The plurality of ports include first ports operating at the first network speed and second ports operating at the second network speed.
An internal repeater is coupled to the first and second stacking buses by the first and second connections. It repeats data received from one of the first ports to all other first ports and to the first stacking bus, and it repeats data received from one of the second ports to all other second ports and to the second stacking bus.
An internal bridge is coupled to the first stacking bus and is coupled to the second stacking bus. It stores data packets from the first stacking bus and forwards the stored data packets to the second stacking bus. A buffered cascading port is coupled to the internal bridge. It receives data packets from an external repeater. The internal bridge forwards the packets to the first and second stacking buses.
A switch is coupled between the internal bridge and the second stacking bus. It disconnects the internal bridge from the second stacking bus when the repeater unit is configured as a cascading unit, but the switch connects the internal bridge to the second stacking bus when the repeater unit is configured as a linking unit.
The internal bridge in the repeater unit links the first stacking bus to the second stacking bus when the repeater unit is configured as a linking unit, but the internal bridge in the repeater unit does not link the first stacking bus to the second stacking bus when the repeater unit is configured as a cascading unit. Thus the internal bridge buffers packets from the external repeater on the buffered cascading port.
In further aspects of the invention exactly one repeater unit connected to the first and second stacking busses is configured as a linking unit, while all other repeater units connected to the first and second stacking busses are configured as a cascading units.
In other aspects multiple buffered cascading ports are coupled to external repeaters. Each of the multiple buffered cascading ports is coupled to the internal bridge. Thus multiple external repeaters are coupled to the internal bridge.