Method and apparatus for providing a multiple-ring token ring hub expansion

A method and apparatus for expanding multiple token rings by interconnecting multiple multi-ring hubs. The computer networking hubs of the present invention are operable to support multiple token ring networks. In addition, the networking hubs of the present invention include a cable interface configured to interconnect the multiple token ring networks to a single cable interconnected with a separate hub, which is also configured to support multiple token rings. As a result, multiple token rings are able to be expanded across multiple networking hubs. In one embodiment, the networking hubs of the present invention are further operable to receive signals from remote nodes via a first signal mode. The signals are converted to a second signal mode to be transmitted internally. To transmit the signals to a separate hub, the signals are re-converted to the first signal mode and transmitted to a separate networking hub via the first signal mode. Transmitting between the separate hubs via the first signal mode helps to preserve the signal integrity and decrease the cross-talk between the wires of the cable interconnecting the hubs.

FIELD OF THE INVENTION 
The present invention relates generally to computer networking systems, and 
in particular, relates to expanding multiple token rings by 
interconnecting multiple multi-ring hubs. 
BACKGROUND OF THE INVENTION 
Several computer systems in a local area network (LAN) may be joined 
together by a single component commonly referred to as a hub. The hub 
typically serves as common network termination point for multiple computer 
systems, as is shown in FIG. 1. 
The computer systems provided in the LAN (otherwise referred to as Nodes, 
when interconnected to a hub) may communicate with each other via the hub. 
For example, node 12 may send a signal addressed to node 14. The signal 
will first be transmitted from the node 12 to the hub 10. The signal will 
then be transmitted from the hub to node 14. 
The hub 10 may also provide the nodes with access to other separate LANs. 
That is, the hub 10 may be connected with a cable which is connected to a 
separate second hub, which provides access to a second LAN. As a result, 
the nodes attached to hub 10 can also send messages and signals to the 
second LAN via the hub 10. 
A network architecture commonly implemented using a hub is referred to as 
the token ring architecture. The token ring network architecture uses a 
ring network topology and a token-passing strategy to control access to 
the network. 
A single token ring implemented in a hub may be extended into a larger 
token ring by joining two or more hubs. The technique of joining multiple 
hubs is sometimes referred to as cascading. In the prior art, however, the 
interconnecting of multiple hubs may only be used to extend a single token 
ring. 
On the other hand, additional intelligence may be implemented on the hub 10 
to support multiple separate LANs (i.e., separate token rings). In such a 
case, the hub is referred to a multi-ring hub. For example, in FIG. 1, if 
hub 10 is a multi-ring hub, nodes 12 and 14 may makeup a first token ring, 
while nodes 14 and 18 may provide a second token ring. 
However, the prior art does not provide a method for extending multiple 
token rings by joining a set of multi-ring hubs. As such, there is a need 
for a method and apparatus of extending multiple separate token rings by 
cascading multi-ring hubs. 
SUMMARY OF THE INVENTION 
The present invention provides a method and apparatus for expanding 
multiple token rings by interconnecting multiple multi-ring hubs. The 
computer networking hubs of the present invention are operable to support 
multiple token ring networks. In addition, the networking hubs of the 
present invention include a cable interface configured to interconnect the 
multiple token ring networks to a single cable interconnected with a 
separate hub, which is also configured to support multiple token rings. As 
a result, multiple token rings are able to be expanded across multiple 
networking hubs. 
In one embodiment, the networking hubs of the present invention are further 
operable to receive signals from remote nodes via a first signal mode. The 
signals are converted to a second signal mode to be transmitted 
internally. To transmit the signals to a separate hub, the signals are 
re-converted to the first signal mode and transmitted to a separate 
networking hub via the first signal mode. Transmitting between the 
separate hubs via the first signal mode helps to preserve the signal 
integrity and decrease the cross-talk between the wires of the cable 
interconnecting the hubs.

DETAILED DESCRIPTION 
A method and apparatus are described for extending multiple separate token 
rings by cascading multiple multi-ring hubs. In the following description, 
numerous specific details are set forth in order to provide a thorough 
understanding of the present invention. It will be apparent, however, to 
one of ordinary skill in the art that the present invention may be 
practiced without these specific details. In other instances, well-known 
standards, structures, and techniques have not been shown in order not to 
unnecessarily obscure the present invention. 
FIG. 2 illustrates the interconnection of multiple multi-ring hubs 
according to one embodiment of the present invention. As shown in FIG. 2, 
a set of token ring hubs are interconnected by a single cable 212. Each of 
the hubs may operate as multi-ring hubs. That is, the hubs are configured 
to support multiple separate token rings among the nodes interconnected 
with the respective hubs. 
In particular, as shown in the hub 210, a set of connectors 214a-214b 
provide nodes 202-204 with a point of connection to hub 210. The nodes are 
typically interconnected to the hub via an analog line such as a telephone 
line. As such each of the connectors 214a-214b are typically coupled to 
circuit logic 216a-216b configured to convert the data and signals 
received from the nodes into digital information. Once converted into 
digital information, the data and signals can be transmitted throughout 
hub 210. 
In addition, in the case of multi-ring hubs, the logic 216a-216b coupled to 
the connectors 214a-214b may further be configured to connect the 
respective node with a particular token ring path. For example, in hub 
210, the logic 216a may be configured to connect node 202 with the token 
ring 222a, and the logic 216b may be configured to connect node 204 with 
the token ring 222b. 
The present invention enables the expansion of multiple token rings of a 
multi-ring hub by interconnecting multiple multi-ring hubs. For example, 
the present invention may enable a first group of nodes attached to hub 
230 (e.g., nodes 232-234) to be interconnected with the token ring 222a, 
which is expanded from hub 210. In addition, a second group of nodes 
attached to hub 230 (e.g., nodes 236-238) may be interconnected with the 
token ring 222b, which is also expanded from hub 210. As a result, the 
token rings 222a and 222b are expanded throughout several hubs, which in 
effect may allow easier upgrades in the field as users requirements 
change. 
In one embodiment of the present invention, the expansion multiple token 
rings across multi-ring hubs is achieved by providing a unique cable 
interface 206 at each of the multi-ring hubs. In particular, in one 
embodiment, the cable interface 206 is configured to keep the token rings 
separate when transmitting the token ring signals between the multi-ring 
hubs. 
In one embodiment, the cable interface 206 of the present invention has at 
least one cable connector 208. The cable connector of the present 
invention is configured to connect with a cable 212 having multiple wires 
242.sub.a -242.sub.b. Each separate wire in the cable is able to transmit 
signals and data corresponding to a separate token ring. 
The cable connector 208 individually interconnects multiple physical token 
rings of a hub with corresponding wires of the cable 212. For example, the 
cable connector 208 of the hub 210 may interconnect token ring 222a with 
the wire 242a of cable 212, and interconnect token ring 222b with the wire 
242b of cable 212, etc. In alternative embodiment, additional cable 
connectors may be provided to interconnect additional cables between the 
multi-ring hubs. 
In an alternative embodiment, to better preserve the signal integrity of 
the multiple token rings and prevent cross-talk when transmitting across 
the wires, circuit logic 218 is provided in the cable interface 206. The 
circuit logic 218 may perform a logic level translation on the token-ring 
signals before the signals are transmitted across the wires. In one 
embodiment, the signals are re-converted from digital to analog signals. 
The signals may also be further conditioned by the logic 218. For example, 
in one embodiment, the token ring signals may be re-timed by a 
phase-lock-loop circuit to place the signals within pre-determined bit 
cell boundary times. The re-timing of the signals helps re-correct the 
encoding of the signals (e.g. re-correct the Manchester encoding). 
In alternative embodiments, the present invention may be applicable to 
implementations of the invention in integrated circuits or chip sets, 
wireless implementations, switching systems products and transmission 
systems products. For purposes of this application, the terms switching 
systems products shall be taken to mean private branch exchange (PBXs), 
central office switching systems that interconnect subscribers, 
toll/tandem switching systems for interconnecting trunks between switching 
centers, and broadband core switches found at the center of a service 
provider's network that may be fed by broadband edge switches or access 
muxes, and associated signaling, and support systems and services. 
The term transmission systems products shall be taken to mean products used 
by service providers to provide interconnection between their subscribers 
and their networks such as loop systems, and which provide multiplexing, 
aggregation and transport between a service provider's switching systems 
across the wide area, and associated signaling and support systems and 
services. 
The logic of expanding multiple token rings by cascading multiple 
multi-ring hubs may alternatively be provided, at least in part, as a 
computer program product which may include a storage medium having stored 
thereon instructions which can be used to program a computer to perform a 
process according to the present invention. The storage medium can 
include, but is not limited to, any type of disk including floppy disks, 
optical disks, CD-ROMs, and magneto-optical disks, ROMs, RAMs, EPROMs, 
EEPROMs, magnet or optical cards, or any type of media suitable for 
storing electronic instructions. 
Furthermore, in the foregoing specification, the invention has been 
described with reference to specific exemplary embodiments. It will, 
however, be evident that various modifications and changes may be made 
without departing from the broader spirit and scope of the invention. The 
specification and drawings are, accordingly, to be regarded in an 
illustrative rather than restrictive sense.