A typical data communication network is configured to operate according to a single predetermined protocol, e.g., an ethernet protocol, a token ring protocol, other LAN protocols, or an isochronous protocol. An example of an ethernet system is an implementation known as 10BASE-T which is described in the draft Nine supplement to IEEE standard 802.3, dated Nov. 15, 1989. Other examples of data communication protocols are X.25, and the Token Ring System, described for example, by IEEE Standard 802.5. Both ethernet and token ring systems convey data in packets but each uses a different media access method.
As shown in
In a token ring system, a node is permitted to transmit data only after receipt of an electronic “token.” as depicted in
Previous systems which were configured to use only a single-type protocol had the disadvantage that it was not possible to operate a mixed-protocol or “mixed-environment” system. Also, when upgrading a network system, it was necessary to upgrade the entire system and it was infeasible or wasteful to upgrade only part of the system (such as only some of the nodes or such as upgrading nodes without upgrading hubs or upgrading hubs without upgrading nodes). Additionally, when a system or system components were installed, or repaired it was necessary for the installing personnel to be familiar with the particular single protocol for which the network was configured and to make such installation, upgrade, or repair in accordance with such a single protocol. Furthermore, it was necessary that apparatus connected to the system be configured for exclusive operation in accordance with the predetermined single protocol.
The present invention includes a recognition of the problems found in previous devices. According to an embodiment of the present invention, apparatus connected to one endpoint of a network link is able to detect the protocol capability of the apparatus connected to the other end of the network link. Preferably, the first end of the network link has a capability of providing data communication under at least two different protocols and can select the appropriate protocol depending on what type of protocol capability is detected in the apparatus at the other end of the link.
Link endpoint capability detection takes advantage of the fact that different data communication protocols provide signals on the physical medium which have different characteristics. The various protocols can typically be detected by their unique timing and data patterns. According to one aspect of the invention, the network has a star topology with at least one hub and a plurality of nodes each node being connected to a hub by physical media constituting the link. The capability detection of the present invention can be performed by apparatus at either end of a link, and in particular, in a star topology network can be conducted by the hub or by any node. In one embodiment, capability detection is initiated by the hub. In a non-star topology at least one node can operate under two or more protocols and can detect the capability of another node with which it is connected.
The apparatus which initiates capability detection, according to one embodiment, transmits a signal onto the physical medium. In one embodiment, the apparatus at the far end of the link outputs, onto the physical medium, a second signal. Preferably, a second signal will be output from the apparatus at the far end of the link, regardless of whether the apparatus at the far end operates according to a first protocol or a second protocol. However, the second signal which is placed onto the physical medium at the far end of the link has either a first form or a second form, depending on whether the apparatus at the far end has a first protocol capability or a second protocol capability. This difference in signal is detected at the first end of the link and this could be used as a basis for determining the protocol capability at the far end of the link.
In another embodiment, the first apparatus outputs a first signal. The second apparatus outputs a response only if it has a first protocol capability. If no response is output, the first apparatus outputs a second signal in an attempt to elicit a response according to a second protocol. This process can be repeated until the first apparatus outputs a signal to which the second apparatus responds, thereby indicating a protocol capability of the second apparatus.
According to one embodiment, the first signal which is output, also carries information regarding the protocol capability of the first endpoint. That is, preferably, the first signal has a first form if the first endpoint has a first protocol capability and it has a second form if the first endpoint has a second protocol capability. Preferably, the apparatus at the far end of the link will respond to either of these forms in the manner described above.
In the preferred embodiment, the apparatus which has detected the capability at the far endpoint adjusts its operation to accommodate that capability. For example, when the first endpoint detects that the far endpoint has a first protocol capability, the first endpoint will configure itself to conduct subsequent communication using the first protocol. However, if the first endpoint detects that the far endpoint has a second protocol capability, the first endpoint is able to configure itself to accommodate the second protocol capability.
In one embodiment, the far endpoint will have only a single protocol capability. However, it is possible to configure a network in which both link endpoints have multiple protocol capabilities and both can detect one or more capabilities at the opposite endpoint. The endpoints can then configure themselves to operate at the best or most desired protocol level.
FIG. 4. is a schematic block diagram of node circuitry for multiplexing and preparing data for transmission over the media and for receiving information from the media and demultiplexing the data;
FIG. 5. is a schematic block diagram of hub receiver circuitry according to an embodiment of the present invention;
Before describing link endpoint capability detection, a general description of one type of network will be provided as one example of a data communication system in which the present invention can operate. A data communication system can be configured in a star-topology with a plurality of nodes 42a, 42b, 42c, (
Each of the nodes 42a, 42b, 42c can include various types of sources and sinks such as strictly isochronous sources and sinks, such as depicted for node one 42a, strictly non-isochronous sources/sinks as depicted for node three 42c or both isochronous and non-isochronous sources and sinks as depicted for node two 42b. The physical layer 52 of the network system depicted in
The hub 44a includes circuitry 54a, 54b, 54c for receiving data from the physical media 46a, 46c, 46e separating the isochronous-sourced data from the non-isochronous-sourced data and the D channel and M channel data and converting separated data into a form suitable for handling by downstream hub circuitry 56. In the depicted embodiment the separated isochronous-sourced data is provided to a time slot interchange controller 58 for placing the data on a high-bandwidth bus (e.g. the TSI bus) so that it can be transported to destination nodes on other TSI controllers in the hub or other hubs (as depicted, e.g. in
According to the present invention, data communication can be provided according to one or more of a number of protocols. Those skilled in the art are familiar with protocols, but in general, a “protocol” includes a standard set of rules that specify the format, timing, sequencing and/or error checking for data transmission. Several network protocols are referenced above, including an ethernet protocol such as 10BASE-T, an isochronous protocol such as FDDI-II, and a token ring protocol. Another possible protocol is one in which both isochronous and non-isochronous data are combined into a frame structure for transmission across physical media. A frame-structure protocol of this type is described in greater detail in commonly-assigned application Ser. No. 07/969,916, titled “Network for Data Communication with Isochronous Capability”, now abandoned, filed on even date herewith and incorporated herein by reference. According to one such protocol, the incoming data from the various sources is provided to a multiplexer 70 (
The present invention will be described below by way of a particular example in which one available protocol is an isochronous-ethernet protocol and another potentially available protocol is a 10BASE-T protocol. However, as will be clear to those skilled in the art, the present invention can also be used in connection with other combinations of protocols such as isochronous-token ring or other isochronous-LAN protocols, pure isochronous protocols such as FDDI-II, and can include three or more protocols.
Table I depicts the manner in which the various data streams, and additional data and control bytes are time-division multiplexed in an isochronous-ethernet protocol. Each symbol in Table I represents four bits of data so that every group of two symbols represents one 8-bit byte of data. In Table I, E represents four bits of data from the ethernet stream 66b (FIG. 4), B designates four bits of data from the isochronous stream 66a. D represents four bits of data from the signaling or D channel stream 66c, and M represents four bits of M channel data stream 66d. In addition, certain byte-length patterns are provided. JK represents a frame synchronization pattern and EM (the first two bytes of block three in Table I) represents an ethernet “pad” followed by a maintenance byte. As seen in Table I, each frame contains 256 bytes which can be considered in thirty-two groups of eight bytes each, or four blocks of sixty-four bytes each. The frame structure is described more thoroughly in commonly-assigned application Ser. No. 07/969,911, Pat. No. 5,544,324, titled “Network for Transmitting Isochronous-Source Data with a Frame Structure”, filed on even date herewith and incorporated herein by reference.
The time-multiplexed data is then encoded by an encoder 72. In the depicted embodiment, the encoder performs four/five encoding. One particular form of four/five encoding conforming partially to the ANSII X3T9.5 standard, is depicted in Table II. The encoding scheme depicted in Table II is described in greater detail in commonly-assigned application Ser. No. 970,329, titled “Frame-Based Transmission of Data”, filed on even date herewith and incorporated herein by reference.
The output from the encoding devices is sent to pre-emphasis circuitry 76. The pre-emphasis circuitry compensates the signal transmitter onto the physical medium to reduce the jitter. The data output by the pre-emphasis circuitry 76 is sent to a transmitter or driver 78b and the signal is transmitted over the physical medium 46c. The physical medium 46c can be any of a number of media types including twisted pair, coaxial or fiber optic cable.
The data sent over the physical media 46a is received in the hub 44a. The hub contains a plurality of circuit devices 54a, 54b, 54c, each one coupled to one of the nodes 42a, 42b, 42c by the physical media 46. As depicted in
Both the non-isochronous-sourced data 94b and the isochronous-sourced data 94a are made available to the various hub circuitry components 54a, 54b, 54c, as needed for transmission back to destination nodes. In one embodiment, the separated isochronous data 94a and non-isochronous data 94b are reconfigured by the respective interfaces 58, 59 to provide isochronous output 102 and non-isochronous output 104 in a form suitable for processing so as to provide the data as needed for transmission to the destination nodes. In one embodiment, the non-isochronous data 94b can be configured by the E interface 59 so that the output data 104 can be processed by a repeater device 60 for provision to hub circuitry 54 and eventual transmission to destination nodes. As an alternative to using a repeater for the non-isochronous data, packet connections may be linked through media access control layer bridges. Preferably, the output data 104 is in a form such that it can be handled by repeater circuitry of types previously available. For example, when the non-isochronous data 94b is data which originated at the node 42b from an ethernet MAC, the output data 104 is in a form such that it can be handled by a standard ethernet hub repeater 60 such as DP83950 “Repeater Interface Controller” (RIC) available from National Semiconductor Corporation, Santa Clara, Calif.
As shown in
The data 198 output from the E transmit interface 168 is provided along with isochronous data output 164 and M channel and D channel data 170 to encoder serializer circuitry 202, as depicted in FIG. 6. The encoder/serializer 202 is configured substantially like the encoding the circuitry found in the node and depicted in FIG. 4. Specifically, the encoder/serializer 202 provides a multiplexer for combining the three streams of data 198, 170, 164, a four/five encoder, an NRZI encoder, and pre-emphasis circuitry. The timing of transmission is controlled by transmit timing circuitry 204. Output 206 from the encoder/serializer is selectively combined with link beats from a link beat generator 208 by multiplexer 210 for purposes of link end point detection, as described below. The clock signal and the data 166 from the repeater 60, in addition to being provided to the E interface 168 is also provided to a second interface which operates according to a second protocol. When a second protocol is an ethernet 10BASE-T protocol, the interface is an ethernet 10BASE-T interface 520. The ethernet 10BASE-T interface transmit 520 can be of a type substantially identical to 10BASE-T interfaces provided previously in apparatus such as model DP83922 Twisted Pair Transceiver Interface (TPI), available from National Semiconductor Corporation, Santa Clara, Calif. The output from the ethernet 10BASE-T interface 520 is provided to the multiplexer 210. Multiplexer 210 is able to select, in response to a control signal 522, whether to output data originating from the repeater 60 according to a first protocol determined by the E interface 168, or according to a second protocol determined by the ethernet 10BASE-T interface 520, as described more fully below. The data sent from the hub 44a to the nodes 42 is sent in a frame format which is preferably substantially the same as the frame format used for the data sent from the nodes 48 to the hub 44a as described above. At the nodes 42, the circuitry 50 includes devices (
As shown in
Although
The node transmitter control 522 in response to the mode select signal 516 (indicating receipt of a link test pulse or other probe pulse) configures the multiplexer to output an appropriate node protocal signal from the link beat generator 208 onto the medium 46. In some embodiments, nodes and/or hubs are configured to output a link test pulse or a probe pulse (depending on the capability of the hub or node), whenever the hub or node is powered-up. For embodiments in which the link beat detect 82 is able to discriminate between a link test pulse and a probe signal such as an iso probe pulse, the mode select 516 can configure the link beat generator 208 to output a link test pulse in response to a link test pulse and an iso probe pulse in response to a probe signal. The signal output by the node transmitter is received in the hub receiver 54 (FIG. 5). The hub receiver link beat detect circuitry 82 detects the output of the node protocal signal from the node transmitter. When the signal is a probe signal, circuitry 82 outputs a mode select signal 516 which is effective to control the multiplexer 514 to connect the output from the E interface 59 to the repeater 60. In this way, the hub receiver is now configured to process future signals received from the node over medium 46 according to an isochronous-ethernet protocol. The node select signal 516 also provides an input to control signal 522 which, in response, configures the multiplexer to place the output 206 from the encoder/serializer 202 onto the physical medium 46, rather than using the output from the 10BASE-T interface 536. In this way, the transmitter is now configured to output data according to the isochronous-ethernet protocol.
If the signal output from the node is a link test pulse rather than probe pulse, the link beat detector 82 outputs a mode select signal 516 which configures multiplexer 514 to connect the ethernet 10BASE-T interface 512 with repeater 60 and configures the multiplexer to send output 536 onto the physical medium 46, rather than output 206.
In view of the above description, a number of advantages of the present invention can be seen. The present invention allows a network to be configured in a mixed protocol or mixed environment, with, for example, a single hub connected to a plurality of nodes which operate according to different protocols, with the configuration being achieved automatically, without the need for manually establishing a predetermined protocol beforehand for each node. The present invention permits networks to be upgraded incrementally so that it is not necessary to upgrade all nodes at the same time. Furthermore, it is not, in general, necessary for service personnel to specifically configure nodes or hubs to accommodate particular protocols since the protocols are determined automatically and the nodes and hub configure themselves in accordance with the determined protocols.
A number of variations and modifications of the present invention can be used. Although an embodiment involving a 10BASE-T protocol and an isochronous-ethernet protocol was described, the present invention is equally applicable to other protocols including other LAN protocols such as a token ring protocol, an isochronous protocol and the like. Although the present invention described one particular signal characteristic used for determining the protocol, other characteristics could also be used. For example, a token ring connection could be detected by the presence of four or 16 Mbit/sec Manchester-encoded data. Other LANs can be detected by their unique timing and data patterns. Protocols could also be detected using such characteristics as the pattern of the presence or absence of a carrier, and the frequency spectrum of signals placed onto the physical medium. When a node has a capability of communicating under two or more protocols, e.g. either an isochronous-ethernet protocol or a pure ethernet protocol, it would be possible for a hub to use both capabilities of a node, i.e., to communicate according to a first protocol during a first time period and a second protocol during a second time period. Although the present invention has been described in the context of a star topology, the invention could also be used in a non-star topology, such as a ring topology or a tree topology. The present invention can be used in networks which do not have a hub, such as direct connections between two nodes with each node determining the protocol capabilities of the other node. As described above, the link test pulse and iso probe signals are related in that, for example, a 10BASE-T node will respond in the same fashion to receipt of either type of pulse. However, the test signals could be provided in forms which are unique to each type of protocol. In such a system, a data source/sink would output a first type of test pulse or other signal and, if no response was received, would output a second type of test pulse or signal, and so forth until a response was received indicating the protocol capability at the other end of the link. A data source/sink could be configured to determine all possible protocol capabilities of the apparatus at the other end of the link, rather than determining the “highest” or “best”capability available or using the first capability detected. The devices at each end could select a protocol capability other than the “highest” or “best” capability. It would be possible for a node to store an indication of its capabilities, such as in a table or other memory device, and to output the information upon receiving an inquiry. It would also be possible for a network to initialize in a common protocol, e.g., a 10BASE-T protocol, and, thereafter, exchange information, using that protocol, indicating additional protocol capabilities of the components of the system. Thereafter, the systems could reconfigure themselves to use desired ones of the available protocols.
Although the present invention has been described by way of preferred embodiments and certain variations and modifications, other variations and modifications can also be used, the invention being defined by the following claims.
This is a continuation of application Ser. No. 07/971,018, filed on Nov. 2, 1992 and now abandoned. The present invention is directed to a method and apparatus for detecting, in a network, such as a local area network, the protocol capability of one or more endpoints of a data communication link, and in particular to a method and apparatus for determining whether a data source/sink at the end of a datalink has the capability of a first data communication protocol or a second data communication protocol.
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Number | Date | Country | |
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Parent | 07971018 | Nov 1992 | US |
Child | 08430143 | US |
Number | Date | Country | |
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Parent | 08430143 | Apr 1995 | US |
Child | 09443250 | US |